Evolutionary psychology is an approach to psychology that sees human psychological traits as adaptations for survival in the everyday environment of our ancestors (the environment of evolutionary adaptedness, or EEA). Because 99% of our history as a species consisted of time spent surviving and reproducing on the African savannahs, evolutionary psychologists point out that our cognitive features are distinctly adapted to success in that environment, and not the environment of the present day, which is a relatively recent phenomenon.
According to Darwinian theory, the organisms best at producing surviving offspring which then go on to produce more offspring are the organisms most likely to survive and persist in any earthly environment. This ability is called "inclusive fitness". Mutational variants of a given species which possess the greatest amount of inclusive fitness are bound to pass their genes on to the future at a higher rate of success than variants with traits which provide a lesser degree of inclusive fitness.
As an example of evolutionary psychology, consider the practically universal reprehension of sibling-sibling romantic relationships in Homo sapiens cultures. Evolutionary psychologists call this the "incest taboo", isolating it as an evolved human reproductive tendency that is adaptive because it significantly lowers the probability of intra-familial copulation. This act constrains genetic diversity and tends to make offspring more susceptible to diseases and genetic defects, especially if the process is iterated over a series of generations. The incest taboo is not a conscious decision that humans reason about in the abstract and then decide upon - it exists because our evolved neurological machinery inserts it into our minds on a subconscious level.
Evolutionary psychologists have isolated and experimentally verified hundreds of human cognitive adaptions, producing great benefits to a variety of fields that involve the study of human behavior. Evolutionary psychology is not merely a field but a phenomenon, overthrowing classical models of psychology on a broad scale and placing the entire field on a firmer empirical foundation. Evolutionary psychology has broad interdisciplinary appeal, being studied by philosophers, military strategists, politicians, businesspeople, and a wide range of scientists.
