How old are you really?
Your rounded globeike skull has existed
for 200,000 years. Your long legs and
arched feet made their appearance a
couple of million years ago. Your
rotating shoulders allowed ape ancestors
to climb in and out of trees 20 million
years ago. And your fingernails, they
evolved close to the time of the
dinosaurs.
16 million years ago, your early primate
ancestors started to lose their claws
for flat nails, allowing them to grip
and grasp rather than scratch and dig.
Around the same time, your eye sockets
began to face forward so you could judge
the distance to the next branch. Three
times older than that are the hairs on
your body and the mammary glands beneath
your nipples. They evolved 200 million
years ago in the earliest mammals
alongside your mers in sizes and canines
developing from teeth that used to all
be the same. Twice as old are your lungs
evolving over 400 million years ago in
the ocean before any finger or toe had
walked the earth. Older still is your
jaw and your heart changed from a simple
tube to a chambered structure around the
same time your eyes developed retinas
half a billion years ago.
And so draw a line back through
generations of your parents and
grandparents, back through each one of
their ancestors, and you will find
direct relatives, the apes, fish, and
even the creatures that predate all of
them. Your lineage, your family tree,
your bloodline, extends even further
than this, billions of years back to the
dawn of life on Earth. Your body today
is filled with features that developed
in vastly different times in vastly
different creatures. And indeed, your
existence today is only possible because
of those who came before. Your ancestors
had to develop and use these new tools
to survive for billions of years in
order to create their greatest great
grandchild,
you.
And so, how did it happen?
What did you evolve from?
In November 2007, the Photon M3 rocket
returned from space. It had spent 12
days orbiting our planet. But its
passengers were not humans. They were
tardigrades.
Tardigrades, affectionately known as
water bears, are some of the toughest
animals on the Earth. Although
microscopic, they can withstand extreme
temperatures, a thousand times more
radiation than other animals, and 30
years without food or water.
Understandably, many think of them as
being virtually indestructible. And so,
in 2007, scientists decided to put that
idea to the test. They sent tardigrades
into orbit on the exterior of the Photon
M3 rocket.
There they experienced extreme
acceleration and violent vibrations as
the rocket launched into space. And once
they reached orbit, the conditions
didn't improve much. Now they had to
contend with zero oxygen, rapid heat
loss, and high radiation from the sun.
No other living organism has survived
such an ordeal. But astonishingly, most
of the tardigrades did. Life finds a
way.
Species like these are particularly
fascinating from an evolutionary
perspective because although our planet
seems perfect for sustaining life, this
hasn't always been the case. The Earth
is approximately 4 1/2 billion years
old. But for most of its existence, it
was an inhospitable place by the
standards of our time. Indeed, for a
long period after its formation, our
planet was a molten ball of magma with
an atmosphere as welcoming as a stellar
nebula. Even after several hundred
millennia had passed, most life as we
know it couldn't have held on. And yet,
we do know from geological evidence that
life evolved relatively early in the
planet's history. By 4.4 billion years
ago, Earth had cooled enough to form a
solid rocky surface. However, the air
was still toxic, made up of deadly gases
like hydrogen sulfide, methane, and
carbon dioxide. With very little oxygen
in the air, it might seem impossible
that life could ever have evolved. But
Earth had something that would spark a
revolution.
Water.
This simple element composed of two
hydrogen atoms and one oxygen is vital
for all life on the planet. So, if there
was water on the Earth 4.4 4 billion
years ago. Could there have been a life?
Could you trace your family back a 100
million generations to find your
ancestor living billions of years ago?
Well, it is possible, but
unsurprisingly, hard evidence is very
difficult to come by.
But in 2017, researchers from University
College London reported that they
believed they had found it. In their
study, they collected samples of rock
from the Novu Agitic belt located in
Hudson Bay in Canada. The rocks here are
thought to be between 3.75 and 4.29
billion years old. So, the research team
had decided it was a logical place to
look for evidence of the very first life
on Earth. And what they found were
traces of life in what appeared to be
the remains of an ancient hydrothermal
vent. Today, hydrothermal vents are like
oases in the desert of the deep sea,
sustaining all kinds of life in extreme
conditions. Footage captured by remote
operated submersibles shows an almost
alien landscape. giant chimneys rising
up from the clean floor that are covered
in fish, crustaceians, worms, snails,
and seephalopods. And so, although
living on a crack in the ocean floor
might seem extreme to us, it could have
been the perfect place for early life to
first appear. The team from University
College London, led by PhD candidate
Matthew Dord, found that the rocks from
Hudson Bay contained microscopic
filaments made of iron oxide. Bacterial
colonies around deep sea hydrothermal
vents today form similar structures,
which suggested that early life could
have existed on these ancient rocks. In
addition, the filaments contained carbon
isotopes that are diagnostic of
biological processes. And so perhaps
4.29 29 billion years ago, you were a
microbe living on a hydrothermal vent.
Of course, life at this time was nothing
like the plants or animals we know
today. Instead, there were only
microscopic single-sellled organisms
that thrived in the extreme environment
of the deep sea. And these tiny
ancestors didn't rely on sunlight for
energy. Instead, they harnessed the
chemical reactions going on inside the
vent. Seawater interacting with
superheated rocks of up to 400° C in the
Earth's mantle, shot out energy richch
minerals and gases like iron and
hydrogen sulfide, providing excellent
conditions for chemosynthesis,
the process by which microorganisms use
chemical reactions between organic
molecules rather than sunlight to
produce organic compounds.
And so we have a fairly good idea where
life began. But what do we know about
how it began? There was of course a time
before life. A time before both the
chicken and the egg. Life therefore must
have started somewhere, not with a cell,
but with a chemical reaction.
In the dark mineral-rich depths of the
southwest Indian ridge, scientists from
the Chinese Academy of Sciences have
uncovered solid evidence that the stage
for life may have been set by simple
rocks and water. Their recent studies
have revealed mysterious carbonrich
material trapped within oceanic crust
basults, a type of matter key for life.
Yet these carbon compounds are truly
non-biological, non-living and sculpted
by the raw energy of geochemical
processes. And so how does this lifeless
rock give rise to the building blocks of
life? The Chinese team combined
cuttingedge microscopy and computer
simulations to show that hydrogen gas
bubbling out of deep sea hydrothermal
vents interacts with material called
goite. It uses it almost like a mineral
workbench. In this process, carbon
dioxide dissolved in seawater transforms
into larger, more organic molecules.
Each time a small carbon-based molecule
joins another, a more complex compound
is born, gradually inching closer to
life as we know it.
So according to this groundbreaking
research, minerals like goite could have
acted like catalysts for simple
molecules to combine and grow. Over
countless years, this organic
condensation might have laid the
foundations for amino acids and fatty
acids, essential ingredients for life,
to appear.
However, this is just one idea. There
are other options on the table.
Another compelling theory is known as
the membrane first hypothesis.
Every living cell from the bacteria in
your gut to the neurons in your brain
has one thing in common. It is separated
from the outside world by a barrier.
This barrier is called a membrane. The
membrane first hypothesis suggests that
before there were genes, proteins or any
of the molecular machinery we associate
with life today, there were membranes.
These would have been simple bubble-like
structures floating around in the
primordial ocean. But how could a bubble
be the first step towards life? Well,
these early membranes were selective.
Small molecules slipped through easily,
but larger, more complex molecules got
trapped inside. That meant that if by
chance some useful chemical reaction
started happening inside, that reaction
would be protected and concentrated
within the bubble. Without that
boundary, any useful molecules could
drift away. But inside they are forced
together and the chances of something
new happening are increased.
Both organic condensation and membrane
first are compelling options for the
origin of life. But there is another
contender and one that many scientists
think has the strongest evidence behind
it.
The year is 1962 and Alexander Rich, a
biohysicist at the Massachusetts
Institute of Technology, is puzzling
over how life began. The conventional
wisdom of the time was that proteins
must have come first. But Rich is not so
sure. Proteins need instructions to be
built, and those instructions are stored
in DNA. But of course, DNA itself is
useless without proteins to copy and
read it. Rich, however, has been
studying polyucleotides
or RNA chains. And he has noticed
something. Unlike proteins,
polyucleotides have a specific
arrangement that could allow them to
catalyze their own reproduction. In
other words, a strand of RNA could
facilitate the formation of matching
strands, creating doublestranded
molecules.
RNA could copy itself.
Alexander Rich was the first scientist
to explicitly propose that life could
have started with RNA like molecules
rather than proteins or DNA. A simpler
RNA world dwelling in the deep ocean
billions of years ago before DNA and
proteins became more dominant.
And so we have traced life back to its
very earliest moments on Earth and been
provided with differing theories. But
whether it was in the form of organic
condensation, RNA molecules, or lipid
bubbles, we still haven't answered a
fundamental question.
What actually is life?
It might sound like a simple question,
but defining life can be surprisingly
difficult. Is a virus alive? It can
reproduce just like we can, but only by
hijacking other cells. And what about
those self-replicating RNA molecules?
Are they alive? They copy themselves and
evolve, but at their core, they are just
chemicals floating around in water. This
is where things get tricky. So,
scientists have proposed various
different definitions for sorting life
from non-life. Some say that life must
be able to reproduce, metabolize, and
respond to its environment. Others argue
that life is anything capable of
evolution through natural selection. But
every definition has exceptions and gray
areas, such as viruses being capable of
evolution and reproduction, yet not
being classed as life. And so perhaps
the line between life and non-life isn't
quite as sharp as we would like to
think. Maybe in those early oceans,
there was a spectrum from simple
chemicals to self-replicating molecules
to primitive cells.
Each step would have blurred the
boundary a little more. Meaning that
maybe the question, what is life?
Doesn't have a black or white answer.
But what we can say for certainty is
this. Once life emerged, however we
choose to define it, it didn't stay
simple for long.
Of
course, life has come a very long way
since the early days of our planet.
Today, billions of animals, plants,
fungi, bacteria, and archa inhabit all
corners of the earth. And so, how did
this happen? How did the earth go from a
desolate planet populated only by simple
microbes to one teeming with life?
To begin with, all living organisms were
unisellular, made up of a single cell.
Unisellular organisms are usually
microscopic, and each cell has to do
everything necessary for its survival on
its own, like converting external
elements into energy and reproducing by
self-replication.
Even when individual cells form colonies
such as bacterial mats, they don't have
different functions. Each cell is solely
responsible for itself. Multisellular
organisms, however, are made up of
multiple cells, all of which rely on
each other for survival. Cells can
protect each other from attack by
viruses or harmful bacteria. And even
when individual cells die, the organism
as a whole can go on living.
While the transition from single-sellled
organisms to true multisellular life may
seem like a colossal undertaking, there
is evidence to suggest that even simple
unisellular organisms had most of the
genes necessary for evolving
multisellularity.
Nicole King, a researcher with the
University of California at Berkeley,
studied a group of simple organisms
called coonoflagelates.
They are singleselled but are considered
to be closely related to animals and are
capable of some things that are usually
unique to multisellular life like sexual
reproduction. Guanoflagelates also form
colonies much like our unisellular
ancestors are thought to have done. It's
hard to say exactly when this may have
happened, but it is thought that between
3 and 3 and 1/2 billion years ago, some
single-sellled organisms may have
grouped together and coordinated their
behavior. After many years of study,
King and her lab team had discovered 350
kinds of genes in the kanoflagillates
that usually only turn up in complex
animals. They found genes that help
control the functions of specialized
cells, cell growth regulators, and even
genes that help cells stick together,
which are used in modern animals for
keeping muscles intact. And so King and
her colleagues believe that
kanoflagelates could be similar to the
unisellular ancestor of animals and that
such organisms were already genetically
equipped for evolving into multisellular
life. The evolution of multisellular
life therefore may have been a series of
incremental steps rather than one sudden
leap.
Of course, multisellular organisms are
much more complex than single-sellled
life. When multiple cells make up one
organism, individual cells perform
different functions. Modern animals have
an impressive diversity of cell types.
For example, humans have as many as 200
kinds, such as nerve cells, skin cells,
and muscle cells. By comparison, plants,
fungi, and algae, have fewer cell types,
but are still classed as examples of
complex multisellular organisms.
This complexity, particularly in
animals, brought about several
advantages over time. Although the first
animals were stationary and didn't look
too different to plants, they eventually
became mobile, which allowed them to
move to different areas in search of
food and mates. And pretty soon, life
was about to do so much more.
In 1996, a rural farmer from Leaing
Province discovered a new species of
dinosaur.
The fossil was preserved across two
slabs of silt stone, offering alternate
views of the dinosaur encased within. In
life, it would have been a small
therapod, weighing no more than a
kilogram. But the most intriguing thing
about it was its extraordinary
preservation.
Not only was virtually every bone
present in the fossil, but so were the
impressions of the animals internal
organs and its feathers.
This newly discovered dinosaur was named
Sinosiopterix.
And although it had feathers, it wasn't
a bird, nor was it closely related to
them. For feathers, despite being
classically associated with birds,
predate the aven lineage, extending far
back into the triacic around 230 to 250
million years ago. Birds are aven
dinosaurs that use their feathers to
fly. But sinosopterics and other
non-avian dinosaurs likely use their
feathers for something different. Their
feathers wouldn't have been strong
enough for powered flight. And so
perhaps they were purely for keeping
warm. Paleontologists have even
discovered evidence of feathers in
terasaur fossils, but they were
concentrated around the torso rather
than on their wings, suggesting that the
first feathers evolved for insulation,
an ancestral trait shared by both
dinosaurs and terasaurs.
