Historic Food Transitions Enabling Growth in Human Intelligence

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Peter Turchin:

"The first step, which took place 5-7 million years ago, was the transition from our chimpanzee-like ancestors, forest apes, to australopithecines that inhabited drier savanna-woodlands. Australopithecine brain size (in anthropologese, “cranial capacity”) was 450 cubic cm, compared to 350-400 cm3 in forest apes.

Incidentally, and as an aside, I find slightly amusing, but mostly exasperating, Richard’s dutiful translation of cubic centimeters into cubic inches. Americans, isn’t it time to grow up? Get used to metric units! Does it really help you to know that the cranial capacity of Australopithecus was 27.5 cubic inches? If I show you an object, will you be able to estimate its volume in cubic inches? End of diatribe.

The food resource that enabled this transition was the underground storage parts of plants, highly concentrated sources of energy-rich starch. Parenthetically, that’s why potatoes, yams, carrots, beets, sweet potatoes, and taro are such great foods for humans – we have been eating them, or equivalents, for millions of years. Australopithecines dug these tubers, rhizomes, and corms (we are now speaking ‘botanese’) with sharpened sticks.

The next step was the transition to ‘habilines’ (such as Homo habilis) more than 2 million years ago: from 450 to 612 cm3. The big dietary change that fueled this increase in brain size was probably meat eating. Or marrow eating – see my blog on this issue.

After that, brain size in early human started growing in a really explosive manner. Early Homo erectus (1.8 million years ago) had brains of 870 cm3. 800 thousand years ago Homo heidelbergensis (which could be simply a subspecies of erectus) had brains of 1200 cm3. That’s awfully close to the modern Homo sapiens, whose cranial capacity is 1400 cm3.

Where did the energy that fueled these oversize brains come from? Wrangham argues that it came from cooking. I find his argument quite convincing. Thermal processing of tubers and meats doubles the ability of our guts to extract calories and nutrients from these food sources.

The use of fire is securely attested at the Gesher Benot Ya’akov site near Jordan River, which is dated to 790,000 years ago. But here we have archaeological evidence of hearths, permanent fires around which human nuclear families would gather around every evening for the most important meal of the day. It is quite likely that hearths were a product of long evolution, with humans using fire for cooking well before the evolution of human family (which as Wrangham argues, was itself a result of cooking food – but you will have to read his book to find out the details of the argument).

Even if you buy Wrangham’s theory (which I do), it raises some questions. When did humans learn how to start fires?" (http://peterturchin.com/cliodynamica/paleo-diet-and-fire/)


Peter Turchin:

"Richard Wrangham: Catching Fire: How Cooking Made Us Human.

It’s a great book, and I recommend that everybody interested in human evolution read it.

What I found most interesting in Richard’s book is his reconstruction of the dietary shifts that enabled the evolution of large human brains. which then made possible culture, living in large groups, language, art, science, and civilization." (http://peterturchin.com/cliodynamica/paleo-diet-and-fire/)