Abstract
There are two basic theories explaining possible principles on which people are attracted to each other and how individuals create sexual and romantic relationships. The theory of homogamy states that in their potential or actual partners individuals prefer characteristics that are similar to themselves ("birds of a feather flock together").
One of the mechanisms that can cause homogamy in partners might be sexual imprinting. According to this theory, individuals prefer in potential partners traits that are similar to those of the opposite sex parent.
In contrast, the theory of complementarity suggests that individuals are attracted to partners with traits that are opposite to their own ("opposites attract"). From an evolutionary perspective, homogamous preferences can be explained by the theory of kin selection and outbreeding depression avoidance, while pairing on the principle of complementarity is advantageous in terms of inbreeding avoidance.
We will critically review these two theories – including their implications and empirical support – from the perspective of evolutionary psychology and human ethology. We will argue that principles of homogamy and complementarity are not necessarily mutually exclusive but, rather, are complementary.