The Domesticated Brain: A Pelican Introduction (Pelican Books)

‘Why do you need a brain?’ Initially, this seems like a silly question with an obvious answer. ‘You need a brain to stay alive,’ is a fairly common response and indeed this is true.¹ You would be dead without your brain. When someone is ‘brain dead’, they lack the vital signs of breathing and a heart beat – functions that are automatically controlled by structures deep at the core of the brain. However, keeping you alive is neither the sole function nor responsibility of the brain. There are many other organs you need to keep you alive. There are also many living things that do not have brains, such as simple organisms like bacteria, plants and fungi.

When you take a closer look at our planet and consider all its different life forms, it soon becomes apparent that the original reason why living things evolved brains was for movement. Life forms that do not move or those that are swept around by the ocean currents or carried in the wind or even transported on or inside the bodies of other animals do not need to have brains. In fact, some start off with brains that they later abandon.

The best example of this is the sea squirt that begins life as a tadpole-like creature, swimming around the ocean in search of a suitable rock upon which to attach. It has a rudimentary brain to coordinate movements and even a simple eye spot to ‘see’, but when it finally attaches to the rock, it no longer needs to search for a home and so loses its own brain.² Brains are expensive things to operate so if you no longer need one, why keep it?

Arguably, the main reason that the brain evolved was to navigate the world – to work out where you currently are, remember where you have been and decide where you are going next. The brain interprets the world as patterns of energy that stimulate the senses, generating signals that stream up into our brain where they are analysed and stored. With experience, these patterns become learned so that the brain knows how to respond more appropriately in preparation for future encounters. As you progress up the tree of life to animals with increasingly complex brains, you find that they have a much larger library of patterns they have stored. This provides greater flexibility, giving the animal more skills and knowledge to deal with potential problems rather than being stuck with a limited set of actions. Without the ability to act, organisms would be completely at the mercy of the environment. They would be easy pickings for any predator, unable to forage or capture their own food and vulnerable to the elements. Some creatures live their lives like this – the inevitable food for others – but many evolved a brain to lash out at the world or scamper away if the threat was too fierce.

The human brain, on the other hand, is not just for solving practical problems of finding food and avoiding danger; it is also a brain exquisitely engineered to interact with other brains. It evolved to enable humans to seek out others who are similar to form social relationships. Many of its specialized operations address the complexities of the social spheres we inhabit. We require a brain with finely honed skills to process different individuals who may be family, friends, workmates or the multitude of strangers we encounter in everyday situations.

In our ancestral past, these encounters would have been few and far between, but in the modern era we need to be expert socializers. We need to recognize who people are, what they are thinking, what they want and how to cooperate – or not – with them. We have to read others in order to understand them. These social skills that may seem trivially easy for many of us turn out to be some of the most complicated calculations our brains can perform. Some people never master them, such as individuals with autism, and others lose these capabilities through the effects of damage and disease to their brains. Our brain may have initially evolved to cope with a potentially threatening world of predators, limited food and adverse weather, but we now rely on it to navigate an equally unpredictable social landscape. The human brain enables each of us to learn about, and from, each other – to become domesticated.

Our brain is equipped with the mental machinery to live together, to breed, to raise our children and to pass on information about how to become a valued member of society. Many animals live together in groups but only humans have brains that enable them to transmit knowledge and understanding from one generation to the next in a way that is unparalleled in the animal kingdom. We can learn the rules about how to behave in ways that are acceptable to the group. We can adopt a moral code about what is right and wrong. We raise our children not only to survive to an age where they are capable of reproduction themselves but also to benefit from the collective wisdom of others that is passed on as culture.

Some scientists are not so impressed with our human capacity for culture. Primatologist Frans de Waal argues that other animals also have culture because they can learn from others and transmit that learning on to the next generation.³ Famous examples of animal culture include the nut-cracking chimpanzees of Africa⁴ or the Japanese macaques who wash the sand off sweet potatoes given to them by researchers.⁵ In each case, juveniles have learned to copy what they observed in older animals. Just recently, three different neighbouring communities of chimpanzees living in the same habitat of the Ivory Coast have been shown to have distinct patterns of tool use to crack open Coula nuts.⁶ At the beginning of the season, when the nuts are hard, stone hammers are used by all; but later in the year when the nuts become softer and more amenable, one group switches to using wooden hammers or tree anvils. A third group makes this transition more rapidly. These distinct behaviours can only be explained by learning, as all tools are potentially available to each group.

There can be little quibble with the evidence in these examples of animal tool use, but this imitation is not the same as the cultural transmission that occurs when we teach our children. There is no solid evidence that cultural learning in animals has led to technologies that are improved upon, modified and developed from each new generation to the next. We return to this issue in later chapters when we explore how human children not only copy an adult’s tool use to solve a problem, but also faithfully copy rituals that have no objective purpose; something that animals have not been observed doing.

The debate about culture in animals is contentious, and our concern here is instead with what animal studies teach us about how humans are different. By addressing social mechanisms that most of us take for granted because they seem so natural and effortless, we examine how our brain has evolved to become domesticated, concentrating on childhood because this is when the major building blocks of domestication are laid down. But first, we must consider some of the basic processes that shaped the human brain to be capable of learning to become social.

Evolution in a nutshell

The only reasonable answer to where our brain came from is evolution by natural selection as famously described by Charles Darwin in the nineteenth century. Following from Darwin, most scientists today believe that life started out billions of years ago as simple chemical compounds in a primordial soup that somehow (we still don’t really know how) developed the ability to copy themselves. These early replicators were the precursors of life, eventually developing structures called cells. Clusters of these cells in time collected together, evolving into the ancient life forms known as bacteria that are still with us today.

