The world has changed. Can life survive?
Birds that nest under street lights are
stressed. The stress hormone
corticostone was measured in song birds
nesting under white artificial lights,
and it was found to be at similar levels
to birds who were being caught or
handled. The same hormone was found
elevated in female woodf frogs triggered
by the noise of traffic. Through either
the disorientation or a stress response,
the increased hum of ambient noise
caused a lower percentage of the frogs
to find the chorus of breeding male
frogs. And even fumes from traffic along
with ozone exposure can have a direct
impact on the neural circuitry of
insects. Honeybees exposed to these
toxins have displayed greatly reduced
memory and even learning ability.
However, the picture is not quite so
simple for other species appear to have
adapted well to the chaos of the modern
world. The London Underground mosquito,
for example, has changed from its life
of feeding on birds and hibernating in
winter. Now it feeds all year round on
mice, rats, and humans. Anoli lizards of
Puerto Rican cities have evolved more
tiny brush-like lamelli on their feet,
allowing them to scale walls and even
glass windows.
We are changing the world around us at a
rapid pace. And in many cases, nature is
keeping up. But the question is, are we?
Humans have built a modern world that is
fast becoming totally unlike anything
seen before on the earth. And now we
live entrenched within it. not only
under artificial light and in the
constant hum of traffic, but in vastly
different social structures, larger
networks, and with frequent triggers for
stress or alarm. And so, are humans
really flexible enough to cope in these
bizarre new concrete landscapes? And
could an anatomically modern homo
sapiens from hundreds of thousands of
years ago with a body and brain
virtually indistinguishable from our own
adapt to our life today?
this yourself, download Opera via my link in the description.
It is 2009 and a team of archaeologists
are lying face down in a trench in White
Sands National Park, New Mexico. They
have uncovered footprints that are
23,000 years old.
For at that time, White Sands was not
the desert we know today, but a lush
landscape of grassy wetlands around the
great paleo lake Otto.
Here in a world alive with mammoths,
direwolves, and saber-tooth cats, lived
a group of humans. One trail of prints
appears to show a small number of
humans, perhaps just two or three
individuals, stalking behind a giant
ground sloth. A short distance away,
another set of footprints suggests that
crowds of adults and children were
gathered together, watching as the hunt
progressed. Of course, the footprints
aren't an exact census, but they seem to
suggest small, highly mobile groups of
perhaps 20 to 50 individuals living off
the resources the ancient lake provided.
And we can see traces of a similar
lifestyle in human footprints found at
Kooie Fora in Kenya. Again, here
evidence seems to suggest around 20 to
50 highly mobile and interdependent
individuals. And again, these footprints
were made near the shore of an ancient
paleo lake that could sustain all manner
of life. But animal bones show this
small group of humans were processing
large game with stone tools near the
lakes's shore. And so clearly the daily
lives of these two groups of humans in
Kenya and North America may have shared
many similarities and would both stand
in stark contrast to the lifestyle most
humans live today. However, these
footprints are separated by more than
just distance because the human group
that lived in Kubora
lived 1.5 million years earlier.
As far back as ancient Homo erectus that
evolved in Africa around 2 million years
ago, we can see elements of a lifestyle
that persisted right through to the
advent of farming between 10 and 20,000
years ago. Of course, over that span of
time, human brains would increase in
size, and our technologies and culture
would develop. And yet, despite this,
many aspects of the living experience
and daily routine of humans would be
similar. Despite the truly vast amount
of time that passed, our ancestors
hunted and scavenged, surviving in small
groups that lived near the resources
they required. Their natural world
dictated where they lived and also when
their days began.
In a world with no blackout blinds or
alarm clocks, ancient sleep and
wakefulness patterns likely aligned
closely to the rising and setting of the
sun. In fact, a study from the sleep and
chronobiology laboratory at the
University of Colorado highlighted the
changes in present-day humans body
clocks after as little as one week
camping. The study investigated the
participants circadian rhythm by
measuring the sleep hormone melatonin
and found that campus circadian clocks
shifted 2 hours earlier during the trip.
The lead author of the paper suggested
that sleeping outside keeps us more in
sync with our biology and went on to run
a follow-up study in the cold of winter
that showed a more disturbed sleep but
more sleep overall. Indeed, this
disturbed but effective sleep is
observed in huntergatherer societies
today. Evolutionary anthropologist David
Samson found the Hadza people of
Tanzania would generally perceive they
had a good sleep even if it was
disturbed. Helen Bore, director of the
Durham Infancy and Sleep Center has even
suggested the idea of one large bank of
consolidated sleep has only existed for
the last two centuries. And so we can
envision the days and nights of ancient
humans. But of course, human days didn't
always end immediately after the setting
of the sun.
