Ground Zero: Dehumanization

Yuri Barzov
28 min readDec 30, 2020

Shrinking Brain, Hippocampus, Cognitive Maps and Objective Reality

Photo by Gerd Altmann

Welcome to the Jungle!

It is impossible to find a reliable source of accurate information in the information jungle. The number of sources grows exponentially. Their reliability decreases at approximately the same speed. The only solution remains to independently verify the accuracy of all information received from any source irrespectively of how reliable that source was in the past.

Imagine that the labels with expiry dates on all the products in the supermarket are mixed up. We’ll need to learn how to determine the freshness of food ourselves, so as not to die of hunger and not get poisoned by rotten food.

Verification of information should become as standard a procedure as brushing your teeth. It is good that our brain does not suffer, but, on the contrary, benefits from such additional activity. Navigation through the information jungle is the simplest and most accessible training of the hippocampus — the heart of the brain — responsible for the creation of the objective reality in our heads.

This book is written with the intention to make you wonder so that you will begin looking for answers and finding them driven only by your curiosity. It will not be guiding you through the information jungle but would rather make you curious to seek your own path. A good old tool of dead reckoning will be at your disposal together with the most magnificent GPS in the universe — your brain.

Hundreds of thousands or maybe even millions of years ago hominids who later became our ancestors found a way to collectively navigate the uncertainty of the real jungle. They evolved to be human in the midst of savagery and laid down the foundation for the unparalleled achievements of humankind.

Now we are in the jungle again. In response to the wild uncertainty of the information jungle, we can either become savage again or re-evolve as humans.

This book is based on a single bold assumption that our brain creates regularities and makes us apply them to the totally unstructured data derived from our sensory fields. We name objective reality the most comprehensive spatially arranged collection of those regularities which produce expected changes in our sensory fields.

To put it even shorter, objective reality is a cognitive map. Humans have the broadest cognitive map of objective reality among all living creatures. It enables us to penetrate the chaos of sensory fields for a maximum temporal depth. Because of that we can predict and prevent most errors before they occur.

Our broadest cognitive map makes us thrive not just survive. The problem is that all cognitive maps are currently shrinking in our heads with an increasing speed. Fortunately, we have the natural intelligence to overcome the shrinkage of reality. From this book, you’ll learn how to consciously use this intelligence, the most primitive, on the one hand, and the most essential, on the other.

This book will put your brain at work in a way that has been almost totally abandoned by modern humans. It is not leisure reading. Initially, you will begin to feel tired very quickly. It’s hard to focus your attention on hidden regularities when your brain is continuously bombarded by the natural chaos of sensations, on the one hand, and by the artificial noise produced by attention-harvesters, on the other.

Yet if you will manage to keep your attention long enough focused on the wonderful things that the book is telling you about, you’ll begin to experience a steady and strong feeling of joy rising in your soul like an ocean tide.

Chapter One. The Miracle

In this chapter, we will learn that the brains of our ancestors were growing very rapidly for three million years, most probably for the reason that expansion of the surface area of the cerebral cortex locked into a positive feedback loop with the cultural evolution of the human species.

About three million years ago the brains of some hominid species began to gain volume much faster than the brains of all mammals including other primates. Since then those hominids had become human species and had tripled the size of their brains that became over six times larger than the brains of any other mammals of similar body size.

Even more importantly, the volume of their brains increased mostly due to the growth of their cortex, a many times folded thin and smooth layer of grey matter consisting of neurons, the brain cells with which we think.

Furthermore, the folding of the cortex had increased beyond the limits set forth by euclidean geometry. If we would take the brains of a mouse and increase them up to the volume of the human brains we would expect the surface area of the cortex to become 480 square centimeters following the rule of geometric similarity. However, the surface area of the human cortex is four times larger, 2000 square centimeters.

It isn’t by accident that the cerebral cortex resembles a crumpled paper ball. When the cortex is folding in a growing skull it follows the same seemingly random pattern as a crumpled sheet of paper when we are filling a glass with it. A fractal structure emerges that makes it possible to accommodate more cortical surface area into the skull. The bigger is the volume of the cerebral cortex the more folded its surface becomes.