Everywhere you look, from the deepest oceans to the highest mountains, from the frozen tundra to the desert furnace, or even in the volcanic acid pools that would strip the skin off most animals, you will find bacteria that have adapted to the most extreme conditions that can be found on our planet. Through the process of evolution, life forms continued to change and develop in ways that enabled them to survive different environments. But why evolve?

The answer is that there is no reason behind evolution, it just happens. Organisms evolve as adaptations to aspects of the environment that pose threats to survival and, more importantly, reproduction. When living organisms reproduce, their offspring carry copies of their genes. Genes are chemical molecules of deoxyribonucleic acid (DNA) encoded within each living cell that carry information about how to build bodies. The biologist Richard Dawkins famously likened bodies to simple vehicles for carrying genes around.⁷ Over time, various mutations arise spontaneously in the genes, creating slightly different bodies that lead to variations in the repertoire of adaptive fit. Some of these variations produce offspring who are better suited to the changing demands of the environment. The offspring who survive go on to produce further offspring with those inherited characteristics which worked so well, and so that adaptation becomes programmed into the genetic code that is passed on to future generations.

Through the relentless culling of those least suited for survival as natural selection dictates, the tree of life sprouted ever-increasing branches of diverging species that gradually evolved adaptations better suited to reproduce. This continuous winnowing process produced the diversity and accumulation of complex life forms that now fill the various niches of our planet – no matter how unforgiving they may be.

The ability to move our bodies purposefully around the world may have been the initial reason that brains evolved, but clearly humans are more complex than sea squirts.

Complexity suggests purpose and goals whereas evolution is a blind process driven by an automatic selection that chooses the best variations that spontaneously arise as part of the copying process. It is for this reason that Dawkins calls evolution ‘The Blind Watchmaker’.⁸ Any complexity that an animal has is usually sufficient to deal with the problems they need to solve. However, as environments are constantly changing, animals need to keep evolving or become extinct – which, when you look back on the course of life on earth, has happened to most. One estimate⁹ suggests that of all the species that have lived on the Earth since life first appeared here some 3 billion years ago, only about one in a thousand is still living today – that’s only 0.1 per cent.

There may be some controversies over the exact details and dates of this brief history of evolution, but as far as science is concerned, the origin of the species by natural selection is the only game in town when it comes to explaining the diversity and complexity of life on Earth. Whether we like it or not, we are related to all other life forms – including those with and without brains. However, human brains have enabled us, like no other animal on the planet, to bend the rules of natural selection because of our capacity to change our environment. That manipulation is largely a product of our domestication as a species.

The cost of big brains

When you consider that humans can survive in the hostile environment of outer space, where there is lethal radiation and no atmosphere, it is clear that we have considerable capacity for adaptation. When our early hominid ancestors first appeared some 4–5 million years ago, the environment was undergoing rapid changes and fluctuations that required a brain capable of versatility to deal with complex situations.¹⁰ We have brains that can think up solutions to overcome the physical limits of our bodies so that we can live under water, fly through the sky, enter outer space and even bounce around on the surface of an alien planet that has no atmosphere suitable for life. However, the processing power to solve complex problems is costly.

The modern adult human brain weighs only 1/50 of the total body weight but uses up to 1/5 of the total energy needs. The brain’s running costs are about eight to ten times as high, per unit mass, as those of the body’s muscles; and around ¾ of that energy is expended on the specialized brain cells that communicate in vast networks to generate our thoughts and behaviours, the neurons that we describe in greater detail in the next chapter.¹¹ An individual neuron sending a signal in the brain uses as much energy as a leg muscle cell running a marathon.¹² Of course, we use more energy overall when we are running, but we are not always on the move, whereas our brains never switch off. Even though the brain is metabolically greedy, it still outclasses any desktop computer both in terms of the calculations it can perform and the efficiency at which it does this. We may have built computers that can beat our top Grand Master chess players, but we are still far away from designing one that is capable of recognizing and picking up one of the chess pieces as easily as a typical three-year-old child can. Some of the skills we take for granted depend on deceptively complex calculations and mechanisms that currently baffle our engineers.

Each animal species on the planet has evolved an energy-efficient brain suited to deal with the demands of the particular niche in the environment that the animal inhabits. We humans developed a particularly large brain relative to our body size but we don’t have the largest brain on the planet. Elephants can make that claim. Nor do we have the largest brain to body ratio. The elephant nose fish (which looks like an aquatic elephant) has a much larger brain to body size ratio than the human. Despite the recent brain shrinkage described earlier, the human brain is still around five to seven times larger than expected for a mammal of our body size.¹³ Why do humans have such big brains? After all, big brains are not just metabolically expensive to run but they pose a considerable health risk to mothers. You only have to look in a Victorian graveyard to see the number of mothers who died during childbirth as a result of haemorrhaging and infection to understand why giving birth can be such a dangerous event.¹⁴ Babies with large brains have large heads, which makes them more difficult to deliver. This became a particular problem during the evolution of our species when we started to navigate the physical world on two legs. When we began to walk upright with our heads held high, this increased the danger of childbirth but, inadvertently, this risk may have been responsible for a significant change in the way we looked after each other. It could have contributed to the beginning of our domestic life as a species.

Although most mammals are up and running about pretty soon after birth, human babies require constant care and attention from adults for at least the first couple of years. The newborn brain also has to undergo considerable growth. At birth, it is nearly twice as large as that of a chimpanzee when you take into consideration the size of the mother, but still only about 25–30 per cent the size of the adult human brain; a difference that is mostly made up within the first year.¹⁵ Both our large growing brains and immaturity have led some anthropologists to claim that humans are born too early.¹⁶ It has been estimated that instead of the standard nine months, humans would required a longer gestation period of eighteen to twenty-one months to be born at the same stage of brain and behavioural maturity equivalent to a chimpanzee newborn.¹⁷ Why do humans leave the womb so early?