Burned animal bone and plant material at
Wanderwork Cave in South Africa suggest
that Homo erectus was using fire around
1 million years ago. Of course, this
would have marked a profound transition
in human evolution. Where earlier
hominins like Oralopythecus would have
retreated to the trees when the sun went
down, groups of Homo erectus could
kindle a flame. It would keep them warm,
cook highquality food, and discourage
predators. And indeed, ever since then,
fire has become a central part of every
human community. For example, just 3,000
years after the footprints were made at
the Paleo Lake Otero, researchers at
O'Haro, Israel, have found that people
built oval brush huts, each constructed
around a central hearth. But of course,
for most of the preceding million years
or more, there were no brush huts. And
so over the vast majority of the time
humans have been making fires, they were
likely kindled in caves or in and around
the most rudimentary of structures. And
anthropologist Pauly Whisner at the
University of Utah argues that fire
light effectively created new time.
For earlier hominins, after dark, there
had been little to do but sleep. Fire
changed everything. To understand what
happened in those fire lit hours,
Whisner spent time with hunter gatherers
in South Africa. During the day, she
observed that conversation tended to be
practical. People would discuss hunting
strategies and resource availability
with only a small amount of gossip or
small talk. But around the fire at
night, something shifted. Talk would
turn to deeper subjects, and the camp
would gather to sing, dance, and tell
stories. For hunter gatherers, these
stories carried practical knowledge
about animals, landscapes, and the land
around them. But they also transmitted
shared identity and social rules. Of
course, we must remember that human
culture and society changed over time,
and it's unlikely Homoctus, for example,
were telling stories around the fire a
million years ago. But even in the
earliest days of human fire, the fire
itself could have been a remarkably
strong shared experience. and the
setting of the fire may have allowed the
practice of storytelling to evolve over
time.
And what's more, around those fires lay
objects that were useful.
Not all materials fossilize well, so
it's hard to inventory what possessions
our huntergatherer ancestors owned, but
it is important to note the relatively
few forms the surviving material culture
of humans more than 100,000 years ago
take. Most items are practical, such as
stone tools for hunting and butchering
or ostrich eggshells for storing and
carrying water. And of course, this
makes sense given that every possession
has to be carried in a nomadic or
semi-nomadic lifestyle. So every
possession has to earn its place.
Anthropologist Marshall Salins called
early hunter gatherers the original
affluent society, suggesting they were
able to satisfy their material needs,
what he called affluence without
abundance. And indeed, although ancient
hunter gatherers lived physically
demanding lives, exposed to the elements
and at risk of predation, perhaps there
was a more straightforward nature to the
challenges they faced in daily life. In
general, their problems would have been
immediate ones, which creates very
different activity in the human brain.
Neuroscientist Judson Brewer has shown
that when people train themselves to
focus on the present moment through
meditation, activity in the brain's
default mode network, the system
responsible for rumination and
self-reerential thought, drops
significantly. It's tempting to wonder
if for our ancestors, a quieter default
mode network was simply the norm.
Without the complex challenges of the
modern world, their lived experience
would certainly be a very different one.
And so these were the huntergatherer
lives our ancestors lived a version of
for over a million years. Culture did
evolve over time, but huge aspects of
their daily lives kept similarities and
contrasts with the lifestyles most of us
live today. But around 12,000 years ago,
something changed. For the first time in
the long history of our genus, people
began to farm the land and settle in
permanent homes. The cultivation of wild
plants gradually became true
domestication as humans became
increasingly dependent on cereals and
grains. And this Neolithic revolution
would not only change our behavior but
even our very DNA. In a paper published
in Nature in April 2026, researchers
found that many alals, variants of a
gene that produces different traits in
different individuals, changed after
farming began. The strongest signals
involve immunereated regions, likely
influenced by the increased spread of
disease within more densely populated
towns and cities. Others include traits
linked to metabolism. One gene led to a
lowering of body mass in more recent
generations, probably due to the surplus
of calories associated with crop
domestication. And so the ancient
huntergatherer lifestyle, what we can
see pieces of from Kooififor to White
Sands, would come to an end.
And so this is the world our ancient
human ancestors from 100,000 years ago
would have lived in. They would have
lived their whole life by the light of
the sun, moon, stars, or fire. They
would have lived in small, tight-knit
social groups. They would have had few
possessions and likely experience the
world without an overactive default mode
network in his mind. And so if we want
to transport one of these prehistoric
humans 90,000 years into his future,
straight into the Neolithic Revolution,
his new surroundings would offer a
mixture of challenges to adapt to. An
abundance of food stores, yes, but
greater risk of disease and the
beginning of a whole new sedentary way
of life. But of course, we know that
generations of real humans did adapt to
this shift, changing their very genetic
makeup over the following thousands of
years. Perhaps this ancient human would
cope. Perhaps not. But of course, a lot
has happened since then, and taking him
a 100,000 years into the future, into
our time, would be very different. And
so, his journey will be like our own.
Not stopping at the Neolithic
Revolution, but continuing to push on
through eras of ever advancing
technology, societies, and ways of life
that get further and further from the
ones he evolved for.
