Evolutionary Developmental Psychology
In evolutionary theory, what matters most is that individuals live long enough to reproduce and pass on their genes. So why do humans live so long after reproduction? Many evolutionary psychologists have proposed that living a long life improves the survival of babies because while the parents were out hunting, the grandparents cared for the young.
According to Paul Baltes, the benefits granted by evolutionary selection decrease with age. Natural Selection has not eliminated many harmful conditions and nonadaptive characteristics that appear among older adults, such as Alzheimer disease. If it were a disease that killed 20 year-olds instead of 70 year-olds this may have been a disease that natural selection could have destroyed ages ago. Thus, unaided by evolutionary pressures against nonadaptive conditions, we suffer the aches, pains, and infirmities of aging. And as the benefits of evolutionary selection decrease with age, the need for culture increases.
Evolutionary Social Psychology
As humans are a highly social species, there are many adaptive problems associated with navigating the social world (e.g., maintaining allies, managing hierarchies, interacting with outgroup members). Researchers in the emerging field of evolutionary social psychology have made many discoveries pertaining to topics traditionally studied by social psychologists, including person perception, social cognition, attitudes, emotions, motivation, and cross-cultural differences.
Adaptationist Perspectives on Abnormal Psychology
As noted in the table below, adaptationist hypotheses regarding the etiology of psychological disorders are often based on analogies with evolutionary perspectives on medicine and physiological dysfunctions (see in particular, Randy Nesse and George C. Williams’ book Why We Get Sick). Evolutionary psychiatrists and psychologists suggest that some mental disorders likely have multiple causes.
Evolutionary psychologists have suggested that schizophrenia and bipolar disorder may reflect a side-effect of genes with fitness benefits, such as increased creativity. It has been noted, for example, that some individuals with bipolar disorder are especially creative during their manic phases, and the close relatives of schizophrenics have been found to be more likely to have creative professions. A 1994 report by the American Psychiatry Association found that people suffered from schizophrenia at roughly the same rate in Western and non-Western cultures, and in industrialized and pastoral societies, suggesting that schizophrenia is not a disease of civilization nor an arbitrary social invention. It has been likewise suggested that sociopathy may represent an evolutionarily stable strategy, by which a small number of people who cheat on social contracts benefit in a society consisting mostly of non-sociopaths.
It should be noted that the above speculations have yet to be developed into fully testable hypotheses, and a great deal of research would need to be done to confirm their validity. Clinical psychology and psychiatry have remained relatively uninfluenced by the field of evolutionary psychology. Therefore, the etiological speculations of evolutionary psychology must still pass the scrutiny and demanding research criteria of these larger disciplines to find wider acceptance. Psychiatrists have therefore raised concern that evolutionary psychologists are seeking to explain hidden adaptive advantages without engaging the rigorous empirical testing required to back up such claims. While there is strong research to suggest a genetic link to bipolar disorder and schizophrenia, there is significant debate within clinical psychology about the relative influence of cultural or environmental factors, and how they may nonetheless play a mediating or moderating role. For example, epidemiological research suggests that different cultural groups may have divergent rates of diagnosis, symptomatology, and expression of mental illnesses. There has also been increasing acknowledgement of culture-bound disorders, which may be viewed as an argument for an environmental versus genetic psychological adaptation It might also be noted that while certain kinds of mental disorders may have psychological traits that could be viewed as ‘adaptive,’ as a whole, these disorders typically cause those afflicted individuals significant emotional and psychological distress, and negatively influence the stability of interpersonal relationships and day-to-day adaptive functioning.
Evolutionary Psychology of Religion
Adaptationist perspectives on religious belief suggest that, like all behavior, religious behaviors are a product of the human brain. As with all other organ functions, cognition’s functional structure has been argued to have a genetic foundation, and is therefore subject to the effects of natural selection and sexual selection. Like other organs and tissues, this functional structure should be universally shared amongst humans and should have solved important problems of survival and reproduction in ancestral environments. However, evolutionary psychologists remain divided on whether religious belief is more likely a consequence of evolved psychological adaptations, or are the byproducts of other cognitive adaptations.