Men are more likely to spoil their female partners and keep a close eye on their movements around the time of ovulation. This could be an evolutionary strategy to keep women away from other men during fertile periods, say the researchers who carried out a questionnaire study.
鈥淣on-paternity鈥� rates vary from country to country but between one and 30 per cent of children are not the offspring of their purported father. Steven Gangestad and colleagues at the University of New Mexico, US, found that women fantasised more about other men just before ovulation and that their partners apparently responded to this increased risk of unfaithfulness.
鈥淚t was clear from the results that the women鈥檚 primary partners were more attentive and proprietary near ovulation,鈥� Gangestad says. 鈥淭he results suggest a conflict of interest between the sexes when women are fertile.鈥�
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Previous studies have found that women prefer 鈥渞ugged鈥� male faces when they are fertile, or when looking for a short-term mate. But for a long-term relationship, they prefer men with 鈥済entle鈥� faces.
The evolutionary explanation apparently fits Gangestad鈥檚 new data neatly, says Magnus Enquist, an expert on mate bonding at the University of Stockholm, Sweden. But he cautions: 鈥淚n popular circles and evolutionary psychology, it is a scientific fact that females may get better genes from other males than from their own partner. However, the evidence for this is still not overwhelming.鈥�
Dangerous behaviour
Gangestad鈥檚 team thinks women do gain genetic benefits through sex with men who are not their primary partner. But being unfaithful could result in adverse effects if they are caught.
To maximise the potential benefits and minimise the risks, women should be most interested in other men during their fertile period, Gangestad thought.
His team gave questionnaires to 51 women. They filled them in within five days of ovulation 鈥� when they were fertile 鈥� and during a non-fertile period. Twenty-four of these women said they had a single relationship, and another seven had primary partners but non-exclusive relationships.
The team found that the women鈥檚 overall attraction to and fantasy about other men increased in the days just prior to ovulation 鈥� but sexual interest in primary partners did not change.
Visual cues
The women with partners also reported about 30 per cent more attention and 鈥渕onopolisation鈥� behaviour during their fertile period, such as frequent telephone calls to check on their whereabouts.
鈥淎nd specifically, the women who were most likely to report that their partners were more vigilant also reported the greatest increases in interest in other men,鈥� Gangestad told New 杏吧原创.
However, none of the women in primary relationships reported actually being unfaithful to their partner. This weakens the team鈥檚 evolutionary explanation for their findings, Enquist thinks.
Gangestad admits he does not know what cues men could be responding to. 鈥淭here may be subtle clues in the partner鈥檚 scent or visual signs,鈥� he says. 鈥淥r it may be a response to behaviour, such as an increased interest in other men.鈥�
Journal reference: Proceedings of the Royal Society B (DOI: 10.1098/rspb/2001.1952)