We do not have records of the brains of our ancient ancestors because the soft tissue deteriorates in the ground whereas bony skulls fossilize, and we can use these to estimate how big the brain they housed must have been. One of our first ancestors in the hominid tree of evolution appeared on the planet around 4 million years ago. Australopithecus or southern ape was very different from all the other ape species because it was able to walk upright on two legs. We know this because of the bone structures of their fossilized skeletons and the analysis of footprints that were preserved in the mud. The most famous fossil of australopithecus is called ‘Lucy’ after the Beatles song ‘Lucy in the Sky with Diamonds’ that was playing on the radio when she was unearthed in Ethiopia in 1974. Although Lucy was a young woman when she died, she was only about the height of a modern three-to four-year-old child and had a brain the size of a human newborn. She had long arms and curved fingers, so she was probably making the transition from living in trees to living on the land. One reason that Lucy may have come down from the trees was that the climate in Africa changed so that there was less jungle and more grassland savannahs. On a savannah, you are more vulnerable to attack from predators and so moving across flat land is much easier and faster on two legs than scrambling around on all fours like other apes.

Most of us take walking for granted, but moving on two legs is remarkably difficult. Just speak to any engineer who has tried to build a walking robot. We are familiar with science-fiction robots walking on two legs, but the reality is that this is extremely complex and requires sophisticated programming as well as a very level surface. This is because two legs provide only two points of contact with the ground, which is very unstable. Just try getting two pencils to balance against each other and you get the idea. Even big feet don’t make it much easier. Add to that the problem of coordinating the shift in weight to lift one foot off the ground and then transfer that weight to the other foot as you stride. No wonder walking is considered to be a form of controlled, continuous falling forwards.

Walking and running were both adaptations to the changing environment of the flat grasslands but they came at a cost. First, even a nimble early hominid was not going to be able to out-run sabre-toothed cats or bears, so they had to be able to out-smart animals that were physically much larger, stronger and faster. Hominids had to evolve a brain not only capable of bipedal locomotion but one that was strategic enough to avoid capture. Second, when our female ancestors began to stand upright, this changed the anatomy of their bodies. For efficient movement on two legs, the hips have to be within a certain size, otherwise we would end up waddling like a duck – which is not the ideal way to run to catch prey or avoid being eaten. So there was adaptive pressure to keep the hips from becoming too wide, which, in turn, meant that the pelvic cavity, which is the space in between the hips, could not become any larger. The pelvic cavity determines the size of the birth canal, which effectively determines the size of the baby’s head that a mother can deliver.

Up until 2 million years ago, the relative brain size of our hominid ancestors was the same as that of the great apes today. However, something happened in our evolution to change the course of our brain development, which grew significantly larger. Human brain-size increased to be 3–4 times larger than the brain of our ancestral apes.¹⁸ As our head started to increase in size to accommodate our expanding brains, this put pressure on hominid mothers to deliver their babies before their heads got too big. However, this is not a problem for our nearest non-human cousins, the chimpanzee. In terms of movement, chimps do not naturally walk upright and so did not develop a narrow pelvis. Their birth canals are large enough to give a relatively easier birth to their babies, which is why chimpanzees waddle when they do try to walk upright. They usually deliver by themselves in less than 30 minutes, whereas human delivery takes considerably longer and is most often assisted by other adults.

This problem of birthing big-brained babies in slim-hipped mothers is known as the ‘obstetrical dilemma’ and until recently was the accepted account of why human infants are born so early relative to other primates. However, anthropologist Holly Dunsworth at the University of Rhode Island has argued that another reason why our infants are born so early is that mothers would starve if the gestation period was any longer.¹⁹ Pregnancy is incredibly demanding on the mother in terms of the energy required to support both herself and the rapidly growing foetus. In primates and across other mammals, there is a reliable relationship between the relative size of the newborn compared to the mother that indicates that each species’s delivery date represents the point where the energy demands of the foetus begin to exceed what the mother can safely provide.²⁰ Bigger foetuses require more energy. Dunsworth argues that pelvic size is not the only problem, but rather feeding babies without starving the mother is why humans are born prematurely.

What is undeniable is that human childbirth is not easy. One of the more intriguing ideas about the evolution of humans and their growing brains is that the difficulty and dangers posed by childbirth could have led to the development of assisted deliveries and ultimately contributed to the evolution of human domestication.²¹ Humans needed help in order to give birth, which means that the onset of midwifery may have contributed to the social development of our species. No other animal has assisted childbirths and this unique feature which appeared early in our history may have been significant in shifting our species towards greater prosocial interactions. Other primates give birth relatively quickly in trees or bushes by themselves. It is possible for humans to give birth alone, and many do, but it is not the norm and especially not for first-time mothers, who typically experience longer, more painful labours. Assisted childbirth is part of our domestication. Having other members of the group present would have helped to protect against predators and reduce the stress of the situation by offering reassurance as well as provide physical assistance in actually delivering the baby.

Assisted childbirth could have been an early behaviour that fostered the right conditions for compassion, altruism, trust and other social exchanges that would become the behavioural foundations of our cultural domestication. Even if helping a mother to deliver entailed nothing more than being present to obscure, distract or confuse a potential opportunistic predator, these behaviours could have been the basis for reciprocal relationships with others in the group. Moreover, the stress and relief associated with a potentially dangerous birth could have triggered emotions that foster motivations to shape behaviours. Those who sought and offered assistance could have passed on such traits to their own offspring, thus increasing the likelihood of this cooperative behaviour becoming an established social pattern in the species.

