The contraceptive pill may disrupt women’s natural ability to choose a partner genetically dissimilar to themselves, research at the University of Liverpool has found.

Disturbing a woman’s instinctive attraction to genetically different men could result in difficulties when trying to conceive, an increased risk of miscarriage and long intervals between pregnancies. Passing on a lack of diverse genes to a child could also weaken their immune system.

Humans choose partners through their body odor and tend to be attracted to those with a dissimilar genetic make-up to themselves, maintaining genetic diversity. Genes in the Major Histocompatibility Complex (MHC), which helps build the proteins involved in the body’s immune response, also play a prominent role in odor through interaction with skin bacteria. In this way these genes also help determine which individuals find us attractive.

The research team analysed how the contraceptive pill affects odor preferences. One hundred women were asked to indicate their preferences on six male body odor samples, drawn from 97 volunteer samples, before and after initiating contraceptive pill use.

Craig Roberts, a Lecturer in Evolutionary Psychology who carried out the work in collaboration with the University of Newcastle, said: “The results showed that the preferences of women who began using the contraceptive pill shifted towards men with genetically similar odors.”

“Not only could MHC-similarity in couples lead to fertility problems but it could ultimately lead to the breakdown of relationships when women stop using the contraceptive pill, as odor perception plays a significant role in maintaining attraction to partners.”

Release date: August 13, 2008
Source: University of Liverpool