Jealousy in a small-scale, natural fertility population: the roles of paternity, investment and love in jealous response

a r t i c l e i n f o Evolutionary scientists have predicted a universal sex difference in response to different forms of infidelity, with men expected to be more upset than women by a sexual infidelity when both a sexual transgression and an emotional transgression occur. Although this finding has proven to be robust, the vast majority of studies have occurred in industrialized countries and student populations. Here I present the first test of the jealousy hypothesis among a small-scale, natural fertility population, the Himba of Namibia. In this population, the majority of both men and women report greater distress over a sexual infidelity, with men reaching an almost unanimous consensus (96%). Despite the skew for both men and women, there is a significant sex difference in the direction predicted by the evolutionary hypothesis, providing further support for this view. The increased risks of both pregnancy and paternity loss that occur in this natural fertility population may help to explain why these results differ from previously studied populations. More broadly, these data suggest that both the type and the intensity of jealousy expressed may be facultative responses and that further investigation of correlates related to life history trade-offs, forms of investment, and the sexual division of labor can help us to understand the inter-cultural variation in jealous response. Traditional interpretations of sexual selection theory in humans predict that men and women will respond differently to threats of it is thought, will tend to be more upset than women by sexual infidelity, reflecting a mating strategy that aims to increase paternity certainty, which is critical to successfully moderating investment in offspring. Women, on the other hand, are expected to be more upset than men by emotional infidelity, which is thought to reflect the reliability of future male support and therefore represents the female strategy of garnering reliable investment from men. Men and women are thought to have benefited reproductively from both emotional and sexual jealousy; however, because only men experience uncertainty of parentage, and women carry a larger investment burden than men (due to pregnancy and lactation), the sex difference in jealous response is thought to be largely impervious to cultural variation and local norms (Buss, Larsen, & Westen, 1996; Buss & Haselton, 2005). For example, even where the majority of both men and women are more upset by one type of infidelity than the other, men are …