In the same way that domesticated dogs seek assistance, when faced with a problem, our earliest ancestors began to look to others for help. Childbirth as shared emotional experience in the evolution of social behaviour may be highly speculative, but for anyone who has witnessed a birth for the first time, the extent of the experience is unexpected, surprisingly emotional and often beyond reason and control, suggesting that it triggers behaviours that lie deep in the history of our species to help others.

Brain size and behaviour

Considering all the problems that giving birth to big brains seems to entail, we are still left with the question, ‘Why did our ancestors evolve much larger brains about 2 million years ago?’ One possibility that is consistent with the argument we began with is that a larger brain enabled animals to move around and keep track of where they have been.²² If you look at the animal kingdom, different patterns of feeding are related to different brain sizes. Primates who eat mostly fruits and nuts have larger brains than those primates who eat only leaves. Leaves are readily available in predictable locations and so require less foraging. Primates who live mostly on leaves have to consume much larger volumes of these low nutritional foods that then have to be broken down by enzymes in the stomach. This is why leaf-eating primates have much larger guts for fermenting the material. It also explains why they have to spend most of their day sitting around and simply eating and digesting.

In contrast, fruits and nuts are more nutritious but they are also sparse, more seasonal and more unpredictable. Coming down from the trees and learning to walk upright meant that foraging over greater distances by our ancestors would become the typical behavioural pattern. Bigger brains would have been necessary to find higher value nutritional foods that would have been necessary to maintain a bigger brain.

This is why fruit-eating primates have to travel much further to satisfy their dietary needs. They also have much smaller guts and proportionally larger brains. Their habitats are more extensive and require greater navigational skills so they are generally more active. Take spider monkeys and howler monkeys, two closely related species that live in the tropical rainforests of South America. The diet of the spider monkey is 90 per cent fruit and nuts, whereas howler monkeys live mostly on the rainforest’s canopy leaves. This difference in diet and the need to forage could explain why the spider monkey’s brain is proportionally twice the size of the howler monkey’s, with a corresponding greater level of problem-solving abilities.

But our early ancestors were not simply foraging for nuts and berries – they were beginning to process food and carcasses with rudimentary stone tools. Animals with large brains are better tool users and humans are experts who far exceed any of the tool-making skills of other animals. Even making the earliest simple stone tools required special skills that are uniquely human. The anatomy of the human hand and the brain mechanisms that coordinate dexterity enabled our ancestors to hold a flint in one hand and knap it into the right shape with the other – a skill so far not observed in non-human primates.²³ Animals also tend to fashion tools from what is immediately available and abandon them soon after, whereas our ancestors hung on to their manufactured tools, carrying them around for future use. That requires a level of knowledge, expertise and intelligent planning to develop technology unprecedented in the animal kingdom – one notable exception being the sea otter that is said to carry a stone in its pouch that it uses for cracking seashells!

As unique as human tool use is, a significant increase in brain size occurred between 2 and 1.5 million years ago, and yet the oldest stone tools are between 3 and 2 million years old, predating the expansion of the hominid brain.²⁴ There have been considerable developments in the sophistication of the tools following the expansion of the brain, but the invention of tool technology itself probably did not seem to depend on the significant increase in brain size.

Another class of explanation is required to explain the need to develop larger brains but one that can include changing patterns of both food exploration and hunting. Early humans not only foraged but they also increasingly hunted, which meant that they had to travel further and they had to collaborate. They had to understand each other and cooperate to satisfy mutual goals. They had to navigate a social environment as much as a physical one and this social environment would soon get crowded.

One big family tree

The fossil record shows that modern humans are the last survivors of a branch of the evolutionary tree or genus of the apes known as Homo that emerged during a period of time known as the Pleistocene that began some 2.5 million years ago. Recent discoveries in Kenya reveal that this was a crowded time, with multiple hominid species co-existing.²⁵ Other members that would emerge later out of this branch include Homo hablis, Homo erectus, Homo heidelbergensis, Homo neanderthalensis and Homo floresiensis, nicknamed the ‘hobbit’ because of its small stature. All have become extinct, with floresiensis being the last to disappear, possibly as recently as 12–15,000 years ago. We are Homo sapiens (‘wise man’), who first appeared in Africa some 200,000 years ago.²⁶

In addition to evidence based on the fossil record, scientists have been able to reconstruct our human past by analysing the human DNA genome and looking for common sequences that reveal our relatedness. By using statistics, they can work out how long it took patterns to deviate to reconstruct our ancestry. One type of DNA, which is found outside the nucleus of cells known as mitochrondial DNA (mtDNA), has been particularly useful because it provides a way of tracing the history of our species and identifying the spread of humans across the globe. In a female, mtDNA is stored in her eggs and mutates at a different rate than cellular DNA. This difference in mutation rates enables researchers to establish various lineages back into the dark prehistory of our species. In 1987, researchers published results of mtDNA analysis and reported evidence that there was a common ancestor who must have lived in Africa around 200,000 years ago who was the ancestor for all modern humans.²⁷ As this was based on the female mtDNA that was passed on to the thousands of her grandchildren, this hypothetical mother became known as ‘mitochondrial Eve’. Just recently, scientists have been able to extract DNA from Homo neanderthalensis to determine that we are related to this extinct subspecies, while also revealing a bit of a prehistoric scandal.