And so it might be surprising when the
features we are familiar with did not
evolve for their current purpose. But
this is actually the most common way new
adaptations evolve in nature. They begin
as an adaptation to a specific
ecological challenge and over time prove
useful for other things. And such
evolutionary developments probably took
place even in our earliest ancestors
around 600 million years ago. Some 4
billion years after the formation of the
Earth, life began to change. Prior to
this point in time, there were no
macroscopic multisellular organisms.
Fossil organisms were much too tiny to
be seen without a microscope, and the
only macroscopic fossils known to
science were from life forms that formed
colonies, like the 3 and 1 half
billionyear-old strumatalytes from
Western Australia. Indeed, for a long
time after the earliest organic microbes
on Earth evolved and multisellular
organisms first appeared, life didn't
change much. Indeed, this was one of the
reasons that scientists coined the term
the boring billion for the period
between 1.8 billion and 800 million
years ago. From a geological and
biological perspective, the boring
billion was characterized by relative
tectonic stability, climate stasis, and
painfully slow evolutionary change. But
then something happened
sometime between 800 and 650 million
years ago. It is believed that extreme
global cooling created a period known as
the cryoggenian glaciation or snowball
earth in which almost all of the
planet's surface became frozen. Of
course, it's hard to imagine how life
could have withstood such conditions.
But instead of being driven to
extinction after the glaciation, life
forms suddenly got a lot bigger and more
complex. This was during a time that we
now know as the Ediakaran.
Life was still very different to what we
are now familiar with, but it was
beginning to sort itself into some of
the basic categories that we use today.
Some edi organisms such as the slug-like
kimberella and spraina are thought to
have been the precursors to animals
while the possible ancestors of plants
and fungi have been linked to
microossils found in China. Other genera
like charia and frtoous superficially
resemble plants but were probably more
closely related to animals. Indeed, the
vast majority of life during the
Idiacarine was cesile, meaning it was
unable to move on its own. Idiaran life
generally survived by anchoring itself
to something else such as rocks or
oceanic substrate similar to modern-day
hydra. This and the leaflike shape of
many genre gives the illusion that edi
organisms were plants. But it is
generally thought that macroscopic
animals were the first to evolve and
plants would come later. So although
macroscopic complex life had finally
arrived on the scene, the ediaran oceans
were quiet subdued places.
But soon an explosion of diversity would
occur.
Dine Castle is located on what is now
the western edge of the Breen Beacons
National Park in South Wales. It was
built in the 12th century at top a hill
overlooking the river Tawi and looms
above it shrouded in trees. When it was
first constructed, it was an important
strategic fortress for Welsh kings. But
by the 17th century, the once great
castle had been converted into a kind of
summerhouse by the English lords who now
owned the land. And so on a warm, sunny
day in 1688, 28-year-old scientist
Edward Lloyd would have been able to
walk the grounds and muse upon the long
history of the place in relative peace.
The sieges and battles that the ancient
stone walls must have borne witness to
long settled.
Although it wasn't really the castle
that Lloyd was there for, he was
interested in something much older.
Fossils.
Since beginning working at the recently
opened Asholian Museum in Oxford, Lloyd
had been traveling all over Wales,
mainly to document local flora, but also
on a personal quest to find evidence of
ancient life in the mountainous
landscape. And after exploring the
grounds of the castle for a short while,
he eventually found what he was looking
for.
The impression of an animal preserved in
stone, but unlike anything he'd ever
seen before. Lloyd sat down in the grass
and sketched the fossil, thinking to
himself that it looked like the skeleton
of a large flat fish. Eventually, it
would go on to publish a description of
the fossil in the Philosophical
Transactions of the Royal Society. But
it would not be until over a 100red
years later that Lloyd's discovery would
be recognized for what it really was. A
trilabite.
Lloyd couldn't have known it in 1688,
but he had just recorded the first known
evidence of a life form from the
Cambrian explosion. Trilobytes appear in
the fossil record some 521 million years
ago and are some of the most common
fossils that have been found in Wales.
In fact, trilobytes were so numerous in
the Cambrian they've almost become
emblematic of the period. The name
Cambrian actually comes from Cambria,
the Roman name for whales. Trilobytes
were among the first animals to develop
complex jointed exoskeletons and they
had compound eyes made of hundreds or
thousands of tiny independent light
sensing units called omitidia. They had
as many as 15 pairs of legs and gills on
their thighs. Trilobytes became uniquely
successful organisms roaming the ancient
seas for over a quarter of a billion
years and were some of the most numerous
animals that lived in the Cambrian seas.
The Cambrian was the period of time that
followed directly on from the Idiacaran,
beginning around 540 million years ago.
Its early days were characterized by the
sudden diversification of life on Earth.
Not only did trilobytes appear during
this time, so did other arthropods like
the predatory anomalicarus, the bizarre
opabia, and the spiky hallucenia. Aside
from arthropods, there were also
molllesks, worms, nidarians, and even
the earliest cordates. For the first
time in Earth's history, life was truly
complex. Animals could move on their
own. They had eyes and mouths, and
predator prey dynamics evolved. But what
was our ancestor during this remarkable
time?
Scientists believe that during the
Cambrian over half a billion years ago,
you were one of the earliest cordates.
But what is a cordate and which one?
It's hard to pin down exactly as we're
dealing with incredibly old material. So
DNA analysis is impossible. But there
are some candidates that are more likely
than others.
The first is a creature called Haikothus
which lived 518 million years ago in the
latter stages of the early Cambrian. It
was originally found in Yunan Province,
southern China and resembles a small
simple fish about 2 and 1/2 cm long. It
was roughly the same size as the tip of
your little finger and had a defined
skull which was rare for animals of the
time. The second is Picaya Grassalins,
an animal that looked like a modern sea
slug. Picaya dates to the middle
Cambrian some 508 million years ago and
ranged from 1 and a half to 6 cm in
length. Although these two animals look
quite different, they both had a few
important features in common as cordates
and perhaps most importantly something
called a noticord.
This is a flexible rod-like structure
that runs along the length of the body.
And its evolution is important because
it served as a precursor to the
vertebral column in later cordates. In
other words, it was a very early
backbone in Hikuis and Picaya. The
noticord provided structural support,
giving their muscles something to anchor
to, which was essential for more
efficient swimming.
And the noticord wasn't the only
important feature shared by these two
early cordates. Both Akawthus and Picaya
had segmented muscles which allowed them
to undulate their bodies in a controlled
wavelike motion. This style of movement
is similar to the motion seen in modern
fish, highlighting an evolutionary step
towards more efficient propulsion
through the water. Another key feature
was the presence of fingial slits. These
were openings along the throat that were
probably used for filtering out food
particles from the water. But they would
eventually evolve into gills and also
jaws.
Together, these shared features mark
Hikawickthus and Picaya as key figures
in the story of our evolutionary
history. Although they were both small
and unassuming even by Cambrian
standards, they represent some of the
first steps towards the development of
true vertebrates, which includes
everything from sharks to frogs, snakes
to birds, cats to whales, and humans.
But why did these little Cambrian
animals evolve notic?
Evidence suggests that like feathers,
the original purpose of a noticord could
have been quite different to what it
would be eventually used for.
In basil cordates like hyoicis and
picaya, the noticord is located close to
the gut tube, which has led some to
suggest that it originally evolved from
a digestive structure and could have
been used for transporting nutrients
throughout the body. Others think that
the noticord may have developed from a
structure found in some softbodied
animals like worms. A study published in
the journal Science found that analid
worms have a muscle that runs along the
dorsal or back side of their bodies.
Similar to how not cords and then
vertebrae run along the back of
cordates.
This muscle has been called an axocord
and it's assumed that it helps worms to
get around. Earthworms for example
require a lot of strength to burrow
through soil. So axo cords could help
them do this. Perhaps protocordates
behaved in a similar way, burrowing into
ocean substrates to avoid predators like
anomalicaris.
It therefore seems possible that analids
and cordates share a common ancestor and
that the basic structure of a noticord
was already present before the evolution
of hikthus and picaya. It just developed
over time to suit the challenges of
their environments.
And so whatever its original purpose may
have been in Hikthus and Picaya, the
noticord became crucial for efficient
movement through the water. Noticords
allowed for unjator swimming which would
have made basil cordates quicker and
more maneuverable than animals like
arthropods which are limited by their
hard exoskeletons.
In an environment as rapidly
diversifying as the Cambrian seas,
competition for resources and space must
have been intense, and noticords could
have given our little ancestors the
advantage they needed to survive.
Noticords even paved the way for the
evolution of other bones, which helped
later cordates maintain the shape of
their bodies and protect their vital
organs. And indeed, within a few hundred
million years, they would help support
animals as they made their way into a
new frontier,
out of the water, and onto the land.
Just how closely related are you to a
bat?
Bats are mammals. They grow hair on
their bodies and give birth to live
young. They are social animals. But that
is where the similarities seem to end.
We humans rely on our legs to get
around, whereas bats have wings. Humans
primarily use sight and touch to
interact with the world around us. But
bats use echolocation, super sensitive
hearing that allows them to navigate and
hunt even in total darkness. But even
with these differences, we do share a
surprisingly close evolutionary
relationship. Indeed, if we trace our
two lineages back through time, we find
a common ancestor with bats that lived
during the late Cretaceous.
But what if we push the hands on the
evolutionary clock back even further?
How related are we to a lizard or a
frog?
Well, if we go back five times deeper
into the past to around 400 million
years ago, we would find a common
ancestor that unites all terrestrial
vertebrates, from amphibians to
reptiles, from birds to mammals.
Imagine yourself standing in the flood
plains of the Gambia in Western Africa.
You look out over the river, a waterway
that flows so slowly local people swear
it sometimes runs backwards. You might
be surprised to find out that these
swampy flood planes are the perfect
place to find a relic from our
evolutionary past.
For during the dry season, when shallow
pools along the flood plane begin to
evaporate, a curious animal can be seen
crawling through the mud. It is a
lungfish.
Broadly eelike in shape, this fish is
equipped with a thick tail and fins that
function like rudimentary limbs,
allowing it to drag itself from one pool
to another. Indeed, the lungfish is one
of only a couple of kinds of lobefinned
fish left in the world. And they may
appear archaic compared with modern
rayfinned fish, but we can learn a lot
from them because lungfish, as their
name suggests, have a pair of lungs
allowing them to breathe while on land.
Today it is one of the only fish in the
world that does this. But this kind of
adaptation may not have been quite so
rare 400 million years ago in a time
known as the Deonian. And in fact,
lungfish themselves are truly ancient
and are thought to have first evolved
during this time.
The Devonian spans 60 million years from
419 to 359 million years ago and is
known as the age of fish, a period of
time when fish became the most dominant
species on the planet. They were
diverse, widespread and grew larger than
any other animals before them. The
Deavonian oceans were filled with a huge
variety not just of lobefinn but also
heavily armored plams, primitive
rayfinned fish and even the ancestors of
sharks and rays. And yet despite this
dominance of fish, this was also a time
that has come to be associated with the
first land animals.
Up until this point, the majority of
life had been concentrated in the seas
with only a few hardy arropods braving
the baron surface. However, by the
deonian plants and fungi had already
begun their colonization of the land.
These pioneer plants such as leopites,
ferns, and horsetales and bizarre fungi
like the towering prototaxities
measuring up to 30 ft tall helped to
create soil for more varieties of plants
and fungi to grow in. Soon there were
primitive trees like Guateza and
Archopterus. And the spread of these
first forests created new habitats for
animals on land, including the earliest
tetropods.
Tetropods are a class of animals united
by one key feature, four limbs.
It includes a vast and diverse array of
species. In fact, if you were to be
asked to name five kinds of animals off
the top of your head, the majority of
them would probably be tetropods.
Indeed, as tetropods ourselves, they the
kinds of animals we encounter most often
in our daily lives. We see animals like
dogs, cats, squirrels, and pigeons, and
farm animals like cows, sheep, chicken,
and pigs. These are all tetropods. And
although we look very different, we all
share an ancient common ancestor, an
ancestral tetropod that can be traced
back to the Deonian.
And so, how did we go from a world ruled
from the oceans by fish to one where
full-limmed animals dominated the land?
In 2008, paleontologist Neil Schuben
published his book, Your Inner Fish. of
a scientific team discovered a fossil
that could answer that question. The
book introduced Tecttalic Rosé, an
ancient creature from the late Deonian
some 375 million years ago. When first
looking at the fossil, which was
recovered from Elmere Island in the
Canadian Arctic, it can be difficult to
say exactly what kind of animal Tectalic
was. Was it a fish, a large amphibian,
or even some kind of reptile? A closer
inspection, however, reveals several
distinctive fish traits, such as gill
arches and bony scales.
So, was it a fish? Technically, yes.
But, Tectonic also had a suite of
features that portrayed its evolutionary
trajectory towards life on land. For
beneath its overlapping scales, it had
bones that closely resemble those found
in tetropods. Within its front fins, for
example, were primitive versions of the
humorus, radius, and ulna, which in
humans form the upper arm and forearm.
