What to expect:

I’ve written articles and made videos on the human brain's plasticity and how malleable it is. It’s one of the most adaptive traits of our species. However, the size of the brain more generally is an even more mysterious idea. Why is it so much larger than the brains of other primates and most mammals?

In this video, we explore 3 hypotheses that try to explain the evolution of the human brain and what caused its grand size. Each identifies specific traits of the human species, like our environments, sociality, and dietary habits, that could have pressured our cognition to surpass that of other species. As you will see, it is likely far more complicated than can be attributed to any one factor.

That being said, we also explore why this trend may be reversing. Research suggests that human brain size is decreasing. Are we devolving? Are we becoming less intelligent? Watch till the end to see what may be causing the decline and its implications for the future of human evolution.

The Evolution of the Human Brain

The human brain quadrupled in size over roughly 4 million years. This period of growth belittles our measly 80-year lives (if we're lucky). From our perspective, 4 million years seems like a ridiculously long time, especially in today's fast-paced short attention-span world. And it is. But, for an organ as complex as the brain, this rate of change is astounding.

We have colloquially deemed our brains “the most complex things in the universe”. It has been estimated that this organ is composed of approximately 100 billion neurons and 100 trillion synaptic connections [1;2]. The sheer quantity of these neurons and their connections is hardly fathomable and intrinsically justifies investigations into what produced such magnitude.

In this video, we’ll look at some of the competing hypotheses that seek to explain the evolution of the human brain. First, we’ll explore the archaeological record to see how we can infer the brain sizes of extinct species. Then, we’ll dive into hypotheses that attribute this growth to things like sociality and even cooking food. Finally, we’ll end with an anomaly in this pattern of brain growth. In recent history, evidence has suggested that the brains of Homo sapiens have actually been shrinking. What caused this trend to reverse? Will it continue? Stay tuned for my thoughts on the matter. 

Human Species and their Brain Sizes

Two areas of research are vital to understanding the evolution of the human brain. One is primatology and the other is archaeology. Primatology allows us to compare our brains to other primate species we are related to and share common ancestors with. Archaeology allows us to see the physical remains of past humans, including the skulls that housed their brains.

When we look at primates as a whole, excluding humans, we see that they already have brains larger than what’s expected for mammals their size [3]. The way we come to this comparison is by measuring their encephalization quotient or EQ. This measurement is the ratio of the species’ brain size compared to its body weight. So, the brain size of a primate that weighs 10 kg is likely going to be larger than that of a non-primate mammal of the same size.

Looking at this graph, humans outshine even our closest primate relatives, regarding EQ. We are most closely related to the class of apes called hominoidea, including chimpanzees, bonobos, gorillas, and orangutans. Our brains are an exception to the linear association between the brain mass and body mass of these apes. This graph uses grams as the unit of measurement but in anthropological studies, we often use cubic centimeters to infer brain size. 

This is because the brain does not fossilize, but the skull does. Therefore, we can estimate the interior volume of fossilized skulls using cubic centimeters as a proxy for brain size - known as cranial capacity. Sometimes it’s used for living species. For example, chimpanzees have a cranial capacity of around 337 cubic centimeters, while anatomically modern humans’ are around 1400 [4]. This is especially helpful, though, for investigating extinct species. 

The human lineage split from chimpanzees roughly 6 or 7 million years ago. Since then, various human species have come in and out of existence. Some have left more evidence than others, discarding tools and faunal remains for modern archaeologists to unearth. Others have left little but their own skeletal remains. Of those remains, only a small percentage have been preserved well enough for us to discover. 

That being said, the archaeological record is sufficient enough to give us an idea of how the cranial capacity of different human species has gradually increased over time. Renowned paleoanthropologist Daniel Lieberman accumulated much of this data and published it in his book The Evolution of the Human Head [5]. This is the source I’ll be referring to going forward

One of the earliest species that many anthropologists recognize as distinct from the other primates enough to call human-like is known as Sahelanthropus tchadensis, discovered in Chad. It had some features that distinguish it from other apes, like where the spine meets the skull being more indicative of upright posture, but the brain wasn’t one of them. The cranial capacity of Sahelanthropus was roughly that of a chimp, coming in at around 360 cubic centimeters. Ardipithecus ramidus, another early species with features common to both chimps and humans, had a cranial capacity similar to Sahelanthropus, between 280 and 350 cubic centimeters. 