In the 1980s, children play on a roof
that is 14 stories high, for it is one
of the only sunny places in Cowoon
Walled City. Below them, people walk the
tunnel-like alleyways. Many of them
clutch umbrellas in the darkness, not to
protect from rain, but from the dripping
of thousands of corroded pipes. The city
is a knotted maze of iron and concrete
with some of its streets formed by vast
amounts of rubbish caught in nets and
trodden into a new walkway between
buildings. A single postman covers this
entire city. There's not that far to go
as it's only a hundth of a square mile
in size. But within that tiny footprint
or over 8,000 premises, 10,000
households, and 30,000 people. Beginning
as an abandoned military fort, Cowoon
grew organically into a truly unique
city that would eventually be demolished
in 1993.
And indeed, before its demise, Cowoon
Wald City was known as the densest place
on Earth.
In the modern world, censuses tell us
that half of all humans live in cities.
What's more, surveys show that the
average person in developed nations like
the US and the UK spend around 87% of
their time indoors and 6% in vehicles.
That means we spend only 7% of our
entire lives outside. Most of our time
is spent inside climate controlled boxes
in a sense disconnected from natural
rhythms of daylight, weather, and
terrain. And this mismatch between the
lives we evolved for and the way we live
in the modern world has been developing
for thousands of years. In evolutionary
psychology, a mismatch refers to the
difference between the selective
pressures that shaped humankind over
millions of years and the novel
conditions of modern environments
leading to potentially suboptimal
outcomes like disease, stress, and
maladaptive behaviors.
Today the average working week globally
is around 33 hours with some regions
hitting 50 or 60. But some ethnographic
studies of people living in extent
foraging communities like the Kungan of
South Africa show that the average
hunter gatherer works only 15 hours a
week. This equates to just a few hours
every day hunting, fishing, gathering,
making or mending. The rest of their
time is theirs to do with as they
please. And indeed, for more than 90% of
our species history, humans likely lived
in a very similar way. But the change
away from this truly accelerated in the
industrial revolution when rural
farmlands gave way to factories and
tenement slums, turning settled villages
into crowded mega cities and cementing
our separation from the wild physical
world that shaped us.
And it was during this time that French
sociologist Emil Durkheim observed
something about society. The more
industrialized a life became, the more
it seemed to come apart at the seams.
Durkheim noticed that as people left
their small, tightlyknit communities for
anonymous city streets and factory
floors, they lost their sense of shared
rules, expectations, and obligations.
Durkheim called this phenomenon anomy.
Anomy is a sense of normlessness. It's
what you feel when the rules that tell
you what to hope for, how much to want,
and how to behave no longer seem to
apply. In a period of rapid change, like
the industrial revolution, old
traditions quickly crumbled and new ones
didn't have time to form. Durkheim was
especially struck by the way this
normlessness showed up in the statistics
of his time. For his railways, stock
markets and factories spread across
European nations and beyond, suicide
rates climbed. For Durkheim, the problem
was not just poverty or hardship, but a
deep mismatch between human minds and
the rapidly changing social world they
were being thrust into.
Industrialization, therefore, was a
significant driver of evolutionary
mismatch, but it wasn't the sole cause
in modern life.
Today, many mammals are nocturnal or
kpuscular, meaning that they are most
active after the sun has set. When
mammals first evolved during the
triacic, they shared the world with
dinosaurs, many of which were dal or
most active during the day. By sleeping
in the day and waking at night, early
mammals could avoid predation and other
dinosaur related dangers. But after
non-avian dinosaurs went extinct around
66 million years ago, mammals started to
diversify. Since there were very few
large predators left after the
Cretaceous mass extinction, several
mammal families began to shift towards
dal lifestyles. They evolved sharper
daytime vision and internal circadian
clocks fine-tuned to bright light
wavelengths. One of these families were
the ancestors of modern monkeys, apes,
and humans. And so our lineage evolved
to be awake during the day and asleep
during the night. But once electricity
became available, our days no longer had
to stop when it got dark or when the
weather turned. Factories and offices
could run longer hours, and later,
computers and the internet made it
possible to work at almost any given
time.
From an evolutionary standpoint, humans
are built for bursts of effort
punctuated by genuine downtime, not for
continuous engagement with tasks around
the clock. And so while our ancestors
expended energy in targeted physical
bursts followed by rest around the fire,
today we sit for 8 to 12 hours at desks,
in cars, or on couches. Constant access
to power has created constant demands on
attention, erasing the line between on
and off. The result has been chronic
stress, low energy, and less time or
motivation to cook, move, and recover.
In the midentth century, endocrinologist
Hanselier noticed this mismatch becoming
more prevalent in society and he came up
with something called general adaptation
syndrome to describe how animals respond
to prolonged strain. This syndrome is a
byproduct of the natural three-stage
response to stress. The first stage
alarm triggers the classic fight
orflight reaction flooding the body with
adrenaline and cortisol. The second
resistance engages coping mechanisms to
maintain balance despite ongoing stress.
