Keith Kloor
If you are one of those people always in search of the ideal diet, then chances are you have stumbled across the idea of “intermittent fasting”. The supposed logic to this diet is that our bodies did not evolve with three square meals a day, which are a legacy of our recent switch to farming. Rather, the theory goes, we evolved with an irregular food supply more in accordance with the feast or famine lifestyle of our hunter-gatherer ancestors.
There’s just one problem with this premise. Palaeolithic hunter-gatherers probably lived a far more food-secure life than is commonly assumed, a paper published in the journal Biology Letters has found.
“My study provides evidence that their lifestyle might be more resistant to famine and food shortages than the agricultural lifestyle,” says lead author Colette Berbesque, an anthropologist at the University of Roehampton in Southwest London.
Using ethnographic literature, the researchers examined a cross-section of hunter-gatherer and agricultural societies over the past 150 years. They found that agriculturalists were more susceptible to famines, probably because they were more rooted to a single landscape than hunter-gatherers, who would move around during times of drought or flood.
Evolutionary biologist Stephen Stearns, of Yale University, cautions that the study is based on contemporary data of hunter-gatherers “who now occupy habitats that are not representative of those occupied by our Pleistocene ancestors”. But as Berbesque points out, most ancient hunter-gathers would have lived in better quality habitats than the fringe lands to which modern agricultural societies have pushed them.
The study’s main finding challenges popular assumptions of the way our evolutionary past clashes with modern living. For example, today’s obesity rates are sometimes attributed to an ancestral trait that the hunter-gatherer supposedly developed as a defence against food scarcity. The theory is called the “thrifty genes hypothesis”, the idea that our bodies are programmed to fatten up in times of plenty, and so are not suited to the modern-day diet of continually abundant food.
Berbesque notes that humans have been hunter-gatherers for most of their 200,000-year history. Before the onset of agriculture 15,000 years ago, everybody ate wild foods. So if hunter-gatherers experience less famine than farmers, this has implications for the thrifty genes hypothesis.
“If famine or food shortages have ever lead to selection for genes that cause obesity,” says Berbesque, “it might be more recent – arriving with agriculture – rather than due to our heritage as hunter-gatherers.”
That, in turn, would upend the logic for today’s health-conscious voluntary fasters, who think that periodically starving themselves is consistent with their long evolutionary history.
This article appeared in Cosmos 55 – Feb-Mar 2014 under the headline “A new look at the paleo diet”