Women can blame unfaithfulness on genes - research
November 26, 2004 Edition 1
Steve Connor
London: Confronted by a cuckolded husband, cheating wives may be able to plead a novel excuse: "Blame my genes".
According to Britain's biggest study into the genetic basis of promiscuity, some women may have inherited a genetic predisposition to be unfaithful to their partners.
Interviewing 3 200 women twins about their sex lives, scientists found the average number of sexual partners was about five. A little over 20% admitted to being unfaithful in a stable relationship.
Professor Tim Spector, director of the Twin Research Unit at St Thomas Hospital in London, said that about 40% of the variation in faithfulness was due to genes. The figure means that if a woman is unfaithful, her identical twin sister would be twice as likely as average to be unfaithful as well.
A non-identical twin sister of an unfaithful woman would be 50% more likely to have an affair outside marriage.
Attempts to link infidelity directly to a specific gene or set of genes failed, although the researchers said that they did manage to locate some of the traits to three of the 23 pairs of human chromosomes.
"There is not an infidelity gene, but 50 to 100 genes are important and give us the tendency to respond to our environments in different ways ... It may be important for women who commit infidelity," Spector said.
The study, published in the journal Twin Research, suggests that a genetic predisposition toward female infidelity may have evolved because it was important in allowing women married to "low status" men to surreptitiously become pregnant to "high status" males.
"Work in the UK has shown that human females generally have affairs with men of higher status than their husbands, perhaps illustrating an effort to mate with a genetically superior partner," they say.
Spector said the conclusions can be generalised to the wider female population of Britain because the sample is representative of the country at large.
The study was one of many involving more than 10 000 twins who since 1992 have been investigated and interviewed for a whole range of medical and psychological differences from high blood pressure to snoring at night.
The average age of the women involved in the infidelity study was 50 with some reporting no extra-marital affairs while others at the other extreme said they have had over 100 sex partners.
A quarter were divorced and 98% were heterosexual. The researchers calculated that 41% of the variation in infidelity and 38% of the variation in the number of sexual partners could be explained by genes.
Interestingly, there was no genetic basis for attitudes towards infidelity. Spector said 90% of the women reported having thought about being unfaithful but only one in four actually did anything about it.
