Evolution might also overgeneralize real dangers.
Less well known than the fear of darkness is the fear and disgust of holes, also known as trypophobia (I personally recommend NOT looking this up). In particular, it seems that lotus seed pods and wasp nests are the most prominent examples in nature that seem to cause a disgust reaction.
Although some psychologists argue that trypophobia is not a real phobia since it seems to mainly operate on disgust, no matter what it is, disliking holes still seems completely irrational.
However, according to
one study, these disgust reactions are much stronger when superimposed on skin. Thus, these reactions might be due to evolutionary adaptation to avoid parasites and disease. Lumps or holes on skin are associated with parasites and pathogens that would have been evolutionarily advantageous to avoid. This kind of avoidance is a part of what is called the “behavioral immune system,” psychological mechanisms that help us to avoid getting sick.
Although seeming illogical at first glance, it turns out that trypophobia, and indeed most phobias have an evolutionary benefit to them.
In order for evolution to select for these sort of traits, there has to be a genetic component to phobias. Research has shown that first-degree relatives (parents, siblings, or children) of those who have a phobia show a
three-fold increase in phobias.
Meta-analysis of twin studies for specific phobias have reported a mean variation of about 30% that can be explained by heritability.
Although often too a lesser extent, many cultures also have collective beliefs, superstitions, that are not rational. Black cats, breaking mirrors, or walking under a ladder are well known superstitions in western culture. In East Asian culture, writing your name in red or whistling at night are considered faux pas.