Who’s cooking your dinner? Who’s looking after your kids? If you are a man, it is probably the woman—or women—in your life. You know that women mainly do the daily domestic grind. And so it has been, not just throughout history but also throughout the last two million years of human evolution, according to Richard Wrangham, author of Catching Fire, and Dean Falk, author of Finding Our Tongues.
There was once a time—not too long ago—when men could wallow with pride in the Stone Age accomplishments of our sex. It was slaying beasts, making tools, and fighting each other that transformed a Stone Age primate, physically and mentally little different from a chimpanzee, into the big-brained language-using primate that strode out of Africa to dominate the world. How lucky for women that their Stone Age menfolk were so brave and clever.
It is now men who need to nod in acknowledgment at the accomplishments of the Stone Age women who undertook the cooking and childcare. For according to Wrangham and Falk, it is those activities that provided the causes and conditions for the evolution of large brains and language. Women should particularly appreciate these two fascinating books about our evolutionary past.
The evolutionary history of our species is by far the best story ever to be told. It is one that needs continual rewriting and retelling as our knowledge of the fossil and archaeological records improves, as the genomes of humans, apes, and monkeys are revealed and compared, as neuroscience penetrates the working of the brain, and as we appreciate the evolutionary significance of activities that have previously been neglected, cooking and childcare being the two cases in point. While the details remain under debate, astonishing progress has been made in our understanding of human origins ever since Darwin explained how natural selection works and the first human fossils were found 150 years ago.
The common ancestor of humans and chimpanzees lived in Africa between seven and five million years ago, a date established by DNA studies rather than the discovery of fossil remains. We have found fossilized fragments of pre-human bone substantial enough for meaningful interpretation that can be dated only as far back as 4.5 million years ago. Anthropologists have found the remains of a diverse range of hominid species from after that date, all slightly different in shape and size, testifying to multiple adaptations to different niches in the African landscapes. Some became highly specialized, exploiting dry seeds and other plant foods, which resulted in species that had a physiology not unlike that of gorillas today but with chimpanzee-sized brains (circa 450cc).
Natural selection took others in a different direction so that after 2.5 million years ago they were adept at making stone tools, reliant on meat eating, and committed to walking on two legs. These species are referred to as habilines (after one of their members, Homo habilis, with a brain size of up to circa 650cc). From that group one species emerged at around two million years ago that looked and behaved far more human-like than all others, one that we now refer to as Homo ergaster, with a brain size approaching 1,000cc. It was this species (we think) that first left the African continent, dispersing into Southeast Asia and Europe while human evolutionary processes were ongoing both within and outside of the African continent. Further dispersals from Africa followed.
By 500,000 years ago, brain size had reached modern-day capacities (on average between 1,300cc and 1,500cc, with significant variation for body size), although there remains no evidence that these species engaged in those peculiarly human activities of art and religion. Homo neanderthalensis—Neanderthal man—evolved in Europe soon after 350,000 years ago, while in Africa Homo sapiens—our species—appeared around 200,000 years ago, these species probably sharing Homo heidelbergensis, a descendant of Homo ergaster, as a common ancestor. The first traces of unambiguous use of symbols appeared in South Africa around 100,000 years ago, and after 70,000 years ago a great diaspora of Homo sapiens began that took our species to the ends of the earth—Tasmania by 30,000 years ago and Tierra del Fuego by 11,000 years ago.
By 25,000 years ago we had become the lonely species, the only member of our genus to survive on the planet except for the “hobbits,” Homo floresiensis, on Flores Island, who went the way of the Neanderthals once modern humans arrived on their island around 12,000 years ago. Why are we the sole surviving member of our genus? My guess is that it was Homo sapiens alone that evolved fully modern language.
The peak of the last ice age came 21,000 years ago, further inspiring remarkable artistic achievements, such as cave paintings at Lascaux, in several parts of the globe from Europe to Australia. Dramatic climate change 11,550 years ago left modern humans in a world that was warmer, wetter, and climatically more stable than they had ever experienced. The cultivation of plants and domestication of animals arose quite independently in several parts of the world; agricultural lifestyles with towns and trade followed, as did civilizations and empires. History began while human evolution continued, as it does today.
The human story is so far without an end, but is probably heading for inevitable global catastrophe. The key question is how our denouement will come about: Will it be by nuclear devastation, man-made global warming, or biological epidemic? What a truly remarkable species we are to have provided ourselves with such options. According to Wrangham we should blame this predicament on our ancestral diet; according to Falk, we can blame our ancestors for having been too kind-hearted to their babies.
