Brent Kearney

As a technologist and a Paleo aficionado, I found this part of Matt Ridley’s latest book fascinating. The book is The Rational Optimist: How Prosperity Evolves. It applies evolutionary analysis to economics and human behaviour at the civilizational scale. I’m only on the second chapter, but like his previous book The Red Queen: Sex and the Evolution of Human Nature, it will likely become one of my favourites.

By the time of the Boxgrove horse butchers, their ancestors had been making it to roughly the same design — hand-sized, sharp, double-sided, rounded — for about a million years. Their descendants would continue to make it for hundreds of thousands more years. That’s the same technology for more than a thousand millennia, ten thousand centuries, thirty thousand generations — an almost unimaginable length of time…

It was part of what Richard Dawkins called ‘the extended phenotype’ of the erectus hominid species, the external expression of its genes. It was instinct, as inherent to the human behavioural repertoire as a certain design of nest is to a certain species of bird. A song thrush lines its nest with mud, a European robin lines its nest with hair and a chaffinch lines its nest with feathers — they always have and they always will. It’s innate for them to do so. Making a teardrop-shaped sharp-edged stone tool takes no more skill than making a bird’s nest and was probably just as instinctive: it was a natural expression of human development.

Indeed, the analogy with a bodily function is quite appropriate. There is now little doubt that hominids spent much of those million and a half years eating a lot of fresh meat. Some time after two million years ago, ape-men had become more carnivorous. With their feeble teeth and with finger nails where they should have had claws, they needed sharp tools to cut the skins of their kills. Because of their sharp tools [including projectile weapons] they could tackle even the pachydermatous rhinos and elephants. Biface axes were like external canine teeth. The rich meat diet also enabled erectus hominids to grow a larger brain, an organ that burns energy at nine times the rate of the rest of the body. Meat enabled them to cut down on the huge gut that their ancestors had found necessary to digest raw vegetation and raw meat, and thus to grow a bigger brain instead. Fire and cooking in turn then released the brain to grow bigger still by making food more digestible with an even smaller gut — once cooked, starch gelatinizes and protein denatures, releasing far more calories for less input of energy. As a result, whereas other primates have guts weighing four times their brains, the human brain weighs more than the human intestine. Cooking enabled hominids to trade gut size for brain size.

Ridley cites:
Foley, R.A. and Lahr, M.M. 2003. On stony ground: Lithic technology, human evolution, and the emergence of culture. Evolutionary Anthropology 12:109–22.

Richerson, P. and Boyd, R. 2005. Not by Genes Alone. Chicago University Press

Aiello, L.C. and Wheeler, P. 1995. The expensive tissue hypothesis: the brain and the digestive system in human and primate evolution. Current Anthropology 36:199–221.

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