A recent study has found that women may be able to recognise each other’s fertility.

This ability is commonly seen in animals that rely on physical signs to determine how fertile a potential breeding rival is. Now scientists are saying women have that ability too.

Without knowing it, women seem to be able to tell if others are in their most fertile phase of their menstrual cycle, around ovulation by just looking at their faces, says the unusual study published in the Royal Society Journal Biology Letters.

This ability is stronger in women with high levels of oetradiol – the female sex hormone that is linked to high general fertility.

As women who are fertile would have more children, they are also better at guarding their mate from potential adultery, says study co-author Janek Lobmaier from the University of Bern.

Lobmaier and a team showed pairs of photographs of women – one taken in the most fertile and one in the least fertile phase of their menstrual cycle. Generally the women did not feel that those photographed, from both versions, to be a threat. However, a subgroup of women who were not ovulating but had high oestradiol sex hormones, were more likely to pick the photo of an ovulatory woman as a potential date or husband thief.

The benefit of having the ability to detect fertility is perhaps to make sure her partner does not commit adultery.

The benefit of having the ability to detect fertility is perhaps to make sure her partner does not commit adultery.

“One explanation for our findings might be that ovulatory women (who are currently fertile) pose a greater threat to women with high oestradiol levels (who are currently not fertile but have a high potential fertility),” says Lobmaier. The study did not test the potential influence of naturally fluctuating oestradiol levels.

For animals, may use signals to show that they are fertile, such as using plumage, colour, scent or with a special mating call.

For people, these signs are more subtle. This has led researchers to suggest that human ovulation is hidden.

“But there is accumulating evidence that there are subtle changes in human females that are not obvious, but they can still be detected,” says Lobmaier.

Previous research had shown that men prefer portraits of women taken around the ovulation period over those of the same women in a non-fertile phase. Few studies, if any, have tested whether women too can discern such cyclical facial differences.

Women are fertile for a relatively short period of their menstrual cycle – a few days before and the day of ovulation.

As with animals, it is theorised that if men can detect this window, it boosts their ability to spread their genes.

“For women, there is perhaps no direct advantage to detect fertility in other women’s faces, but their might be indirect benefits, for example by making sure her own partner does not commit adultery,” says Lobmaier.

Lobmaier said the effects of this evolutionary ability were probably a “really, really, really small” part of human behaviour.

“They are interesting from an evolutionary point of view, but how big the influence is on our daily lives we can’t really say.” – AFP Relaxnews