Imitating the carnivorous ways of our Stone Age ancestors is one of the central aims of the modern paleo diet. But according to new research, our prehistoric ancestors may have eaten much less meat than previously believed.
Many contemporary paleo diet gurus advocate a diet that’s 50 percent or more animal products (though contrary to what some people think, this doesn’t just mean chowing down on bacon and burgers — paleo dieters stress the importance of eating lean meat, fish and eggs that come from grass-fed livestock). This is based on the conventional wisdom that paleolithic humans ate a diet of between 60% and 80% protein, mostly from animal sources.
Yet a diet of 60 to 80% animal protein is “very hard to explain physiologically,” said Tamsin O’Connell, an archaeologist at the University of Cambridge.
Eating that much protein would literally poison 21st century men and women, by introducing toxic amounts of nitrogen into the body. Today, our diets are typically less than 45 percent protein, from any source.
Because protein is the only macronutrient that contains nitrogen, scientists can measure the amount of nitrogen in fossilized bones to figure out how much protein ancient people ate. In a study published in the November issue of the American Journal of Physical Anthropology, O’Connell and her team used this method — with one important distinction. While previous studies have relied on animal diet as a control, O’Connell’s team measured fossilized bones against human blood samples.
Using this new model, they determined that both Paleolithic hunter-gatherers and the first (Neolithic) farmers ate a much less meat-heavy and protein-heavy diet than previously estimated — “about a third to a half” less, in fact.
Previous studies have overestimated the importance of foods such as meat, milk and fish, the study concludes. Using the new model puts estimates for prehistoric diets “in line with dietary animal/plant protein ratios” in today’s horticultural/agricultural populations.