These bones were hidden within
Tectalik's fins, but were arranged in a
way that allowed for a degree of
flexibility and strength. For instance,
Tectalic may have had something akin to
a wrist, which would have allowed it to
prop itself up and crawl around in muddy
shallows and even onto land for a short
time. Tictalic also had a much more
robust rib cage than any other fish,
which would have supported its body
weight while on land.
Schubin and his team had been searching
for this kind of fossil animal for a
long time. Because although it had been
suspected that tetropods must have
evolved from fish, there were no
transitional fossils to prove how fins
gradually developed into limbs. These
transitional animals that fall somewhere
between a fish and a tetropod have since
come to be known informally as
fisheropods.
Without access to a time machine, we can
only ever guess at the way fisher pods
like tictalic might have behaved. But it
seems likely, given their physical
adaptations, that they were ambush
predators. Like modern crocodilians,
fishopods would probably lie in weight
in the murky shallows before lunging at
smaller fish or invertebrates. Their
powerful pectoral fins and flexible
necks allowed them to strike with
precision, a feature uncommon in fish,
but vital for life on land.
And fishods were far from the only
predators of the Deonian. Massive
hunters like the 4 m long dunlers and
even uriperid sea scorpions lurked
beneath the surface. So, it seems likely
that our fisherod ancestors might also
have put their sturdy fins to use in
evading such monsters, pulling
themselves out of the water and onto the
relative safety of the land. And so, in
the Devonian 375 million years ago, you
were a transitional creature. Although
you were a fish, you had features in
common with future tetropods, which your
lineage would give rise to. He had
muscular fins, a flexible neck that
allowed you to scan your environment and
catch prey more efficiently, and strong
ribs that supported your weight during
your forays onto land.
So, we know how tetropods and the
earliest limbs gradually evolved from a
lineage of lobe finn fish. But how did
these pioneering animals develop the
ability to breathe on land?
All fish, including ancient fish, have
gills. These allow them to filter oxygen
from the water, but obviously not from
the air. Tetropods, on the other hand,
have lungs, which do the opposite of
gills. We can breathe in the air, but
we'll drown after just a few minutes
underwater. So, where did our lungs come
from? The answer to that question lies
within the lungfish.
Despite their name, lungfish also have
gills. This combination of gills and
lungs allows them to survive both in the
water and on land. However, soft tissues
do not preserve well in the fossil
record, making it more or less
impossible to say for sure whether our
fish ancestors also had them. But
luckily, lungfish are not alone, for
there are other ancient monsters that
have survived until our time that may
offer some clues.
It is a breezy summer afternoon in 1938
and a fishing boat is trundling through
the water near the mouth of the Chalumna
River in South Africa.
She is a trollwler, so her crew is used
to pulling up all kinds of strange
looking bottom dwellers from the sea
floor. But nothing could have prepared
them for the creature they caught in
their nets that day. It was huge, about
1 and 1/2 m long, with a vivid steel
blue body, dappled in pale milky white
spots that contrasted with the more
familiar catches of the day. Its scales
were thick and armor-like, rough to the
touch, and its head was covered in bony
plates. And even more startling were the
fish's fleshy, almost limblike fins that
projected from its body like arms and
legs. The captain of the troller quickly
called a local museum curator to come
and investigate. Marjgerie Courtney
Zatimer, who worked at the Museum of
East London, had no idea what the
primordial looking fish was, but she
immediately took it back to the museum
to be preserved and studied. She then
contacted JB Smith, an ichthyologist at
Roads University, who was stunned by
what she showed him.
The specimen looked exactly like fossils
of an ancient kind of fish known as a
celacanth. But celacanths had gone
extinct 66 million years ago. And so how
could one have been alive and swimming
around in the West Indian Ocean just a
day before.
This was one of the greatest zoological
surprises of the 20th century. Against
all expectations, the celacanth turned
out to have survived the extinction that
wiped out the dinosaurs and had been
living in the depths of the ocean all
this time. These primitive looking fish
have been called living fossils because
their appearance has changed very little
since they first showed up in the fossil
record 410 million years ago during the
early Devonian. There are only a few
other examples of living fossils known
to science, including the horseshoe
crab, which first appeared over 250
million years ago and has remained
fundamentally the same ever since. The
ginko baloba tree is another example,
dating back over 200 million years, but
no other living fossil holds quite the
same ancient pedigree as the celacanth.
Indeed, most of the other living fossils
have their origins in the Perian or
Mesazoic eras, whereas celicanth
ancestors were swimming through Earth's
oceans before the first land plants had
evolved to form forests and before
vertebrates had ventured out of the
water.
Based on their fossils, scientists in
the 1930s already knew quite a lot about
celacanths and had long suspected that
they might have lungs just like their
lungfish relatives. But it was very
difficult to prove without access to
live specimens. Even now that we know
sea aren't extinct, they are notoriously
difficult to study. They live in the
deep sea in small isolated populations
that inhabit underwater caves and rocky
outcrops. So, it's hard to get to them
without specialized diving equipment.
But in 2015, a team led by researchers
from the University of Rio de Janeiro
got their hands on a few preserved
celacants from museum stores and
performed dissections on them. And what
they discovered was both a vindication
and a surprise. For rather than a pair
of functional lungs, the cedacants had
just one vestigial lung.
This suggested that ancient celacants
also had at least one lung. But as their
descendants adapted to spend more time
at greater depths, they stopped being
useful and became vestigial.
Even though it is vestigial, the
presence of a lung in celacants led to
an important conclusion.
Since celicants and lungfish both come
from ancient lineages of lobefinned fish
that originated in the early Devonian
and both have lungs, that means lungs
are actually an ancestral trait. An
ancestral trait is an anatomical feature
that is shared among related taxa and
are inherited from a common ancestor.
For example, taillessness is an
ancestral trait in humans and apes. No
living ape has a tail and neither do
fossil apes, which tells us that our
common ancestor likely also didn't have
a tail. And so when it comes to lungs,
their presence in both kinds of living
lobefinned fish means that the last
common ancestor of all lobefinned fish
and therefore all tetropods also had
lungs. Lungs are a lot older than you
might have thought.
But does this necessarily mean that
lobefinned fish have always been able to
breathe air just as modern lungfish do?
Probably not. If you consider what land
was like back in the early Deonian,
practically devoid of all life, it makes
no sense for these fish to have evolved
the ability to breathe out of the water.
Instead, just as our backbones may have
evolved for a different reason to that
which they have today, it seems likely
that lungs too originally held a
different purpose. And scientists think
that an organ found in modern-day fish
could hold the key to this mystery.
All rayfinned fish, from salmon to
sardines, have something called a swim
bladder, which helps them stay buoyant
in the water. Sharks, rays, and other
fish don't have swim bladders, which
means they always have to keep moving or
they end up sinking to the bottom.
It's thought that since rayfind and
lofinned fish share a common ancestor,
swim bladders or something like them
could be an ancestral trait, but instead
of being used for buoyancy in lobefin
genera, they eventually evolved into
functional lungs. These new air
breathing organs would have helped them
venture above the water's surface as
plants spread across the land and new
terrestrial habitats became available.
This meant that our fish ancestors in
the late Deonian didn't have to come up
with a brand new solution when it came
to adapting to a semi-aterrestrial
lifestyle. They already had the perfect
hardware for the job. Evolution just had
to finetune it.
But what species was this Deonian
ancestor? Which species in particular do
we have to thank for the development of
our limbs, ribs, and lungs?
Once again, we're dealing with
incredibly vast time scales, so it's
difficult to be sure. But one of the
earliest genera to exhibit a combination
of fish and tetropod traits was
Eustthanopteron, which lived around 385
million years ago, 10 million before
Ticttalic. Esanopteron lacked the
strong, flexible wrist-like structure of
later fish, although it may have had
some degree of strength and mobility in
its fins, potentially allowing it to
push itself along the bottom of shallow
waters. But these fins were not yet
strong enough to support Eustanopteron's
weight on land, and it didn't have a
strong rib cage like Tectalic. But it
clearly provided an important foundation
for the gradual evolution of loadbearing
limbs.
And so lobe finned fish and early
tetropods gave us a lot of the features
that today we take for granted. Indeed,
in many ways, we still resemble our lobe
finn ancestors. We retain the basic body
structure that evolved over 400 million
years ago in the Deonian. We have four
limbs which evolved from four-lobed
fins, flexible and supportive wrists and
ankles, a set of digits at the end of
each hand and foot, a distinct head, a
strong skeleton made of bone, and a pair
of lungs to let us breathe the air.
But of course, that would be far from
the end of our adaptations to new
environments.
The young Mary Anning lived so close to
the sea that storms could flood her
house. Her father took her and her
brother Joseph fossil hunting and this
lit her curiosity. At the age of 12, she
discovered the first ichthyossaur
skeleton, becoming known as the princess
of paleontology. Sparking curiosity at
kids aged three and over. Or go to kiwi.com/humankind.
In the southern United States, there is
an entire species of lizard that is
female.
The New Mexico whiptail arose from the
crossbreeding of two other whiptail
species, a hybridization that appears to
have prevented males from forming.
Although these all female populations
still engage in mating behavior, which
some researchers believe is necessary to
stimulate and trigger ovulation.
A single female lizard will then lay a
clutch of eggs, each one hatching into
offspring that is a genetic clone of the
mother. It is one rather unique example
of continuing the survival of a species
through reproduction.
All life on Earth reproduces. It's one
of the core features that classifies
something as being a life form. If a
species can't replicate itself and pass
on its genes to the next generation,
then it is not living. Even the most
simple unisellular organisms reproduce
to pass on their DNA.
DNA or doxy ribboucleic acid is the long
molecule that contains the genetic
instructions used in the growth and
reproduction of all organisms. This
structure consists of two long chains of
nucleotides twisted into a double helix.
Each nucleotide is made up of a sugar, a
phosphate group and one of four
nitrogenous bases adinine, thymine,
cytosine and guanine. And the sequence
of these bases forms a code that directs
cellular processes and inheritance. Of
course, from an evolutionary
perspective, the structure of DNA is
hugely important. It allows for accurate
replication during cell division,
ensuring the genetic information is
passed from one generation to the next.
The double helix structure helps this
process by unwinding and splitting into
two strands, each serving as a template
to create a copy. And this precise
copying is essential for heredity as it
ensures that offspring inherit genetic
traits from their parents, maintaining
the continuity of their species.
This genetic information can be passed
down through either quick and efficient
asexual reproduction as used by bacteria
and in some very rare cases animals like
the New Mexico whiptails or through
another method that introduces genetic
diversity, sexual reproduction.
Over hundreds of millions of years of
evolution, life has developed myriad
ways of sexual reproduction. One of the
earliest to evolve was external
fertilization, which is still used by
many living fish and amphibians. It's a
pretty straightforward process in which
the females release their eggs into the
water and the males fertilize them.
Since the earliest tetropods were very
closely related to fish, it's safe to
assume that they too used external
fertilization to reproduce. But at some
point in the long evolutionary history
of reptiles, mammals and birds, another
method evolved,
internal fertilization.
This kind of fertilization happens
inside the body of the female. And it
gives the developing offspring a better
chance of survival than external
fertilization does. But despite this,
early reptiles and mammals, despite
evolving internal fertilization to
better protect their developing
offspring, probably wouldn't have made
great parents. In fact, many living
reptiles do not offer their offspring
any parental care. Sea turtles, for
example, lay hundreds of eggs, but other
than burying them in the sand to hide
them from potential predators, the
females do very little to look after
their babies, and the males do nothing
at all. This might sound heartless, but
it's a strategy that works and has done
for hundreds of millions of years.
Rather than caring for their offspring
to ensure their survival, turtles lay
large clutches of eggs because it's
statistically probable that at least
some of them will survive. If a sea
turtle lays 100 eggs, even if half of
them are eaten by predators, 50 of her
babies will still have a chance of
making it to adulthood and producing
their own offspring. The sea turtle has
ensured that her genes are passed on.
So, in her instinctual mind, her job is
done.
But if this strategy works, and it
clearly does because turtles have been
around for 230 million years, why did
our ancestors evolve to invest so much
time and energy in their offspring? To
answer this question, we will need to go
back to the Jurassic.
It is 117 million years ago. The world
and its inhabitants have changed
drastically since the evolution of the
earliest life forms. It might have taken
billions of years for organisms with
shells, bones, and lungs to appear. But
in just a few hundred million years
since then, life has been thriving.
Pangia, the great superc continent that
once incorporated all of Earth's land
masses, has already started to break
apart. There are now two separate land
masses. Lorasia in the north and
Gonduana in the south. Pole to pole is
covered in lush forests leading to a
great diversity of animal life. Indeed,
the Jurassic is home to true giants.
Long sorapods, Axunosaurus, and
Ciosaurus browse the leaves of towering
trees, while predatory therapods like
Megalosaurus stalk from the shadows.
There are Leviathans in the seas, too.
Leopuridon with teeth like hunting
knives and Opthalmosaurus whose eyes
were bigger than dinner plates. But far
from the notice of all of these giant
reptiles, a quiet revolution is taking
place. In a burrow several feet below
ground, an egg is hatching. It is tiny,
only a few centimeters in diameter, and
from inside comes an equally tiny baby.