A pathological decrease in cortical volume and folding leads to intellectual disability. Therefore there is a threshold in the size of the brain that defines human intelligence. We became human because of the unprecedented growth of cortical volume and cortical folding of the brains of our ancestors. The expansion of the surface area of the cerebral cortex enabled distinctively human broad cognitive maps to emerge.

Many theories have been proposed to explain the miracle of brain growth. Unfortunately, any theory about the events that took place millions of years ago can’t be conclusively proven.

The three most common hypotheses are climate change, ecological demands, and social competition. Anthropologist Drew Bailey and cognitive scientist David Geary from the University of Missouri-Columbia in the USA analyzed data on 153 hominid skulls over the past two million years testing the feasibility of each hypothesis. They found out a clear correlation between population density and the size of skulls. The denser the population was the larger skulls it had. They also established a less clear correlation between the growth of the skull size and climate change.

A team of researchers from the School of Biology, the University of St Andrews in the UK proposed a model based on the metabolic cost of having larger brains. According to their model, the growth of the human brain was driven by “a combination of 60% ecological, 30% cooperative, and 10% between-group competitive challenges”.

The importance of between-group cooperation and competition was also emphasized in the research of Robert Boyd and Peter J. Richerson from the University of California in the USA. They coined the term cumulative cultural evolution to underline the non-genetic nature of the adaptation that human ancestors went through using winnerless competition for better adaptive solutions between groups of strangers that were connecting and disconnecting frequently but randomly.

Also writing about cultural evolution, the father of modern anthropology Claude Levi-Strauss strongly underlined the special nature of such brain and cognitive map expansion driving winnerless competition. In the essay Race and Culture he wrote, “The great creative eras were those in which communication had become adequate for mutual stimulation by remote partners, yet was not so frequent or so rapid as to endanger the indispensable obstacles between individuals and groups or to reduce them to the point where overly facile exchanges might equalize and nullify their diversity.”

Indeed, the value of receiving the information that you already know is zero. The value of information that you can’t understand is also zero. Cultural evolution and winnerless competition lay in between. A bigger brain and wider cognitive map scale up the volume of information that you don’t know but can understand.

You will meet the term winnerless competition in the section dealing with the mathematical modeling of the natural learning process. The universality of some simple but deep ideas is stunning.


The brains of our ancestors began to rapidly increase about three million years ago. Since then and until about ten thousand years ago the unprecedented growth continued. Humans needed wider contacts with stranger clans to gain access to information they didn’t know. The brain capacity to carry wide cognitive maps was required to be in accord with strangers and to understand dissenting knowledge that strangers possess. In the face of frequent and severe environmental fluctuations, cumulative cultural evolution became the crucial condition for the survival of the human species and stimulated individual brains to grow.


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Chapter Two. The Grand Reversal

In this chapter, we will discover that an abrupt reversal in the direction of the change in the human brain’s volume took place about ten thousand years ago and will search for its cause.

After three million years of growth, the miracle vanished in the blink of an evolutionary eye. Measurements of fossil skulls from all inhabited continents clearly show that our brains have become about 10% smaller in the past 10,000 years.

‘’I’d call that a major downsizing in an evolutionary eye-blink,’’ says John Hawks, an associate professor of anthropology at the University of Wisconsin–Madison who completed in 2010 the most comprehensive measurement study of fossil skulls found in Europe, the Middle East, and Asia.

According to his findings, Cro-Magnons were Homo sapiens with the largest brains. The average size brain of modern men has decreased from 1500 to 1359 cubic centimeters, the size of a tennis ball since Cro-Magnons left cave paintings of large animals in the Lascaux cave some 17,000 years ago. Women’s brains, which are smaller on average than those of men, have experienced an equivalent drop in size.

The downsizing of human brains reported by Hawks didn’t take scientists by surprise. It was a well-known secret in anthropology for quite a while. As early as 1988 Maciej Henninberg collected in a uniform way craniometric data on approximately 9,500 individual male crania and 3,300 female. His research showed a decrease in cranium volume of 157 cubic centimeters (9.9%) in males and 261 cubic centimeters (17.4%) in females over the last 10–20 thousand years. The decrease has been “smooth, statistically significant and inversely exponential”.