The first branch of the human tree that breaks through the 400 cubic centimeter ceiling is the Australopithecus genus. This genus consisted of various species that existed from roughly 4 to 2 million years ago. Some of them were lean and gracile, while others were notoriously thicker, known as the robust australopithecines. Anamensis, afarensis, and africanus were among the gracile forms and they had cranial capacities ranging from 275 to 550 cubic centimeters. The robust forms included aethiopicus, boisei, and robustus, and their cranial capacities ranged from 410 to 545 cubic centimeters. 

Starting around 2.5 million years ago, we see the emergence of the genus to which we belong - the Homo genus. Unsurprisingly, this is when we begin to see more dramatic increases in brain size. Homo habilis is the earliest known species in our genus, and it makes the jump to around 609 cubic centimeters on average. Also not to our surprise, this is when we start to find the widespread use of stone tools in the archaeological record. Hence the name Homo habilis, which translates to “handyman”.

This association between brains and tool use becomes a fascinating area of research, looking to decipher the actual cognitive abilities of extinct species and how they perceived the world. It’s like archaeological neuroscience, and I plan on making a video on the matter at some point in the future. Let me know in the comments if that’s something you’d like to see.

Another species that made massive strides in technological development was Homo erectus. They expanded the human toolkit from the crude Oldowan stones to the more symmetrical blades of the Acheulean industry. Many recognize Homo erectus as the first truly human species, with more human-like behavior. Following Homo habilis, they lived from around 1.9 million to 110,000 years ago. They had cranial capacities ranging from 725 to 1,125 cubic centimeters. 

Finally, we come to two of the most recent species in the human lineage - us and the Neanderthals. This is where things get really interesting. As I said earlier, modern people have an average cranial capacity of around 1,400 cubic centimeters. Neanderthals lived mostly in Europe from around 500,000 to 30,000 years, and their brains were comparable to anatomically modern humans. In fact, archaeologists have found Neanderthal skulls that exceed the cranial capacity of many Homo sapiens, reaching higher than 1,600 cubic centimeters in some cases.

Homo sapiens and Neanderthals represent the pinnacle of human brain evolution and behavioral modernity. Though similar, Neanderthal brains had a different shape. They were more elongated, with the occipital lobe representing a larger percentage of their brain. The occipital lobe is largely responsible for visual processing, which has led some researchers to believe that Neanderthals had superior visual acuity to contemporary humans [6].

Despite these contrasts in brain organization, both Neanderthals and early Homo sapiens displayed examples of modern behavior. At one point they shared the same stone tool technology, the Mousterian industry. Neanderthal sites in Europe and Homo sapiens sites in North Africa have both yielded stone flakes derived from this form of tool construction. Both species also engaged in symbolic behavior. This is very obvious when it comes to modern humans, but did you know that Neanderthals made ornamental jewelry, and bone instruments, and even buried their dead [7;8]? They probably had language too.

The difference between the cognition of Homo sapiens and Neanderthals seems to be one of degree more than type. We shared many adjacent technological abilities and symbolic behaviors, but Homo sapiens simply took them further. Historian Yuval Noah Harari calls this the Cognitive Revolution, whereby Homo sapiens made great strides in terms of applying our mental information processing to our cultural world - resulting in large-scale social cooperation and rapid innovation [9]. Now, we have spaceships, atomic bombs, and the Internet. 

In 4 million years, we went from chimp-like apes to a species with immense intellectual power. How is it that our brains got so big? What were the selective pressures that cornered our species and forced us to prevail with our mental acuity? We don’t know for sure, but what follows are some of the most compelling theories explaining how we evolved our big brains.

The Ecological Intelligence Hypothesis 

When we think of evolution by natural selection, we most often think of the interactions between a species and its environment. Individual organisms that are best suited to their local ecology will outcompete others, and their genes will propagate and increase in frequency over time. For example, the earliest hominins who were better at walking upright had the advantage when traveling long distances to find food, because bipedalism is more energy efficient. The patchy distribution of food in the physical environment was what selected for that upright posture. 

The ecological intelligence hypothesis applies this line of thought to the evolution of the human brain. It’s the idea that our large brains are an adaptation to solving ecological problems, mostly related to finding food. Today, we have supermarkets, restaurants, and generally convenient and reliable locations where we can find our food. However, when living in the wild, finding food is more cognitively demanding.

In a paper published in 2017, professor of psychology and anthropology Alexandra Rosati outlined three cognitive skills used during food foraging and their implications for human brain evolution [10]. 

