Infidelity is usually defined as the action or state of being unfaithful to a spouse or other sexual partner. Being unfaithful in general terms may mean more than just being unfaithful sexually, but also being unfaithful emotionally and psychologically. Nevertheless, infidelity is mostly defined in terms of being unfaithful sexually. In modern civilization, a sexual/marital relationship is defined in monogamous terms. However, historically, most cultures have been polygynous. Most species are socially monogamous (males and females pair to breed or raise offspring), but not sexually monogamous (97% of mammals are not monogamous, among primates only gibbons are predominantly monogamous, gorillas are polygynous and chimpanzee do not pair at all)). The reason for most humans being monogamous is unclear, it may be a reflection of societal, religious and moral pressures.

To examine possible biological determinants of monogamy and infidelity.

Literature review

Infidelity is fairly prevalent, reported more frequently by males than by females. The literature presents numerous reported ‘causes,‘ such as sexual dissatisfaction, partner incompatibility, liberal values and sexual permissiveness. Some authors propose a biological side to infidelity, for example a brain system which is purely ‘sex drive” (dopamine vs. oxytocin), or evolutionary factors such as access to high quality genes. Biological factors of infidelity in humans are not well studied.

Humans are not exclusively monogamous. Infidelity may have some biological underpinning (genetics, brain chemistry), but it seems to be modified/moderated by societal, cultural, religious and other factors.