Scientists had quickly and commonly accepted the idea that the shrinking of brain volume occurred as a result of the decrease of the body mass of humans that took place during the same time period. It was hard to absorb the idea that the brain volume that was considered to be the most significant indicator of intelligence in human evolution over millions of years suddenly stopped working during the period of the highest intellectual achievements of the human species.

However, by combining anthropology and genetics Hawks had conclusively proved that the body mass decrease was by far not sufficient enough to justify such a huge shrinkage of brains. A new explanation was required.

Hawks speculated that a smaller “brain that yields the most intelligence for the least energy” could develop as a result of several very favorable mutations. Maybe the boom in the growth of the human population between 20 000 and 10 000 years ago could somehow facilitate such mutations, however, they were not likely to happen in such a short period of time.

Therefore, Hawks also speculated that: “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.”

Bruce Hood, the author of The Domesticated Brain and a psychologist at the University of Bristol, UK, explains the shrinkage by self-domestication of humans. Every species that has been domesticated by humans has lost brain capacity as a result.

Richard Wrangham, a primatologist at Harvard University, supports Hood’s view because, according to him, every one of about 30 animals domesticated by humans has lost 10 to 15 percent of brain volume in the process.

“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.”

David Geary, a cognitive scientist mentioned in the previous chapter who conducted the research on the reasons for the unprecedented increase of the volume of human brains from 3 million to 10 thousand years ago, puts his view on the reasons for the brain shrinkage very baldly. “You may not want to hear this,” he said to Discover magazine, “but I think the best explanation for the decline in our brain size is the idiocracy theory.”

In his research, he came across a surprising observation. When the population was sparse, the cranium was getting bigger along with the growth of the population density. But when the population density had reached a particular threshold, cranial size began to decline with the further population density growth.

According to Geary, the average brain became smaller because people did not have to be as smart to stay alive and they could survive with the help of others. He warns about the misunderstanding that can arise from the fact that modern humans know much more than our more brainy ancestors. “Practically speaking our ancestors were not our intellectual or creative equals because they lacked the same kind of cultural support,” but in terms of raw natural intelligence they were “as bright as today’s brightest.”

Some scientists also claim that mutations in the human genome indeed took place very rapidly over the last ten thousand years but they weren’t necessarily positive for human intelligence.

“Analysis of human mutation rates and the number of genes required for human intellectual and emotional fitness indicates that we are almost certainly losing these abilities”, says Gerald Crabtree, a professor of developmental biology at Stanford University, “the recent sequencing of 6515 human genomes and the discovery that most predicted deleterious human mutations appeared within the past 5000–10 000 years, corresponding to the transition from the dispersed hunter-gatherer lifestyle to the agriculture-based, high-density lifestyle. This is what I predicted, but I did not expect to see the evidence appear so soon. The transition to the agricultural-based high-density lifestyle appears to have led to relaxation of selection and the accumulation of deleterious mutations in the human genome, along with population expansion.”

“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,” Crabtree commented to his research published in 2012.

A team of researchers from the University of California, Irvine, USA, and the University of Queensland, Australia provided in 2018 some evidence supporting Crabtree’s conclusion. Researchers utilized in their study a set of genetic and phenotypic data of half a million Britons to demonstrate that direct and stabilizing selection in modern humans is going on in favor of a bigger body mass index and against higher fluid intelligence index and educational attainment.

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

As compared to agricultural settlers hunter-gatherers needed much larger territory and much better knowledge of plants and animals inhabiting it in order to support themselves. That striking difference between the two ways of living was observed by scientists as late as in the Twentieth century.

Claude Levi-Strauss cited in his book The Savage Mind the following observation of a biologist on pygmies of the Philippines: “Another characteristic of Negrito life, a characteristic which strikingly demarcates them from the surrounding Christian lowlanders, is their inexhaustible knowledge of the plant and animal kingdoms. This lore includes not only a specific recognition of a phenomenal number of plants, birds, animals, and insects, but also includes a knowledge of the habits and behaviour of each.”

