Marrying women 15 years younger maximized men's evolutionary fitness in historical Sami
Abstract
Most men marry younger women. This has been attributed to men selecting young women due to their high reproductive value and women preferring older men due to their wealth and high social status. Such mate preferences have been suggested to be adaptive, but despite a flourishing number of studies on the mate selection patterns themselves, little is still known of their actual fitness consequences. We examined how the age difference between spouses who married only once affected their lifetime reproductive success in historical monogamous Sami populations. We found that men maximized their fitness by marrying women approximately 15 years younger and vice versa. However, most couples failed to marry optimally. Only 10% of marriages fell within the optimal parental age difference, suggesting that cultural and ecological constraints for maximizing fitness were considerable. Those who succeeded in marrying optimally were the most preferred partners: young women and old men. Our findings indicate that, in Sami, parental age difference was under natural and sexual selection, as suggested by evolutionary theory.
References
Bereczkei T& Csanaky A . 1996Mate choice, marital success, and reproduction in a modern society. Ethol. Sociobiol 17, 17–35.doi:10.1016/0162-3095(95)00104-2. Crossref, Google ScholarBrommer J.E, Gustafsson L, Pietiäinen H& Merilä J . 2004Single-generation estimates of individual fitness as proxies for long-term genetic contribution. Am. Nat 163, 505–517.doi:10.1086/382547. Crossref, PubMed, Google ScholarBuss D.M . 1989Sex differences in human mating preferences: evolutionary hypotheses tested in 37 cultures. Behav. Brain Sci 12, 1–49. Crossref, Google ScholarChapman T, Arnqvist G, Bangham J& Locke R . 2003Sexual conflict. Trends Ecol. Evol 18, 41–47.doi:10.1016/S0169-5347(02)00004-6. Crossref, ISI, Google ScholarFieder M& Huber S . 2007Parental age difference and offspring count in humans. Biol. Lett 3, 689–691.doi:10.1098/rsbl.2007.0324. Link, Google ScholarGillis J& Avis W . 1980The male taller norm in mate selection. Pers. Soc. Psychol. Bull 6, 396–401.doi:10.1177/014616728063010. Crossref, Google ScholarHelle S, Lummaa V& Jokela J . 2005Are reproductive and somatic senescence coupled in humans? Late, but not early, reproduction correlated with longevity in historical Sami women. Proc. R. Soc. B 272, 29–37.doi:10.1098/rspb.2004.2944. Link, ISI, Google ScholarKäär P, Jokela J, Helle T& Kojola I . 1996Direct and correlative phenotypic selection on life-history traits in three pre-industrial human populations. Proc. R. Soc. B 263, 1475–1480.doi:10.1098/rspb.1996.0215. Link, Google ScholarKäär P, Jokela J, Merilä J, Helle T& Kojola I . 1998Sexual conflict and remarriage in pre-industrial human populations: causes and fitness consequences. Evol. Hum. Behav 19, 139–151.doi:10.1016/S1090-5138(98)00007-5. Crossref, Google ScholarKenrick D.T& Keefe R.C . 1992Age preferences in mates reflect sex differences in reproductive strategies. Behav. Brain Sci 15, 75–133. Crossref, Google ScholarManning J.T& Anderton R.H . 1998Age difference between husbands and wives as a predictor of rank, sex of first child, and asymmetry of daughters. Evol. Hum. Behav 19, 99–110.doi:10.1016/S1090-5138(98)00017-8. Crossref, Google ScholarMealey L . 2000Sex differences: developmental and evolutionary strategies. San Diego, CA:Academic Press. Google ScholarNettle D . 2002Women's height, reproductive success and the evolution of sexual dimorphism in modern humans. Proc. R. Soc. B 269, 1919–1923.doi:10.1098/rspb.2002.2111. Link, Google ScholarStoeckel J& Chowdhury A . 1984Spouse age difference and fertility in rural Bangladesh: implications for raising the age at marriage of females. Biol. Soc 1, 139–143. PubMed, Google Scholar
The title is now presented in the correct form.
6 December 2007