First, is spatial memory, which she defines as “The ability to recall the location of resources and navigate efficiently between them.” The construction of a mental map of the local ecology is integral to complex foraging behaviors. When looking at primates, she shows how some environments require a greater degree of spatial memory. 

For example, chimps and bonobos are two closely related species that are nearly indistinguishable in appearance, but they have different diets. Chimps rely more on dispersed patches of fruit while bonobos are more dependent on evenly distributed vegetation. Accordingly, chimps have been shown to perform better at memory tasks. Moreover, the part of the brain that deals with memory, the hippocampus, is larger and has greater connectivity in chimps.

The second is value-based decision-making. There is often more than one food option available for wild foragers and it would be optimal to have the ability to choose the option with the best return on investment - meaning the most nutrient-rich food that takes the least amount of energy to obtain. According to Rosati, “There is emerging evidence that the ecological features that vary with primate memory - diet and home range size - also shape preferences about value.”

Part of the decision-making process deals with time, what she calls intertemporal. Should I eat this less-optimal food now or wait for the better option later? Studies have shown that primates with larger home ranges, who travel more for their food, have greater patience in delayed gratification experiments. This sort of skill, dealing with self-control and impulsivity, is associated with the prefrontal cortex. 

Third, is executive control - another brain region associated with the prefrontal cortex. “Executive functions are a suite of cognitive processes that allow individuals to flexibly control their behavior, overriding reflexive responses that would otherwise be performed automatically.” Studies looking at the inhibitory control of primates have shown that ecological factors like breadth of diet are better predictors of performance than social factors like group size. 

So where does the human niche fall in this framework? It may be that the environments humans evolved in placed extra pressure on these cognitive skills for foraging. Rosati provides three examples of our ecological uniqueness. First, humans target high-value foods, like large mammals, that are risky or costly to acquire. Second, hunter-gatherers tend to travel longer distances than other primates to acquire these valuable resources. Third, humans have sociocultural practices, like stone tools and group food sharing, that aid our foraging abilities. 

Therefore, the human brain could have adapted to these conditions through increased spatial memory and patience due to our large food ranges. Also, things like food sharing, that override the instinct to impulsively consume, likely require better executive control. 

Food sharing is a central aspect of our human sociality, which brings us to our next hypothesis. Maybe it wasn’t the environment that selected our brain size. Maybe it was our fellow humans. 

The Social Brain Hypothesis 

A strictly ecological view of human brain evolution discounts a defining feature of the human species - complex sociality. 

The viewpoint of those in favor of the ecological intelligence hypothesis would argue that the local ecology poses problems to the individual organism, who solves those problems themself through trial and error. After some time, the pressure to use their problem-solving cognition will result in a more intelligent population, and complex sociality will emerge from that. So, the chain of causality is this: the environment presents a problem, which is solved by an individuals’ cognitive adaptations, and then those individuals have a greater capacity for social organization because of their increased cognition. 

The Social Brain Hypothesis posits the reverse: environmental problems are solved by increases in group size and organization, which then select for greater brain size and cognition in individuals. It makes sense that individuals are not solely affected by their immediate physical environments but by their social environments as well. And these social influences can have downstream effects on survival and reproduction. Therefore, the nuances and complexities of navigating group life are what drove brain expansion in primates. 

How does belonging to a group help solve ecological issues? A great example comes from vervet monkeys. Vervet monkeys use specific alarm calls to warn group members about different types of predators [12]. Different sounds signal different predators. Eagles, snakes, and leopards each have their own call. Group members can respond appropriately to the type of predator, increasing their chances of survival. For instance, they climb trees to avoid leopards and look up to spot eagles. According to the Social Brain Hypothesis, the group's social dynamics are creating a solution to the ecological problem and cognitive adaptations would ensue to recognize, recall, react to, and manifest those communication cues.

So what evidence do we have that supports the Social Brain Hypothesis in humans?

The term was first coined by Lesley Brothers in 1990 [13], but Robin Dunbar's research in the subsequent decades solidified the hypothesis as an empirically backed explanation. Dunbar publishes a paper or book on the matter regularly. The data he’s amassed and the experiments he’s conducted have culminated in a body of evidence supporting the notion that primates in general and humans specifically are cognitively adapted to our social worlds [11].

For example, when we look at the relationship between group size and different parts of the brain, we see something very interesting. Not only do primates have relatively large brains, but certain parts of our brains are more pronounced than others. 

