In The Story of the Human Body Daniel Lieberman builds a strong case that making fully informed decisions about diet and lifestyle is only possible through the lens of evolutionary history. If you want to know where your body comes from, you need to understand its evolutionary history. Why do humans stand and walk on two legs? Why are we weak compared to other primates of comparable size? Why are our legs and feet shaped the way they are, with springy tendons and arched feet? Why does our spine have a special S-curve? The answer to these questions lies in the the evolutionary history of our species.
Now ask, why do people in modern societies suffer from “diseases of affluence” like obesity, type-2 diabetes, tooth decay, metabolic syndrome, flat feet, nearsightedness, lower back pain, and sleep disorders? Daniel Lieberman argues that these questions can only be fully answered by understanding the evolutionary history of our species. Lieberman argues these diseases are examples of “mismatch diseases” i.e. a disease that is primarily caused by our bodies not being sufficiently adapted to novel gene-environment contexts. We know they’re mismatch diseases primarily because they used to be rare, are largely preventable, and are almost unheard of in hunter-gatherer populations.
Lieberman argues that all of these diseases are in some sense a result of cultural evolution speeding ahead of natural evolution with the result that have humans manufactured a psychologically comfy and satisfying environment that is paradoxically unhealthy without fundamentally affecting our reproductive fitness. Lieberman calls this this paradoxical unhealthiness “dysevolution”. It turns out that surrounding ourselves with unlimited sources of cheap junk food is a bad idea because humans are genetically wired to crave food with dense amounts of fat, sugar, starch, and salt.
Lieberman is no luddite, and certainly doesn’t advocate a return to the caves and giving up on modern science and technology. His position is more nuanced than many of the extreme black and white positions out there, as befitting the complexity of gene-environment interaction. In many senses, the agricultural and industrial revolutions have propelled humans to new heights of health and longevity, with modern science curing diseases and fixing people better than ever before. At the same time, we are living longer but spending many of those years suffering from chronic, preventable diseases. The paradox of the modern world is reduced mortality but greater morbidity i.e. living longer, but spending more of those extra years with an illness of some sort. Lieberman argues that too often the incentives of modern medicine aim at fixing symptoms but not the underlying structural causes: the toxically comfortable environments we built for ourselves.