Homo sapiens and Homo neanderthalensis were known to be living close to each other in the same parts of Europe at around 40,000 years ago. Eventually, Homo sapiens became the last survivors. The more ancient Homo neanderthalensis, who first appeared on the scene 700,000 years ago, disappeared in Europe and it was assumed that they had been out-manoeuvred or wiped out by the Homo sapiens from Africa through competition for resources. However, it would now appear that there was some ‘Pleistocene hanky panky’ going on, as British-born palaeoanthropologist Ian Tattersall called it, referring to the genetic evidence of interbreeding.²⁸ Analysis published in 2011 revealed that, on average, billions of people outside Africa have about 2.5 per cent of Neanderthal DNA in their genome.²⁹ Of course, we cannot know whether this interbreeding was cooperative or forced, but it does paint a completely different picture of our species.

Homo psychologicus – the social brain hypothesis

Evolutionary psychologist Robin Dunbar at Oxford University has argued that humans evolved large brains to enable them to live in large social groups.³⁰ Domestication in recent human history may have triggered a reduction in brain size over the last 20,000 years, but brains had to initially grow larger during the much longer extent of hominid evolution over the past 2.5 million years in order to live in social groups. This idea, known as the social brain hypothesis, argues that communal living required the development of large brains to navigate the social landscape but not all animals that live in large groups have particularly big brains. If that were so, we would expect the wildebeest that migrate in vast numbers across the plains of Africa to be particularly cerebrally well endowed – which they are not. They form large herds but they are not organized and coordinated by complicated social relationships. So merely living as part of a social group does not adequately explain the increased size of brains. Rather, you have to look at the nature of the social interaction of animals that live in groups to understand why big brains confer social adaptation.

UCLA anthropologist Joan Silk has studied the social organizations of different apes and monkeys and thinks that it is the ability to recognize the relationships between other members, or ‘third-party knowledge’ – a sort-of ‘he knows that she knows’ type of understanding – that is the critical skill for living in social groups.³¹ Many primates are sensitive to such third-party knowledge. Upon hearing the distress call of an infant monkey, wild vervet monkeys hidden in the bushes will turn towards the mother and the direction of the call, which shows they recognize the mother–infant relationship. In chimpanzees, males form dominance hierarchies that confer all the advantages of fathering more offspring. These chimp gangs are based on allegiances formed by pretenders to the throne who recruit followers through social interactions in much the same way individuals form gangs to rule the school playground. Once in place, the new top boss or ‘alpha male’ has the pick of the females, but he will tolerate attempts to mate from those who helped him establish the new regime.

If today’s non-human primates engage their social skills for power struggles, then it is likely that early hominids did the same. To support his social brain hypothesis, Dunbar analysed the relative brain size of many different animals and discovered that those with proportionately the largest brains are the ones that live in larger structured groups and possess more social skills. Primates in these groups have a larger repertoire of calls that enable them to communicate more complex information, a feat that requires larger brains.³²

This relationship between brain size and social behaviour is found throughout the animal kingdom. It is not only true for social animals such as elephants but also sea-dwelling mammals such as dolphins and whales. It is also true in the bird world. A good case in point is the Corvidae family of crows, jays and magpies. Caledonian crows have bigger brains than the larger chicken and not surprisingly they are also considerably smarter. In fact, when faced with puzzles that are suitable for birds, Caledonian crows outperform many primates, which is why they have been called feathered apes.³³

Longer childhoods are another feature of social animals who invest time raising their young. A chicken is independent by four months after birth and reaches maturity by six months, whereas Caledonian crows are still fledgelings at two years and require continual feeding from the parents. This is why corvid parents pair-bond for life, because it is an evolutionary strategy for sharing the responsibility of raising offspring that take so long to mature. Bigger brains may provide these animals with more flexibility in their problem solving, but they need it to be able to provide for their demanding kids.

Cultural explosion

When our species appeared on the scene some 200,000 years ago in Africa, Homo sapiens lived in organized social groups, communicating through gesture and simple language to enable them to cooperate and coordinate. We know this because the ancestor to both Homo sapiens and Homo neanderthalensis, Homo heidelbergensis, who had been around for maybe as long as 1.3 million years, was already a skilled hunter. In Schöningen, Germany between 1994 and 1998, eight exquisitely fashioned wooden throwing spears measuring 2 metres long were found among the skeletons of twenty horses. They were carved so that the weight was towards the front of the spear, making it fly straighter, similar to the design of a modern javelin. As a boy scout, I unsuccessfully tried to make spears and I doubt many of us today would know what the optimum design is. The Schöningen spears date to around 400,000 years ago, proving that Homo heidelbergensis was sophisticated enough to make a weapon sufficiently lethal to bring down a larger animal. This technological advance could not have suddenly appeared but rather must have been passed on through social learning. Since horses are difficult to corner, a hunting party would be needed to coordinate the attack, suggesting they had the ability to communicate. Given their expert skills in hunting horses, Homo heidelbergensis proves that culture was already present before the appearance of Homo sapiens 200,000 years ago.³⁴

Soon after the appearance of Homo sapiens, other examples of social learning and culture began to show up in the fossil record. Samples of haematite, a red iron oxide that can be used as pigment for body adornment, have been found in Zambian sites dating to around 160,000 years ago. Ceremonial burials including a man clutching the jawbone of a wild boar have been dated to around 115,000 years. Other graves of the same period contained beads. Why go to this effort unless there was some symbolic meaning for the objects?

