: Evolutionary theory proposes that adaptive traits are reproduced more successfully than maladaptive traits. Accordingly, natural selection should favor heterosexuality as it facilitates reproduction and the propagation of genes. However, the question becomes, what has maintained homosexuality in a small but consistent percentage of the human population? Research into the evolutionary and hormonal factors associated with a homosexual orientation have yielded provocative but inconsistent results. It also suggests that human sexual orientation, and in particular homosexual orientation, is too complex to be described by one simple model or a single research discipline. The current paper treads a new path and emphasizes an integrative approach for the understanding of homosexuality. The authors examine the combined effects of evolutionary factors and neurohormonal processes on the development of a homosexual orientation. It is suggested that research into the topic could benefit from an examination of and change in some of the assumptions upon which much past research has been based.