Hormones have always played a vital role in evolution, by contributing to the species' survival, and two new studies carried out by New Mexico and California, Los Angeles, Universities come to detail some of the (rather unpleasant aspects) connected to these compounds.

The two research teams found that members of "the gentler sex" may have evolved to cheat on their mates during the most fertile part of their cycle. It's worth mentioning that this valid only for those mates who are less sexually attractive than other men.

"Women know they have attractions that come and go, but they probably don't realize that these urges are tied to their cycle, as well as our evolutionary past. They just know that suddenly one day they're attracted to their hunky neighbor or handsome co-worker," said Martie G. Haselton, a UCLA researcher and author.

It seems that men subconsciously notice these changes, which take place during ovulation and adapt their behavior accordingly, just like the protection offered by males to their females in the animal world.

"It's not just that men are more jealous and possessive when their partners ovulate, but they're also more attentive to their partners and more giving to their needs," said collaborator Steven W. Gangestad, a University of New Mexico psychologist.

"Although men are probably not aware of it, they behave as though they're genuinely concerned about being cuckolded. It turns out that there's some basis for the fear", Gangestad continued.

During the first study, the researchers asked 38 female participants to rate their partner's sexual attractiveness as measured by his desirability for a fling as well as his suitability as a long-term mate.

For the second part, participants reported the strength of their attractions that day to men other than their mates and the frequency and manner with which they flirted or otherwise acted out those attractions.

Haselton and Gangestad found that ovulation has a powerful effect on all women and that all of them felt more desirable, attractive and powerful in their relationships during the mid-point of their ovulation.

For the second study, the researchers' goals were similar, the only difference being that the questions specifically focused on the ovulation period.

The conclusion is as simple, as it is, let's face it, disturbing: during ovulation, most women have fantasies with other men and are likely to cheat on their partners, especially if they are less attractive.