She and her siblings are born blind and
instinct tells them what to do. In the
darkness of the burrow, they crawl
towards their mother, nestling into her
warm fur and drinking her milk.
This little family belongs to a species
called Morganucodon Watson, egg laying
mammals from the late triacic and early
Jurassic. The mother, Morgan Ugodon,
will care for her babies for many
months, feeding them and providing them
with warmth and protection in the safety
of the burrow until they grow strong
enough to venture up to the world above.
There, she will teach them everything
they need to know about surviving in the
Jurassic. And eventually, they will
leave their mother to go in search of
mates and raise offspring of their own
so the cycle can begin again. Such
devotion to a small number of helpless
offspring is a very risky reproductive
strategy. Indeed, if something goes
wrong and the offspring die, then the
parents have wasted their time and
effort and will need to start all over
again. However, if the offspring survive
to adulthood and manage to reproduce,
then the parents can ensure their DNA is
passed on not just through one but at
least two generations. And so in this
case, survival of the fittest doesn't
mean that only the strong survive. It
means that certain adaptive traits like
having a driving instinct to care for
offspring can help certain individuals
survive long enough to breed and pass on
those traits. And gradually through
evolutionary adaptation, caring for
offspring becomes more and more
advanced, leading to animals like
humans, elephants or killer whales who
care for their offspring for many years
and often maintain close bonds for their
whole lives.
But that wasn't the end. For by the late
Jurassic, evolution had driven the
appearance of a new reproductive
strategy. one that is used by thousands
of species today and one that was
recently discovered millions of years
further into the past than previously
known.
In 2011, a team of Chinese researchers
led by Professor Leo Ji discovered a
small and exceptionally wellpreserved
skeleton in the Chiaoji Shan Formation
of Leaing Province, northeastern China.
Lean Ning is an area famous for its
messoic mammal fossils, and Professor
Leo and his colleagues had already made
a few important Jurassic discoveries
there, including a paperclipized mammal
whose skull helped us investigate the
evolution of the ear, and a beaver-like
swimming mammal that showed early
mammals were far more ecologically
diverse than previously thought. And so,
once again, Leoning would reveal more
about our early Mamalian relatives. They
had discovered Jeremiah, meaning of
course Jurassic mother who lived 160
million years ago. And rather than
laying eggs like Morgan, she gave birth
to live young.
For Jeremiah, there were several
adaptive advantages to this new trait.
Unlike her ancestors, she carried her
babies inside her body, freeing her from
the obligation of guarding a clutch of
eggs. Jeremiah could also run away from
danger without having to abandon her
nest. And as long as she protected
herself, she also protected her
offspring. And since her babies grew
inside of her, they could develop for
longer and be born more prepared for the
world.
Today, 94% of mammals are etheran. What
started as a novel adaptation in
Jurassic species like Jeremiah quickly
spread and became dominant. Jeremiah's
unique ability to gestate young inside
the body and give birth to developed
offspring gave it a clear advantage and
it was able to breed and raise its young
more successfully than its competitors.
Jeremiah passed on this novel adaptation
in its genes. And we and all other
Ethetherian mammals carry on that legacy
in our DNA.
And so 160 million years ago, all the
way back in the Jurassic, you were an
early ethetheran mammal. You were born
not from an egg, but directly from your
mother's body. Even though evolution had
been relatively slow for mammals during
the Mesazoic compared to the doineering
dinosaurs, these new methods of
reproduction gradually gave them the
edge they needed to excel in a variety
of environments. Indeed, by the time of
the Cretaceous 145 to 66 million years
ago, Ethetherian mammals had rebranched
into all kinds of niches. Omaya was a
tree climber feeding primarily on
insects. But there was also protulatum
which was relatively large for an early
mammal and leptic tidium whose short
forlims and long back legs suggests a
bipeedal kangaroo like way of getting
around. Although still most etheran
mammals in the Cretaceous period were
small and fed primarily on insects.
Dinosaurs, terasaurs, and marine
reptiles occupied the other niches. They
were the predators, the big grazers, the
fishes, and the flyers, leaving little
room for mammals to branch into those
specialtities.
But of course, all of that was about to
change.
In 2025, more than half the world's
population lives in cities. Mega cities
like Tokyo, Beijing, and New York are
home to tens of millions of people.
Skyscrapers rise above streets packed
with cars, bikes, and pedestrians,
creating landscapes that seem like the
exact opposite of the natural
environments that came before. But if
you stop and think about it, wildlife is
everywhere in cities. London, for
example, is home to an estimated 3
million pigeons. New York is estimated
to be home to 3 million rats, while
thousands of coyotes live in cities like
Toronto and Los Angeles. These animals
are thriving amongst concrete around the
world, exploding into urban
environments, even as we build them. Of
course, urban wildlife species did not
originally evolve in cities, but a
combination of traits made it possible
for them to make homes for themselves in
them. Most, like coyotes, are highly
adaptable animals. Indeed, coyotes are
opportunistic and will eat just about
anything that they can sink their teeth
into. They're even capable of adapting
their behavior, learning to navigate
traffic, and modifying their activity
patterns to avoid conflict with humans.
But perhaps the biggest influence which
has allowed coyotes to take over so many
American cities is a lack of competition
with other animals. Out in the plains
and woodlands where they originally
evolved, coyotes have to deal with large
predators like wolves and mountain
lions. And in many cities, they are the
top carnivores. And so they thrive in
urban environments where food is
plentiful and competition is scarce.
Animals like coyotes offer us a
fascinating glimpse of how a species can
adapt relatively quickly to a new
environment, especially one in which
they have fewer rivals. And the fossil
record and specifically our deep past is
full of examples of similarly ingenious
creatures. Species that became highly
diverse and exploited new worlds.
During the Jurassic and Cretaceous,
dinosaurs reign supreme on the land,
terasaurs occupied the skies, and marine
reptiles dominated the seas. But in the
preceding triacic, these environments
had been ruled by arosaurs like the
rurukians and etosaurs. It was only with
their extinction at the end of the
Triacic that dinosaurs, terasaurs, and
marine reptiles were able to take over.
They were dominant for 135 million years
through the Jurassic and Cretaceous
periods. But eventually, they met a
similar fate to their Arasaur relatives.
For 66 million years ago, Armageddon
struck. The end Cretaceous mass
extinction event wiped out 75% of all
species including all non-avian
dinosaurs, terasaurs, and large marine
reptiles. The asteroid that hit the
Earth is thought to have been 15 km in
diameter and understandably severely
disrupted the delicate balance of
ecosystems. Indeed, it wasn't just these
large reptiles that faced extinction.
Many plants, insects, fish, amphibians,
mammals, and even microorganisms were
also driven to extinction. And it would
take millions of years for the world to
recover. But when it did, the surviving
animals, those that had previously been
small and unobtrusive to avoid
competition with the dinosaurs, suddenly
found a world full of opportunities.
Extinction is a vital part of life. If
we were to witness the scale of the
destruction caused by the asteroid
impact 66 million years ago, we might
find it implausible that the planet
could ever recover. However, the Earth
has actually been through at least five
big mass extinction events in its
history. And the End Cretaceous event
wasn't even the worst of them. At the
close of the Triacic, for example,
massive volcanic activity in the central
magmatic province had caused the
extinction of 2/3 of all the world's
species. Before this, there was an even
worse catastrophe. This too caused by
volcanism. 252 million years ago, long
before the first dinosaurs walked the
Earth, volcanoes in Siberia wiped out
95% of life on the planet in an event
cheerfully known as the Great Dying. And
roughly two billion years before that,
life brought about its own demise.
Unicellular creatures started
photosynthesizing and suffocated all the
other life on the planet with oxygen.
But of course, after all of these
events, life persisted and came back
with a bang. Dinosaurs thrived in the
Jurassic. Arasaurs rose to prominence
after the Great Dying. And
photosynthesizing life took control of
the globe after the great oxidation
event. In fact, every time a mass
extinction event destroys a huge number
of species, it clears the way for other
species to diversify and become more
numerous. So even if almost all life is
driven to extinction, it is always
returned, albeit changed. And this is
exactly what happened after the end
Cretaceous extinction.
Unlike in the Jurassic and Cretaceous,
when reptiles grew to truly giant sizes,
the Cretaceous Paleogene extinction was
a very bad time to be big. Only small
animals, those who didn't need much food
and could borrow into the earth,
survived. Indeed, all large animals over
40 kg died out.
Large predators during the Cretaceous
had occupied different niches to avoid
competing with each other. There were
predators who specialized in ambushing
their prey, like modern crocodiles that
stay hidden until the very last moment
before they attack. There were also
predators who chased their prey,
evolving to run exceptionally fast like
a cheetah. And there were social
predators who relied on teamwork to take
down prey. But after the extinction
event, these niches would all be left
empty, ready to be taken over by
whatever came next.
By the early eosene epoch some 55
million years ago, the earth had fully
recovered from the apocalypse. As in the
Cretaceous, temperatures were still
warm, and even though habitats had been
decimated by the mass extinction,
forests had already bounced back,
spreading across the globe as they had
done before. There were lush green
ferns, towering conifers, broad palms,
and colorful flowers, just as they had
been before the asteroid. But the animal
inhabitants of these forests were more
familiar to us than they had been in the
Cretaceous.
For in the place of the dinosaurs and
the terasaurs, the land and skies were
now teeming with mammals and birds.
Hierratherum, a dimminuative horse
ancestor, browsed the low growing shrubs
and ferns while predatory crayodons
watched hungrily from the shadows.
Overhead, the first bats took wing and
early songirds flitted between tree
branches, their songs filling the air.
And among the highest branches in a
forest of what is now China, there was
an animal that would have a big impact
on the world to come. It was a primate
and its descendants would one day rise
to dominance like no other animal had
before.
Arusibus, one of the earliest known
primates, is hunting.
His tiny body, no longer than 20 cm from
head to tail, clings to a branch with
strong fingers. He has large forward-
facing eyes, allowing him to accurately
judge distances between tree branches,
which he leaps between in search of
food. Up here in the dense canopy,
Arcibus is protected from large
terrestrial predators and has plenty to
eat. Fruit, flowers, and insects are
abundant in the eosene forests, and
primates like ourus have evolved to take
full advantage.
You might not realize it, but primates
are an extraordinarily ancient family.
Unlike most of the mamalian orders we're
familiar with today, such as the
carnivorans and rodents, which evolved
after the Cretaceous Paleogene
extinction, primates likely had their
origins in the Cretaceous with proto
primates like Purgatorius.
Purgatorius, as was the case in many
early etheran mammals, resembled a
shrew. But Arabus, a true primate that
lived 10 million years after, looked
very different. But what makes a primate
a primate? When Arabus was discovered in
2003, it was clear from the outset that
it was our ancient relative because it
possessed a suite of osteological traits
that we associate with all living and
extinct primates. For instance, Arabus
had grasping hands and feet with
opposable thumbs and big toes, as well
as flexible limb joints. Both
characteristics of a specialized aroreal
lifestyle. It also had forward- facing
eyes and a shortened snout, suggesting a
reduced reliance on smell and an
investment in eyesight. Finally, Arbus
had nails instead of claws, which is an
adaptation for improving the sensitivity
of touch. Of course, many of these are
characteristics of humans as well. So,
it seems we have these early eosene
primates to thank for many of the traits
that seem so essential to us today. And
yet, Purgatorius lacked many of these
traits. Purgatorius had flexible limb
joints, but it didn't have opposable
thumbs, and its eyes were located on the
side of its head. It also retained a
relatively long snout, something that
was common in early mammals, but is
absent in true primates.
And so although there were already proto
primates like Purgatorius living in the
Cretaceous, it was only after the
Cretaceous Paleogene extinction event
that the primate lineage really began.
In a world that had just recovered from
an apocalypse, you were an early primate
and you and your kind were flourishing.
But what was so special about primates?
What niche did we fill?
During the eosene, at the time of our
early primate ancestors, some of the top
predators were mammals called crayodons.
These carnivorous mammals evolved to
fill the spaces once held by the
theropod dinosaurs. Crayodons were often
fast and agile, much like the raptors of
the Cretaceous, and they were well
adapted to hunting prey that had
flourished in the absence of the
dinosaurs. Indeed, some crayodons, such
as hyenodon, had extremely sharp teeth
and strong jaws, allowing them to take
down much larger animals and crushed the
bones of their unfortunate victims.
While these early mamalian predators
might not have been as large as the
dinosaurs they replaced, they were no
less effective in their role as the top
carnivores of their time. Meanwhile,
other animals began to evolve to fill
the roles of the herbivores. The
extinction of mega herbivores from the
Cretaceous created space for the
earliest herbivorous mammals to thrive.
Primitive unulates, mammals with hooves,
including hierarchum, began to graze the
lush vegetation that had sprung up in
the postmass extinction world. But in
the trees, Arcibus and other early
primates evolved to occupy a very
different niche. Even though their proto
primate ancestors had also been aroreal,
eosene primates took things a step
further and became more highly
specialized to thrive in the dense leafy
canopy of forest habitats. Ouras, for
example, would have fed on small insects
and fruits, using its grasping hands and
feet to navigate through the trees in
search of food. And unlike many aroreal
animals of its time which were
nocturnal, recent research suggested our
gaseous was dal foraging in the day and
sleeping at night.
