By Steve Connor
Some women may have inherited a genetic predisposition to be unfaithful to their partners, scientists believe.
In a bid for fresh insight into the old debate on whether individuals are shaped by nature or nurture, scientists talked to 3200 women - all identical or non-identical twins - about their *** lives.
They found wide variations in attitudes towards infidelity and in how many sexual partners women admitted to having.
The average number of sexual partners was between four and five. Slightly more than 20 per cent admitted to being unfaithful in a stable relationship.
Professor Tim Spector, director of the Twin Research Unit at St Thomas Hospital in London, said about 40 per cent of the variation in faithfulness in the group was due to genes, with the rest down to environment and upbringing - nurture.
Attempts to link infidelity directly to a specific gene or set of genes failed, although the researchers said they managed to pinpoint some of the traits to three of the 23 pairs of human chromosomes.
Professor Spector said: "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."
The study, published in the journal Twin Research, suggests that a genetic predisposition towards female infidelity may have evolved because it was important in allowing women married to "low-status" men surreptitiously to become pregnant by "high-status" men.
"If female infidelity and number of sexual partners are under considerable genetic influence, as this study demonstrates, the logical conclusion is that these behaviours persist because they have been evolutionary advantageous for women," the researchers write.
"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."
The average age of the women involved in the infidelity study was 50. Some reported no extra-marital affairs or no sexual partners but others said they had had more than 100 *** partners.
Interestingly, there was no genetic basis for attitudes towards infidelity. Professor Spector said 90 per cent of the women reported having thought about being unfaithful but only one in four actually did anything about it.
women are born to cheat?
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