Documenting this evolutionary story is challenging enough. It is a much greater task to try to explain how we began as just one of several run-of-the-savannah primates in Africa yet became the only creature introspective about its own past and future. Anthropologists have looked toward modern-day hunter-gatherers, once thought to be direct relicts of the Stone Age, and sought to find the single evolutionary shift that differentiated our species from our ape and monkey relatives. During the 1950s and 1960s “man the hunter” and “man the tool-maker” became popular ideas—the word “man” being significant beyond the colloquial designation of our species. Hunting and tool-making were espoused as activities that are unique to humans and were responsible for all things good: bipedal walking, big brains, pair-bonding. Then along came Jane Goodall, who took the time to actually find out how chimpanzees lived. She discovered that they also make tools, hunt animals, and eat meat. She found that chimpanzees also brutally kill members of their own species.
During the last two decades evolutionary anthropologists have shifted their attention away from the challenges that faced our ancestors when interacting with the physical world to those of the social world. Rather than worrying about how the habilines of some 2.5 million years ago managed to locate ripe fruit and swollen tubers, ambushed antelope and produced stone flakes to butcher a carcass, anthropologists have become concerned with how they negotiated the complexities of living in relatively large social groups. This increase in group size compared to that of their forest-dwelling ancestors appears to have been a perquisite for the habilines, who needed to find a means of defense against predators in their increasingly open savannah habitats without the protection that trees provide. But who to mate with and who to trust? Who to back in a fight and to whom should one be subdued? Who to share food with? Who to avoid and who to cheat?
The complex politics of chimpanzee societies, as revealed from the studies of Franz de Waal and others, has lent substantial credence to the claim that it would have been those individuals who could think rather than fight their way through the social maze that were ultimately rewarded with reproductive success. It was they who set our species on course for a bigger brain. Such thought is likely to have required enhanced abilities of understanding different minds, or at least knowing that the beliefs and desires of another individual are different from one’s own. This does indeed appear to be something that is lacking to any significant extent among chimpanzees.
But one can’t just think one’s way to a bigger brain: one has to eat, and big brains are particularly hungry. While complex social life may have provided the selective pressure for the evolution of bigger brains, this could be realized only if sufficient food could be consumed to provide the required energy. How could that have been achieved? By catching fire and cooking food is Richard Wrangham’s answer.
He tells a simple but convincing story. It draws not only on what we know about the fossil record for changing anatomy, observations of modern-day primates, and the behavior of hunter-gatherers but also the science of cooking, digestion, and nutrition. The essence of his argument is that the evolutionary path from ape to human, to big brains and pair-bonding, could only have begun once our ancestors began to cook their food. The simple reason is that cooked food, whether vegetables or meat, provides significantly more energy than the same foodstuffs in their raw state. Cooked food is easier and quicker to digest; it can be digested with a smaller gut, releasing metabolic energy for a larger brain; it opens up a more diverse natural larder than is available to those reliant on raw foods; the reduced time and strength required for chewing allows the size of the jaw and teeth to be reduced, freeing the oral capacity for a greater range of vocalizations. Cooking literally provided the meat for the male–female pair-bonded sandwich on which human social organization is based.
Wrangham writes with the authority of someone who has personally made many of the studies on chimpanzees and hunter-gatherers to which he refers and with the pleasure of having drawn an assortment of scientific studies and anecdotes from academic obscurity to public attention. So he recounts his meetings with raw-foodists, those dedicated to eating their food raw in the mistaken belief that this provides a more natural and healthier diet than cooked food. He describes having dinner with two members of their militant wing, who style themselves as “instinctotherapists.” They mimic chimpanzee feeding habits by taking only one type of vegetable at a time and eating their meat raw, often in the form of marrow taken straight from the bone.
Wrangham finds that raw-foodists, including those who have been forced into this diet by being shipwrecked or lost in the jungle, can be perfectly healthy. But they are always thin and frequently seem tired: eating raw food is an ideal way to lose weight because relatively little energy can be extracted from it during digestion compared to cooked food. A raw food diet is just about feasible for modern-day, urban-living people who can drive to work and stroll to their supermarket to find the very best fruit and vegetables. But such a diet is likely to be impossible for anyone else: there are no accounts of “traditional people” who survived on raw foods alone.