Dehumanization: Shrinking Brain and Hippocampus

Yuri Barzov
Apr 17, 2018 · 9 min read

My first post about dehumanization was not dramatic enough. Let’s add some drama.

Human brain grew for two million years

In 2009 in the study Hominid Brain Evolution published in Human Nature authors Drew Bailey and David Geary from the University of Missouri-Columbia announced that during the period from 1.9 million years to 10 000 years ago the size of human brain grew almost three fold. They tested three hypotheses of the reason for such a huge increase of the brain volume in an evolutionarily very limited period of time. Their findings suggested human brain size increased so rapidly because of growing intensity of social interactions.

“Our findings suggest brain size increases the most in areas with larger populations and this almost certainly increased the intensity of social competition,” cited Phys.org David Geary, Curator’s Professor and Thomas Jefferson Professor of Psychosocial Sciences in the MU College of Arts and Science. “When humans had to compete for necessities and social status, which allowed better access to these necessities, bigger brains provided an advantage.”

The last 10 000 years tell another story.

Lately human brain is shrinking really fast

‘’I’d call that a major downsizing in an evolutionary eye blink,’’ Dr John Hawks, of the University of Michigan, told Discover magazine. In 2010 he completed a measurement study of fossil skulls found in Europe, the Middle East and Asia.

The Cro-Magnons, who left cave paintings of large animals in the monumental Lascaux cave more than 17,000 years ago, were the Homo sapiens with the biggest brain. The average size brain of modern humans, homo sapiens, has decreased about 10 percent, the size of a tennis ball, during that period, from 1500 to 1359 cubic centimetres. Women’s brains, which are smaller on average than those of men, have experienced an equivalent drop in size.

The downsizing of human brains took science by surprise. The results of John Hawks were many times reproduced however. In 2011 at Britain’s Royal Society, Dr. Marta Lahr from Cambridge University’s Leverhulme Centre for Human Evolutionary Studies presented her findings that the height and brain size of modern-day humans is shrinking.

Different explanations emeged. John Hawks himself attributed the shrinkage of brain to its improved energy efficiency. David Geary and his collegue claimed that as complex societies emerged, the brain became smaller because people did not have to be as smart to stay alive.

The study, published in 2012 in the journal Trends in Genetics, argued that humans lost the evolutionary pressure to be smart once we started living in dense agricultural settlements several thousand years ago. “A hunter-gatherer who did not correctly conceive a solution to providing food or shelter probably died, along with his/her progeny, whereas a modern Wall Street executive that made a similar conceptual mistake would receive a substantial bonus and be a more attractive mate. Clearly, extreme selection is a thing of the past,” study author Gerald Crabtree, a researcher at Stanford University, wrote.

A group of Chinese scientists reproduced the results of John Hawks in 2014 and argued “that these changes can be caused by random genetic mutation and epigenetic change in response to changes in the environment.”

Animal Farm: are we livestock?

For Bruce Hood, the author of The Domesticated Brain and a psychologist at the University of Bristol, UK, the shrinkage is best explained by changes in society. “We have been self-domesticating through the invention of culture and practices that ensure that we can live together,” he writes. Our brains, he believes, are getting downsized by domesticity. Domestication tends to have that effect. According to Hood, every species that has been domesticated by humans has lost brain capacity as a result. If we recall that slavery was abolished by civilised nations only 150–200 years ago domestication appears as a viable hypothesis.

Richard Wrangham, a primatologist at Harvard University, supports Hood’s view. According to him, some 30 animals have been domesticated and in the process every one of them has lost 10 to 15 percent of brain volume.

When you select against aggression, you get some surprising traits that come along with it,” Wrangham says. “My suspicion is that the easiest way for natural selection to reduce aggressiveness is to favor those individuals whose brains develop relatively slowly in relation to their bodies.”

Smaller means smarter?

John Hawks believes that “a brain that yields the most intelligence for the least energy” could develop as a result of several very favourable mutations, which were, however, not likely to happen in so short period of time. He speculates that maybe the boom in growth of human population between 20 000 and 10 000 years ago somehow facilitated such mutations.

“As to why is it shrinking, perhaps in big societies, as opposed to hunter-gatherer lifestyles, we can rely on other people for more things, can specialize our behavior to a greater extent, and maybe not need our brains as much,” he also pointed out the importance of environmental changes.

Some anthropologists were suggesting that our shrinking brain is actually getting smarter due to higher connectivity or better computational locality.

Hawks noted fluctations in the pace of decline. Anthropologist Richard Jantz of the University of Tennessee measured the craniums of Americans of European and African descent from colonial times up to the late 20th century and found that brain volume was moving upward for the last 150 years. Hawks says the explanation of the last short fluctation is “mostly nutrition.”

We adapt to artificial environment

It looks like the vast majority of scientists who were actually involved in relevant research come to a conclusion that in one way or the other the shrinkage of the brain is caused by our adaptation to artificial environment. Artificial environment that began to rapidly emerge and shift the balance between brainy exploration and habitual exploitation towards the later about the same time when our brains began to shrink is a viable explanation of the phenomena.

In a study published in 2015, Researchers at the George Washington University discovered that human brains exhibit more plasticity, propensity to be modeled by the environment, than chimpanzee brains and that this may have accounted for part of human evolution.

“We found that the anatomy of the chimpanzee brain is more strongly controlled by genes than that of human brains, suggesting that the human brain is extensively shaped by its environment no matter its genetics,” said Aida Gómez-Robles, postdoctoral scientist at the GW Center for the Advanced Study of Human Paleobiology and lead author on the paper. “So while genetics determined human and chimpanzee brain size, it isn’t as much of a factor for human cerebral organization as it is for chimpanzees. The human brain appears to be much more responsive to environmental influences. It’s something that facilitates the constant adaptation of the human brain and behavior to the changing environment, which includes our social and cultural context.”

