The new paper published by Cell Press in the October issue of the journal Trends in Ecology and Evolution has reviewed emerging evidence suggesting that contraceptive methods which alter a woman's natural hormonal cycles may have an underappreciated impact on choice of partners for both women and men and, possibly, reproductive success.
Human females are only fertile for a brief period during their menstrual cycle, just prior to ovulation. Many scientific studies have established that partner preferences of both women and men vary significantly according to predictable hormonal fluctuations associated with the natural menstrual cycle. Ovulation is associated with a profound shift in some female physical characteristics, behaviors and perceptions related to mate attraction.
Ovulating women exhibit a preference for more masculine male features, are particularly attracted to men showing dominance and male-male competitiveness and prefer partners that are genetically dissimilar to themselves. This is significant because there is evidence suggesting that genetic similarity between couples might be linked with infertility.
The oral contraceptive pill alters the hormonal fluctuations associated with the menstrual cycle and essentially mimics the more steady hormonal conditions associated with pregnancy.
"Although mate choice studies in humans have routinely recorded pill use during the last decade to control for its confounding effects, little effort has been invested in understanding the consequences of such effects of the pill," offers study author Dr. Alexandra Alvergne from the Department of Animal and Plant Sciences at the University of Sheffield.
Dr. Alverne and colleague Dr. Virpi Lumma reviewed and discussed new research supporting the conclusion that use of the pill by women disrupted their variation in mate preferences across their menstrual cycle.
The authors also speculate that the use of oral contraceptives may influence a woman's ability to attract a mate by reducing attractiveness to men, thereby disrupting her ability to compete with normally cycling women for access to mate.
Of particular interest is the fact that women taking the pill do not exhibit the ovulation-specific attraction to genetically dissimilar partners.
"The ultimate outstanding evolutionary question concerns whether the use of oral contraceptives when making mating decisions can have long-term consequences on the ability of couples to reproduce," suggests Dr. Lummaa.