Premenstrual syndrome (PMS) is a set of symptoms that affect 90% of people who menstruate, and that can consist of cramps, malaise, headache, acne or emotional changes, among others. Usually this happens a few days before menstruation occurs.
The most common belief is that it is PMS that causes mood swings in women. However, two investigations published in the journal Evolution and Human Behavior found another key point in the reproductive cycle itself: ovulation .
Ovulation is part of the menstrual cycle, and it occurs when an egg is released from the ovary. From that moment on, the egg can be fertilized by a sperm. If it is fertilized, it can reach the uterus and implant itself, to become an embryo. If it doesn’t, it will simply disintegrate and the lining of the uterus will shed during your period.
According to the results obtained by these studies, women tend to be more interested in sexual relations during their most fertile days . One of these studies found that fertile women felt more open to the idea of being intimate with an acquaintance or a stranger. While the second investigation found that those women who had less masculine-looking partners were more likely to desire men with certain traits, such as a strong jaw , during the days of greatest fertility.
Until a few years ago, most research on the menstrual cycle focused solely on premenstrual syndrome (PMS). Until then, experts had not investigated whether and how ovulation affects women.
Why did we humans lose ‘zeal’?
Unlike other mammals, which tend to go into heat during fertile periods, women can have sex and become pregnant at any time of the month. According to evolutionary theorists, it is believed that humans lost their heat in order to hide ovulation: in this way, if a man did not know what specific sexual encounter would pass on his genes, he was much more likely to stay and will help in the upbringing of their children.
According to experts, men seem to know when their partner ovulates , albeit unconsciously. At the moment, no one knows for sure how men can know (it is suspected that smell could be related), but different studies have found that women say that their male partners become more jealous and attentive on the days of greatest fertility. For example, a study published in 2006 in the same journal found that when women were most fertile, their partners viewed other men as a greater threat to their relationship.
A wide variety of studies have found that women, when ovulating, seek out men with a more masculine appearance . This was reported by a review published in 2008 in the journal Proceedings of the Royal Society B , in which scientists came to identify some of the male traits that women preferred at times of greater fertility: faces with stronger jaws, dominant behaviors, muscular bodies, deep voices and greater stature.
But, on a day-to-day basis, knowing how much ovulation affects is more complicated. Especially when we consider that, every month, many women take the contraceptive pill. According to experts, taking the pill would eliminate much of the variation in hormonal changes that typically occur throughout the cycle, so it would be expected that it would have an impact on a woman’s behavior. In short, men may not be as able to identify when their partner is most fertile .
In any case, from a more evolutionary perspective, unraveling ovulation could help reveal a lot about how human reproduction evolved.