As they rapidly spread geographically across the planet, Homo sapiens must have been equipped with a brain capable of much more culture than ever seen before. Based on a statistical analysis of the global data set of mtDNA sequences, it is believed that there was an increase in the Homo sapiens population around 100,000 years ago that would have produced a demographic that was ripe for enabling culture to flourish through the exchange of ideas and migrations of individuals.³⁵

From around 100,000 to 45,000 years ago, there had been sporadic examples of cultural practices such as ceremonial burials and symbolic behaviour like art and body decoration. However, in Europe around 45,000 years ago, Homo sapiens became anatomically modern humans engaging in all the trappings of primitive civilization. They were as close to us today as we can find in terms of their bodies. They also behaved much more like us than any other ancestor. Around this time there was a cultural explosion as evidenced by the advances in tool technology, elaborate jewellery, symbolic sculptures, cave paintings, musical instruments, talismans and the spread of religious ceremonies and burials.³⁶ Each of these activities was undertaken for a purpose that required a level of social interaction far in excess of anything seen before or remotely present in the animal kingdom. Humans had clearly begun to trade, as many of the raw materials for the artefacts had been transported great distances. In other words, we were already becoming vain. Art and jewellery are primarily made to be seen and admired by others. Making jewellery and creating art took considerable time and effort and would only have been undertaken and appreciated for the social value such activities conveyed. Burials and religious ceremony reflect an awareness of death and thoughts about the afterlife and creators. It may be true that some primates show the behavioural signs of mourning their dead, but modern humans are the only species that engage in death rituals.

The psychologist Nick Humphrey has suggested that it would be more appropriate to call our speciesHomo psychologicus (psychological man), given the ability of Homo sapiens to read minds – not in any supernatural psychic way, but simply by imagining what someone else is thinking and predicting what they may do next.³⁷ You need to be able to read others if you are a member of a species that has evolved to co-exist and, more importantly, cooperate. You also need these skills if you are producing helpless infants who need childcare and shared rearing. In order to make sure that you have enough resources for yourself and any offspring, you must be able to understand and anticipate the intentions and goals of other members of the group.

This is particularly true of primates who engage in deception and coalition formation, sometimes called ‘Machiavellian intelligence’ after the Italian Renaissance scholar who wrote about how to govern through cunning and strategy.³⁸ This ability requires a set of social skills known as ‘theory of mind’ in the psychological literature and represents a powerful component of social intelligence.³⁹ When you have a theory of mind, you are able to mentally put yourself in another’s shoes to see things from their perspective. This enables you to keep track of others, to second-guess their intentions, to outwit them and to exchange ideas. As we will read in later chapters on child development, theory of mind has a protracted progress and for some unfortunate individuals remains impaired, which presents a considerable hurdle in communicating with others.

The chattering brain

One uniquely human social skill that we regularly use for problem solving is language. Although we sometimes talk to ourselves, the primary purpose of language is to communicate with others. We learn to speak by listening to others, and if we were raised in an environment where we heard no language, then all the evidence indicates that we could not learn to speak normally at a later age, no matter how much training and effort we put in. There is something in our biology that dictates that we must be exposed to language at a critically early age to acquire it.⁴⁰ Even learning a second language becomes increasingly harder as we age, indicating that there is a biological window of opportunity for language acquisition.

Just about every facet of human activity involves language, whether it is work, rest or play. No other animal on the planet communicates like we do. They may have squawks, barks, grunts, squeals, snorts, screams, cries, hoots and all manner of noises, but the information they are communicating is extremely limited and rigid. Despite what Walt Disney and other animators would like us to believe, animal communications are nothing more than elaborate signalling systems to convey one of four simple messages:

‘Watch out, there’s trouble about.’

‘Back off, man, I mean business.’

‘Come and get it, there’s food over here.’

Or more often than not,

‘Come and get it, ladies, I’m over here.’

Animal communication is primarily for the four Fs of fleeing, fighting, feeding and fornicating – basic drives that keep us alive long enough to pass on our genes by reproduction. Humans also spend a considerable amount of time communicating on these very topics but when we communicate, there is nothing we better like to do than talk about others. An analysis of typical conversations in a shopping mall revealed that two thirds of the content was related to some social activity – who’s doing what with whom.⁴¹ Human communication is not restricted to biological drives that are necessary for survival and reproduction. We can talk about the weather, politics, religion and even science. We can pass on opinions, instructions and all manner of other high-level, complex information, though in all likelihood our initial communications when language first appeared were probably directed to the same four Fs that were necessary for survival. After all, human communication is complicated and difficult to execute and therefore must have evolved for a good purpose.⁴²

Why can’t we talk with the animals? First, we are the only primates with the motor machinery that enables us to vocalize the controlled sounds that form the building blocks of speech.⁴³ Most notably, unlike other primates, we have a descended larynx. The larynx or ‘voice box’ serves a number of roles. As we exhale, the air passes by the vocal cords that vibrate to create sound in the same way that blowing across a blade of grass produces a quacking sound. Changing the shape of the mouth, tongue and lips as well as controlling our breathing can further modify these sound segments to produce the differing vocalizations. The other main role of the larynx is to close up in order to protect us from inhaling food, but it does not begin to descend in the human until around three months of age, which explains why babies can swallow and breathe at the same time when they are breastfeeding.

With our descended larynx, we have a much longer vocal tract, enabling us to produce a much greater variety of sounds. Coupled with this extra-long sound pipe, we also have greater muscular control over our lips and tongues compared to other primates, which is why human speech is physically impossible for other animals. But that physical limitation is not the only reason that animals do not speak. They simply don’t have the right brains for it. Karl Lashley, the American psychologist, originally proposed in 1951 that the unique basis of human speech must involve brain circuitry responsible for sequencing movements.⁴⁴ In recent years, this hypothesis has gained support from the discovery of the FOXP2 gene that governs the embryonic development of brain structures that support speech production. Even if animals could control the required movements, linguist Noam Chomsky emphasizes decoding the underlying structure of language itself as requiring specialized brain mechanisms that humans alone have evolved.⁴⁵ The major difference between our language and the social communication of other animals is that we have a system of grammar – words and rules that can combine together to generate an unlimited number of new sentences about anything. Most of us are not even aware that we are using these rules. As native speakers, we can spot that there is something wrong with the utterance ‘complex human is language’ because it does not follow the rules, but very few of us know exactly what these rules are. Before we discovered the rules of language, humans were speaking grammatically.