Andrey Kolmogorov, the Russian mathematician known as the father of modern probability theory and algorithmic information theory, discussing the possibility of the creation of artificial life, drew attention to the point that seemingly intellectually undemanding spatial activities were in reality very information processing-intensive: “A slalom skier, racing through the course, in ten seconds perceives and processes significantly more information than people engaged in other seemingly more intellectual activities, in any case, more than a mathematician processes through his head in forty seconds of intense work of thought.”


The rapid shrinking of human brains began about ten thousand years ago. Although there’s no decisively plausible explanation of the process, the growth of the population density beyond a particular threshold linked to the switch from the hunter-gatherer style of life to the one of an agricultural settler coincided with the u-turn of brain volume dynamics. Rendering of the rapidly changing objective reality is the most computationally intensive function of our brains. The brain of an average person was less in use once the reality became settled with recurring predictable changes.


  1. Bridget Alex, The Human Brain Has been Getting Smaller Since the Stone Age, Discover Magazine, April 9, 2019
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  8. A film by Mike Judge, Idiocracy (2006)
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Chapter Three. Dead Reckoning

In this chapter, we will find out how the huge improvement in the efficiency of human performance has been achieved at the expense of the reduction of the raw human brainpower.

There are no such directional instructions as ‘turn left’ or ‘turn right’ in several languages of Australian aborigines, the language of Maya in America, and some rural languages in Asia. Those languages use an absolute rather than relational reference frame, as linguists name it. Left and right are relational to the orientation and position of a person using them as a reference. West and east remain the same irrespectively of the person’s orientation. Therefore the former frame of reference is named relational or egocentric while the latter is absolute or allocentric.

In modern languages, we much more frequently use an egocentric frame of reference than an allocentric one in defining the location of an object in space. It turns out to be a much more convenient way in navigating across well-familiar spaces with a lot of signs in immediate proximity.

The absolute reference frame turns out to be more adequate for navigating a jungle, steppe, savannah, or an ocean for foraging or exploration of new or rapidly changing spaces which are lacking familiar close signs to follow using a reference frame relative to oneself.

Navigation using the absolute reference frame can be successful only if we are always holding cardinal directions (south, north, east, west) in our minds and constantly yet unconsciously updating our position in relation to them. That way of navigation is called ‘dead reckoning’.

Christopher Columbus did not know how to use either the astrolabe or the quadrant. Several times he tried to determine the latitude with their help but missed terribly.

His caravels charted a course across the ocean in the old fashioned way. More precisely, according to the then most widespread method of navigation on the high seas. This method was called dead reckoning. Nobody knows why it was called dead.

For the dead reckoning, a compass was needed to determine the direction of movement, a wood float on a rope in order to determine the speed of the ship, and an hourglass with a cabin boy that turned them over to determine the time. The course of the ship was displayed in the ship log as a continuous line of pinholes leading from the port of departure to the current location of the vessel marked with a pin.

Dead reckoning in navigation means the same thing as path integration in neuroscience — making a route using a wide cognitive map with an allocentric (absolute, cardinal) orientation system.

In the Indian city of Varanasi, philologists blindfolded children and twisted them around in place, forcing them to look for a path blindfolded to prove that Sanskrit more than Hindi help children integrate the path according to cardinal directions, just as Columbus did, only using not external but built-in compasses, clocks, and pedometers. The children who studied Sanskrit did just great.

Yet any neuroscientist will tell you that rats can do this in Morris’s water maze too. Only no one taught rats Sanskrit or Hindi.

People with a narrow cognitive map, whose hippocampus is either damaged by accident or atrophied due to non-use, can navigate a route using another technique — tracking visible or otherwise felt cues in close proximity to the path. One fixes the mark and direction in relation to oneself. Therefore, this method is called egocentric and relative. This is a superficial way, but it works great in familiar spaces and saves energy on brain activity.

