Yesterday I had a email from a friend alerting me to an interesting piece in the Sunday Times. I went out especially to buy a copy. The piece, entitled ‘Farmers, you’ve shrunk mankind’, is based around a presentation given at the Royal Society in London, last week. The lecture was delivered by Dr Marta Lahr of the Leverhulme Centre for Human Evolutionary Studies at Cambridge University, UK. It seems that the fossil record shows our ancestors 200,000 years ago to be about 10 per cent bigger and taller than we are now. And 20,000-30,000 years ago, our ancestors had brains about 10 per cent bigger than ours are now too.
A shrinking in the size of our bodies and brains happened about 10,000 years ago. What was it that caused this? The answer is our transition from hunter-gathering to a more farming-based existence.
The Sunday Times piece also relates research from Amanda Mummert, an anthropologist from Emory University in Altanta, US. Mummert has recently co-authored a paper [1] which provides evidence supporting the idea that our move to agriculture was bad news for our height and our health. One of the reasons that would explain this, according to Mummert, is an over-reliance on a grain-based diet deficient in key nutrients. Sound familiar anyone?
To my mind, the nutritional inadequacy of grains is compounded by the fact that they tend to be rich in phytates that impair the absorption of nutrients, and minerals in particular. Some of the anti-nutrients in grain have been shown to impair vitamin D metabolism – not good news bearing in mind vitamin D plays a key role in the functioning of calcium in the body. Grain also contain substances that impair digestion, and these won’t help matters either.
What might explain the reduction in brain size though?
The brain is a fatty organ, and two forms of fat that play an integral part in its development are arachidonic acid and docosahexaenoic acid. Arachidonic acid is found in, among other things, meat. Docosahexaenoic acid is also found in fish, seafood and meat, as well as bone marrow and, perhaps not surprisingly, brain (there is good evidence that our early ancestors used stone tools to break open skulls and bones to gain access to brains and bone marrow respectively).
In some respects, therefore, the diet we ate as hunter-gatherers, rich in animal foods as it was, provided an abundance of brain food.
Of course our move to grains as a staple food would have seen a fall in our intake of crucial brain-building fats.
The Sunday Times piece posits the idea that we humans may have passed our physical peak, and that “agriculture is the likely cause.” The advent of agriculture saw us turn our backs on the diet that sustained us for the vast majority of our time on this planet. Should we be too surprised that this didn’t turn out too well, and that we’re continuing to pay the price today?
References:
1. Mummert A, et al. Stature and robusticity during the agricultural transition: Evidence from the bioarchaeological record. Econ Hum Biol. 2011;9(3):284-301.