Language is also a symbolic system, which means we use sounds to stand for something. In speech these are the words, but before there were words there must have been specific sounds that we learned to associate with meaning. Animals can also learn to associate sounds to stand for things if they are trained to do so. They can even learn to associate gestures with meanings. There are some famous cases of chimpanzees that learned sign language, but this is not something they can do spontaneously. It requires lots of training with rewards and they cannot make up new sentences as easily as children do.

There is something special about human language in both production and understanding that other animals just do not get because it was never part of their evolution. Our capacity for language is arguably the major species-specific ability that catapulted modern humans into an unparalleled league of social interaction. It has not always been like this. A hunter-gatherer ancestor did not wake up one day and blurt out to the rest of the tribe, ‘Let’s go hunting.’ Our language must have evolved into the complex behaviour that is universally enjoyed today. Some argue that evolution cannot explain something as complex as language but it is precisely because of that complexity that language had to evolve gradually by natural selection. In the same way that the eye is a complex biological adaptation that could not have suddenly appeared from a one-off mutation, the same must be true for language.

Babies do not need to be taught how to speak; most children are fluent by three years of age, irrespective of where they grow up in the world, so long as there are people around speaking to them. The grammars of industrialized societies are no more complex than those of so-called primitive tribes and all languages share the same underlying linguistic rules that were only relatively recently discovered. Language can also be knocked out by certain head injuries, it activates specific networks of neural circuitry in the brain and some language disorders are genetically transmitted. Taken together, these facts indicate that the development of language belongs more to the realm of human biology than cultural invention, which is why language has been called an instinct.⁴⁶ Language not only enabled humans to pass on information, but it allowed us to domesticate our children by instructing, scolding and encouraging those ideas and behaviours that would be most suited to getting on with others peacefully.

The architecture of the mind

Many scientists believe that language did not suddenly appear but rather must have evolved from a number of different sub-skills – almost like making a new machine by recycling other parts. Evolutionary psychologists Leda Cosmides and John Tooby propose that much of the mind must also be considered like a toolbox that has accumulated specialized skills over the millennia to deal with specific problems.⁴⁷ Like every other aspect of the human body, they argue that the brain must have evolved to solve problems through the process of gradual adaptation. As Cosmides and Tooby quip, ‘the human brain did not fall out of the sky’, ready prepared to address all of life’s problems. Rather, it must have evolved in stages, dealing with one set of problems at a time. As humans evolved increasingly more complex lives, we also had to evolve new behaviours that provided the best opportunity for reproduction. We needed to find the best mate, refine attentive social skills and learn what was necessary to be accepted.

With these sorts of recurring problems, humans evolved a repertoire of coping skills that are passed on in our genes. Our ability to navigate, count, communicate, reason about the physical properties of objects and interpret expressions are just some of the candidate functions that might be part of our evolved behaviours. These can all be found in humans across the planet today, irrespective of where they live. If these functions are universal and largely independent of the culture or society, then this strongly suggests that they are wired into our biology and transmitted by our genes. However, this is where the theoretical arguments take place. To what extent is a particular human attribute an evolved adaptation and to what extent has it been created and transmitted in recent evolutionary history by culture? Is jealousy a cultural artefact of prevailing sexual attitudes or could it be something that conferred an adaptation in our evolutionary past? Even though we cannot go back to see how our ancient ancestors evolved, we can look for clues that support the idea that functions we possess are the legacy of natural selection.

Human evolution took place over millions of years and must have been gradual for a number of reasons. First, as an organism evolves from simple to more complex activities, the types of problems it encounters over time will change, spurring on the necessity for further adaptations. The complexity of the brain could not have resulted from one massive mutation in our DNA. Rather, the complexity would have had to emerge as each successive version of ancestors had to deal with a new set of problems. Second, adaptation works for solving specific problems, so a brain that was not especially equipped to deal with a problem would not be selected for. In effect, the brain had to have a collection of specialized problem-solving solutions rather than being a good all-rounder. If the brain had only been a good all-rounder problem-solving system, then it could never be as efficient as one made up of multiple specific skills. Different problems require different solutions with tailored mechanisms. In other words, a jack-of-all-trades is a master of none.

One way to imagine the mind is as a Swiss Army knife with lots of blades that perform different functions. You have blades for removing stones from a horse’s hoof (who uses that these days?), corkscrews, scissors and an assortment of other bespoke blades. In the same way, the brain has specific functions such as language, spatial navigation, face processing, counting and so on. If our mind was like our metaphorical knife but only had one general-purpose blade good for cutting but not good for opening bottles, then we would be limited in dealing with specific problems. For example, vervet monkeys have evolved an alarm-call system to identify three different types of predator: snakes, eagles and leopards. Each predator requires a different course of action: either standing on hind legs looking down at the grass around them (snake), looking up in the air and diving into a bush (eagles) or climbing up a tree (leopards). Get the response wrong and the vervet monkey becomes dinner. This is why they instinctively respond to different alarm calls. A general-purpose ‘Look out!’ would not have been a good adaptation.

