Have you ever read a diet advice column that suggests your inability to resist deep-fried fast food was actually adaptive in your evolutionary past? This is an example of the popular application of evolutionary psychology (EP), which is the blend of evolutionary biology and cognitive psychology.
Two of the most prominent evolutionary psychologists, John Tooby and Leda Cosmides, view the human mind as a Swiss army knife with hundreds or even thousands of "modules" that perform specific tasks. These modules, just like other parts of the body, evolved at different stages of hominin evolution between the LCA and prior to the advent of agriculture and civilizations around 10 Kya when all humans lived in small-scale foraging societies like contemporary hunter-gatherers. Examples of mind modules include those for food preferences (like fats and sugars), mating, theory of mind, predator avoidance, alliance formation, and language—all of which evolved to solve adaptive problems that were crucial for passing on genes.
For example, the theory of mind module allows humans to understand the mental states ofothers. Before reaching four and a halfyears of age, children cannot comprehend that others can hold different beliefs than them and as a result, they cannot lie convincingly. This uniquely human, but not learned, trait plays a crucial role in empathy, deception (of self and others), and manipulation in political/social situations.
Principles of EP are often applied to our eating and drinking habits and disorders. According to EP, humans have evolved food preference modules. These modules evolved for survival on the unforgiving African savannah and they govern the desire for certain foods and the dislike of harmful ones. Fat obtained from scavenging or hunting animals and sugar obtained from ripe fruits offer nutrients that would have been relatively scarce on the savannah. Both fat and sugar are needed for growth, maintenance, and metabolism (energy production).
Carcasses and fruiting trees are stages for between-species competition, and certainly would have been dangerous interaction zones between carnivores and hominins or between other primate species and hominins. In order to sustain a behavior, the benefits must outweigh the costs. So according to EP, fat and sugar preference modules evolved to make individuals desire the foods strongly enough to incite them to take risks.
There has been no observed selection for modern humans to lose the fat and sugar desiring modules even though many humans live in an environment where fat and sugar are readily available. Our evolutionary history has encountered a modern environmental mismatch. Now we run the risk of overeating fat and sugar to the point where obesity and heart disease are the number one killers of humans in industrialized countries. Binge-eating behaviors, which are considered eating disorders that lead to obesity and heart disease, could have been adaptive in the past if humans, like other large carnivores, were eating large meals spaced days apart.
One of the arguments over EP pits those that see everything as adaptations against those that see many traits as mere by-products of a limited number of adaptations. For example, the universal, cross-cultural belief in supernatural explanations for events or for a "higher power" is considered by some researchers to be due to a module that is hard-wired into all of our brains, but others consider it a spin-off from other functions involved in higher cognition and awareness.
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