So in a sense early primates like ourus
didn't just occupy an empty niche, they
created a new one. The arboral lifestyle
they adapted to was a highly specialized
ecological role. one that allowed them
to escape the fierce competition that
would have been common among mammals in
the postext extinction world. And in
fact, this niche in the forest canopy
would continue to shape the evolution of
primates. Just as today's adaptable
coyotes exploded into urban
environments, primates ability to adapt
to new ecological roles and their
advanced cognitive abilities became
their key evolutionary advantage.
It is April 1815.
Mount Tambbora, a volcano on Sumbawa
Island in Indonesia, is erupting.
Millions of tons of ash and toxic
chemicals are shot into the atmosphere
and deadly pyrolastic flows wipe out
entire villages. 71,000 people died and
this eruption was felt all over the
world. The eruption was and remains the
worst for over 10,000 years.
More than a year later in Geneva, a
group of young writers were on holiday.
18-year-old Mary God Gordwin was amongst
them along with her lover Percy Shelley
and the poet Lord George Byron. Although
it was June, the weather was awful.
Indeed, the world was still recovering
from the Tambora eruption and 1816
became known as the year without a
summer. Forced to stay indoors, the
group decided to have a competition for
who could write the best scary story.
Young Mary came up with the idea of a
man who creates sentient life, but flees
in terror when his monstrous creation
awakens. And she later published the
story as a novel, Frankenstein.
And so a volcano oceans away in
Indonesia inadvertently sparked the
writing of a novel that is now widely
considered as the first of the science
fiction genre. Sometimes shifts in the
climate can have unexpected consequences
and 20 million years ago changes in the
may earth's climate had knockon effects
that would go on to shape our own
evolutionary story ultimately resulting
in the emergence of a whole new lineage.
Apes.
At nearly 7,000 kilometers long, the
River Nile stretches across 11
countries. It is among the longest
rivers on Earth and has nourished human
civilizations for millennia. With its
predictable annual floods, depositing
nutrient-rich silt on its banks,
agriculture flourished in ancient Egypt,
and people used the Nile as a crucial
transportation highway. Boats would
transport materials for monumental
building projects such as stones for
temples and pyramids, as well as goods
like papyrus, pottery, and food.
But back in the Oligene, the Nile was
very different.
Geological studies show that the Nile
had its origins around 30 million years
ago when the tectonic uplift of the
Ethiopian highlands created a new source
of water and sediment for northeast
Africa. This uplift combined with
rifting and shifting of the regional
fault lines helped channel rainfall and
groundwater northwards, laying the
foundation for the Nile's ancient
drainage system. Today, the banks of the
Nile are green and fertile, but the rest
of the region is extremely dry. But back
in the Oligene, the climate of all of
Egypt was warm and humid. And there were
subtropical forests, mangroves, and
swamps. And these thriving habitats
sustained by the ancient water courses
that were developing into the modern
Nile provided ideal conditions for
ancestral catarine primates to evolve.
Around 40 million years ago, Haplline
primates branched off in two different
directions with one lineage giving rise
to what we now call the new world
monkeys or platterines like capucins and
howler monkeys and the other leading to
the old world monkeys like baboons and
apes called catarines.
New World monkeys are exclusively found
in Central and South America and are
thought to have evolved from African
ancestors who inadvertently became
transatlantic passengers on floating
rafts of vegetation after an extreme
storm or tsunami. Oldworld monkeys,
however, are found in Africa, Asia, and
historically in Europe. And some of the
earliest fossil karines were found in
North Africa.
And so imagine Egypt as it was 30
million years ago with early catarines
like Egyptus climbing through a lush
forest canopy feasting on ripe fruit and
abundant insects. The abundance and
stability of these floodplane forests
allowed Egyptus and its relatives to
become key links in primate evolution.
In fact, it's often believed that this
oligosine species could have been the
common ancestor of all modern catarines.
A 2019 paper published by Sergio Alma
and his colleagues found that the shape
of the Egyptocus hip joint was
intermediate between modern monkeys and
apes. Apes are characterized by more
upright posture, greater flexibility of
the shoulder and hip joints and
adaptations for more suspensory
brachiating locomotion unlike the more
quadripedal imposture seen in many
monkeys. According to the 2019 study,
Egyptythecus retained a primitive
quadripedal climbing style, but also
showed key anatomical features that
hinted at the way apes move around. And
so, Egyptus illustrates how changes in
anatomy set the stage for the distinct
locomotion, social behaviors, and
ecological roles seen in today's apes.
From their earliest origins in Egypt,
the descendants of Egypt went on to give
rise to true apes. But it wouldn't be
until the early measine around 23
million years ago that the earliest
fossil apes would appear.
It is August 1931. Arthur Hopwood, a
British paleontologist, is standing at
the edge of an excavation site in
western Kenya near the small town of
Koru. Hopwood is here on behalf of the
British Museum and a small tent at the
edge of the site has been his home for
almost 5 weeks, but he's due to depart
in just a few days. Although he misses
the creature comforts of his home in
London, he will be sorry to leave Kenya,
for in the short time he's been here,
some truly extraordinary fossils have
been found. Many of them are teeth, but
there are also pieces of jaw and even
skull fragments. HP knows immediately
what they are. the bones of long extinct
apes and among them are the remains of a
new species which Hopwood would later
call Proconsul Africanis.
But not only was Proconsul a new
species, it was also one of the earliest
apes to ever exist.
What sets Proconsul apart as an early
ape is its combination of both ape-like
and monkeylike features. It lived in
eastern Africa around 21 million years
ago. And unlike monkeys, both modern and
ancient, proconsul lacked a tail.
Indeed, this is a key difference in the
ape lineage, one that all modern apes
and humans share. Proconsul also had
more flexible limb joints than those of
old world monkeys, which is thought to
signal a higher emphasis on brachiation
or suspensory behavior instead of
quadripedal climbing. However, since Bro
Consul was a very early ape, it still
retained many monkeylike
characteristics. Its body had a long,
flexible back, still adapted for
four-legged locomotion on branches
rather than the hanging behavior seen in
modern apes. And its skull and teeth,
including its large canines, did share
traits with today's apes, but did not
fully match the pattern we see in great
apes like chimpanzees, orangutans,
gorillas, or humans. Taken together,
this mosaic of features suggests that
proconsul represented a very basil form
right at the beginning of the ape
lineage.
And so 21 million years ago in the early
years of the measine, you were a basil
ape, a transitional creature that
blended aspects of the older monkey
family and of a new lineage that would
eventually give rise to one of the most
intelligent and adaptive species on the
planet, humans.
But before any of that could happen, the
early measine apes had their own story
to tell. For during this period of
Earth's history, apes became a vibrant,
diverse, and ecologically successful
lineage. Indeed, the meiosene fossil
record paints a picture of a true planet
of the apes.
By the middle, there were Kenyopythecus,
nacalopycus, and cororapythecus living
in Africa. But apes were not just
restricted to one continent. It had
spread far and wide with driopythecus in
Europe and lufangithecus in Asia. So
what exactly was it about the meiosene
that made it the perfect time for so
many ape species to thrive? Well, just
as Frankenstein was born in the fires of
a distant volcano, so was our evolution
pushed and pulled by globe spanning
climatic forces. Like the preceding
oligosine and eocine, the mayene began
as a relatively warm period of time.
Temperatures had come down slightly
since the oligosene, but average global
temperatures still reached 3 or 4° C
warmer than today. Forests stretched
across most of Africa, Europe, and Asia,
providing the ideal conditions for
primates to thrive and diversify.
Primates like plyopycus could be found
as far north as France and Germany,
regions that are unsuitable for most
nonhuman primates today because of their
lack of fruit and leaves during the
winter months. And just as in the
oligosine, the early measine was
conspicuous in its relative lack of arid
environments. In fact, if you were to
look down at the early Mayene Earth from
space, you'll be only able to spot a few
large areas that were not completely
green. The rest of the planet, barring
Antarctica, was covered in trees, and
the tropical zone extended further from
the equator than it does today. Indeed,
in the early Mayene, the vast Sahara
desert that covers much of northern
Africa today didn't exist. Instead,
there were forests, swamps, and lake
environments for apes to thrive in. But
change was on its way. Just as the
climate of the earth had spurred on the
rise of the apes, so did its continuous
motion bring about their downfall. The
mine earth could not stay the same.
Gradually, the abundant forests began to
retreat. Grasslands opened up and
deserts crept back in. This meant the
end for many of the previously
successful ape genera that had spread
across the old world. But it certainly
wasn't the end of the ape lineage in
general. For millions of years later, at
the end of the Mayene, a new group of
apes would have its origins.
Around 7 million years ago in the late
Mayene, evolution took a big swing.
Elortos was a genus of bears living in
what is now southwestern China. Like
most bears around today, Alocto was
descended from omnivorous ancestors that
were adapted to eat a wide range of
foods, including meat, fish, insects,
fruit, and pretty much anything they
could get their paws on. But Isltose was
different. It evolved to eat a far more
specialized diet, one that heavily
featured a single plant, bamboo. This
was because during the late measine,
central and southwestern China's climate
drove a flourishing of its bamboo
forests, which in turn encouraged
eeroctos to shift towards a specialized
bamboo diet. At first, this somewhat
risky evolutionary journey was a huge
success and ether octose and its
descendants were able to spread around
much of China. However, today the giant
panda is the only remaining member of
this once great lineage. In a sense, is
octo put all their eggs in one
unreliable basket. And so, because of
this hypers specialization and the
destruction of their habitats, giant
pandas are now an iconic endangered
animal with only around 2,000
individuals left in the wild.
And around the same time that either
octose was evolving its specialized diet
in China, another kind of animal was
similarly trying something new in
northern Africa, but with results that
would prove wildly successful.
It is July 2001 in the Jurab desert of
northern Chad. This is a truly
inhospitable landscape. yellow orange
dunes and dust stretching as far as the
eye can see. At a site called Tauros
Manala, an international team is in the
middle of a breakthrough excavation. So
far, they have unearthed several fossil
teeth, a few jawbone fragments, and most
exciting of all, a skull. It is heavily
damaged and will require a lot of
painstaking work to reconstruct, but it
is remarkably complete with nearly all
of its component bones still present.
This skull belonged to a homminin we now
know as Sahalanthropus tradencis, an
ancient human species thought to be the
earliest known member of our
evolutionary family and one who we
believe may have walked on two legs.
Why?
Even though we now associate its home
with arid desert landscapes, Chad wasn't
always like this. Animal bones at Taurus
Manala revealed that at least 55
different animal species lived alongside
our early homminin ancestors. And so
instead of endless desert, imagine a
lush green landscape inhabited by early
hominins, giraffes, gazels, elephants,
porcupines, and miniature horses. And so
why take such a drastic biological risk
as bipedalism in an environment as
plentiful as this? Indeed, bipedalism is
not common in mammals. And surely
Sahalanthropus would have got along just
fine as a quadriped just as modern
chimpanzees and gorillas do in similar
habitats today. While that is probably
true, evolution does tend to take a
certain course for a reason. Random
mutations are common enough, but they
don't usually get selected for unless
they improve a species chance for
survival. Although 7 million years ago,
Chad was a much more suitable habitat
for primates than it is today, we need
to consider the bigger picture. For
paleoclimatological reconstructions show
us that by the time of Sahilanthropus,
the world was already in the grips of
significant climate change. One study
published in the journal of human
evolution analyzed fossilized plant
remains called phytoliths from 45 sites
in northern Chad. The sites ranged in
dates from 8 to 1 million years ago. And
from the fossil phytoliths, the research
team was able to reconstruct the
environmental conditions at these sites
by analyzing what kind of plants were
present. The phytolith analysis revealed
that at the time of Sahilanthropus
around 7 million years ago, Chad was
dominated by mosaic habitats. There were
patches of forest, palm groves, and
grasslands. However, by 4 1/2 million
years ago, the same sites were almost
exclusively covered in grass. With the
placetoene ice age, which began 2 and a
half million years ago just around the
corner, homminin environments were
already starting to change during this
pivotal period in early hominin
evolution. Chad in particular was
experiencing a decrease in tree cover
and an expansion of open savannah
consistent with a shift towards colder
drier conditions characteristic of ice
ages.
There are certainly advantages to
walking on two legs in the mosaic grass
and woodland environments early hominins
were generally found in. For one,
standing upright allows an animal to see
over greater distances. Modern mircats
are a great example of this. Although
they are predominantly quadripedal
animals, they are capable of adopting an
upright bipedal posture when on lookout
duty. In addition, standing vertically
exposes less body surface area to the
harsh sun. This could have helped early
hominins to regulate their body
temperatures and avoid overheating in
areas with less tree cover and fewer
places to find shade. But this line of
thinking isn't without its critics. For
some researchers, the fact that early
homminins are usually found in mosaic
habitats such as wooded savannah where
there still would have been many trees
means that our earliest ancestors were
probably still reliant on forests and
woodlands. This coupled with the
presence of aroreal characteristics in
early homminin fossils suggests that
they still likely spent a good deal of
time in the trees and walking bipedily
through open grassland might not have
been a major feature in their daily
lives. Indeed, other researchers have
suggested that hominin bipedalism could
have evolved not in the open savannah
but in the trees. Professor Kevin Hunt,
for example, believed that early
homminins adopted an upright posture
while foraging and feeding from overhead
branches. By standing on two legs, they
could use both hands to efficiently
gather food that would normally be out
of reach or difficult to carry for a
quadripedal primate. Such behavior is
seen in wild chimpanzees, which is where
Professor Hunt got the idea from.