In a myriad of common situations, the two navigation methods are very difficult to distinguish from each other. It is even more difficult to understand that humans use both methods not only for navigation in the physical space of their objective reality but also in any other conceptual space. After all, we have already figured out that an object is a concept. It differs from any other type of concept only by the degree of proximity to the barrier from the sense organs through which we receive signals of different fields of sensations.

The better the environment is labeled, the more human-imposed structure there is in it, the more often tracking is used. And this is justified. Automatism appears in the performance of repetitive operations. The danger arises when our consciousness begins to take automatism for autonomy. But that is another story.

In a meticulously designed experimental study conducted by researchers from the University College of London, participants were navigating videos of the Soho district of London while their brains were scanned with fMRI equipment. Some videos (control task) contained instructions akin to an external navigation system while others didn’t (navigation task). While performing the control task experiment’s participants demonstrated way more accuracy (95 vs 80 percent) but the built-in GPS system — the hippocampus and entorhinal cortex in their brains were idle. During the navigation tasks performance, they were lightening up like Christmas trees.

Dr. Hugo Spiers, the lead scientists of the research, also commented on how the results of his team might explain the well-known fact that London taxi drivers have more grey matter in their hippocampus than ordinary people: “Our results indicate that it is the daily demand on processing paths in their posterior hippocampus that leads to the impressive expansion in their grey matter.”

More intensive engagement of the brain was sacrificed for the sake of more accurate and faster navigation. The experiment of Spiers and his team provides a good illustration of the type of trade-offs that humans made many times during the last ten thousand years. A long-lasting series of such trade-offs have been inevitably leading to the cognitive decline in humans.

Routine activities such as everyday navigation through a physical space may appear much less cognitively demanding than tasks that we traditionally consider intellectual.

However, the way our brains process and render objective reality to our consciousness makes the navigation that requires path integration (dead reckoning) very engaging for our hippocampus and cortex.

In the process of navigation across objective reality, our consciousness is dealing with two types of structure: the natural structure based on the raw sensory data, and the artificial structure embedded in the environment by humans.

The processing of the natural structure for the purpose of navigation is less accurate, slower, and more energy consuming than the processing of artificial structure specifically designed to assist navigation.

Dead reckoning (path integration) is based on the processing of the natural structure. It’s a continuous process like watching a movie. Technology-assisted tracking is based on the processing of the artificial structure that’s less dense and detailed than the natural one. It’s a discrete process like a slideshow. In the case of path integration, the brain is rendering a 4G movie whilst in the case of assisted tracking it only renders a set of low-resolution pics.

Vector tracing neurons were discovered in the hippocampus of the human brain just very recently. Now we have a candidate neural substrate for rendering the objective reality — the hippocampus. Yet before we dig deeper into that substrate let us see how the environment shapes our brains.


We structure the environment around us from the first day of our existence. The objective reality as we perceive it in our consciousness is itself a product of that structuring. Humans achieve the best result with the lowest energy cost by following already existing patterns. Structuring the environment or navigating it anew consumes much more energy and is way less efficient than the utilization of an already existing structure. However, such a huge efficiency improvement comes at a cost: our brain shrinks and we become less smart.


  1. Toni Gomila, Verbal Minds: Language and the Architecture of Cognition, Elsevier, 2012,
  2. Asifa Majid, Melissa Bowerman, Sotaro Kita, Daniel B.M. Haun, and Stephen C. Levinson (2004) Can language restructure cognition? The case for space, Trends in Cognitive Sciences. 8 (3): 108–114. doi:10.1016/j.tics.2004.01.003
  3. Penelope Brown (2012) Time and Space in Tzeltal: Is the Future Uphill? Frontiers in Psychology. doi: 10.3389/fpsyg.2012.00212
  4. Ramesh C. Mishra, Sunita Singh, Pierre R. Dasen (2009) Geocentric Dead Reckoning in Sanskrit- and Hindi-Medium School Children, First Published August 17, 2009,
  5. Lorelei R. Howard, Amir Homayoun Javadi, Yichao Yu, Michelle M. Loftus, Laura Staskute, Hugo J. Spiers. The Hippocampus and Entorhinal Cortex Encode the Path and Euclidean Distances to Goals during Navigation. Open Access Published: June 05, 2014, DOI:
  6. New research explains how we use the GPS inside our brain to navigate, 9 June 2014, UCL News
  7. Eleanor A Maguire, Katherine Woollett, Hugo J Spiers. London taxi drivers and bus drivers: a structural MRI and neuropsychological analysis. Hippocampus 2006;16(12):1091–101. DOI: 10.1002/hipo.20233
  8. Poulter, S., Lee, S.A., Dachtler, J. et al. Vector trace cells in the subiculum of the hippocampal formation. Nature Neuroscience (2020).

