Men's murky motives for romance

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.

"Non-paternity" 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 fantasized more about other men just before ovulation and that their partners apparently responded to this increased risk of unfaithfulness.

"It was clear from the results that the women's primary partners were more attentive and proprietary near ovulation," Gangestad says. "The results suggest a conflict of interest between the sexes when women are fertile."

Previous studies have found that women prefer "rugged" male faces when they are fertile, or when looking for a short-term mate. But for a long-term relationship, they prefer men with "gentle" faces.

The evolutionary explanation apparently fits Gangestad's new data neatly, says Magnus Enquist, an expert on mate bonding at the University of Stockholm, Sweden. But he cautions: "In 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."

Dangerous behaviour

Gangestad's 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 maximize the potential benefits and minimize 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 - when they were fertile - 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's overall attraction to and fantasy about other men increased in the days just prior to ovulation - but sexual interest in primary partners did not change.

Visual cues

The women with partners also reported about 30 per cent more attention and "monopolisation" behaviour during their fertile period, such as frequent telephone calls to check on their whereabouts.

"And 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," Gangestad told New Scientist.

However, none of the women in primary relationships reported actually being unfaithful to their partner. This weakens the team's evolutionary explanation for their findings, Enquist thinks.

Gangestad admits he does not know what cues men could be responding to. "There may be subtle clues in the partner's scent or visual signs," he says. "Or it may be a response to behaviour, such as an increased interest in other men."

Journal reference: Proceedings of the Royal Society B (DOI: 10.1098/rspb/2001.1952)

Emma Young

Source: NewScientist.com news service

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