But regardless of the exact reason, the
gamble of bipedalism clearly paid off
and by around 4 and a half million years
ago, there was a new homminin species.
Ardipythecus Ramdus emerged to the yeast
in what is now Ethiopia. Aripythecus has
adaptations for both walking on two legs
and for living in trees. While its
pelvis and leg bones were more similar
to ours, suggesting that it was a biped,
it also had an opposable big toe adapted
for grasping tree branches. Ethiopia was
a dangerous place to be a hominin,
especially for one that was now taking
the risk of spending more and more time
outside the safety of the tree branches.
Indeed, during the time of Artipythecus,
predators would have been a constant
concern. Paleontological finds reveal a
wealth of carnivores that lived
alongside Artipythecus, including
hyenas, saber-tooththed cats, gigantic
shfaced bears, and wild dogs. In this
carnivore environment, competition among
big hunters would have been intense, and
there is evidence of high scavenging
rates, suggesting that many predators
frequently fought over carcasses. And so
for Artipythecus, this meant danger was
never far away. And yet unlike their ape
cousins or their later homminin
descendants, Artipythecus wasn't
particularly strong or fast.
Modern great apes are equipped with huge
canine teeth and are much stronger than
us. They're also excellent climbers and
can quickly evade predators by darting
up a tree. Modern humans, meanwhile,
lack the natural weaponry of canine
teeth and the tree climbing skills. But
we are efficient runners and make tools
that can be used to defend against
dangerous predators.
But Artipythecus had none of this. They
were probably less efficient on two legs
than we are, but also not quite as
graceful in the trees as modern apes.
They had small canine teeth and no tools
are known from 4.4 million years ago.
And so with this natural vulnerability,
Artipythecus Ramadus may have stuck
closer to the trees where they could
quickly clamber away at the first sign
of danger. Indeed, going out into open
grassland would have been very risky for
hominins. Although it wasn't long before
more and more of them would venture out.
In July 2011, a small team of scientists
were driving to a dig site near the
western shore of Lake Turkana in Kenya.
Jason Lewis, a paleo anthropologist,
sits in the passenger seat, while
archaeologist Sonia Harmon is at the
wheel. It's the middle of dry season, so
the scientists are able to drive their
tough old SUV straight across dry
riverbeds. It's very bumpy, but it's
also a relatively efficient way to get
around a landscape nearly totally devoid
of roads.
From the passenger seat, Lewis, who has
a map laid across the dashboard and a
GPS in his hands, tells Harmon to take a
left up ahead. She follows his
instructions, but soon enough, the SUV
runs into a dead end. Lewis squints at
the map and quickly realizes his
mistake. They have taken a wrong turn.
Frustrated, Harmon gets out of the
vehicle and scrambles up to the edge of
the dry riverbank to take a look around.
Suddenly, one of the team, Sammy Loari,
sees something and calls the others over
to check it out.
At first glance, they appear to just be
chunks of stone. But to Harmon's trained
eyes, though, it is obvious what they
are. Tools. Their wrong turn had ended
with one of the most serendipitous
archaeological discoveries ever made.
The site the tools were found at is
called Lamechi 3. And the tools have
been dated to 3.3 million years ago,
making them the oldest stone tools yet
found. Tools are one of the hallmarks of
our genus. Indeed, almost everything we
modern humans do involves some kind of
tool. From watching this video to
getting dressed in the morning and going
to sleep at night, we spend our entire
lives surrounded by things that we or
other humans have made. And it seems
that the lives of many of our ancestors
were not so different. They also made
and used a variety of tools to make
their existence easier. A few different
primates around the world are known to
use tools. Capucins use stones to crack
open shellfish, and chimps have even
been seen hunting down bush babies with
rudimentary spears. And so, stone tools
aren't necessarily a tried and tested
signifier of humanlike intelligence or
above average survivability. But there
is something unique about the ones found
at the MechUqu. And a major candidate
for the creator of these tools is
Orolopycus Apherenis.
Around 3.9 million years ago, Oralopycus
apharensis started roaming the Afar
region of Ethiopia. Despite still
retaining some adaptations for climbing
trees, such as long arms and curved
finger bones, Orolopycus apherensis
likely spent a lot more time than their
ancestors walking around on the ground.
And they had bigger brains than those
that came before. Whileus had a brain
volume of around 300 to 350 cm, similar
to a modern chimpanzee, Orolopycus
apharensis brains are estimated to have
been between 400 and 500 cm.
And so to create the tools of Lamechi, a
hominin, perhaps Oralopythecus, had to
select a piece of stone, perhaps taking
into account its durability or even
aesthetics. Then they had to sit down
and chip away at it until it took the
shape they wanted. Napping, which is
what archaeologists call the process of
making a stone tool, is not easy. It's
time inensive, requires planning and
practice, and often results in bleeding
fingers, which makes it all the more
surprising that creatures with brains a
third the size of ours are committing to
it. And so, though it is impressive that
a chimpanzee knows that if they strip
the leaves off a tree branch and sharpen
it a bit, they can go hunting, there is
significant cognitive distance between
that and what our ancestors were doing
at the Mechi. Since we think that they
spent a lot more time on the ground,
it's likely that they would have faced
plenty of dangers from predators and
other animals, just as previous
homminins did whenever they ventured
down from the trees. However, unlike
earlier species, these homminins had
something to defend themselves with. A
trend to note is that in general, as
time went on, hominin teeth got smaller
while their brains grew larger. Just
compare the size of our canines to those
of our closest living relatives, the
chimpanzees. This was also the case for
Orolopycus apherenis, which suggests
that they might have shifted to rely on
tools rather than teeth for defense as
well as offense. And it's also around
this time that researchers think our
ancestors began to eat a lot more meat.
So it seems likely that Orolopycus
apherensis was also using tools to
butcher prey, making them less reliant
on plant foods over time, which may have
allowed them to finally break free from
forested habitats.
And so 3.3 million years ago, you were a
tool making hominin. You and your kin
descended from ancestors that took a
risk leaving the trees. And now you
carefully choose sharp, durable stone
and transform it into tools that help
you find food, defend yourself, and make
your mark on the world. And soon enough,
tools would become even more important
as another kind of hominin emerged.
Where does the solar system end?
Does it end at Neptune, the farthest
planet from the sun? It is roughly 4 and
a half billion km away. And due to its
irregular orbit, it is sometimes even
farther than its dethroned sibling,
Pluto. Pluto was in fact closer to the
sun between 1979 and 1999.
So pretty far, although beyond Neptune,
lies the Kyper belt, home to dwarf
planets and many thousands of pieces of
rock and frozen gas that also make up
the solar system. And the sun's reach
extends much farther than that. The
heliosphere, the full extent of its
magnetic influence, stretches out to
four times the distance between the sun
and Neptune. Yet many astrophysicists
still do not consider this the edge of
the solar system. Over 800 times farther
from the sun is the outer edge of the or
cloud theorized to be composed of
billions of icy objects that still orbit
our home star. To quote astronomer Shaun
Raymond, "I don't understand how anyone
considers anything other than the old
cloud to be the edge of the solar
system." Any other definition seems
ludicrous. It is literally the edge of
where something can orbit the sun.
In the natural world, boundaries are
often fluid and perspectives can change.
It's very hard to tell when one thing
ends and another begins. And just as
this problem plagues astronomers,
charting the heavens, so it does
biologists, plotting our history. As
above, so below.
There are around 2 million recognized
species on Earth. All of which have been
carefully studied and categorized to
help us understand them. Indeed, just
the primates alone are sorted into at
least 504 species. Over the last
century, researchers have proposed
several methods for drawing boundaries
between species. Although the labels
differ, they cluster around three main
questions. Can the populations breed
with one another? Can we tell them apart
consistently? And how closely related to
each other are they? Most distinct
species cannot or do not interbreed and
produce fertile, healthy offspring.
Lions and tigers can mate in zoos, but
they occupy different habitats and do
not breed in the wild. And this
biological species concept works fine
for living animals, including modern
humans. Any two living people, even if
their ancestors have been on opposite
sides of the planet for tens of
thousands of years, can produce viable
offspring together. We are all therefore
the same species. But when we bring our
ancient relatives and ancestors into the
conversation, things become a little
more tricky. How do we define the first
true humans?
2 million years ago, a homminin stands
somewhere in the open plains of eastern
Africa. As the sun relentlessly shines
down, it feels as if the landscape grows
drier with each passing season. Although
the homminin doesn't know it, this place
was once blanketed by lush forests. His
ancestors have lived here for hundreds
of generations. And they used to be
trees as far as the eye could see,
stalked with fruits, insects, and
nutritious leaves. But the old habitats
are fast retreating. In their place,
grasslands are spreading, dotted with
only scattered trees and shrubs. This is
the plea scene, a period of some of the
most dramatic environmental upheaval
since the end of the Cretaceous. Many
people think of this period in Earth's
history as the ice age, but sediment and
ice cores tell us that for the last 2
and a half million years or so, our
planet has been regularly cycling
between glacial periods and
interglacials.
These profound changes in climate and
environment were devastating for much of
the world's biodiversity. Forest
dwellers were particularly slow to adapt
as their habitats gradually disappeared.
And genera like the last calicothes
vanished from the fossil record around
the boundary of the pleoptoene.
But these challenging conditions also
created new opportunities for
evolutionary innovations including the
emergence of our own genus
homo.
Carving its way through the Great Rift
Valley in Tanzania, Oldi Gorge is such a
distinctive geological feature, it can
be seen from space, the local Masai
people call it the place of the wild
sisle because of the abundant sisle
plants that grow there. But also, it has
another very different significance. In
the early 20th century, much of Eastern
Africa was colonially occupied by
Germany, which prompted German scientist
Wilhelm Katvinkle to travel there.
Kadvinklel was a physician by training
and he went to Tanzania in 1911 to
conduct research on sleeping sickness,
an infectious disease that causes fever,
pain, and trouble sleeping. However,
while in Tanzania, Kadvinkle took a trip
to Ulivite Gorge and came across many
ancient fossils, including the remains
of Hipparion, an extinct three-toed
horse. News of Katvinkle's discoveries
spread around the scientific community
and eventually came to the attention of
Hansre Wreck, a German geologist. He
later led a team to Ulivi in 1913 where
he unearthed the remains of ancient Homo
sapiens. But the most enduring legacy of
this find was bringing the gorge at
Ulivi to the attention of an up
andcoming archaeologist called Lewis
Leaky. And through Leaky, our distant
past would never be the same.
Leaki's investigations at Oldi began in
the 1930s and with his wife Mary
continued for decades and in 1960 they
were accompanied on site by their son
Jonathan who celebrated his 20th
birthday while at Alivi Gorge and it
would be a hot afternoon on May 4th when
the young Jonathan suddenly cried out to
his parents that he had found something.
It was a partial skull and it was
different to anything the Lee had seen
before. Far less ape-like than the jaws
of the orolopiths, it was also not quite
like a modern human. Soon enough, more
fossils belonging to this individual
were found and it became the first
member of a new species, Homohabilis.
Alongside Homohabilis, excavations also
uncovered a wealth of stone tools, which
is why its name translates as handyman.
And what's even more significant is that
Homohabilis is now considered the
earliest species in the Homo genus,
which makes it a possible ancestor of
everyone alive today, as well as extinct
homo species like the Neandertos and
Denisovans.
And that was not all. But when Habilis
was alive, it may have been one of two
distinct homo species living alongside
each other on the African continent,
joined as it was by Homo erectus, which
may have been descended from Habilis and
evolved around 2 million years ago. But
of course, these weren't the only
hominins that lived in Africa at this
time. In fact, the African record during
the early plea scene is strikingly
crowded. Field teams working in eastern
and southern Africa have showed that at
least four other homminin species
overlapped with homo erectus and
homohabilis and a fifth probably
vanished just before homohabilis came
along in eastern Africa. Paranthropus
boise with their impressive jaws had
already been established for some
300,000 years while its sister species
paranthropus robustus lived south of the
zambi. Paranthropus Ethiopicus lived
around 2 and a half million years ago
right at the beginning of the plea
scene. Meanwhile, South Africa was the
stronghold of Oralopythecus Africanis
and Oralopycus Ceda.
And so with so many homminin species
running around the African continent,
what exactly made Homo different?
Historically, the clearest adaptive
signal for the homogeneous has been
brain size. When homohabilis was first
scientifically described in 1964, Lewis
Leaky, Philip Tobias, and John Napia set
the boundary for brain size in Homo at
600 cm. But the first cracks in this
thinking came from East Turker in Kenya.
For KN&N ER1813,
a fossil skull universally regarded as
homohabilis has a capacity of only 510
cubic cm, but its facial profile,
cranial shape, and teeth slotted
securely within the homohabilis species.