Chapter Four: The Blessing and the Curse of Artificial Environment

In this chapter, we review the paradox of human adaptation to the artificial environment that, on the one hand, makes us more fit as a species and, on the other hand, reduces demand for our individual natural intelligence.

“The world we live in today is much more a man-made, or artificial, world than it is a natural world. Almost every element in our environment shows evidence of human artifice,” Herbert Simon, the American scientist who was awarded both the Nobel Prize in Economics and The Turing Prize in Artificial Intelligence wrote in his seminal book The Sciences of the Artificial. He believed that the human mind and brain belong to the family of symbol systems, which “are almost the quintessential artifacts, for adaptivity to an environment is their whole raison d’être. They are goal-seeking, information-processing systems, usually enlisted in the service of the larger systems in which they are incorporated.”

“Human beings, viewed as behaving systems, are quite simple. The apparent complexity of our behavior over time is largely a reflection of the complexity of the environment in which we find ourselves,” Simon wrote and claimed that humans use their minds as artificial instruments of adaptation to the environment. This claim brought me to the idea that the artificial environment created by humans including technology at its core is itself the main instrument of adaptation of the human race to the natural environment.

The artificial environment is a way to adapt to the natural environment. For modern people, it’s a way of group adaptation. Now it has already become a way of adaptation of the entire population.

A mutual understanding between people requires a high level of cognitive abilities, moreover, it requires flexible, fluid, natural intelligence that has developed in us, thanks to the adaptation of our ancestors to the uncertainty of the natural environment.

In us, this intelligence has weakened simply because we spend most of our lives in an ordered artificial environment and adapt to it willfully or against our will.

It turns out to be a vicious circle. We need natural intelligence to preserve and continue to develop an artificial environment that ensures our survival as a species. But it is precisely our adaptation to this ordered artificial environment that leads to the loss of our natural intelligence.

Many scientists in one way or the other keep pointing out that the artificial environment began to rapidly emerge and shift the balance between brainy exploration and habitual exploitation towards the latter about the same time when our brains began to shrink.

Indeed, human brains exhibit more plasticity and readiness to be modeled by the environment, than brains of other animals, including our closest living relatives — chimpanzees.

In a paper published in 2015, researchers at the George Washington University shared their findings “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.” Aida Gómez-Robles, the lead author of the paper says: “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.”


Human brains are shrinking because of their evolutionary advantageous ability to adapt to the environment better than the brains of other animals. Humankind has created for itself an artificial ecological niche that, on one hand, is enhancing our chances for survival and successful reproduction but, on the other hand, is leading to the decrease of our intellectual abilities. Brain shrinking happens because our brains are adapting to the well structured artificial niche without the need to structure the raw signal from the natural environment.


  1. Herbert Simon (1969) The Sciences of the Artificial
  2. Aida Gómez-Robles, William D. Hopkins, Steven J. Schapiro, and Chet C. Sherwood, Relaxed genetic control of cortical organization in human brains compared with chimpanzees, PNAS December 1, 2015, 112 (48) 14799–14804; first published November 16, 2015;
  3. George Washington University, Nature and nurture: Human brains evolved to be more responsive to environmental influences,, November 16, 2015

Chapter Five. The Hippocampus Is Shrinking in Our Brains Right Now

In this chapter, we find out how switching to narrow cognitive maps in navigation through the well structured and labeled artificial environment leads to the decrease of use of the hippocampus, the brain area responsible for rendering and support of broad cognitive maps.

