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Women’s Infidelity Gene 2004-11-25

Posted by clype in Articles of Interest, Intolerance, Science.

In the first ever academic study of its kind, Professor Mr.Tim Spector, professor of genetic epidemiology at Guy’s and St Thomas’s Hospital in London, looked at whether there is a “genetic basis to infidelity” and 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.

  • Mr.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.

[Picture of Tim Spector]
‘Personal circumstances and personal environment are a factor, but not someone’s upbringing, because your upbringing would be shared by your twin’, said Mr.Spector.

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

Mr.Spector believes his research could explain infidelities noted in certain families, and 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 Mr.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.

Mr.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 Mr.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.

Mr.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’.

Mr.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: A Guide to How Your Genetic Inheritance Can Shape Your Life”, 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, Mr.Spector’s findings have caused some controversy. Ms.Petra Boynton, a sex and relationship psychologist from University College London, said:

[Picture of Petra Boynton]
‘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’



1. The infidelity/monogamy genes « eleven minutes - 2008-11-06

[…] study on humans (non surprisingly – see above) found strong genetic influences on adultery (women did follow their twin sisters in deciding whether or no…, however, the Vasopressin allele didn’t seem to do the […]

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