The paleo diet is one of the latest fads to hit the world of dieting. It is supposedly based on eating only foods that our ancestors in Paleolithic times, some 12,000 years ago, supposedly would have eaten. Thus, the diet permits meat, fish, fruit, most vegetables, nuts, and plant-based oils (such as olive and avocado) while excluding dairy, grains, cereals, legumes (beans, peanuts), processed oils, processed sugar, alcohol, and coffee. The idea behind the diet is the claim that our bodies had, by the end of the Paleolithic, evolved to survive on the foods available at the time and are not designed to process foods that were introduced since then. There are many fatal flaws in this whole idea.

The most serious flaw is the assumption that evolution “designed” us to be an ideal match for our environment and diet 12,000 years ago. This is completely wrong, as any high school biology student should be able to tell you. Evolution doesn’t “design” anything, all it does is favor the continuation of genes that are associated with leaving more offspring. Thus, a caveman who was sickly and died at 25, but left 12 children, was an evolutionary success and his genes would continue in the population. In contrast, another caveman who lived a healthy life to the age of 60, but left only 1 or 2 children, was not a success in evolutionary terms. In other words, the notion that Paleolithic folks were ideally adapted to their diet is pure nonsense. As long as their diet allowed them to leave children, that was enough.

A second serious flaw is the diet’s assumptions about what foods people did and did not eat back then. There is, for example, quite a bit of evidence that Paleolithic humans ate grains and legumes, but these foods are forbidden by the diet. In fact, there is evidence that humans were cooking and eating tubers and other starchy vegetables as much as 300,000 years ago. Paleo humans did not eat peppers, tomatoes, avocados, potatoes, pineapple, or blueberries (among others) because these are new world plants that were not available during Paleolithic evolution. Yet the diet allows them all. Dietary flexibility was a hallmark of humans and one reason for our evolutionary success—we did not evolve to eat certain specific foods, we evolved to eat pretty much anything. Would anyone care to argue that Paleolithic humans in the sub-arctic zones, the rain forest, the plains, and the tropical coastal regions ate the same or even similar diets? I don’t think so.

A third flaw is the claim by diet proponents that human genetics have not changed in any meaningful way since Paleolithic times and therefore the human digestive and metabolic systems cannot have adapted to deal with “new” foods. This is flat-out false. It is well documented that human genes have changed in response to the introduction of dairy into the diet and to the development of agriculture, with the greater availability of wheat and other grains. While on the subject of genetics, it’s impossible to understand why humans have multiple copies of the gene for amylase, an enzyme whose sole purpose is digesting starches, if starchy foods had not been an important part of the human diet for a long time.

That’s strike three, I believe!

As if we needed a strike four, the life expectancy of humans in Paleolithic times was somewhere in the mid-30s. Is theirs the diet you want to eat? Of course, many other factors have contributed to the increase in life expectancy, including improvements in medicine, public health, and nutrition. Oh wait, did I say nutrition? You know, like eating grains, legumes, and dairy?

There are good aspects to the paleo diet, namely the avoidance of overly processed foods and of excess carbs and sugar (emphasis on excess). But, there’s nothing “paleo” about these ideas, they are part of many dietary regimes. So if you want yet another trendy fad diet to waste your time and money on, be my guest and go paleo.

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