In the very depths of the temporal lobes of the brain, a pair of seahorses is lurking — the left one and the right. The sixteenth-century Venetian anatomist Julius Caesar Aranzi was highly imaginative. It was with his light hand that seahorses settled in the brain. It’s good that not silkworms. At first, Aranzi thought that the hippocampus extracted from the brain looked more like them.

The hippocampus in the brain has a head, body, and tail, much like the seahorse for which it was named.

The hippocampus consists of two convolutions of gray matter interwoven together. I remember words from childhood meaning I did something stupid: “You have only two convolutions!”

“Yes, there are only two, — I would respond today, — but look at how important they are!” In the tail of the hippocampus, for example, the entire objective reality has settled. People whose hippocampal tails have shrunk from the loss of gray matter no longer distinguish between objective reality and hallucinations, which, like reality, are produced by their brains.

The hippocampus, of course, does not create reality. It belongs to the archicortex, and only the neocortex is large enough to accommodate the cognitive map of the entire reality. However, the tail of the hippocampus can easily distinguish the objective reality that is woven from our real subjective sensations, from hallucinations — the fantasies of the brain itself. So the seahorse, among other things, is also a classifier of realities.

Psychoses in epilepsy and schizophrenia clearly correlate with a decrease in the volume of gray matter in the tails of the hippocampus, both left and right. Until recently, the disease was thought to cause the hippocampus to shrink. There is now growing evidence that hippocampal atrophy is a cause, not an effect of diseases that manifest in loss of objective reality.

“Whereas the hippocampus is essential to spatial navigation via a cognitive map, its role derives from the relational organization and flexibility of cognitive maps and not from a selective role in the spatial domain. Correspondingly, hippocampal networks map multiple navigational strategies, as well as other spatial and nonspatial memories and knowledge domains that share an emphasis on relational organization. These observations suggest that the hippocampal system is not dedicated to spatial cognition and navigation, but organizes experiences in memory, for which spatial mapping and navigation are both a metaphor for and a prominent application of relational memory organization,” Howard Eichenbaum from Boston University gave an excellent overview of the core importance of the hippocampus.

Indeed the hippocampus is crucial for our thinking process. Especially it plays a pivotal role in building objective reality as a cognitive map. Yet it’s shrinking in humans during aging. Minor hippocampal atrophy is considered a normal, healthy process but is it?

Several biological changes typical for normal brain aging in humans are also found in other species. However, the volumetric decline of the hippocampus takes place only in humans.

Although some scientists keep attributing the shrinkage of the hippocampus in elderly humans to aging today our hippocampus is shrinking because with gaining more experience we more and more heavily rely on habits and don’t feed the hippocampus with a sufficient amount of unstructured sensual data. Without such a workload our brain remains in an energy-saving narrow cognitive map mode for too long and our hippocampus loses its grey matter.

Comparative studies of humans and chimpanzees also suggest that the cause of shrinkage of the human hippocampus is the environment and lifestyle rather than just aging. They clearly demonstrate that only the human hippocampus shrinks dramatically over time while chimpanzees’ hippocampus retains its volume across the entire lifespan.


The hippocampus and cortical areas anatomically connected to it create, render, update, and objective reality and other wide cognitive maps in our brains. The hippocampus is shrinking in the brains of modern humans because the need for wide cognitive maps in day to day life of modern humans is diminishing.


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  3. Howard Eichenbaum. The role of the hippocampus in navigation is memory. Journal of Neurophysiology, Vol. 117, №407, APR 2017,
  4. Lisa Nobis et al. Hippocampal volume across age: Nomograms derived from over 19,700 people in UK Biobank. NeuroImage: Clinical, Volume 23, 2019, 101904,
  5. John O’Keefe and Lynn Nadel (1978) The Hippocampus as a Cognitive Map
  6. Veronique D. Bohbot et al. Virtual navigation strategies from childhood to senescence: evidence for changes across the lifespan, Frontiers in. Aging Neuroscience, 15 November 2012,
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Chapter Six. Reduction of the Hippocampus Shrinks Objective Reality and Damages Health

You will learn more about the major cognitive functions of the hippocampus in Section Four of this book.