Afterwards, the third stage, exhaustion
sets in, leading to breakdown,
vulnerability, and burnout.
Imagine an oustropythecus like the
famous Lucy living somewhere around 3.2
million years ago in the wooded
grasslands of what is now Ethiopia.
Picture her group facing a sudden
crisis. Her leopard ambush near their
leafy home. Her body reacts perfectly.
Her heart races. Adrenaline and cortisol
floods her system and her muscles tense
for a desperate climb into the branches
or a sprint across the savannah. She and
her group make it to safety and their
brief period of alarm fades. The stress
system resets, conserving energy for the
next day's foraging. And so Lucy's
system is perfectly matched to brief
life or death pulses in a dangerous but
episodic world. Fast forward to today,
that same ancient machinery grinds
without release. In the constant hum of
modern life, it can become a slow but
steady source of mental exhaustion. And
a century or so of industrialized living
has not only assaulted our mental state,
but our physical state, too.
During the early 20th century, developed
nations began to face what physicians
called diseases of civilization. For
most of human history, the main threats
to life were infections, injuries, and
famine. In small mobile bands of hunter
gatherers, people faced parasites,
dangerous animals, wounds, and the risks
of childbirth. Early farmers added new
problems like close contact with
livestock and poor sanitation which made
diseases like small pox, tuberculosis
and measles part of everyday life. Over
the 20th century, things seemed to
improve dramatically. Clean drinking
water, sewer systems, vaccination,
antibiotics, and safer childirth drove
infectious disease and infant mortality
down to historic lows in many developed
countries. While average life expectancy
shot up. But as the old killers
retreated, new ones took their place.
Today, in highincome nations, the
leading causes of death are not
infections, but chronic non-communicable
diseases like heart attacks and strokes,
clogged arteries, type 2 diabetes,
obesity related conditions, and many
forms of cancer. And so, why do humans
living in modern urban settings fall
victim to these diseases of
civilization?
In 1962, geneticist James Neil proposed
the idea of a thrifty genotype. He
suggested that our huntergatherer
ancestors evolved genes that made their
bodies exceptionally efficient at
storing energy. This thrifty adaptation
would have been put to the test during
the last glacial maximum, the height of
which occurred around 27 to 20,000 years
ago. This was a time when massive ice
sheets covered most of the northern
hemisphere and food scarcity would
likely have hit brutal extremes. This
meant that humans that could rapidly
store fat from rare kills, then ration
it through famine, were far more likely
to survive these periods of extreme
scarcity. But those same genetic
tendencies that once protected people
from starvation now leave many of us
vulnerable to abundance. Indeed, in
modern developed nations, we have
constant access to food. Much of it is
cheap, high in calories, and
ultrarocessed. However, the human body
still behaves as though scarcity is just
around the corner, storing excess energy
rather than burning it off. Combine this
with sedentary lifestyles and long hours
spent under artificial light, and the
result is a physiological mismatch
between an ancient metabolism and a
modern environment designed for excess.
And yet, even though we are surrounded
on all sides by abundance, abundant
food, abundant stimulation, abundant
people, in many ways, we are becoming
more isolated than our distant ancestors
ever were.
When Mitiko Kamayyama shut the apartment
door behind her, she thought she was
making the right choice. She had told
her 8-year-old daughter, Julianne, that
she was going out for a while and
reminded her not to open the door for
anyone. Kamiyama had come to the United
States years before with her husband,
but then he had died, leaving her alone
with a small child in a foreign country,
and so she did what she could to
survive, including working long hours as
a waitress. However, it wasn't enough to
pay the bills in 1990s California. And
feeling the pressure, she applied for a
second job as a singer in a lounge bar.
Unable to find a babysitter, Kami Arma
went for an audition and left Julianne
alone in their apartment. But her
daughter was alone for a total of half
an hour before Camama got a call from
the police. A neighbor had heard the
girl crying and alerted the authorities.
Camama rushed home, but Julianne had
already been taken by child protection
services and Kamyama was arrested and
jailed.
Migo Kamiyama faced choices that would
have been unthinkable for our ancestors,
and she was far from alone in facing
this kind of strain in modern times. For
most living huntergatherer groups,
however, infants receive hours of close,
responsive contact each day from dozens
of caregivers. Everyone chips including
all the siblings, grandparents, aunts,
uncles, and even neighbors.
Anthropologists call this alo parenting
and it appears to be a core human
adaptation.
Caring for another parents offspring is
rare in the animal kingdom, found in
only 9% of bird species and about 3% of
mammal species. Indeed, within the
primate lineage, other than in humans,
alo parenting is only truly found within
our distant relatives of marmicetses and
tamarind. But despite this, American
anthropologist and primatologist Sarah
Herdy believes that our ancestors began
to alo parent over a million years ago
in the time of Homo erectus. As well as
allowing skilled parents time to conduct
tasks for the group, Herdy also believes
this variety of care gave young
homminins challenges unlike any other
rape. creating a selection pressure for
heightened social ability. Today,
however, much more common than alo
parenting are sole caregivers that are
also in full-time employment. In fact,
across many wealthy countries, surveys
show that a significant number of
employed adults work multiple jobs. In
the United States, labor statistics show
that roughly 8 or 9 million people hold
more than one job at the same time, with
women and young adults the most likely
to be moonlighting. And global surveys
paint an even starker picture. A 2025
workforce report found that 23% of
workers worldwide held two or more jobs.
