According to evolutionary psychologists, our predisposition to overconsume fatty junk foods most clearly illustrates that we are biologically prepared to behave in ways that promoted the of our ancestors.

reproductive success

Explanation:

Evolutionary psychology refers to a psychological discipline that explores human behavior by applying the implications of evolution. Proponents of this theory believed that the mind is influenced by the need to reproduce and our emotions and language capacity reflect adaptations that enabled our human ancestors to thrive. According to this theory claim that when our ancestors encountered challenges and found ways to solve them, they had some natural intuition and knowledge that gave them the ability to seek out the most appropriate solutions and implement them.

answer; researchers typically cannot control people's sexual behaviors as would be necessary in an experiment;

as university of miami psychologists debra lieberman and adam smith pointed out in a recent article in the journal current directions in psychological science, humans have social and psychological mechanisms to deter incest. with very few exceptions, marriages between brothers and sisters and between parents and their children are verboten in every human culture. the primary psychological anti-incest mechanism is the yuck response. even the idea of sex with their mom or dad, bro or sis is upsetting to most people. the psychologist jonathan haidt has found that nearly everyone is repelled by the prospect of brother-sister sex, even in hypothetical situations in which there is no chance of pregnancy).

the biological cost of incest

this raises an interesting question: just what’s so bad about incest? sure, having sex with your dad or your sister seems gross — but why? some anthropologists have argued that incest taboos are learned social conventions. this explanation, however, doesn’t make sense to me as it does not explain the widespread existence of anti-incest mechanisms in creatures ranging from cockroaches to chimpanzees. second, the incest taboo is about as close to a universal law as human moral rules get.

why should mechanisms to avoid incest be so widespread both in nature and across human societies? the answer is simple. the problem with having sex close with relatives is that there is an astonishingly high chance that your offspring will be born with a serious birth defect.