The Evolutionary Mismatch Hypothesis
How does the evolutionary mismatch hypothesis pertain to our diet and weight?
If processed foods are so common nowadays, why is the human body still incapable of learning to adapt to those foods, but rather develop diseases such as obesity, diabetes, and chronic heart failure?
As we all know, processed foods that are filled with added sugars and fat takes up such a big portion of our modern-day diet. However, it has not always been like this. Our ancestors in Africa often ran into a scarcity of food sources, let alone processed foods. So, how do these drastic differences in food habits and environments explain the increasing rates of obesity and health problems across the world? In this article, I explain the evolutionary mismatch hypothesis, and how we can look at obesity from an evolutionary perspective.
So, what is evolutionary mismatch? According to Elizabeth Lloyd, the chair of history and philosophy of science at Indiana University, evolutionary mismatch occurs when a trait that evolved as beneficial in one environment becomes maladaptive in another (1). Although species can constantly adapt to the changing environments by ways of natural selection, the unprecedented rapidity and extreme degree of human-induced environmental changes (1) can render evolutionary adaptive mechanisms incapable of keeping up with the surroundings. Evolutionary mismatch has often been discussed in aspects of contemporary lifestyle such as diets, sleep deprivation, and chronic stress, but can also apply to certain controversies of our contemporary society like income inequality, gender pay gap, and child abuse (2). Still, the most observable evidence of evolutionary mismatch can be seen in our increasing rates of obesity and diseases due to dietary changes.
Let's look at the example of Turkana, a pastoralist population from an isolated desert in Kenya (3). Mpala NSF Genomics and Stable Isotopes Lab performed a research project on the local, remote communities of Turkana to investigate the effects of their changing diets and test the evolutionary mismatch hypothesis.
In the 1980s, Turkana's population experienced a rapid transformation after an extreme drought and the discovery of oil nearby. A large group of their population migrated to villages and cities, abandoning their traditional nomadic lifestyle. While those who maintained their pastoralist lifestyle still relied mainly on live-stock for their diets, those who had moved to the cities switched to diets largely composed of carbohydrates and processed foods. The project studied the health profiles covering 10 biomarkers of Turnaka who lived in cities, villages, and rural areas. The results? All 10 biomarkers were excellent among those still leading a pastoralist lifestyle in traditional Turkana fashion, as well as those who lived in rural villages. However, those who were living in urban cities showed higher levels of diabetes, heart diseases, obesity, and high blood pressure, and exhibited substandard cardio-metabolic health (3). A relationship was also observed between the time spent living in the city and overall health. As the health metrics have shown, the longer Turkana had spent dwelling in the city, the more unhealthy and at risk of cardiovascular diseases they tended to be (3). As Lea, an interviewer of the project puts it, "the key to metabolic health may be to align our diet and activity levels with that of our ancestors" (3).
The research says a lot about how our differences between our modern-day diet and that of our ancestors contribute to obesity and metabolic diseases. In the days of our ancestors, food was scarce. Famines were often, and people did not get a lot to eat. Therefore, our bodies have adapted to store abundant food as fat to preserve energy to be used when famines arrive again. According to the Wellness Garage, the body, during times of scarcity and famines, also goes through a process called autophagy, where it cleans up damaged cells and organelles while recycling dysfunctional proteins (4). This process of cellular clean-up seems impossible to occur these days with the abundance of food in modern-day society. Moreover, due to the lifestyle of hunter-gatherers, the human body's genetic makeup has come to be used to foods like lean meat and nuts and seeds. However, as human civilization has developed methods of food production such as agriculture and animal domestication, food supply became abundant and food variations increased. More recently, due to technological advancements, the world has also seen more advanced ways of food production by altering the biological and nutritional composition of foods.
The human body and its evolutionary mechanisms simply cannot catch up with the rapidity of such advancements. We still prefer to store excessive calories as fat and haven't had enough time to adapt to farmed or processed foods. This evolutionary mismatch has given the rise to many health problems such as obesity, high blood pressure, diabetes, etc. That said, is it better to just eat foods that our ancestors ate? Read more about this on my explanation of the Paleo diet, a diet aimed at mimicking the eating habits of our ancestors.