The neocortex is the outermost shell of the brain and is involved in higher-order functions like perception, cognition, and language. It turns out that there is a linear relationship between group size and neocortex size. Primate species that live in larger groups have larger neocotices. Unsurprisingly, humans top the leaderboards for both metrics. Additionally, research in humans has shown that the size of one's social network is correlated with regions of the brain involved in theory of mind, which is the ability to recognize that others have beliefs and intentions that may differ from one's own. In other words, to put yourself in their shoes. These brain regions are enlarged in people with bigger social networks.

Now think about the features of human sociality. We live in cities with millions of people and likely lived in tribes of over 100 for most of our history. We cooperate to hunt prey, then we bring that prey back to camp where we share it amongst our group. We not only have speech but language with grammar and nuance. We share fictional stories that help align our groups toward common beliefs and goals.

Would the human brain have grown to the degree it has if it wasn’t for these complicated social structures making us better adapted to the world around us? Maybe not. Larger social groups necessitate greater cognitive abilities to manage intricate social networks. This interrelationship underscores the importance of social living in the evolutionary development of primate brains, particularly the brains of humans.

At the end of the day, it’s unlikely that there was any one, single factor that caused the evolution of the human brain. In all likelihood, specific features of our environment influenced certain cognitive mechanisms while specific social dynamics influenced others - and surely there was overlap.

But there is one thing we need to consider. The brain is the most energetically expensive organ in the human body. How did we manage to afford such sustained growth over evolutionary time? Some anthropologists believe they have the answer to this paradox.

The Cooking Hypothesis

In my last video, I talked about the diets of prehistoric humans. I’ll leave a link to that video in the description, but in short, our prehistoric diets were highly adaptable. Our species is exceptional at finding food by whatever means necessary, no matter the environment. We capitalize on meat and seafood if we’re in the frozen tundra. If we’re surrounded by foliage, fruit will probably be on the menu. 

One thing I touched on briefly was cooking. But, I wanted to save a more in-depth analysis of this food processing technique for this video, because its implications for the evolution of the human brain are immense.  

Humans aren’t unique in that we process our food before eating it. Sea otters use rocks to break open shellfish. Capuchin monkeys have been observed performing a similar technique to crack open nuts, using one stone as a hammer and one as an anvil. Which, as a side note, is a super interesting topic in its own right. Other primate species are now entering the Stone Age. 

But again, humans take food processing to the extreme. We not only use stone tools to hunt down prey and butcher the meat, but we summon fire to cook it.

- that is a quote by historian Will Durant, who claimed that the control of fire was one of the ten peaks of human progress [14].

Anthropologists Leslie C. Aiello, Peter Wheeler, and Richard Wrangham would concur with this statement, and probably take it so far as to say cooking is actually what made us human - in the modern sense. 

How so? It goes back to the paradox of our brains being so energetically expensive, yet so valuable in their function. For most of human evolution, we lived in a world where food was finite, and allocating those calories appropriately would have been essential for survival. To support the caloric demands of a big brain, one needs to increase their total caloric intake and/or sacrifice by not spending calories elsewhere. 

According to Aiello and Wheeler’s highly influential paper published in 1995, there were two stages whereby ancient hominins made these sorts of energetic strides toward affording a big brain [15]. It argues that certain "expensive tissue" organs, primarily the brain and gut, compete for energy within an organism and a shift in diet was necessary to provide sufficient energy to the brain. If a higher-quality diet could have reduced the size and metabolic cost of the gastrointestinal tract, it would have permitted brain growth. 

Accordingly, they suggested that there have been two dramatic increases in brain expansion within the hominin lineage, both of which were associated with dietary transitions. The first was with the emergence of Homo habilis, whose brains were about 20% larger than their Australopithecine predecessors.  The authors concluded that the introduction of underground foods (like bulbs and tubers) and meat into hominin diets was a major factor in this first change. The second era of brain expansion correlates with archaic Homo sapiens. They proposed that cooking may have been responsible for this second change. By “externalizing part of the digestive process”, cooking reduces toxins in the food and increases its digestibility.

It increased the quantity of energy extracted from food, decreased the energy required for the digestive tract to absorb that food (leading to reductions in gut size over time), and in so doing, granted humans the reservoir of calories needed to power their brains.