And as well as this, most of them
reported living paycheck to paycheck
despite the extra work. Of course, these
problems and resulting behaviors would
be truly alien for anyone who had always
lived a hunter gatherer lifestyle.
Indeed, for many living huntergatherer
groups who live the kind of lives our
species is more adapted for, daily life
is organized around strong community
ties, resource sharing, and an active
resistance to steep hierarchies and
wealth inequality. Among the Hadza in
Tanzania and the Kung in the Kalahari,
successful hunters do not gain prestige
by hoarding meat all for themselves.
They earn it by sharing it and being
humble about their achievements. In
these communities, people are expected
to share food and other resources with
everyone else. Anyone who tries to keep
too much for themselves is teased,
gossiped about, and openly criticized.
Personal property does exist, especially
for things like tools and weapons, but
there is very little accumulation of
durable wealth. Anthropologists
sometimes describe these groups as
egalitarian or immediate return
societies. They do not store resources,
so one person can't have much more than
anyone else. There is still conflict now
and then, but in a very real sense,
these huntergatherer societies with
their small groups and clear
expectations are much closer to what our
minds evolved for.
And indeed, as the 20th century became
the 21st, small groups and clear
expectations would become more and more
alien to our day-to-day lives.
Imagine a teenager posting a short video
to social media. It's nothing special,
and they don't expect anyone other than
friends and family to see it. But by
morning, the video has 10,000 views. The
following evening, it has a 100,000.
The teenager has unwittingly found
themselves at the center of a huge
amount of attention and they have no
idea what to do about it. The only thing
that seems to make sense is to post
again. This is the variable reward cycle
and it is the same mechanism that makes
slot machines so difficult to walk away
from. Each like, flattering comment or
new follower is an unpredictable
intermittent hit of positive feedback
that locks social media dependency in
place. But it wasn't the internet that
created our sensitivity to this kind of
feedback. The root is far more ancient.
In the small bands our ancestors lived
in, knowing where you stood with the
people around you was a matter of
survival. Approval could have meant the
difference between life and death. And
so, modern social media simply takes
advantage of this ancient human
instinct. Systematic reviews of social
media and our psychological well-being
find that the relationship between the
two are not straightforward. Indeed,
social media is not always harmful. For
some people, it provides genuine social
support and a space to explore personal
identity. But there are also consistent
patterns of harm, and they cluster
around two things in particular. How
social media platforms are used and how
much. When humans endlessly scroll
through curated images of people who
seem more attractive, more successful,
and more fulfilled than we are,
something in us registers it as a
deficit. In fact, even the basic premise
of social media might be one that our
brains are not built to handle.
In the late 1980s and early 1990s,
British anthropologist Robin Dunar was
studying primates when he noticed
something interesting. Across different
species, there was a remarkably
consistent relationship between the size
of the neoortex and the size of the
social groups those species typically
lived in. The bigger the neoortex
relative to the rest of the brain, the
larger and more complex the social group
the animal could manage. Dunar's
argument was that primate brains,
including our own, didn't grow large
primarily to solve technical problems
like making tools or navigating
landscapes. He proposed that they grew
large, above all, to handle the demands
of social life. The kind of social
tracking that primates do is
extraordinarily demanding on cognition.
So it appears to have been a primary
driver of the expansion of the primate
brain over millions of years. And when
Dunar applied this relationship to
humans, he proposed that there is an
upper limit to the number of stable
meaningful social relationships that the
human brain can realistically maintain
at one time. This has since become known
as Dunar's number, and it seems to
correspond surprisingly well to
realworld social structures.
From
hunter gatherer bands and Neolithic
villages to modern offices, factories,
and military companies, groups of
roughly 150 people appear again and
again across human history and cultures.
Anything beyond that number, Dunar
argues, humans can't cope. And now
consider what social media asks the
brain to do. Even a relatively modest
social media presence routinely exposes
a person to more faces, names, opinions,
and social signals in a single scrolling
session than our ancestors would have
encountered in a lifetime. Our brains,
however, don't know the difference. They
try to process all this extra social
information as if every notification is
a social event and every comment is a
status symbol. The processing happens
automatically, relentlessly, in the
background of everything else we do. And
so where does this all leave us? We are
a species shaped by millions of years of
evolution for a world that no longer
exists. We are built for small groups
and intimate knowledge of the people
around us. But we live among millions of
strangers. We are built for immediate
return lives where effort and reward are
closely linked. But we now inhabit
economies that demand constant striving
towards goals that recede faster than we
can chase them. And this is the world
that our ancient Homo sapiens, taken
from a 100,000 years ago, would land in.
