Scientists Find Genetic Link to Infidelity
Scientists in London have given unfaithful women a perfect excuse for their promiscuity - it’s in the genes.

The first-ever academic study looking at whether there is a genetic basis to infidelity concluded that there was, up to a point.

Almost 40 per cent of the culpability for women’s infidelity was put down to the genes, although other factors such as culture, the state of a relationship and opportunity are also important.

The study, carried out at Guy’s and St Thomas’s Hospital in London, may help explain the infidelity of women such as the former Tory cabinet minister Edwina Currie, who admitted having had an affair with the former prime minister John Major, and Amanda Holden, the actress who cheated on her husband, Les Dennis, with the comedy star Neil Morrissey.

Another high-profile female philanderer is Tamara Mellon, who separated from her husband Matthew after a fling with Oscar Humphries, son of the television celebrity Barry.

The research was carried out only on women, but Tim Spector, professor of genetic epidemiology at St Thomas’s, believes that a similarly significant proportion of male infidelity could also be down to genetic factors.

"I believe we’ll find an equally heritable trait in men because of the cultural studies that suggest that men have a similar desirability of a number of partners in different cultures and environment," he said.

Prof Spector said that while there was "no specific gene for infidelity or fidelity", the infidelity trait is caused by a "suite" of genes, originating on three separate chromosomes.

The gene findings have emerged from his study of 1,600 female twins - used in order to separate "nature from nurture", or environmental factors from genetic. The twins - brought up in identical environments - were asked a range of questions relating to their sexual attitudes and behaviour.

The women reported previous episodes of infidelity, total lifetime number of sexual partners and also their attitudes towards infidelity.

The research found that while genetic factors accounted for 38-40 per cent of the reasons for an affair, other issues such as a shared family environment, and individual life events, accounted for the remaining 60 per cent.

"Personal circumstances and personal environment are a factor, but not someone’s upbringing, because your upbringing would be shared by your twin," said Prof Spector.

The study also found the number of sexual partners a woman has is 38 per cent due to her genes.

Prof Spector believes his research could explain infidelities noted in certain families.

The Redgrave acting family, for instance, has a high number of individuals who have strayed, beginning with Sir Michael Redgrave, a bisexual who had affairs with both Edith Evans and Noel Coward.

Vanessa Redgrave divorced Tony Richardson, the film director, because of his affair with Jeanne Moreau, the French actress, while one of the couple’s daughter’s, Natasha Richardson, began her relationship with Liam Neeson, now her husband, while she was still married to Robert Fox, the theatre producer.

Diana, Princess of Wales, who was reportedly unfaithful to the Prince of Wales with a string of lovers, could have inherited the gene from her mother, Frances Shand Kydd, who cheated on her then husband, Johnny Spencer, with Peter Shand Kydd, whom she later married.

The US president John F Kennedy, his senator brother, Teddy and the Kennedy patriarch, Joseph, were all notorious womanisers.

Prof Spector said having an unfaithful brother or sister would significantly increase your changes of being unfaithful: "If your identical twin has been unfaithful, you double your risk of being unfaithful, while if it is a non-identical twin, or a brother or sister, you would increase your risk."

The normal likelihood of infidelity in women is 22 per cent, but having an identical twin who is unfaithful would push this up to 44 per cent. Having a sister who is unfaithful would push it up to 30 per cent, according to Prof Spector.

He identified what he believed to be the genetic factors involved in this trait, through a "linkage scan".

It found a clear linkage to chromosome numbers three, seven and 20, but did not identify a single gene. "If it was just one or two genes for these traits, we would have found it by now. There could be five genes, there could be 500," he said.

Prof Spector believes his findings lend support to evolutionary theories on the origin of human behaviour - that infidelity and other sexual behaviour persists because they may have been evolutionary advantages for women.

"It may have been important for a woman to be unfaithful," said Prof Spector. "[For example], when she has a violent husband or when she sees that the genes of her husband are not good enough."

For a woman, the advantages of securing a long-term partner are clear - given the amount of parental investment needed to bear and raise children. However, once a woman has established a relationship with such a partner with whom she is socially monogamous, sexual monogamy is not necessarily advantageous to her - unless her long-term partner is the most genetically fit male available.

From an evolutionary perspective, a woman’s best short-term strategy would be to clandestinely pursue men with better genes.

Prof Spector points out that women tend to have affairs with men of higher status than their husbands. However, the system would break down, he said, if "everyone was unfaithful, because there would be no pair-bonding".

Prof Spector has written a scientific paper on his findings and submitted it to academic journals.

He has also outlined them in a book, Your Genes Unzipped, which describes how people’s behaviour and lives are affected by genetic factors.

The average age of respondents was 50, the average number of sexual partners was between four and five, and just over 20 per cent admitted to infidelity, 25 per cent were divorced and 98 per cent were heterosexual.

However, Prof Spector’s findings have caused some controversy. Dr Petra Boynton, a sex and relationship psychologist from University College London, said: "I don’t agree with it and I don’t think the research is robust enough to prove it.

"It taps into this view of quick-fix sex, when people can say, ‘Oh I couldn’t help it, it’s my genes’, when what they should be saying is ‘I was unable to articulate my needs, I’ve got into this mess and I don’t know what to do.’

"Since this research has come out, I’ve had people e-mailing me and saying, I think I’m at risk from this gene, what can I do about it? Is there anything I can take?

"If you live in a family where it goes on, if your mother or father cheated and you can see people turn a blind eye, you will see those signs and signals. It could be genetic but it’s just as likely to be in the home."