In brief, the hippocampus, densely interconnected with the cortex and other major parts of the brain, supports the flexible use of information in all possible contexts. Damage to the hippocampus can produce inflexible and maladaptive behavior in such diverse areas as memory, navigation, exploration, imagination, creativity, decision-making, character judgments, establishing and maintaining social bonds, empathy, social discourse, and language use.

As researchers from Duke University and the Universities of Illinois and Iowa pointed out after analyzing results of many studies of different methodologies: “the contribution of the hippocampus to flexible cognition is perhaps most apparent in the complex dynamics of social interactions”. Therefore the hippocampal decay leads to impairment of the ability to meaningfully and flexibly communicate with other humans.

Even the objective reality itself can become distorted due to severe hippocampal atrophy. In the pathological case of Alzheimer’s disease shrinkage of the cognitive map of objective reality manifests itself in narrowing down of the visual field without any damage observed in patients’ eyes.

“Patients by mid-Alzheimer’s disease have to struggle with a 12-inch field of vision where they have lost the ability to see everything at the top, on the bottom, and on the sides,” writes an author of a popular blog for seniors.

A wide array of psychiatric and neurodegenerative disorders is linked to atrophy and other abnormalities of the hippocampus.

Atypical hippocampal functioning has been observed in people with autism. It is proposed as a possible source of structural learning difficulties in ASD. Volume reduction and shape abnormality of the hippocampus is associated with bipolar disorder. Reduced hippocampal volume is strongly associated with major depressive disorder (MDD).

Researchers frequently observe a correlation between hippocampal volume reduction and the development of schizophrenia symptoms. As the shrinkage of the hippocampus can be observed earlier than psychological symptoms, it can be either an early sign or the cause of the development of the disease.


As you can see now, the hippocampus is a very sensitive and very dynamic area of the brain. The comfortable and highly efficient artificial environment is our major competitive advantage in the adaptation to the natural environment given to us in an unstructured and unpredictable form of natural (not artificially structured) sensations. That artificial environment protects us from structural (unexpected) uncertainty that has shaped our brain and hippocampus. Structuring of the objective reality keeps our brain and hippocampus in particular in good shape because they were designed for that purpose.

We can’t return to savagery in order to protect our brain and hippocampus. However, the information jungle provides us with an outstanding opportunity to rejuvenate our natural intelligence and our brains. Let’s have a closer look at the hippocampus in the next section to see what can be done about it.


  1. Rachael D. Rubin et al. The role of the hippocampus in flexible cognition and social behavior. Frontiers in Human Neuroscience, Published online 2014 Sep 30. doi: 10.3389/fnhum.2014.00742
  2. Aaron Barriga (Feb 21, 2019) What Alzheimer’s Has to Say about Your Eyesight
  3. Russell W. Chan et al. Low-frequency hippocampal–cortical activity drives brain-wide resting-state functional MRI connectivity. PNAS August 15, 2017, 114 (33) E6972-E6981; first published July 31, 2017;
  4. Guo-Ping Peng et al. Correlation of Hippocampal Volume and Cognitive Performances in Patients with Either Mild Cognitive Impairment or Alzheimer’s disease. CNS Neuroscience & Therapeutics 21 (2015) 15–22
  5. Melanie Ring et al. Structural learning difficulties implicate altered hippocampal functioning in adults with autism spectrum disorder. Journal of Abnormal Psychology, 126(6), 793–804.
  6. B Cao et al., Hippocampal subfield volumes in mood disorders. Molecular Psychiatry 22, 1352–1358 (2017).
  7. Nils Opel et al. Hippocampal Atrophy in Major Depression: a Function of Childhood Maltreatment Rather than Diagnosis? Neuropsychopharmacology. 2014 Nov; 39(12): 2723–273. doi: 10.1038/npp.2014.145
  8. Katherine L.Narr et al. A Twin Study of Genetic Contributions to Hippocampal Morphology in Schizophrenia. Neurobiology of Disease, Volume 11, Issue 1, October 2002, Pages 83–95.