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4.5
In this book a skilled science journalist surveys the palaeontological and anthropological state of play through to late 1999.In the course of surveying the last 5m years of human evolution, McKie brings out some fascinating evidence relevant to important contemporary debates. I look at these in this review.(The page references are to McKie's book.)In terms of diet, our pre-Homo ancestors were herbivorous (vegetarian) and our digestive system is basically unchanged since that time. However, there were immense evolutionary advantages in our ancestors also consuming meat - indeed, without consuming meat we might still be the Australopithecene genus which preceded Homo through to 2m years ago.Climate change gave the Australopithecenes the stark alternative: adapt or perish. Some of our ancestors adapted, becoming tool makers and omnivores (and Homo) rather than herbivores. They also survived - as meat eaters with a herbivorous gut.McKie quotes Richard Potts: "About 2.5m years ago, hominids encountered great fluctuations in the climate. At the same time we see the appearance of stone tools. That is no coincidence. They indicate that at least one hominid species was responding to these changes by becoming even more adaptable, rather than becoming specialized in the way that robustus and bosei did. By making tools, dietary choices became greater. Not only could people skin the large dead and doubtless smelly carcasses they occasionally found, they could crack open their bones for marrow. In addition tools would have helped pound and break down vegetables and nuts that could otherwise only have been eaten by animals with specialized dentures, and also helped dig up tubers rich in protein and calories. Just as Australopithecines responded to oscillating climates by walking, by becoming more versatile movers, so did the first members of the Homo line 2m years later. They made tools and became more versatile eaters" [66f]. The richer diet led to bigger brains, bigger brains led to intellectual growth and intellectual growth led to: (a) improved memory (including mental resource maps of the terrain and the seasons), (b) the ability to co-operate and take advantage of social complexity, (c) the ability to solve problems which led to the ability to create and use tools. These benefits in turn led to a more reliable diet which was also richer [114]. "We became less tethered to our habitats. Our ancestors' behaviour was becoming increasingly diverse, our menus more adventurous" [67]. Meat eaters were more free to migrate so they could survive, herbivores being more limited to the spread of their familiar staple plants [96]. The complexity of societies, the importance of memory and skills led to adults having a benefit beyond their reproductive age - they had knowledge and culture (wisdom) to pass on, not just physical genes[115].The second theme concerns the evolution of human society and the differentiation of male and female roles.Humans had a small pelvic gap for the birth canal, yet a more intelligent species would need a larger head to accommodate the large brain. A larger head could not fit through the pelvic gap. The evolutionary response was twofold: (a) for humans to be born while their brain was still relatively small. This means that mothers needed to provide intensive care (suckling, nurturing, warmth) while the brain developed. If mothers devoted themselves to nurturing, they need the reliable support of others [88]. The second response was (b) for women to evolve wider hips. This development survives today: women are less efficient bipedalists than men. The male shape was better adapted than the female shape for many of the activities of being the provider [89]. Because human brains take years to develop, there is a need for sustained social bonds (families) to support the maturing human for the duration of its immaturity (i.e., its childhood).The third theme concerns the physical activities of our ancestors. "The numerous injuries on Neanderthal skeletons pointed to a dangerous, perhaps violent, side to their lives. Trinkaus analyzed the bones of 17 Neanderthals who had 27 traumatic wounds. They were mostly injured to the head and upper body. I got a statistical fit with rodeo riders; they get thrown off their animals a lot. In other words, it looked like Neanderthals were being flung around by the creatures they hunted. Not for them the low-risk, careful business of stalking and spearing. They went in for the kill and paid the consequences. These were people with physical prowess beyond the aspirations of even the best Olympic athletes [157f]." Survival in this environment would have evolved a body suited to vigorous, intense exercise, not gentle aerobics.The fourth theme concerns the use of fire. This is important for us as the historical timing of its regular use can indicate whether our diet should - for scientific rather than aesthetic reasons - include cooked meat. Sites 500,000 years old have no signs of fire. Some hearths and the remains of burnt bones have been found in China 300,000 to 400,000 years ago. Fireplaces do not appear regularly until about 40,000 years ago [160], just 1700 generations, not long in evolutionary terms.The fifth theme concerns mental and emotional skills, apart from quick reactions and coordination. McKie's beautiful account indicates that people who were tenacious and innovative were survivors. More than that, it was those who had social skills - who trusted others and were trusted in return, who showed compassion [90, 154, 156-7], who sustained long-term relationships of trust [80f] (and love?), who contributed to the group who survived best of all. People with good memories and who organized their thoughts in a way that could be communicated effectively (a) for immediate practical purposes [124] and (b) down the generations were also at a premium. Remember, the oral tradition was the only tradition.This beautiful book is superbly illustrated.
