In recent years, the word “paleo” has transcended the realm of scientific jargon and become commonplace in the American vocabulary. Sadly, this not due to the fact that Americans have suddenly become interested in paleontology and anthropology (sigh), but because of the explosion in popularity of the Paleo diet. This diet, which is modeled after the feeding behaviors of our human ancestors, has created a paradigm shift in how some nutrition experts and enthusiasts interpret “optimal” nutrition, though it is not met without significant controversy. Unfortunately, most nutrition professionals have little to no understanding of even the most basic concepts in the field of evolutionary biology, or even realize how fundamentally important it should be to approach nutritional science from an evolutionary perspective. As Theodosius Dobzhansky, a prominent evolutionary biologist once famously said, “Nothing in biology makes sense, except under the light of evolution.”
Seeing that nutrition is inherently a biological science, it should not be exempt from this evolutionary light, and furthermore the Paleo diet should be praised for illuminating that light. However, as with any good scientific hypothesis, it should not be met without critical examination and/or rigorous testing based on the best evidence available.
So, what is the Paleo Diet?
The Paleo Diet encompasses a short list of foods that either come from animals or directly from the earth. This includes grass fed meats and seafood, fresh fruits and vegetables, eggs, nuts, seeds, and plant oils from sources such as olives, walnuts, avocados, and coconuts. This diet strictly prohibits grains, legumes such as peanuts and beans, refined sugar, and virtually any food that has been processed.
At the most basic level, the Paleo diet offers many improvements to the typical Western diet that are comparable to those of the highly touted Mediterranean diet. One of the most significant improvements is the replacement of processed, chemical, and sugar laden foods with whole foods like fruits, vegetables, and meat. This simple replacement will not only improve the nutrient density of one’s diet, but there is mounting scientific evidence that it can improve a plethora of health issues including diabetes and metabolic syndrome and anecdotal evidence suggesting improvements in depression and digestive disorders.
Aside from a few controversial foods such as butter, coconut oil, and red meat, the majority of the foods on the Paleo diet promote health in many ways. This diet has been shown to be particularly effective at reducing inflammation and may be capable of restoring the body’s microbiome, which mounting evidence links to a host of modern day chronic diseases. This is largely due to the fact that the Paleo diet is rich in nutrients that are rare in the Western diet, particularly omega 3 fatty acids, phytonutrients, and prebiotic fiber.
In addition, “empty calories,” especially those in the form of simple sugar, bread, cookies, candy, etc. are virtually non-existent on the Paleo diet. Carbohydrates are in relatively low supply compared to what most Americans consume or are recommended to intake, and when carbohydrates are consumed, they typically come in the form of fruits, starchy vegetables, plant fiber, and small amounts of honey.
The Paleo diet cuts out a tremendous amount of the foods that comprise the American diet (which in some cases can be a good thing); however, it also eliminates beans, dairy, and whole grains, which are considered to be healthful by the vast majority of dietitians. Non-paleo plant based foods such as chickpeas, beans, whole grain cereals, and peanuts are high in protein and other essential nutrients, and many “healthy” people eat these foods in large quantities. While Paleo supporters argue that there is evidence that properties in these foods are inflammatory and/or toxic, others argue that the evidence for the existence of these negative properties is weak and that we should probably just ignore this line of reasoning all together.
The Paleo diet also tends to come with a dogmatic, all-or-nothing culture surrounding it, which is almost never beneficial for nutritional quality. Certain foods, such as arrowroot, spark endless internet debates about whether they qualify as worthy of being considered Paleo, even though your ancestors probably never ate them. The Paleo diet also allows breads and pastries to be recreated with nut flours such as almond and coconut flour, which your ancestor probably never ate.
In addition, the use of cooking oil in the Paleo diet is interesting as the development and use of cooking oil occurred after the Paleolithic era ended (for example: the earliest accounts for the use of olive oil occurred within the past 6,000 years, well past the end of the Paleolithic era of 10,000 years ago). Finally, the Paleo diet relies upon the use of butter and ghee, which are both dairy products and thus should technically not be part of the Paleo portfolio.
In other words, the “paleo-ness” of many foods is debatable and often subjective.
The Paleo diet is very rigid in its nutrition guidelines, which are over-simplified compared to what the data suggests “cavemen” were likely eating. There is no single ancestral diet, rather, human populations all over the planet ate different foods in different amounts depending on the environment in which they lived. Paleolithic humans were opportunistic eaters, which means that they ate whatever was available to them in order to survive. To assume that all early humans ate the exact same foods is scientifically inaccurate. Ironically, humans were probably able to successfully radiate across the globe partly because they are physiologically flexible enough to survive off of such a variety of foods. This trait is actually favored by natural selection, and is not unique to humans.
Take Home Message
Survival is the essence of what drives evolution. A species that cannot pass its genes down to the next generation will go extinct unless it can adapt to a changing environment and reproduce even when conditions are less than optimal. A common misconception in evolutionary science is that evolution produces species that are perfectly adapted to their environment. The success of a species depends on whether or not it produces offspring, not on how well suited it is to its environment. The Paleo Diet assumes that Paleolithic humans were perfectly adapted to the food they consumed, but there is no evidence to suggest that this is true. Like all other species, early humans probably cared little about consuming an optimal or specific diet and more about surviving on what was “good enough.”
The premise of the Paleo diet is founded on several evolutionary misconceptions, which should be taken into account by anyone who is strictly following it. From an evolutionary perspective, it seems reasonable to hypothesize that the foods listed on the Paleo diet should be optimally suited for the human diet. The rate at which foods such as grain and dairy were introduced into the human diet was at the evolutionary speed of light (i.e. within the last 10,000 years), however, the human genome did not stop evolving after the Agricultural Revolution. Nor was it ever ideally adapted to the Paleolithic food supply in the first place. While there are many positive aspects of the Paleo diet, particularly its emphasis on whole, unprocessed foods, it is certainly not the “perfect” diet. It is a model which, like all other evolutionary hypotheses, should questioned and rigorously tested. As of now, there has been little research on how the Paleo diet impacts human health, especially when compared to other diets. Until more experimental data is available, it is hard to draw meaningful conclusions that support the diet’s health claims.
Meredith Fontana, MS
Paleontologist and future dietitian