Indeed, even early Homo erectus
experienced this kind of significant
brain size variation. A cranium from
Demoni designated D450
has a capacity of a mere 546
cm which makes it dramatically smaller
than the standard for erectus but
otherwise seems to match the expected
cranio dental proportions for the
species. Small brain species like
homoflloresensis and homoi have weakened
the boundary even further. Homo
floresensis with a cranial capacity of
only 400 cm made complex stone
technology and homoi has been speculated
to have buried their dead and yet had
brains of only 465
cm.
And so today paleo anthropologists do
not rely on brain measurements alone
when they decide that a fossil belongs
to our genus. Throughout ancient
skeletons and even in the objects they
left behind, there are other recurring
clues that set early humans apart from
the other hominins that shared their
world.
A good place to start is the face and
jaws. In every accepted member of Homo,
the lower portion of the face is flatter
than it is in other hominins and apes.
In addition, the cheeks are less flared.
That reshaping goes with the reduction
of the chewing apparatus which includes
our canines. These became much less
prominent in homo and our smaller mers
and preolars and even the roots that
anchor our teeth to our jaws shrunk down
and became more slender. Moved down to
the hands, our thumbs are long, strong,
and pivot on a saddle-shaped joint that
allows the tip to sweep across the pads
of the fingers and form a precision
grip. Homohabilis already shows this
arrangement. Although its finger bones
are slightly curved, they end in broad
flat tips that suggest it would have
been capable of pinching and fine-tun.
And the rest of the skeleton follows
suit. As soon as Homo erectus appears in
the fossil record, we see an immediate
shift towards more modern body
proportions. Indeed, from the neck down,
Homoerectus was functionally
indistinguishable from 21st century
humans. They were taller than other
contemporary homminins and noticeably
narrow hipped. Their arms were shorter
while their legs grew longer and their
limb joints became bigger and stronger
to deal with the stresses of traveling
long distances on two legs. In short,
they were endurance runners.
These anatomical shifts were accompanied
by behavioral changes.
Before the Leakys discovered Homohabilis
in Oldi Gorge, they had discovered a new
kind of stone tool. They named them
older tools, and Mary Leaky produced
schematic drawings of them. Mary's
systematic excavation and documentation
at tool sites in Oldi Gorge revealed
stratified layers where tools appeared
in association with animal bones bearing
cut marks, revealing that old tools were
primarily used for cutting, scraping,
and butchering meat. Although simple to
our eyes, they had sharper edges from
more controlled stone napping than the
lamean industry from 3.3 million years
ago and would have made the task of
butchering animals for the meat a lot
more straightforward.
Homo erectus meanwhile is associated
with a different stone tool industry
known as theulon. It starts showing up
in the archaeological record 1.76
million years ago and features the
iconic bfacial handax. A generally
symmetrical almost teardropshaped tool
that could be used for multitude of
different tasks. With these trusty
handaxes, Homo erectus could probably
take down large prey and would have made
short work of their carcasses. Indeed,
we often assume that our homminin
ancestors were more limited in their
creative and technical skills. But
anyone who has ever attempted to create
their own handax can tell you that they
are not easy to make. In fact, it can
take years of training and dedicated
practice to achieve the kind of
precision we see in Ashulian handaxes.
This complexity suggests an advancement
in the cognitive capabilities and fine
motor control of Homo erectus compared
to their predecessors. And given that
their brains were often not that much
smaller than our own at around 1,000
cubic cm, perhaps this increased
intelligence shouldn't come as a
surprise.
And it was also during the time of Homo
erectus that the earliest evidence for
the controlled use of fire began to
appear at sites like Kubora and
Swatrans.
Taken together, this evidence reveals a
package of adaptations that distinguish
the homogeneous from other hominins.
Although many scientists have argued
that Homo erectus with their runner's
bodies, big brains and use of fire and
complex tools are more deserving of
being part of our genus than homohabilis
who some argue should be reclassified as
Oralopycus habilis. And so as with the
edge of our solar system, drawing a line
in the sand in the natural world is
never straightforward.
But on the whole, a little more than 2
million years ago, you were a human
standing with modern body proportions,
exploring the globe, and using ever more
advanced tools. But of course, this
would not be the end of the human
journey. Several more species, including
our own, would arise within the
homogeneous to live alongside and
perhaps even compete with one another.
A battle is being fought.
Two men face one another in a frosty
landscape somewhere in Western Europe.
One is tall, lean, and quick on his
feet. The other is short, stocky, and
powerful. They circle wearily. The
shorter man, a Neanderal, lunges with a
heavy spear. But the taller man, a homo
sapiion, slips aside. The Neanderal's
breath is coming harder. His energy is
fading. He hasn't eaten since the day
before. The animals he relies on for
food are increasingly rare. Chased down
by these new homminin arrivals. Another
thrust, but the modern human counters
swiftly. The blow glances off, but the
force jars through the Neanderal's arm,
and he feels something crack.
Finally, the Neanderal staggers away,
clutching his broken limb and vanishing
into the forest.
Scenes like this may once have played
out countless times across Ice Age
Eurasia. Modern humans, our ancestors,
were expanding into new lands, but they
weren't empty. Neandertos already lived
in Europe and Western Asia, while Dennis
So populated the East. They had long
been unchallenged in these territories,
but now they had company.
We know from fossil DNA that
interbreeding happened between these
populations. Indeed, all humans on Earth
still carry the legacy of these
encounters in our genes. But that wasn't
the whole story. The archaeological and
skeletal records also suggest a darker
side. Conflict. Many Neanderl skeletons
bear the scars of violence. fractured
arms and shattered skulls, trauma
consistent with parrying attacks and
blows to the head. And yet, for all the
clashes that might have taken place, the
differences between these groups of
ancient people were surprisingly small.
After all, they were all descended from
a common ancestor and bred with each
other. So, who was this mysterious
common ancestor? And what caused these
branches of the human family to split
and go their separate ways?
It is 1993 and a chilly day in West
Sussex.
32-year-old archaeologist Mark Roberts
is digging a small pit. His size,
remembering how just a few years ago,
this same stretch of land had been
bustling with an excavation team all up
to their elbows in the muddy orange clay
that lay just beneath the pasture.
Roberts, who had been directing
fieldwork here at Bogs Grove since he
was in his early 20s, had overseen the
discoveries of thousands of flint tools
and the bones of many extinct animals,
ancient horses, rhinoceroses, deer, and
even lions and bears. But now, all the
funding has dried up and excavations
have ended. Roberts has been told
there's nothing left to find, but he
can't quite let Boxgrove go. Something
about the site never sat right with him
because despite the wealth of tools that
were discovered, no one has yet found
any human remains.
So, over 3 years after official
fieldwork came to an end, Roberts and a
handful of other dedicated excavators
are back, convinced that Box Grove has
more to give. And it doesn't take long
for them to be proven right.
That day in 1993, Roberts and his small
team discovered the lower leg bone of a
human, a man who died almost half a
million years ago. He belonged to a
species that emerged long before our
own. And that may have been our shared
ancestor with Neandertos and
Dennisovvens, Homo Hidlebeensis.
And so nearly half a million years ago,
you were a member of a species that
faced a great crossroads. Your kind
would spread across the globe and
devolve into many different forms. Some
would inhabit the lands to the north,
what is now Europe. They eventually
become the Neanderals. Some would travel
east to Asia and become the Denisovvens.
But most remained in the African
heartland where they would evolve into
us, Homo sapiens.
So far, scientists have been able to
confidently date homohyalbeensis fossils
to between 600,000 and 300,000 years ago
during a time called the middle place.
The homohybensis bone found at Boxgrove
in West Sussex is the oldest known
hominin fossil from so far north in
Europe. It suggests that H Highleberg
beagensis was already widespread around
the globe by this time, but the box
grove man is far from the oldest
representative of his species. That
honor officially goes to Mau One, a
mandible dug up at a German sand mine in
the early 1900s, which is approximately
600,000 years old. Both of these fossils
are from Europe. And so is this where
Homohyldensis first evolved? Not
according to recent evidence. In 2016, a
reanalysis of an old discovery showed
that although there are many ancient
hidensis fossils found in Europe, the
species actually emerged in Africa. Back
in the 1970s, researchers digging in
Gore in Ethiopia discovered skull
fragments belonging to a mystery
hominin. The sediment around the fossils
is 875,000
years old. So, they assumed the homminin
was a homo erectus since no other
homminin was known to exist in Africa at
that time. But a closer look by a new
team in 2016 found that things were not
quite that simple. By comparing the
shape of the skull fragments with others
in the fossil record, the team found
that the fragments were intermediate in
shape between late homoerectus and early
homohyalensis.
This means that the Gbor skull belonged
to someone who wasn't quite a
homoerectus, but also wasn't yet a
homohyalensis.
They were somewhere in the middle, a
transitional being at the very beginning
of a new species.
But why does scientists think homohidal
beensus was our last common ancestor?
Well, as the Gbori skull demonstrates,
Homohidalbensis likely descended from
Homo erectus and the species generally
displays a mix of traits associated with
both erectus and later species like the
Neanderals and Homo sapiens.
Evolution, however, is rarely neat, and
homoidal begunis lived during the middle
plea scene, a period of time that is
notoriously confusing for anyone trying
to piece together the puzzle of human
evolution. It's so complex, in fact,
that paleo anthropologists call it the
muddle in the middle.
It's not clear why, but between around
900,000 and 600,000 years ago, right as
homohidensis was likely emerging,
homminin fossils suddenly become rare
and fragmentaryary. To add another layer
of complexity, there's often confusing
overlap between different species.
For instance, early Neandertos can be
mistaken for late surviving
homohyleensis.
And as with the Gbor skull fragments,
early hidelenses might be mistaken for
Homo erectus. And as well as this, as
we've seen with identifying the very
first humans, the mosaic nature of
evolution can make the distinctions
between them blurry. Also, fossil
hominins are sometimes known only from a
handful of remains. A finger bone here,
a few teeth there, maybe a jawbone or a
piece of skull if excavators are lucky.
A famous example of this is the
Dennisovvens who discovered in 2010
through genetic analysis of a tiny
fingerbone. And so without a complete
skeleton or any genetic data,
researchers don't have the full picture
and are forced to make inferences based
on isolated anatomical features. Indeed,
even subtle differences like the
thickness of bones or the curvature of a
tooth can be interpreted in very
different ways. With researchers being
forced to focus on scattered minute
details, a long list of potential middle
pleaene species has emerged over time.
Aside from homohyagensis and homoensis,
there are also homoadesiansis and homo
anticcessor all living at roughly the
same time and possessing similar yet
slightly different features. The problem
is homoidensis was an incredibly
widespread species just like Homo
erectus before it and Homo sapiens
after. Although they originated in
Africa, they spread across huge swaves
of the old world. Box Grove seems to be
the extent of their northern range, but
they may also have been found as far
east as Darly in China.
Being so widely spread across the globe,
many argue that anatomical variation was
inevitable. So could it be possible that
all these differing proposed species,
bodoensis, rhdesiansis, and antessor are
actually all just variations of
homohybensis?
Many scientists now think that this is
the case and that regional diversity was
just particularly strong in this
species.
Homohidalbensis, therefore, was not a
monolithic creature. It was a species
that changed as it spread across the
globe. Where they made their homes and
what environmental pressures they dealt
with inevitably shaped different
populations. And over time, these
regional populations diverged, drifted
and adapted into many distinct forms. In
Africa, homohybensis could have given
rise to homo sapiens, an evolutionary
trajectory that is reflected in their
anatomy. Rounder craniums, more subtle
brow ridges, and smaller noses.
Meanwhile, in Europe, homohybensis may
have been evolving down a different path
towards Neandertos. The colder weather
could have given them more robust bodies
and thicker bones, while their craniums
retained the more primitive, long, low
shape. And a very similar story likely
played out in Asia where another
species, the Dennis Sovens, split off
from a different population of
Homohyensis.
Although it was long assumed that other
homminin species were more archaic than
us, evidence now suggests that many of
the behaviors we once considered unique
to our species, like art and language,
were present in Neandertos and probably
were in Dennisovvens, too. But what's
even more intriguing is that these
behaviors could have already been
present over half a million years ago in
Homohidal Pagensis.
Buried in a waterlog layer of coal at
Shurningan in Germany, a set of long
wooden spears laid for over 400,000
years until they were unearthed in the
1990s. Looking at them now, they are
practically indistinguishable from
something a modern human would make,
except that they were made by
Homohidensis.
They expertly sharped, carefully
tapered, and balanced like javelins. One
even had a sharpened fireh hardened
point. To make something like this takes
vision. You have to choose the right
tree, shape it, and straighten it. Wood
isn't like stone. It bends and splits.
It's alive and needs understanding to
work with. And indeed, Homo
Hidlebeagensis used wood for more than
just weaponry. In 2023, a discovery was
made that rewrote what we thought about
H Highlebergis. On the banks of the
Columbbo River near the edge of the
Zambian plateau, archaeologists found
two interlocking wooden logs that were
shaped with deliberate notches. One log
had been carved to fit snugly across the
other, forming an architectural join,
one that was at least 476,000
years old. That made it the oldest
evidence of a wooden structure in human
history. Researchers aren't exactly sure
what the structure was. It could have
been a platform, a walkway, or even a
shelter. But whatever it was, it shows
that Homohidle Beagensis could visualize
and manipulate the world in three
dimensions. They were doing a lot more
than just reacting to their environment.