Supposing for a moment he could learn
modern language and gestures, could get
used to wearing clothes and opening cans
and bottles. What then? If we grant him
those capabilities, could he adapt to a
world of long artificially lit work
days? Or would his ancient mind collapse
under the new challenges? And indeed
similarly, are all humans destined to
feel the strain of evolutionary mismatch
forever? Or could we one day fully adapt
to this modern world?
In the late 1990s, neuroscientist Dr.
Ellena Maguire climbed into a black cab.
She was running behind schedule and
asked the driver to go as fast as
possible. However, 5 minutes into the
journey, Maguire glanced up from the
research notes she was reading and
spotted a line of cars caught in a
traffic jam. She groaned to herself,
dreading to think how much longer the
congestion was going to set her back.
But to her surprise, her cab driver
turned onto a side street, completely
bypassing the traffic up ahead. He then
took them down a network of back roads
and cobbled lanes that Maguire had never
seen before, despite having lived in
London for several years. But what
impressed her most was that her driver
never once needed to look at a map. And
so Magguire asked the driver how he knew
where to go. And he told her about the
vast mental map he had built up during
his years as a London cab. As a
neuroscientist researching spatial
memory, Dr. Maguire immediately started
to wonder how exactly these mental maps
worked.
And a couple of years after that
journey, in the year 2000, she published
a groundbreaking study.
In it, she scanned the brains of a group
of London cab drivers and compared them
to scans of a control group. The control
group were ordinary people of equivalent
health and intelligence. But the key
difference was that they did not drive
cabs and Maguire found a striking
difference between the two groups. The
cab drivers had a significantly larger
posterior hippocampus than the
non-drivers. This part of the brain is
used in navigation and spatial memory
and the size of the posterior
hippocampus in the cab drivers grew
relative to their years on the job. This
graded relationship demonstrated an
experience dependent effect. It wasn't
that people with naturally enlarged
hippocampi became cab drivers. It was
the process of navigating a city from
memory that reshaped their brains. And
as well as this, the front part of the
hippocampus in the cab drivers was
slightly smaller than in the control
group, suggesting that the enlarged
posterior hippocampus came with a
trade-off. In a follow-up study, Maguire
and her colleagues compared the cab
drivers with London bus drivers. Both
had to navigate a large metropolis, but
the bus drivers followed the same route
every day. The researchers gave both
groups a series of cognitive tests,
including tasks that measured different
kinds of memory. On tests that required
navigating around a virtual London or
recalling the layout of routes, the cab
drivers outperformed the bus drivers.
But on other tasks, they actually did
worse. When the researchers tested their
ability to form new associations or
remember lists of unrelated information,
the cab drivers underperformed compared
to the bus drivers. The very patterns of
brain restructuring that boosted their
navigational skills appeared to come
with subtle costs to other forms of
memory.
The human brain is flexible and
scientists call this flexibility
neuroplasticity.
Neuroplasticity is the brain's ability
to grow, change, and adapt. Unlike most
other organs, the brain can reorganize
and rewire itself in response to
environmental changes, injuries,
illnesses, or disorders, or more
positively, learning new things. For a
long time, scientists have believed that
this flexibility belonged almost
entirely to childhood. And once the
brain set in adulthood, it became more
or less fixed. We now know, however,
that this just isn't true. Adult brains
remain plastic, too, just in a different
way. They can still form new
connections, strengthen or weaken old
ones, and even shift functions to new
regions when circumstances demand it.
Indeed, every time you learn a new skill
at work, recover after an injury, or
slowly get used to a new environment or
routine, your brain is reshaping itself.
This ability to adapt is an essential
part of being human. And it's why small
bands of Homo sapiens could leave
Africa, cross deserts and icy tundra,
and still find ways to live.
Throughout the history of our species,
homo sapiens have experienced several
severe population bottlenecks, driving
us perilously close to extinction. But
no matter the cause of these sudden
plummets in population numbers, whether
it be rapid climate change, competition
with other homminin species, or even
natural disasters, Homo sapiens has
always bounced back. And if anything,
these brushes with extinction have made
our species stronger than ever. Because
natural selection favored individuals
who could learn quickly, improvise, and
switch strategies when environments
shifted. Some researchers even think the
differences in how flexible our learning
and social networks were may have been
the thing that tilted the balance in our
species favor. Archaeological evidence
continuously shows us that our closest
human relatives, the Neanderals and
Dennis were probably not inferior to us
in terms of their intelligence. And this
is reflected in the material culture
they left behind in complex tools, cave
paintings, and jewelry. But the key
difference between our species may have
been in how plastic or moldable our
brains were. Homo sapiens may simply
have had greater capacity for learning
and behavioral flexibility, meaning that
our ancestors could adapt to a wider
range of situations. And so, human
neuroplasticity likely evolved hundreds
of thousands of years ago. And we can
see it helping us adapt to modern
challenges today. And not just in the
mental maps of cab drivers.
