How are our brains changing in the Modern Era?
Our brains are changing size and we are getting stupider?
It’s enough to give you a brain-ache. Do any search on the human brain today and there is a lot of contradictory information about what we know about it. Some believe it’s getting larger, others that it’s shrinking. We’re getting more intelligent or getting dumber. What is clear is that we’re not the same animals as our ancestors; the urban ape we are today appears to be changing the physiology of our brains and how we think. Furthermore, it appears technology and culture-shifts are starting to make us think in different ways. When you look at this, it’s not just the perspective of how we have changed on some drawn out evolutionary timescale of tens of thousands of years, there are a host of more immediate environmental factors that are believed to make our brain sizes grow or shrink from the choices we make every day.
What are our brains like? From a psychological perspective, it’s always fascinating to consider the human capacity to think, through the lens of the Triune Brain Hypothesis.
This hypothesis proposed by the neurologist Paul MacLean suggested that the brain structure reflects the evolutionary course of the human psychology from Reptilian, to Paleomammalian to Neomammalian evolutionary phases. Very simply, the reptilian part organises our body’s functions, the limbic, behaviours and emotions; and the neocortext, our learning abilities and capacity for consciousness, imagination and abstract thought. The three parts of this model are interconnected and influence each other.
Why this is interesting psychologically is not limited to the biological formation of our brains from an evolutionary perspective, it’s that this genetic inheritance plays a role on how we think today. The consumer psychologist, Clotaire Rapaille, suggests a lot of shopping decisions are influenced by our reptilian brain that is more compulsive in nature. We might think we think we are making a conscious choice but our reptilian brains are very influential in the background. Parallel to this thinking is the ‘rider and elephant’ metaphor which Johnathon Haidt uses to describe the conscious mind and its ‘divided self’:
‘the division that really matters is between conscious/reasoned processes and automatic/implicit processes. These two parts are like a rider on the back of an elephant. The rider’s inability to control the elephant by force explains many puzzles about our mental life, particularly why we have such trouble with weakness of will. Learning how to train the elephant is the secret of self-improvement’.
The conception of our thinking as a subconscious primordial brain recalcitrant to our conscious thoughts is an interesting one. Raising an important question, why did our brains end up like this?
One of my favourite observations was by Desmond Morris is a reminder that many of our behaviours are driven by our nature – that we are social-apes regardless of how sophisticated we get. So it’s informative to look more deeply at the current thinking on why our brain is the way it is and what insights this might suggest about our current behaviour in culture.
Any discussion of the evolution of the primate brain is one of those areas where there are competing hypothesis, overlapping facts and theories and some degree of academic imagination. While you can establish a picture, it’s likely that many of these factors were simultaneously at play and there was no one driver of our unique brains. But we can start with what makes us different to other mammals.
Is bigger always better?
Hominids had their biggest brains around 20,000 to 30,000 years ago
The Homo sapiens with the biggest brains lived 20,000 to 30,000 years ago in Europe. Called the Cro-Magnons, they had barrel chests and huge, jutting jaws with enormous teeth. Consequently, their large brains have often been attributed to brawniness rather than brilliance. In support of that claim, one widely cited study found that the ratio of brain volume to body mass—commonly referred to as the encephalization quotient, or EQ—was the same for Cro-Magnons as it is for us.
The studies in this field present many different theories as to what caused the spectacular change in brain size of the early primates. Moving into this discussion, we have to accept that these theories are still being evaluated and hypothesis tested:
The process by which some species evolved larger brains – called encephalization – is not well understood by scientists. The puzzle is made more complex because evolving large brains comes at a very high cost
The high cost is that mammalian species tend to have large brains when compared to their body size and the energy required to power our minds is proportionally high.
Large brains are characteristic of most mammals; it’s not exclusive to primates. If we go back to the first mammals in the evolutionary record, it has been suggested that the development of the neocortex, the outer layer of cerebral hemispheres participates in ‘higher functions like sensory perception, refined motor coordination and language’. In looking at the early Mammals that evolved roughly 200 million years ago, it has been found the brain of the mouse-sized Morganucodon had a brain 50% bigger than early Triassic reptiles.
This size expansion is mainly driven by the enlargement of the olfactory bulb and olfactory cortex, which are both involved in the sense of smell. The rest of the brain also changed; the cortex and the cerebellum increased in size, making the brain closer in appearance to those of modern mammals than it was to reptiles.
Mammals smelt their way to a larger brain.
The human brain does not have the same olfactory abilities of many other mammals, our brain evolved in very different ways.