Now, Richard Wrangham’s cooking hypothesis is an extension of Aiello and Wheeler’s expensive tissue idea. In his book Catching Fire, Wrangham dedicates an entire chapter entitled “Brain Foods”, to this very topic [16]. He agrees with the general sentiment put forth by his contemporaries but is more precise and pushes the timeline back a bit. He argues that there were four important increases in brain size over the course of hominin evolution, and each can be attributable to specific dietary shifts.

First, the shift from a chimpanzee-like ancestor to the Australopithecines was likely due to the incorporation of like roots and tubers that were more digestible than fiber-rich foliage. Next, the transition to Homo habilis was linked to the integration of meat and simple food processing, like butchering carcasses with stone tools. Then, it was the emergence of Homo erectus that was accompanied by the use of fire for cooking. Lastly, the increases in brain size associated with Homo sapiens and the like are attributed to improvements in cooking methods, including earth ovens, containers, pottery, etc. 

Wrangham believes that cooking predates Homo sapiens and can be pushed back to Homo erectus for several reasons. He says,  

By cooking their food, Homo erectus became adapted to their softer more easily digestible diets, which we can see in their fossilized anatomy. They no longer needed big teeth to grind down raw foods. Their rib cages shrunk in response to their shrinking guts. Additionally, Homo erectus marks the species that committed to full-time terrestrial living, including sleeping on the ground - which would have been risky before fire kept us safe at night. 

Might I add that since the publication of Wrangham’s book, studies have been published pushing back the earliest evidence of human-controlled fire to around 1 million years ago [17]. At Wonderwerk Cave in South Africa, archaeologists believe they’ve found charred plant and animal remains from a soil layer that also included Acheulean tools attributable to Homo erectus. 

The Cooking Hypothesis fundamentally shifts the way one looks at primate and human brain evolution by placing less emphasis on cause and more on allowance. Most researchers prior to this may have been overly committed to finding the precise selective pressure that caused primate brain growth, like ecology or sociality, as discussed earlier. This idea puts that question on pause and asks the meta-question of how the body can metabolically afford dramatic brain growth in the first place, regardless of the selective pressure.

Personally, I find all three of these hypotheses extremely compelling. In all likelihood, there is no single-factor that resulted in the grand size of the human brain. Rather, it was the result of multiple causal factors converging to construct a complex system of problem-solving and communication. The need to remember the locations of food in physical space surely influenced the development of the hippocampus and the the need to coordinate group hunts surely influenced the development of the neocortex.

It was the perfect evolutionary storm. 

For millions of years, all of this growth was restrained by nutrition, despite the presence of these selective pressures. Cooking was the tool that increased our access to calories sufficiently enough to remove that constraint. 

But the paradoxical nature of human brain evolution does not end there. After millions of years of progress toward larger cranial capacities, bigger brains, and more intelligent species, we see a dip in more recent times. Research suggests that the human brain has gotten smaller in recent years. 

The Shrinking of the Human Brain

Since at least the eighties, it has been recognized that the brains of modern humans are slightly smaller than those found in the prehistoric archaeological record. Starting around 50,000 years ago, brain size has steadily declined and is now more than 5% smaller than it once was [18]. Note how this is right around the Cognitive Revolution described by Harari - a time when symbolic thought and the manipulation of the physical world were becoming widespread in humans. However, the most rapid decrease in brain size has occurred in just the past 3,000 years or so [19].

One of the earliest studies investigating this decline came to this interpretation of the data, “It may be concluded, based on the numerical evidence presented, that a considerable decrease in cranial capacity, and, most probably brain size, occurred during the period of the most intense and abundant development of culture including many of the most significant intellectual achievements of mankind,” [20].

How do we reconcile the fact that the human brain is getting smaller as our species is becoming more culturally and technologically complex? Wouldn’t it make more sense that this complexity would continue putting cognitive strain on us, pressuring our brains to continue growing exponentially?

It could be that brain size is simply not a perfect metric for intelligence. Absolute size certainly matters, but other metrics should also be considered, such as the relative size between different brain regions, the density of neurons and their connection, and the degree of neural plasticity - the brain's ability to change and adapt. So while they might be getting smaller, they may be more efficient and adaptable, which could account for the complexity we produce all around us.

But here is another idea: maybe that very technology is the reason why our brains are shrinking. 

Plato once said,

Plato might have had a glimpse into the future of human culture and technology, prophetically noting how our mental faculties may be affected. 

