Evolutionary Theory of Sexual Jealousy
'Jealousy can lead to an obsessive vigilance that crowds out all other thoughts and to terrifying violence that threatens the safety and well-being of the partner.' (Buss, 2000)
Jealousy was a necessary mechanism for our ancestor's survival as those who were indifferent to their partner's sexual contacts lost resources (in females) and raised others offsprings (in males). It seems therefore that our jealous ancestors won the evolutionary race as those indifferent to sexual contact might have not managed to pass on their genes.
Due to the different nature of problems that men and women faced in our ancestor's lives, different mechanisms were adopted towards sexual jealousy. Evolutionary psychologists hypothesize that males could not know whether the child is theirs, therefore they react more strongly to sexual infidelity. Females on the other hand, having no doubt about their offspring, react more strongly to emotional infidelity so as to not lose resources from their partner needed to support their offspring and themselves.
A leading study or as C. Harris puts it, 'a particularly influential and widely cited study', was conducted by Buss in 1992 who examined the physiological responses of college students to imagined sexual and emotional infidelity. Buss claims that the study clearly supports the evolutionary theory of jealousy, but Harris argues that the evidence is weak as from the three methods of measurement, namely heart rate (HR), electrodermal activity(EDA) and electromyographic activity of the brow(EMC) only the EDA shows a difference between the sexes when imagining the different infidelity scenarios. Furthermore, men, she argues, show more physiological activity compared to females even when there is no infidelity involved at all. Perhaps, she suggests, men find it easier and are aroused more easily by imagining sexual intercourse than females.
Many of the studies which do support the evolutionary theory of jealousy have used forced choice method and most of the studies are conducted with university students therefore generalisation should be made with caution. To overcome this, Harris conducted two studies, one with college students and another with adults, which examined the self-reported experiences of individuals who had actually experienced infidelity. She concluded that men and women do not differ in their rating of emotional or sexual infidelity. According to Harris, both men and women find emotional infidelity more disturbing. These two studies however may lack objective validity as the reliability of the self reported experiences may be question as it may have been affected by numerous other considerations.
However, an interesting study conducted by a group of psychologists examined the difference of response between the sexes and between a young group of a mean age of 20 and an old group of a mean age of 67. The study suggests that younger and older males do not differ in their response, but older females rate sexual infidelity as more important. This strikingly asymmetrical response between the two sexes surly is another support for the evolutionary theory of jealousy as women do not fear a los of resources at such an old age as they would not have any dependant children. It would have been interesting to learn the hypothesizing by this group of psychologists concerning the unchanging male response as surly women at that age cannot give birth to children. Unfortunately they were silent on this point. One of the reasons why sexual infidelity is more disturbing throughout the ages for men may be explained by what Harris termed as 'jealousy of specific innate module'. Due to the evolutionary process, Harris suggests that males and females are now evolutionary programmed to respond in a certain way as far as jealousy is concerned. This however might fail to account for the changing response by female participants in this study. This study uses the forced choice method which Harris has criticised for lacking ecological validity. Also, the vast difference of mean age between the two groups leaves many questions unanswered. A study might be needed with participants of different but continues age groups so as to understand better the different response of males and females towards sexual infidelity.
The final study of importance is a cross cultural study which aimed to test whether evolutionary theory of jealousy explains the sex differences in infidelity type or an alternative hypothesis which suggests that beliefs about the conditional probabilities of sexual and emotional infidelity account for these sex differences. An American sample of 234 participants was asked to identify which aspects of infidelity was more upsetting. To determine the unique contribution of sex and beliefs regressional techniques were used. The study was then replicated with a Korean and Japanese sample. The findings were that across cultures the evolutionary theory rather than the belief hypotheses accounted for sex differences in jealousy.
From the above discussion it can be seen that there is an ongoing debate amongst psychologists as to whether the evolutionary theory of jealousy explains the differences between the sexes and more importantly whether such difference exists. The studies highlighted above support the evolutionary theory of jealousy. However, numerous studies have shown contradictory findings which leaves the debate open.