Hippocampus is shrinking in our heads

Today our hippocampus is shrinking with the growth of experience across our lifespan because we more and more heavily rely on habits, on one hand, and don’t feed hippocampus with a sufficient workload of prediction errors, on the other. Without such a workload our brain remains in an energy saving mode for too long and our hippocampus loses gray matter.

Some scientists continue to believe that the shrinkage of hippocampus and cortical areas connected to it is induced by age, but comparative studies of humans and chimpanzees suggest that the cause of shrinkage is in the environment and lifestyle. They clearly demonstrate that only human hippocampus shrinks dramatically over time while chimpanzees’ hippocampus retains its volume across the entire lifespan.

Shrinkage of hippocampus impairs major cognitive functions

I tried to describe the major cognitive functions of hippocampus in this post.

Let researchers from Universities of Illinois and Iowa, and Duke University provide a brief outline of what hippocampus means for our cognition. “Here, we propose that the hippocampus also plays a critical role by forming and reconstructing relational memory representations that underlie flexible cognition and social behavior. There is mounting evidence that damage to the hippocampus can produce inflexible and maladaptive behavior when such behavior places high demands on the generation, recombination, and flexible use of information. This is seen in abilities as diverse as memory, navigation, exploration, imagination, creativity, decision-making, character judgments, establishing and maintaining social bonds, empathy, social discourse, and language use. Thus, the hippocampus, together with its extensive interconnections with other neural systems, supports the flexible use of information in general,” they stated in a paper published in Frontiers of Human Neuroscience in 2014.

Atrophy of hippocampus is linked to many diseases

A wide array of psychiatric and neurodegenerative disorders is linked to hippocampus, a thumb sized curved single layer of neurons at the root of cortex, that some scientists call the heart of the brain. I mentioned below only one research paper on the link of hippocampus to each of them from dozens existing.

Alzheimer’s disease. Among many other studies findings of a group of researchers from Zhejiang University, Hangzhou, China “provide evidence of a close relationship between hippocampal volume and cognitive performances in patients with AD and aMCI, both at baseline and over follow‐up.”

Autism. In the paper published in Journal of Abnormal Psychology in 2017 a group of researchers from the City University of London pointed out that their “observations implicate atypical hippocampal functioning as the source of structural learning difficulties in ASD.”

Bipolar. Volume reduction and shape abnormality of the hippocampus was associated with bipolar disorder by a group of researchers from the University of Texas as described in their paper published in Molecular Psychiatry.

Depression. “Reduced hippocampal volumes are probably the most frequently reported structural neuroimaging finding associated with major depressive disorder (MDD),” researchers from the University of Münster, Germany state in their paper in Neuropsychopharmacology journal.

Schizophrenia. Results of a study presented in Neurology of Disease by a group of researchers from UCLA and the University of Helsinki suggest that hippocampal volume reduction may be a trait marker for identifying individuals possessing a genetic predisposition for schizophrenia.

Hippocampus is a very sensitive and very dynamic area of the brain. The artificial environment that protects us from surprise (unexpected uncertainty) severely damages it.

Is idiocracy our future?

Maybe the current shrinkage of hippocampus has nothing to do with the overall shrinkage of human brain over the last 10 00 years but the cause of both processes appears to be very similar. There is no pressure of natural selection for retaining the current volume of human hippocampus.

However, the process of hippocampal shrinkage is reversible. For instance, researchers from the University of Montreal demonstrated that playing Super Mario 64 increases hippocampal grey matter in older adults. There are studies which link increase of hippocampus in adult brain to physical exercise.

We can protect hippocampus from shrinking and even make it grow with the change of the environment and in particular with enriching it with surprise because surprise turns on the most intensive and rewarding learning mode of hippocampus. It is highly unlikely, however, that modern humans will agree to change their current stable and predictable environment to the life of their savage ancestors full of dangerous surprises.

The problem is that while our hippocampus is starving on a surprise-free and low-dopamine diet we don’t consciously feel it. We enjoy video games which all require developing skills and gaining experience for winning. We can’t consciously comprehend that we may enjoy a detection of a prediction error more than even making the right prediction.

Maybe the human exemptionalism bias is to blame? “The artificial environment humans have created ever since the development of agriculture about 12,000 years ago has promoted an increasingly exemptionalist mind-set. We have excluded ourselves psychologically, physically, and emotionally from nature,” Simon Hoyte, a PhD researcher at University College London, wrote in his guest post in Nature in 2015.

It will be too dystopian to think that the modern successors of those people who once domesticated the rest of the humankind as their slaves are simply not willing to allow people to regain their cognitive power that will be equal to freeing them. Or will it be?

AI can save human intelligence

The solution can be to create compelling artificial virtual environments which will generate surprise but without dangers which it might induce in real life situations. For instance, neuroscientists are already using six-arm restless bandit problem from probability theory to design experiments which create unexpected uncertainty for human participants. We can use machine learning algorithms to power artificial agents and the environment, which will generate authentic surprise for players. In PvP format players will become sources of unexpected uncertainty (surprise) for each other under AI guidance.

Can there be a way out? I hope, there is, but it’s another story.

Yuri Barzov

Written by

Curious about life and intelligence

Welcome to a place where words matter. On Medium, smart voices and original ideas take center stage - with no ads in sight. Watch
Follow all the topics you care about, and we’ll deliver the best stories for you to your homepage and inbox. Explore
Get unlimited access to the best stories on Medium — and support writers while you’re at it. Just $5/month. Upgrade