Starting with the first stone tools constructed millions of years ago, and accelerating through the Cognitive Revolution, humans have been externalizing their thoughts and ideas to the physical world. Subconscious survival instincts were reflected in the conscious efforts to sculpt those stone tools. The decorative jewelry of ancient humans reflected their growing need for social identity and status, symbolizing personal and cultural significance beyond mere utility, and marking a shift towards complex social interactions and the expression of abstract ideas.

That shift from strictly utilitarian tools to symbolic tools that contain abstract ideas is extremely important here. Not only do humans manipulate the physical world, but they do so in such a way as to instill meaning in what they create. In doing so, we externalize information and information processing to the material world. We store information outside of our brains.

Some of the earliest evidence of this comes from cave art Kapova Cave. The precise meanings behind most of these are frequently debated and will likely never be truly understood. However, we can all agree that the people who painted them likely did so intentionally - they were no accident. Those paintings are more than just colors thrown at a rock wall. They contain information that can be interpreted by the individual who created it and/or a separate individual. So, it not only acts as a form of idea storage for its creator but also as a means of communicating those ideas to another person.

The brain was responsible for these tasks for most of human evolution, but they’ve incrementally been outsourced to the external world for the past 50,000 years or more. There is no sign of this outsourcing stopping anytime soon. It has only become more common.

Around 6,000 years ago, the ancient Sumerians of Mesopotamia developed the first formalized iteration of written language. Known as cuneiform, it consisted of lines incised into clay tablets. It was used to document everything from menial day-to-day tasks like recording economic transactions to communicating legendary mythical stories like the Epic of Gilgamesh. 

The Egyptians developed a system of hieroglyphics not too long after. This was central to Egyptian culture, allowing them to record their history, religious beliefs, and administrative matters, while also serving as a means to communicate with the divine in the afterlife. Often carved into tombs and other sacred structures, the information stored within them can now be interpreted by us people living in the year 2024. 

Mathematics played a similar role to written language and had a parallel trajectory. Math is a system of symbols and rules for manipulating numbers and quantities, which began to take shape in ancient civilizations like Mesopotamia, Egypt, and later Greece. It serves as a universal language for describing patterns, structures, and relationships in the physical world, laying the groundwork for advancements in science, engineering, and philosophy. It became an essential tool for everything from architecture and astronomy to navigation and economics. It too was written down to aid us in our conceptualization efforts. 

As time went by, our documentation capacities increased. We developed books, the printing press to reproduce them at scale, and libraries to store them at scale. By the 1800s, the information processed by our senses of sight and sound could be documented through audio recordings, photographs, and film. 

Today, we are consumed by the digital world. We are constantly exporting our ideas and memories immediately to social media. We are saving them to the cloud. We are using artificial intelligence to augment our cognition and creativity. These tools are extensions of our brains and they began as mere cave art. But, they might be subverting our cognition. 

Let’s look again at the cooking hypothesis to make a comparison. Cooking reduces the amount of energy needed to operate other expensive organs (like the gut), allowing the brain to capitalize on that caloric reservoir. Technology might be having the opposite effect. Similar to how we outsourced aspects of digestion to cooking, we are now outsourcing aspects of cognition to technology. Just as the gut atrophied as a result of that cooking, our brains may be atrophying as a result of outsourcing our cognition. 

I have yet to dive too deep into the literature on this topic, so if you’re familiar with any relevant studies please let me know in the comments. That being said, I have found a few interesting points that seem to support this idea.

IQ is a metric often used by psychologists and other social scientists to measure intelligence, albeit it’s an imperfect one. In the IQ literature, there is something called the Flynn Effect. It describes the significant increase in average IQ over the past century [22]. However, the Flynn Effect is not universal. Studies have shown a slowing down of this trend and even a reversal in some populations in recent years. A meta-analysis published in 2015 showed that IQ is increasing at a higher rate in developing countries than in technologically industrialized countries [23]. 

Another area of concern deals with the brain development of our youth. In young children, screen time is associated with poorer language development and executive functioning, particularly when replaced with reading [24]. That same study found that screen time was associated with decreased connectivity between brain regions controlling language and cognitive control.

It should be noted that there are counter studies suggesting that offloading our cognition to technology may be beneficial. Experiments have shown that writing improves memory [25]. Others even suggest that searching the internet is actually a form of neural exercise [26].

