Taking a contraceptive pill messes with Mother Nature in more ways than one

According to a new study by a scientist at the University of Liverpool in England, in its effort to prevent pregnancy, the pill alters a woman's sense of smell, which is one of the ways she decides, consciously and unconsciously, which men she is attracted to. When on the pill, she is attracted to men with similar genes, the study revealed. With these men, she is more likely to have a miscarriage or a baby who has a compromised immune system, or suffer from infertility. When she is not on the Pill, her nose tells her to choose men who are genetically dissimilar, which increases her chances of producing a healthy child. It is Survival of the Fittest 101.

In the study, which was led by Dr. Craig Roberts, lecturer in evolutionary psychology, 100 women were asked to indicate their preferences of six male body odor samples. Roberts tested women before and after their use of the Pill, which took research one step further from the 1995 study by Claus Wedekind that linked scent to selection by genes.

"Makes sense," says matchmaker Barbie Adler, president of Chicago-based Selective Search. "We don't usually hear the word 'smell' when people tell us if they like or don't like someone, but that is part of it. Usually, they use the word 'chemistry' or 'intuition.' "

When people meet potential mates, their noses tell them if they have similar or dissimilar genes and immune systems, according to Herz and Roberts. Mating with someone with similar genes increases the chances of a baby having negative recessive traits such as Tay-Sachs.

In terms of hormones, the Pill tells a woman's body she is pregnant. This could explain why women on the Pill choose men who smell like family members, because they could protect her while she is vulnerable. Off the Pill, nature takes over, so she seeks genetically dissimilar mates.

The time of month affects a woman's ability to sniff out mates too. Her gene-smelling ability is keenest around ovulation, says Herz, when it exceeds a man's. During menstruation, her ability is less than a man's. Men, on the other hand, are more likely to use sight to locate what their eyes tell them are fertile mates: women with healthy-looking skin and hair and a waist-to-hip ratio of 7:10.

Excerpts courtesy of the Chicago Tribune