The rapidly increasing brain size was a key feature that set humans apart from the walking apes that lived before 2.5 million years ago. Since then our brains have trebled in volume. This increase was not gradual and steady: most of it came as a doubling of volume in Homo erectus 2 million years ago. In other words, the greatest acceleration in relative brain size occurred before 1.5 million years ago, rather early in our genus, and then gradually slowed down. The paradox is that our apparent behavioural explosion is mostly recent and is accelerating.
However, before we discuss how our brains evolved, we need to recognise that the energy needs of the brain are relatively enormous. This is the high cost of this evolution. The human brain accounts for 20% of the calories we eat, it only represents 2% of your body’s weight, needs 20% of your oxygen supply and 20% of your blood flow. Our big brains are high maintenance organs.
What fueled this increase? Richard Wrangham has linked the invention of the ‘BBQ’ or cooked food to the rapid increase in the early hominid brain. He has found evidence that around 1.9 million years ago, there was a corresponding shrinking of gastrointestinal organs and an increase in brain size. ‘Cooking makes both plants and meat softer and easier to chew, providing more calories with less effort.’ Cooking allowed for easier calories to fuel brain size expansion, also meaning that we didn’t need the same size of gastrointestinal organs.
An alternative theory is the shore-based diet, suggesting that fish were essential to early hominid development.
In particular, two fatty acids — docosahexaenic acid (DHA) and arachidonic acid (AA) — make up almost 60 per cent of the brain’s structural material, the former being vital for the development of neuron membranes, the latter for the construction of blood vessels in the brain…. In effect, our access to seafood created a biological loop. We ate more and more seafood, got smarter, and thought up ever more cunning ways to obtain seafood.
Although, this role of meat as a primary driver of brain growth has been challenged, in that neurons run on glucose not the calories of meat to be powered, suggesting it was our love of high-protein foods such as nuts, roots and tubers, and potatoes that lead to our larger brains. Without wanting to get too bogged down in contemporary Paleo/Vegan discussions; from the paleontological record, Paranthropus boisei a hominid ancestor of approximately 2 million years ago, was believed to have doubled its brain size and it was the teeth that suggested it was a specialist vegetarian grinder. Although, a mixed omnivore diet might link into the shore-based hypothesis. However, as Stephen Oppenheimer raises the question that if meat alone = bigger brain, why didn’t other predators evolve the same? There must have been other factors at work.
A Sea Change?
A frequent hypothesis is that climate change and the ability to adapt to these new environments was a driving factor behind the success of a smarter ape. More generally, brain size predicts the success of mammal species when they are introduced into novel environments.
Large brains, relative to body size, can confer advantages to individuals in the form of behavioural flexibility. Such enhanced behavioural flexibility is predicted to carry fitness benefits to individuals facing novel or altered environmental conditions, a theory known as the brain size-environmental change hypothesis.
As a result, it has been suggested that large-brained mammals live longer making for a more successful species. One possible advantage is facilitating the construction of behavioural responses to unusual, novel or complex socio-ecological challenges. There is also evidence that just living in a more complex environment, makes a brain larger. Gerald Crabtree, of East Africa has suggested that
Life on the veldt was tough, and prehistoric humans’ genes were constantly subjected to selective pressure in an environment where the species’ survival depended on it. For humans, that meant getting smarter.
It is believed that movement of the early primates away from the cradle-of-humanity in East Africa might have been prompted by climate change. The ecology hypothesis states that as our ancestors migrated away from the equator, they encountered environmental changes, such as less food and other resources. A benefit of moving into colder climates is this reduced the body’s exposure to parasites that use up calories in the body’s defense.
A more nomadic and increasingly peripatetic ape also suggests other impacts on our evolution. There are links between our shift to bipedalism and Brain Size. Our brain development and the ability to walk upright have been linked – this need to walk facilitating our exploration of better quality foods:
One of the advantages of bipedalism is the freeing up of the hands to produce more technologically advanced stone tools which may have led to a better diet that affected brain size.
Perhaps related to our development as upright walkers,Dr David Robinson believes there is a link between brain and pelvis
Reasoning from the shape of his pelvis suggested that the female would have had a small birth canal which would have limited the brain size of an infant. The brain size – and hence head size – of modern humans is only just narrower than the birth canal, so it is a reasonable assumption that pelvis size and brain development are linked: one can’t increase without the other
The Bigger the brain, the smaller the talk
Gossip is the art of saying nothing in a way that leaves practically nothing unsaid.
If you felt the urge to read any of these it’s not your fault, blame your inner-monkey.
