How fragile are our paleolithic bodies in today’s environment? According to some researchers, many noninfectious diseases may result from our biological inability to adapt to certain aspects of modern society. Conditions like osteoporosis, allergies, acne, asthma, anxiety, and depression could all stem from an evolutionary discrepancy between the society and its citizens.
Evolutionary biologist Daniel Lieberman of Harvard University believes that in order to understand the current human condition, we must first understand our early ancestors. In his new book, The Story of the Human Body: Evolution, Health, and Disease, Lieberman argues that a diachronic, evolutionary interrogation of the human body may not only shed new light on current diseases, but eventually explain why we get sick in the first place.
“Many of the illnesses that we confront today are what evolutionary biologists called ‘mismatch diseases’: ... Diseases that occur because our bodies are poorly or inadequately adapted to environments in which we now live,” he explained in a recent interview with NPR. “An example would be eating large amounts of sugar or being very physically inactive leads to problems like diabetes or heart disease that then make us sick.”
In this sense, our changing lifestyle has resulted in a clear rift between our biological and cultural evolution. As a result, our bodies are becoming maladaptive and prone to mistakes. Stress, for example, appears to have gone from being a defense mechanism to an independent threat. Whereas paleolithic stressors were limited to wild animals and rapacious tribes, contemporary stressors include employment, commutes, interpersonal contact, self-fulfillments, and text messages. By generalizing stress and anxiety to include pointless, everyday things that cannot be removed, we begin to induce chronic levels of stress.
Similarly, autoimmune diseases and the rise in allergies may be a direct effect of an accelerated cultural revolution. Today, exceedingly clean and sterile environments tax our immune system by precluding necessary activity. In its struggle to keep its guard up, the body may target the wrong cells.
“[The immune system] is still there, and it's primed and ready and waiting to attack all those germs and worms that used to make us sick, but now those pathogens are absent, so it sometimes by chance finds the wrong targets,” Lieberman explained. “So that's the hypothesis for why so many allergies and autoimmune diseases are on the rise — is that our immune systems are essentially not being used properly, and as a result they go into overdrive; they attack ourselves.”
Still, our biological evolution is churning along at a steady pace. Some studies show that hundreds of genes have undergone positive selection in the past 10,000 years. Perhaps we’ll catch up?