Having said that, I can’t help but think of the role that time plays in all of this. This process of outsourcing our brains’ functions to external symbols and technology has been increasing for thousands of years and has been accelerating dramatically in the past hundred. Even if this can’t account for the decrease in brain size leading up to today, What about the future?

The digital age that this process has culminated in is still in its infancy. The computational power of things like quantum computing and artificial intelligence is going to make human cognition obsolete. It's only a matter of time until attempting certain intellectual feats ourselves will be a waste of time because the efficiency of outsourcing it to these technologies will be far more efficient. Using our cognitive power will put us at a disadvantage. Given enough time, say, over the next million years or so, it is not out of the realm of possibility that our species will experience greater brain atrophy as a result.

Have you ever seen those images of aliens and advanced humans from the future, whose brains are so huge and bobblehead-like? This might actually be the complete opposite of what happens.

Final Thoughts

The human brain is not only the most energetically expensive tissue in the human body, but its neuronal complexity surpasses anything in the known universe. Exactly how it achieved this is a mystery, though it was probably a combination of factors unique to the human niche. 

Humans and our ancestors most likely had large home ranges and traveled far and wide for food, requiring us to store greater amounts of ecological information. Our social worlds surely influenced our cognitive capabilities too, requiring us to keep track of group members, their social statuses, and how to communicate with them. 

Incorporating calorically rich meat into our diets and using fire to cook it was the most likely impetus for supplying the brain with the energy needed to adapt to those ecological and social selective pressures. 

Now we’ve reached a point in which the technology we’re creating using those big brains is on its own trajectory - one that will soon exceed the possibilities of our biologically restricted cognition. The implications of this possibility are grand. The one hypothesized in this video is that our brains will continue to shrink as these technologies continue to replace our cognitive responsibilities. 

And to what extent could we be replaced? Will our creations supplant us entirely, leading to the extinction of Homo sapiens? Was our species just a vehicle to reach an evermore god-like technological entity, like the species that walked the earth before us? Will evolutionary principles apply to the non-biological beings of the future? 

The questions are endless, but I’m curious what you guys think. Leave a comment letting me know what you think the end product of the evolution of our brain-technology relationship will be.

References:

[1] Sherwood, Chet C., and Aida Gomez-Robles. 2017. "Brain Plasticity and Human Evolution." Annual Review of Anthropology 46 (1): 399-419.

[2] Herculano-Houzel, Suzana. 2012. "The remarkable, yet not extraordinary, human brain as a scaled-up primate brain and its associated cost." Proceedings of the National Academy of Sciences - PNAS 109 (Supplement 1): 10661-10668.

[3] Schoenemann, P. Thomas. 2006. “Evolution of the Size and Functional Areas of the Human Brain.” Annual Review of Anthropology 35:379-406.

[4] Rilling JK, Insel TR. 1999. “The primate neocortex in comparative perspective using magnetic resonance imaging.” J Hum Evol. 37(2):191-223.

[5] Lieberman, D. 2011. The Evolution of the Human Head. Cambridge, Massachusetts: The Belknap Press of Harvard University Press.

[6] Pearce Eiluned, Stringer Chris, and Dunbar R. 2013. “New Insights into differences in brain organization between Neanderthals and anatomically modern humans.” Proc. R. Soc. B. 28020130168

[7] Jaubert, J. et al. 2022. “Chapter 14 - Spiritual and symbolic activities of Neanderthals.” In Updating Neanderthals Understanding Behavioural Complexity in the Late Middle Palaeolithic. Academic Press. 

[8] Turk, I., Dirjec, J., Kavur, B. 1995. “The oldest musical instrument in Europe discovered in Slovenia?” Razprave 4. Razreda Sazu 36, 287–293.

[9] Harari, Y. 2015. Sapiens: A Brief History of Humankind. London,UK: Vintage.

[10] Rosati AG. 2017. “Foraging Cognition: Reviving the Ecological Intelligence Hypothesis.” Trends Cogn Sci. 21(9):691-702.

[11] Dunbar, R.  2016. “The Social Brain Hypothesis and Human Evolution.” Oxford Research Encyclopedia of Psychology. 

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Song Suggestion

Music is a human universal. It’s found in every culture, at every corner of the globe. The Evolve.2 song suggestions are hand-picked by yours truly. I love all types of music, but here, I like to share some of my more extreme tastes.

(Caution: These songs consist of heavy, brutal guitar riffs and gruesomely guttural vocals. I timestamp what I believe to be the best riff of the song. You’ve been warned.)