Evolution and the Paleo diet myth

Summary

Humans have more characteristics in common with herbivores than carnivores. We are not suited to eating raw meat and cooked meat, even at moderate levels, is associated with a wide range of health problems. The idea that we are suited to a hunter-gatherer diet, rich in meat and fish with no grains or pulses, is flawed. Humans continued evolving past the Palaeolithic era and our Neolithic ancestors adapted to be able to digest carbohydrates for example and we now know that they relied on plant protein more than previously thought. The research simply doesn’t support the notion that humans were designed to eat meat, especially in the quantities consumed in some affluent countries. 

Wheat-eaters or meat-eaters?

Carnivores (such as cats, dogs and wolves) have strong jaws that can only move open and shut and sharp teeth and claws to tear off chunks of raw meat and ‘wolf’ them down. Their acidic stomachs help digest flesh and short intestines allow the quick expulsion of rotting meat remains. On the other hand, herbivores (such as rabbits, horses and sheep) chew from side-to-side, their saliva contains digestive enzymes and they have longer intestines to absorb nutrients.

When asked if humans are herbivores, carnivores, or omnivores, Dr William C. Roberts, Editor-in-Chief, of The American Journal of Cardiology said: “Although most of us conduct our lives as omnivores, in that we eat flesh as well as vegetables and fruits, human beings have characteristics of herbivores, not carnivores” (Roberts, 2000). Researchers from Harvard University say that although increased consumption of meat during human evolution certainly contributed to dietary quality, meat-eating alone was insufficient to support the evolution of human traits, because modern humans fare poorly on diets that include raw meat (Carmody and Wrangham RW, 2009). They suggest it was the cooking of food that substantially improved the quality of the diet. Indeed, meat-eating may have necessitated cooking because raw meat is difficult and takes time to chew, thus limiting consumption in large quantities (Luca et al., 2010). 

The Paleo diet myth

In the 1980s US anthropologists Boyd Eaton and Melvin Konner suggested the Paleo diet as a model for modern human nutrition (Eaton and Konner M, 1985). The Paleo (Palaeolithic or hunter-gatherer) diet contains high protein (meat and fish but no dairy) and fibre but no grains or pulses. Proponents say the mismatch between this and modern diets is to blame for high levels of obesity, diabetes and heart disease. However, we have evolved to be flexible eaters (Henry et al., 2014) and genetic evidence shows that we continued to evolve over the last 40,000 years, well into the Neolithic era (Hawks et al., 2007). Modern adaptations include increased production of amylase, an enzyme that helps us digest carbohydrates or starch (Turner and Thompson, 2013). Furthermore, geochemical analysis of grains and pulses from Neolithic sites reveal that early farmers relied much more heavily on plant protein than previously thought (Bogaard et al., 2013).

Meat made us smart is a dumb idea

In the 1990’s British scientists Leslie C. Aiello and Peter Wheeler proposed the ‘expensive-tissue hypothesis’ whereby there is a trade-off between the size of the digestive tract and the brain (Aiello and Wheeler P. 1995). The brain is ‘expensive’ because it requires so much energy and a high-quality diet enabled us to reduce the size of our digestive tract and free up energy to increase brain size. In other words ‘meat made us smart’. However, recent research, published in the journal Nature, refutes this saying a higher quality diet, coupled to energy saved by walking upright, growing more slowly and reproducing later, fuelled the growth in brain size (Navarrete et al., 2011). Prehistoric humans ate some meat but it didn’t make them smart.