Of course, our ancestors were social apes and a frequent theory about the growth of the human mind has been the connection to our ability to think abstractly, be self-conscious and communicate with language. A current hypothesis is that a driver of our brain’s growth was to facilitate our ability to gossip better. While we have a certain perspective on ‘gossips’ as a type of person, gossip is a useful social function in bonding group members together . Gossip allows for relative social comparisons to be made between different group members within the group dynamic. We might talk metaphorically of being ‘top dog’ or at the top of the ‘pecking order’; but society is still very status driven in the desire to be King Kong.
This reflects what Ralph Adolph calls the:
“Complex and dynamic interplay between two opposing factors: on the one hand, groups can provide better security from predators, better mate choice and more reliable food; on the other hand, mates and food are available also to competitors from within the group.” You’re part of a team, but you’re competing with team members. Your teammates hope you’ll contribute skills and intergroup competitive spirit — without, however, offering too much competition within the group, or at least not cheating when you do. So, even if they like you, they constantly assess your trustworthiness. They know you can’t afford not to compete, and they worry you might do it sneakily.
David Geary, in an interview, speaks more generally about the need for social intelligence as a competitive advantage, when resources are competitive, that would have driven brain growth
Finally, other researchers think that social competition for scarce resources influenced brain size. As populations grow, more people are contesting for the same number of resources, the thinking goes. Those with a higher social status, who are “a little bit smarter than other folks” will have more access to food and other goods, and their offspring will have a higher chance of survival, Geary said. Those who are not as socially adept will die off, pushing up the average social “fitness” of the group. “It’s that type of process, that competition within a species, for status, for control of resources, that cycles over and over again through multiple generations, that is a process that could easily explain a very, very rapid increase in brain size,” Geary said.
This has also been called the Social Brain Hypothesis or Machiavellian Intelligence hypothesis. This argues that the cognitive demands of living in complexly bonded social groups result in increases of the neocortex part of the brain.
This is why it still impacts on us today
Our modern-day infatuation with celebrities reveals the ancient evolutionary psychology of gossip in sharp relief: anyone whom we see that often and know that well becomes socially important to us.
Neil Bearden warns that the human brain is too weak for gossip, from a contemporary psychology perspective
To begin with, when we encounter new information, there is good evidence that our mind’s default mode is first to assume it is true. Only when the receiver has sufficient motivation and time to reflect on the information, will it potentially be tagged in the memory as false. Until then it’s stored as if it were true. With gossip, that’s clearly dangerous.
This social aspect to the brain has been looked at from other perspectives, Robin Dunbar, et al (2012) have been able to link brain size with how good you are at maintaining your friendships. They link the size of the prefrontal cortex with a person’s skills at ‘mind reading’, understanding what others are thinking.
If we are socially connected, we tend to have larger brains than those that don’t Scientists have found a direct link between the number of “friends” a person has on Facebook and the size of certain brain regions, raising the possibility that using online social networks might change our brains.
If we’re evolving, why are our brains shrinking?
As we’ve been discussing, human brains expanded roughly by half between Homo erectus and modern Homo sapiens sapiens.
It’s hard to shake the norm that bigger is better; recent thinking in the area suggests that they are now shrinking in the relatively modern era.
“Over the past 20,000 years, the average volume of the human male brain has decreased from 1,500 cubic centimetres to 1,350 cc, losing a chunk the size of a tennis ball. The female brain has shrunk by about the same proportion. “I’d call that major downsizing in an evolutionary eyeblink,” (John Hawks) says. “This happened in China, Europe, Africa—everywhere we look.” If our brain keeps dwindling at that rate over the next 20,000 years, it will start to approach the size of that found in Homo erectus, a relative that lived half a million years ago and had a brain volume of only 1,100 cc.
While it’s getting smaller there is evidence this might be euphemistically called a refinement:
Recent studies of human fossils suggest the brain shrank more quickly than the body in near-modern times. More important, analysis of the genome casts doubt on the notion that modern humans are simply daintier but otherwise identical versions of our ancestors, right down to how we think and feel. Over the very period that the brain shrank, our DNA accumulated numerous adaptive mutations related to brain development and neurotransmitter systems—an indication that even as the organ got smaller, its inner workings changed. The impact of these mutations remains uncertain, but many scientists say it is plausible that our temperament or reasoning abilities shifted as a result.
The correlation of brain size and intelligence has been questioned more broadly in the animal world. Simply, elephants and whales have larger brains than us so why are they not more intelligent? Brain size is linked to muscle mass not intelligence.
“Stupid is as stupid does” – Forrest Gump
Don’t panic! Our brains are shrinking and we are getting more stupid?