This evolutionary approach has led to the view that the architecture of the mind is not a general problem solver but rather a collection of systems dedicated to addressing specific problems. In the same way that dedicated mechanisms for solving recurrent problems during human evolution could have emerged through the process of natural selection, culture-gene approaches to understanding human evolution propose that our species possess mechanisms that reliably seek out cultural input.⁴⁸ In other words, there are genetic dispositions to learn efficiently. The reason for this is that culture changes faster than genes. Unlike examples of cultural learning in animals, humans continually refine, develop and expand on knowledge that is passed on. This is possible because we have brains that are evolved to learn from others. Our efficiency is guided not only from our capacity to communicate, but also by our biases to attend to specific aspects of others that signal who are most valuable as teachers. As we will learn in the coming chapters, babies are tuned into their mothers from the very start in a reciprocal relationship. But they also pay more attention to others who are older, who are the same sex, who are friendly and who speak the same language. Babies are born with dispositions encoded in their genes to learn from those who are going to be most useful to them in terms of acceptance by the group.

Cognition, cooperation and culture

Psychologist Mike Tomasello at the Max Planck Institute for Evolutionary Anthropology in Leipzig is one of the world’s leading experts on what makes us human. He studies the development of children and how they compare to other primates. He believes that the traits that distinguish humans from our primate cousins are our capacity to think about others, cooperate with them and share ideas and behaviours. All of these are necessary for cultures to thrive. Human culture differs from any other social groups in the animal kingdom because there is a cumulative build-up of knowledge and technologies that is passed on from one generation to the next. With every generation, our world becomes more complex because we educate and share information by cooperation. In this way, knowledge and understanding ‘ratchet up’, with each successive generation expanding and improving the complexity and collective knowledge of the group.⁴⁹

Other animals also live in groups and exhibit a host of social skills for working out what others are thinking, but these abilities are mostly restricted to situations where there is a potential fight or conflict. Most non-human primates are opportunists, only on the lookout for situations where they can take advantage of other members for either food or sex or to establish a better position in the dominance hierarchy. There are examples where chimpanzees will help others, but these are mostly situations where there is the potential for some personal gain.⁵⁰ In contrast, people will sacrifice personal gain for others. They will even spontaneously help strangers who they will never meet again. The capacity for altruism seems to be characteristically human. Examples of animal altruism are rare and restricted to those species that exhibit strong codependence, such as marmosets. In these cases, it is strategically in their interests to be promiscuously prosocial to increase their likelihood of breeding.⁵¹

Humans may be opportunists too, but all societies are held together by tacit assumptions of reciprocity and moral codes to prevent individuals taking advantage. These are the rules we abide by. Some of these codes are enshrined as laws. We enter into social contracts where we submit to authority or the state on the assumption that those who abide by the rules will benefit, whereas those who violate or break them will be punished. Members who benefit from these social arrangements do not even have to be family. Indeed, when you think about it, much human sharing of resources is altruistic – doing good deeds for the benefit of others who remain anonymous without necessarily benefiting ourselves.

No other animal on the planet behaves as altruistically as we humans do. Of course, there are some species, such as worker ants and bees, that make the ultimate sacrifice for the good of the nest or the hive when it comes under attack, but they do so because they are genetically closely related to those that benefit. Evolution has programmed their brains to be self-sacrificial. Humans are different. We cooperate with others because it makes us feel good. It is the thought of helping that is the reward, because we feel connected to the group. These feelings are the emotions that motivate us to be prosocial towards our fellow man (or woman) and fuel the drive towards altruistic collaboration, cooperation and ultimately human culture. However, we are not slavish drones that automatically bend over backwards to help anyone; we are always on the lookout for those who are trying to cheat the systems of reciprocity. We are inclined to lend a hand but we will seek retaliation if we believe we have been wronged. In order to make these sorts of decisions we have to have brains that are sophisticated enough to interpret others in terms of their motives, their goals and their affiliations.

What makes the human brain different?

For many animals, the problems of living long enough to reproduce were basic and immediate – how to navigate the world to find food, avoid harm and so on. Solitary animals figure these out for themselves because this is how they have evolved. Other animals that live in groups evolved the capability for coordination and cooperation for mutual benefit. For them, the environmental pressures they had to adapt to were not only physical, geographical or climate-based but also social. In a group, there would have been multiple potential mates competing to pass on their genes. This led to the evolution of social behaviours that increased the likelihood of successful breeding within a group.

This increase in social skills is considered one of the reasons that primate brains grew larger and why our species in particular have become the most skilled at interacting and learning from others. But then the human brain began to shrink again with the birth of large civilizations, when we started to live together more peacefully. It could be that humans went further than all other social animals by developing culture – the ability to communicate, to share ideas and knowledge, to engage in ritualistic symbolic activity and develop rules about how to behave for the benefit of the group. We had to learn to live together in greater harmony as our numbers started to increase. We needed to learn to become diplomatic. While physical environments tend to be static, social environments by comparison are constantly changing and providing considerable feedback, which in turn changes the dynamic of the interaction. In short, expertise in social interactions required considerable processing power and flexibility.

To enable humans to do this, we developed long childhoods to provide sufficient time and resources to ensure that our offspring were educated in the skills necessary for harmonious social living. Why else would humans have evolved into the species that spends the longest proportion of their lives dependent on adults? This amount of time was an evolutionarily big commitment for both parents and their offspring. With domestication came wisdom passed down the generations. We may have taught our own children some basics, but there was more to learn from the group. Our ability to communicate meant that our children could learn more about the world they needed to negotiate by listening to others without having to rediscover everything from first principles. But to benefit from that, the most critical knowledge they learned during childhood was how to be liked and valued by others – in other words, how to behave.