Although rare in prehistory, there
probably were still some instances of
language learning for our ancestors.
When homo sapiens migrated out of Africa
into Europe and Asia, they would have
encountered Neanderals and Dennis so
these species were closely related to
our own, but they had evolved in
isolation for thousands of years and
surely would have had their own ways to
communicate. Our homo sapiens ancestors
therefore would have needed to learn how
to speak with them and vice versa. But
of course, this wouldn't have been
anything like the demand for
bilingualism or multilingualism that the
modern world demands. Our societies are
increasingly global, and switching
between languages is a part of daily
life for more and more people. And
indeed, neuroscientists have started to
see the effects of this in the brains of
children. When researchers scan the
brains of children who speak more than
one language, they often find that
certain regions show greater gray matter
density than in children who grow up
with only one language. Gray matter is
where the brain's processing power is
concentrated. It's made up of densely
packed cells that do the hard work of
thinking, deciding, and remembering. In
bilingual children, this gray matter
appears thicker or more developed. It's
as if the daily effort of choosing the
right language at the right time nudges
these regions to grow a little more, to
wire up a little more efficiently.
And brain plasticity also helps us with
something that would have probably
baffled our very early ancestors.
For most of human history, nobody read
books, scanned text on signs, typed on
keyboards, or scribbled down notes. Like
in many indigenous populations around
the world, stories and knowledge were
carried in voices, gestures, and
memories, not in lines of ink. And so
literacy is a remarkably recent
invention in evolutionary terms. The
oldest known written document ever found
was recovered from the Sumerian city of
Kish in modernday Iraq, dating to the
4th millennium B.CE. And yet in the
modern world, literacy is almost as
essential as knowing how to find food or
shelter once was. The written word is
everywhere and our neuroplasticity has
let us adapt the same neural machinery
that once helped our huntergatherer
ancestors survive to read it. When
neuroscientists compare the brains of
literate and illiterate adults, they can
see clear traces of what it takes to
bolt this new skill onto an old brain.
For it turns out learning to read
systematically reshapes regions in the
vententral visual temporal cortex. As we
practice turning marks on a page into
sounds and meanings, these regions
become finely tuned to letter shapes and
word forms, and their connections with
language areas in the temporal and
frontal loes grow stronger and more
efficient.
And so when we look at mental maps,
written and spoken language, we can see
the plasticity of the human brain
helping us adapt to the modern world.
And when it comes to other challenges
such as facing the general adaptation
syndrome of prolonged strain or dealing
with social groups far above the size of
Dunar's number, there is every chance it
is helping us there as well. But no
studies have yet been undertaken on the
brains of parents that work long hours
at multiple jobs. But from what we have
seen, it seems likely that
neuroplasticity would be at work in
situations like these also. To some
degree, our brain's plasticity is
helping us all adapt to the changes of
the modern world. But of course, we
shouldn't forget the modern world has
also come with a great many benefits.
Average life expectancy has rocketed and
infant mortality has cratered and all
this has been achieved even with the
looming threat of evolutionary
mismatches like diseases of
civilization.
Indeed, despite the strain some modern
inventions can cause, they are at heart
useful situations to problems. An
extension of the very first chopping,
scraping, and pounding stone tools made
millions of years ago. Despite the
mismatches social media can cause, the
ability to find community with the press
of a button can help us fill a social
need that has existed for hundreds of
thousands of years. And so in this sense
there is a complex interplay between the
technology we create and the benefits
and mismatches it presents us. The human
story has been unfolding for millions of
years. A tale of behavioral flexibility
and invention so unique it would come to
test to the very flexibility that made
it all possible.
And so then how would our ancient homo
sapiens fare trying to adapt to our
modern world? It would obviously be
quite a shock both physically and
culturally. But what we do know for sure
is that his brain would make some steps
in trying to adapt to the new tasks, new
ways of thinking. His brain, like ours,
would still have plasticity. It wouldn't
remain the same brain that it existed
100,000 years ago. A few years of new
experiences, and it would be physically
changed forever. But what would happen
if he then returned? Could those changes
be undone?
In the 21st century, we find ourselves
adapting and surviving in a world that
feels as if technology is rapidly
accelerating all around us. Is there any
way that we could go back to a simpler
time?
In 2022, a group of Australian
researchers grew a brain in a petri
dish. Affectionately called dish brain.
It was grown from a cluster of human and
mouse brain cells. The researchers
wanted to see if it could react to
external stimulation and modify its
behavior. And to do this, the team came
up with a test. They taught it to play a
computer game. By wiring up the petri
dish to the game Pong, a 2D tennis-like
game, the researchers taught Dishbrain
where the ball was and rewarded it with
electrical stimulation every time the
ball was hit. Remarkably, it took less
than 5 minutes for the brain cells to
learn what they needed to do. And
Dishbrain quickly began to play the game
on its own. Of course, Dishbrain wasn't
a full brain. It was a cluster of about
a million living neurons on a silicon
electrode array the size of a postage
stamp. But just two centuries after the
industrial revolution, a blink of the
eye in evolutionary terms, such wild
possibilities are becoming reality.