They were changing it.
And buried within this long history of
technological skill and environmental
adaptation lies an even more enigmatic
piece of evidence.
The engraved elephant bone from Bilzing
Slyban, Germany. Dating back around
350,000 to 400,000 years, this
beautifully etched ivory fragment is
considered one of the earliest known
examples of symbolic behavior among
archaic humans. Likely associated with
homohylebagensis or very close
relatives, the bone bears deliberately
insized groups of parallel lines in two
distinct sets with regular spacing and
carefully formed grooves. These patterns
are widely interpreted as intentional
engravings rather than accidental
scratches. But what makes this engraving
so significant is its deeper
implication. It signals that homoidal
begensis possessed the cognitive
capacity not only for tool use and
survival, but for symbolic thought,
planning, and perhaps even rudimentary
communication beyond practical needs.
These engravings hint that the root of
human symbolic culture stretch back far
earlier than previously believed and
well before the appearance of homo
sapiens.
For so long we have drawn the boundary
of what it means to be human at our own
species. But homohidleensis proves that
the boundary line could be much older.
However, even the most adaptable species
can't stick around forever. Soon,
homohidybensis would vanish from the
fossil record, and three new lineages
would take its place.
But when did our own species, Homo
sapiens, emerge? Where have
archaeologists found the earliest Homo
sapiens remains? And what did these
ancestral people look like? And of
course, finally, what was it about them
that ensured that they survived? while
our close cousins, the Neanderals and
Dennisovvens, all died out.
It is late August 1939 and geologist
Otto Ving is working on an excavation at
Hollenstein Stard, a cave in southern
Germany. Buried in the ancient
sediments, he uncovers hundreds of ivory
fragments. The find is exciting, but
it's difficult to tell what it actually
is. So, he has the fragments sent off to
a local museum, intending for them to be
analyzed. However, mere days later, on
September the 1st, World War II breaks
out. Hitler invades Poland. Fieldwork at
Hollenstein startle is abandoned and the
fragments are shoved in a stool room,
forgotten. and they stay there long
after the war ends until archaeologist
Yoim Han starts taking inventory of the
museum stores. Curious about the ivory
fragments, he wonders if he can fit them
back together like an ancient jigsaw
puzzle.
Gradually, as he does so, a figure takes
shape. The body of a human standing tall
and upright with the head of a cave
lion. a fantastical creature that the
figure's maker had to imagine into
being.
Today, we know the figure as the Lowen
Mench, the lion person, and it's been
dated to 41,000 years ago. It's one of
the oldest known examples of artistic
symbolic expression and the oldest
confirmed statue ever found.
Around the same time that the people of
Hollenstein startle were carving the
Lian Mench, other groups across Europe
were painting animals and patterns on
cave walls. At Quaver del Castillia in
the Contabrian region of Spain, people
used red ochre to create hand stencils
and draw a bison. At Grochau in southern
France, people recreated scenes from
around them, painting incredibly lielike
horses, rhinos, deer, and lions. And so
to many archaeologists, it looked like
this art signal the beginning of a new
period in human prehistory around 40,000
years ago and Europe appeared to be at
its center. Scholars started talking
about a revolution when our ancestors
suddenly became behaviorally modern.
But was this really the whole story?
About 50 kilometers southeast of Safi, a
small city on the western coast of
Morocco, is a site called Jebel Earhood.
Until relatively recently, Jebel Earhood
was a cave, but it now lies open to the
blazing North African sun. In the 1960s,
the rocky foothills of the Atlas
Mountains saw intense mining, and Jabel
Earhood had its entire ceiling removed.
And yet, despite the destruction, it was
during this intense mining activity that
a valuable human fossil was discovered.
It was a skull, and the miner who found
it gave it to the University of Rabbat.
Intrigued, the university then organized
an expedition to the site led by
anthropologist Emil Anuki. As it was the
1960s, Anuki and his team used
explosives to uncover the archaeological
layers they were interested in, but
still managed to recover a further two
homminin fossils which were interpreted
to be an adult and a child. The
excavation also unearthed a number of
stone tools in situ thought they looked
like Neanderal tools and so he initially
assigned the fossils to the Neanderal
species. This was the first in a long
list of confusions surrounding Jebel
earhood. Indeed, the homminin remains do
resemble Neandals in several ways, but
Neanderals are first and foremost a
Eurasian species. They've been found as
far south as Gibraltar, but appear to
have never set foot into Africa. Then
came the problem of dating the finds.
Techniques for figuring out the age of
fossils and archaeological materials
were limited in the 1960s. So, Anuki
tried what was available to him. At the
time, this was radiocarbon dating. But
this technique can only date material
that is 50,000 years old or younger. And
the remains from Jebelhood were older
than that.
And nobody knew quite how old until 2017
when a team led by the Maxplank
Institute for Evolutionary Anthropology
carried out thermoluminescence dating on
the Jebel Earhood assemblage.
Some of the tools at the site had been
burned. So the Maxplank team were able
to find out when the burning took place.
By proxy, this provided a minimum age
for the other tools and the homminin
remains that were buried next to them.
And to everybody's surprise, the burnt
tools were 315,000
years old. So were these 315,000y old
Neandertos living in North Africa or
were they something else? Right from the
beginning, the Jebel Earhood fossils
were seen as an oddity. The skull has a
long cranium, a strong brow ridge, and
relatively large teeth. However, it also
has plenty of more derived features that
look similar to our own, like delicate
cheekbones, a slightly rounded brain
case, and a smaller nose. Some
researchers suggested that the Jebel
earhood hominins could have been
Neanderal sapion hybrids, which would
explain their curious mix of features.
But the leading hypothesis is even more
surprising. These homminins were our
ancestors, a group of some of the
earliest homo sapiens to emerge. These
early sapiens didn't have all the
physical characteristics of our species
because 315,000 years ago, they hadn't
evolved yet.
This new discovery of old evidence was
big news. until 2017. The oldest known
homo sapiion fossils came from Omo
Kibish, an Ethiopian site then dated to
195,000 years ago. Jebel Yehood
therefore pushed back the origin of our
species by over 100,000 years. And since
then, the fossils from Omo Kibish have
also been revealed to be older than we
thought, dating to around 233,000 years
old. So, what were the homo sapiens like
at Omo Kibish? Were they similar to the
people from Jebel Ehood or were they
different?
The excavation team at Omo Kibish
uncovered the remains of two individuals
Omo 1 and Omo 2. Unlike their more
ancient relatives from Jebel Earhood in
Morocco, the Omoans are classified as
anatomically modern. That means that Omo
1 and 2 were close to indistinguishable
from 21st century people. They have the
characteristic globular brain case,
subtle brow ridge and pointy chin
amongst other things. The expansion and
rounding of the brain case is especially
significant. It reflects a
reorganization of the brain,
particularly areas linked to visual
spatial integration, memory, and social
cognition, which could have given them
an adaptive edge in the rapid shifts
between wet and dry phases happening
between 400,000 and 100,000 years ago.
Researchers have also proposed a
pan-African model for the evolution of
anatomically modern humans. As African
environments fragmented under climate
pressure, populations of early homo
sapiens would have become isolated in
different ecological niches. These
pockets of isolation may have lasted
thousands of years, allowing local
populations to evolve distinctive
traits.
When more stable climatic conditions
returned and habitats recovered, those
populations could then merge and
exchange genetic material. This scenario
suggests that homo sapiens did not
necessarily arise from a single cradle,
but from multiple interconnected
populations across the African
continent, with each contributing
different anatomical traits. Jabalihood
in the northeast, Omoibish in the east,
and another site, Floresbird in the
south. Each represents a distinct
population that was maybe part of a
continentwide evolutionary mosaic, and
physical genetic traits weren't the only
things to be exchanged by these
populations. Human technology gradually
began to change as well. At Jibble
Earhood, we see people using an entirely
new approach to tool making. One of the
best known methods from this period is
called the Lavalwis technique. Rather
than simply chipping away at a piece of
stone to produce a cutting edge, the
Valwis toolmakers carefully shaped a
stone core so they could remove a single
well-formed flake with a single strike.
The result was a thin sharp flake that
could be further retouched into points,
scrapers, or blades. People also began
to experiment with hafting, attaching
stone points to wooden shafts to create
composite tools like spears and knives.
In some cases, they even used plant
resins as adhesives.
Over time, distinctive regional
traditions emerged. In North Africa,
there was the industry characterized by
tanged points that could be fitted onto
handles. In southern Africa, later
middle stone age industries like Still
Bay and Harrison's Port produced finely
worked spear points and tiny razor-sharp
blades known as microliths, which were
likely mounted in handles made from
wood, bone, or ivory. So, not only does
the panafrican hypothesis explain how
the physical traits of homo sapiens
evolved, but it could also explain how
behavioral and technological evolution.
It's clear that physical and behavioral
modernity wasn't a sudden development,
but a gradual coming together of
populations, a sharing of genes,
knowledge, and culture.
And while all this was happening, Homo
sapiion populations were growing and
expanding into new territories.
By around 200,000 years ago, small bands
of early humans had already began to
explore new environments beyond their
African homelands. Indeed, the earliest
evidence for Homo sapiens outside Africa
comes from a cave in southern Greece.
Although sites like Abide Cave are few
and far between, and it wouldn't be
until much later, around 70,000 years
ago, that Homo sapiens truly began to
colonize the world. They followed the
shifting grasslands and coastlines that
opened up during colder, drier periods,
gradually making their way across the
Arabian Peninsula into the Levant and
onwards into Europe and East Asia. As
they migrated across this new world,
they encountered other human species,
Neanderals and Dennisovvens.
For a time, these different species
lived alongside each other. Sometimes
there was conflict and sometimes there
was cooperation. But there's no getting
around the fact that by around 40,000
years ago, we were the only human
species left. Not long after the arrival
of Homo sapiens in Eurasia, both the
Neanderal and Denisovven population
began to shrink until they eventually
went extinct. The reason why is hotly
debated, but our homo sapiens ancestors
likely played a big part.
Some researchers suggest that
competitive exclusion took place. This
is the idea that Homo sapiens out
competed their Neanderl and Denisovven
cousins for land and resources. Others
point to the instability of the climate
during the last ice age which could have
pushed small isolated populations of
Neanderals and Dennisovvens beyond the
point of recovery. But whatever the
reason, Homo sapiens became the sole
human survivor of the late pleaine.
And as time went by and our ancestors
expanded into more new territories, they
encountered new challenges and endured
some of the harshest conditions humanity
has ever faced.
Around 26,000 years ago, the world
entered the last glacial maximum, the
coldest, driest, and least forgiving
phase of the last ice age. Impenetrable
ice sheets smothered huge swavthes of
the northern hemisphere, dropping global
temperatures and significantly lowering
sea levels. Land that was once part of
the sea floor suddenly became exposed,
which created land bridges between
previously disconnected regions and
altered coastlines beyond recognition.
Indeed, some even think this is how
certain populations made it into North
America by traveling over a land bridge
called Bingia that connected Siberia to
Alaska. Survival in this harsh glacial
world demanded adaptability and
ingenuity, and our ancestors rose to
meet the challenge. Indeed, the last
glacial maximum was a time of many
firsts. The first known tailored
clothing, the first confirmed houses,
the first pottery.
Life for most people would have been
hard, but for a select few, life perhaps
became more lavish.
A burial discovered at Sunir in Russia
contains two children laid head to foot,
covered in red ochre, and accompanied by
high value items like finely carved
spears and clothing that had over 13,000
ivory beads sewn into it. Clearly, a
huge amount of effort went into burying
these bodies despite their young age.
This makes researchers think that
perhaps burials like this reflect the
origins of hierarchical societies, the
division of wealth and inherited status.
And this was a trend that would continue
long after the ice retreated. By roughly
12,000 years ago, the climate was
warming and a new epoch began. This was
the holene,
the period we are currently living in.
The world gradually transformed with
forests spreading across the previously
grassy steps and rivers swelling with
meltwater. With much more stable climate
and generally warm temperatures, some
populations around the world began to
settle down. In the Levant, otherwise
known as the fertile crescent, people
experimented with growing crops and
keeping the livestock. Soon as people
put more time and effort into producing
their own food instead of foraging or
hunting for it, the first villages,
towns, and even cities sprang up.
Although in other regions, including in
Britain and the US, people remained
nomadic for many thousands of years,
maintaining their traditions of hunting,
fishing, and gathering. And so, Homo
sapiens would go on to raise monuments
like Stonehenge, create the first
written word, and build mega cities.
Everything we associate with our species
from writing and philosophy to science,
architecture and art proliferated in the
holene.
But we cannot forget what led us to this
point.
Our story stretches back far beyond the
holysine, beyond the ice ages, and even
beyond the first appearance of homo
sapiens. We are part of a much longer,
much older tale. One that stretches back
billions of years to when single-sellled
organisms first appeared in Earth's
ancient oceans.
It is a story of endurance and
adaptation, of conflict and cooperation,
of innovation and creativity,
and it's a story that's far from over.
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