8 October 2009
Unnatural selection: Courtesy of The Pill
by Kate Melville
Hormonal contraceptive methods - such as The Pill - may be having an underappreciated impact on a woman's ability to choose, compete for and retain her preferred mate, suggests a new paper in the journal Trends in Ecology and Evolution. The new paper builds on previous research (see related links below) which found that the contraceptive pill appears to disrupt a woman's natural ability to choose a genetically dissimilar partner.
The paper's authors, Dr. Alexandra Alverne and Dr. Virpi Lummaa, from the University of Sheffield, explain that many scientific studies have established that partner preferences of both women and men vary significantly according to the hormonal fluctuations associated with the menstrual cycle. Ovulation is associated with a profound shift in some female physical characteristics, behaviors and perceptions related to mate attraction.
During ovulation, women exhibit a preference for more masculine male features, and are particularly attracted to men showing dominance 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. Furthermore, some studies have suggested that men detect women's fertility status, preferring ovulating women in situations where they can compare the attractiveness of different women.
But, say the researchers, The 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," noted Dr. Alvergne.
The authors 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.
In conclusion, the authors suggest that The Pill is likely to have an impact on human mating decisions and subsequent reproduction. "If this is the case, [there are] implications for both current and future generations, and we hope that our review will stimulate further research on this question," said Dr. Lummaa.