Ancient inventions like the handax or
the spearthrower took thousands of years
to appear in the archaeological record
and then thousands more years to be
replaced by new improved technologies.
Handaxes especially were around for
almost 2 million years before they were
eventually replaced by new kinds of
tools. Modern technologies, however,
change at breakneck pace by comparison.
Indeed, in less than 100 years,
computers have gone from huge, costly
machines that would fill a room to
devices that nearly everyone in the
modern world carries around with them in
their pockets. And so, why does the path
of our invention follow this exponential
shape?
Human
evolution has a very peculiar quirk.
Like other organisms, we evolve
biologically through the gradual process
of natural selection. But we also have a
second kind of evolution, the evolution
of culture. Very few other animals show
anything similar, and none do on the
same scale or with the same complexity
as humans. Chimpanzees, whales, and some
birds pass on local traditions, but
their toolkits and behaviors change at a
glacial pace compared with ours. Human
cultural evolution, by contrast, can
transform how we live within as little
as a generation. New ways of doing
things can spread across continents in
years rather than millennia, and our
descendants inherit not just our genes,
but our languages, technologies, and
institutions.
For decades, researchers puzzled over
the question of why human culture seems
to accumulate and accelerate rather than
simply drifting. And psychologist
Michael Thomas proposed a neat answer
using an idea borrowed from economics.
Back in the 1960s, two British
economists coined the term ratchet
effect to describe how public spending
tended to work after a crisis. They
observed that budgets would rise to meet
the emergency and afterwards they rarely
fell all the way back down. Like a
mechanical ratchet, they clicked up a
new level and stayed there. And so in
the 1990s, Thomas Cello suggested that a
similar ratchet is at work in human
culture. When people invent a new tool,
technique, or an idea, it doesn't simply
vanish when they die. Others copy it,
improve it, and combine it with other
different innovations. Indeed, once a
community has mastered something like
fire making or bronze smelting or the
motor engine, it is very unlikely to
revert permanently to a state where that
knowledge never existed. This means that
each generation starts from the
accumulated achievements of the previous
ones and pushes them a little further.
This works because human cultures are
shared and cumulative. We don't just
learn by trial and error on our own. We
watch, imitate, teach, and correct each
other. Knowledge is stored in stories,
rituals, recipes, blueprints, and now in
vast digital archives. As long as a
community remains connected enough to
pass these things on, culture clicks
forward like a ratchet, making it hard
for our collective knowhow to slip all
the way back to zero.
And some clicks of the ratchet have been
larger than others.
In the late 19th century, people like
Thomas Edison were learning how to
harness the power of electricity to
improve everyday life. And within a few
decades, that mastery of electrons set
the stage for something new. Electronic
computation.
Early machines like Eniac in the 1940s
filled whole rooms and could only be
used by teams of specialists who needed
to rewire computer panels by hand. These
behemoths were essentially giant
calculators built for specific heavyduty
numberc crunching tasks. They were also
surprisingly fragile and eyewateringly
expensive. And yet once they had been
brought into existence, there was no
going back. Just like our ancient
ancestors, learning how to make fire or
inventing a new kind of stone tool, the
ratchet effect took hold and drove
upward progress.
Of
course, it also helps that the modern
world has an order of magnitude more
people in it than the Paleolithic world.
Back then, the entire population of Homo
sapiens probably numbered only in the
low millions at most. For much of the
place, it may have been closer to a few
hundred thousand. Yet today, there are
over 8 billion of us, and that number is
set to increase to 10 billion in the
next few decades. This means there will
not only be more minds available to form
new ideas, but vastly more chances for
those ideas to be developed and
improved. In this sense, human culture
has more hands on it than ever before.
So there's no reason to expect
technology will do anything but continue
to accelerate. The future of humankind,
therefore, will likely be defined by
accelerating, irreversible dependence on
increasingly complex interconnected
systems. And so as human society becomes
more and more dependent on complex
technology, the mismatch between the
stable small band huntergatherer lives
we evolved for and the accelerating
churn of modern existence could grow
much wider in the near future.
As the ancient homo sapiens brought
forward from a 100,000 years ago ages in
our world, he like us would be
confronted with technologies and a
lifestyle that rapidly changes every
decade. And even if he had managed to
partially adapt, there would come a time
when his children would be more suited
to the world. raised around newer
technologies, using them when their
brains are at their most plastic. They
would certainly be better placed to live
and innovate in our modern times.
As digital technology advances, the
stage is now set for the next
generations of inventive human minds to
decide the course of our future. How it
will look is uncertain, but its shape
will be decided by the cumulative work
of our species. And this species, Homo
sapiens, has so far manage to adapt to
anything it has ever faced.
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