It has been suggested that the relatively cushy life of a post-agricultural world has removed some of the challenges that early man faced. This has weakened natural selections ability to prune mutations associated with deficiencies in intelligence and emotions over the last 3000 years.
Gerald Crabtree suggests that evolution is, in fact, making us dumber — and that human intelligence may have actually peaked before our hunter-gatherer predecessors left Africa.
The reason? Life on the veldt was tough, and prehistoric humans’ genes were constantly subjected to selective pressure in an environment where the species’ survival depended on it. For humans, that meant getting smarter. “The development of our intellectual abilities and the optimization of thousands of intelligence genes probably occurred in relatively non-verbal, dispersed groups of peoples before our ancestors emerged from Africa”
Of course, the challenge to this is the Flynn Effect. In the 1980’s, James Flynn noticed a strange trend over the last century; in every industrialized nation the average IQ scores were rising about 3 points a decade. The answer to this appears to be a socio-cultural influences on the IQ measurement – how we think through education is impacting on average scores.
The Flynn effect does not reflect gains in general intelligence, it reflects a shift to more abstract thinking brought about by a changing social environment. We aren’t getting smarter; we are getting more modern.
Although, contrary to this, other studies using IQ measures believe that our generation are not as intelligent as the Victorians . This raises the usual raft of questions as to the merits alone of an IQ measurement in this area.
This doesn’t close the loop on why we developed bigger brains than we need; John Skoyles believes the answer might lie in the nature of the IQ test:
Why did evolution increase brain size (with its associated costs) when humans (as these individuals demonstrate) can have normal IQ without bigger brains? I propose that the advantage may be related to increased capacity for an aspect of intelligent behaviour not measured by IQ tests but critical to the survival of our simple hunter-gatherers ancestors: the capacity to develop expertise.
This would explain why the environmental challenges caused a change in diet; that a moving more tightly social ape might develop the need to communicate better. While we are getting dumber in one sense, we are changing our minds in a more modern world that is different in intelligence from our ancestors.
In the Modern world, what influences brain size?
There are a range of different lifestyle influences that impact on the modern human’s brain size on a day –to-day basis.
Socially, the role of gossip has been discussed above. Also, that people’s ability to make and keep friends appears to be influenced by brain size or the size of specific regions of the brain. If we think of the discussion of gossip in creating group dynamics, it’s interesting that a study linked those that are altruistic and involved in well-being are more likely to have larger brains. Different personality types have been linked to brain size that also fit into this context.
Not surprisingly, with food as a driver of our psychological evolution, how and what we eat has a big impact on brain size. If we over-indulge, this reduces our brain size ‘Obesity can cause a clear and distinct reduction in brain size without additional contributing factors.’ . The reverse appears to be true as well, with eating disorders like Anorexia nervosa linked to an enlargement of ‘left orbitofrontal, right insular, and bilateral temporal cortex grey matter’ which is associated with a decline in ‘sweet tastes’. Unhealthier diets might impact as well, e.g. diets of saturated fat and high cholesterol have been linked to negative impacts on memory.
Other vices appear to impact on brain volume as well. People that are attached to pornography tend to have smaller brains. The consumption of alcohol is also linked to consistent declines in brain volume.
Some environmental factors such as living in urban areas might be detrimental as well. With air pollution like smog being linked to declines in cognition.
But we can also proactively counter these effects by walking; just one year of walking three times a week can increase the size of the hippocampus, a part of the brain that is key to memory. You can also play video games ‘Video gaming causes increases in the brain regions responsible for spatial orientation, memory formation and strategic planning as well as fine motor skills.’ Playing or learning musical instruments has also been shown to to have a positive impact on the brain.
One thing we can’t really halt is the mortal coil and there are declines in cognitive ability as we age: ‘A small decline in brain volume, 2 percent a decade, is a natural part of aging’
Perhaps the interesting thoughts for any study of contemporary culture is whether the adversity and technological changes of the last 100 years are impacting on our brain structures. Just as much as being forced out of East Africa from climate change was influential 2 million years ago, we’re in a world where there are different expectations in how we think. That video games can change your brain volume hint at the role technology might have moving forward. A consideration is suggested by Gerald Crabtree that as we became more civilized we have favoured peoples that are smarter, the dullards or even aggressive people were ‘weeded out’. This is a kind of self-domenstication, much like our long partnerships with wolves that become dogs. What will future generations of human brains be like when we increasingly favour creativity and abstract thinking? The broader impact of the culture trajectory on social and individual intelligence and thinking is a topic for an upcoming post.