Cuckoldry and Sexual Jealousy
Unlike women, men can never be entirely certain that they are the fathers of their children. As a result men are at risk of cuckoldry, the reproductive cost that may be inflicted on a man as the results of his partners infidelity. The consequence is that a man may unwittingly invest his resources in offspring that are not his own. The adaptive functions of secual jealousy may therefore would have been to deter a mate from sexual infidelity > minimising the risk of cuckoldry. Displays of aggression will dissuade a man's partner from having sex with another man.
As jealousy is found in all human cultures, it is believed that it is a genetic rather than a learned behaviour. The purpose it serves is to ensure exculsively in our mates. For women, especially in the EEA (environment of of evolutionary adaption) having children was very costly in terms of protection and finding adequate resources. Having a mate who would stay with her throughout her pregnancy and help her with the raising of her offspring was vital. If her partner left her for another woman. it would compromise her ability to obtain the resources that she and her children needed to survive. Jealousy is a reaction to this possibility. It is an aggressive behaviour designed to prevent one's partner from commiting his resources to another woman.
Mate retention and violence
Buss (1988) suggests that ales have a number of strategies that have evolved specifically for the purpose of keeping a mate. Including 'direct' guarding of the female and 'negative inducements' that prevent her from straying. By restricting their partners' sexual autonomy (direct guarding) our male ancestors would have been able to deter rivals from gaining access to their mates.
A modern example of direct guarding is 'vigilance' (e.g. coming home early to see what a female partner is up to). Wilson et al (1995) found that women who agreed with questionnaire items such as 'he is jealous and doesn't want you to talk to other men' were twice as likely to have experience serious violence from their partners, with 72% of these having required medical attention following an assult. Men may also attempt to retain their partners by offerng threats (negative inducements) for any infidelity. Because sexual jealousy is a primarycause of violence against women, those who are percieved by their partners to be threatening infidelity (looking at another man) are for example have shown that in the majority of cases, women cite extreme jealousy on the part of their husbands or boyfriends as the key cause (Dobash and Dobash, 1984).
Men can guard against their partners infidelity either by conferring benefits or by inflicting costs, including violence. As not all men possess resources that might be used to provide benefits, some men are especially prone to using violence (Shackelford et al, 2000), According to Daley and Wilson (1988), death of a partner from physical violence may be an unintended outcome of an evolutionary adaption that was designed for control rather than death.
Case study: In July 2000 Piper Lueprastikul a former university lecturer was freed after having been sent to prison for battering his wife to death in a jealous rage after discovering she had visited a former boyfriend. He was given a two year suspected prison sentence after the court took into account the age of his children and his background.