Despite the advances that science has developed, the most valid study about menstrual synchronization, was carried out by the American psychologist Martha McClintock and was published in 1971 by the Nature journal.
According to these studies, the direct causes of the “McClintock Effect” or “Social Regulation of Ovulation” are pheromones. These chemical substances that our body segregates are closely related to sexuality and reproduction and have direct effects on the individuals around us, causing several women who live in the same house or spend many hours of their day to day together to have their menstruation at the same time.
Pheromones are secreted through urine or sweat (pubis and armpits), but the sense of human smell is not as developed as that of animals, so we do not ‘smell’ those substances that someone has expelled. We are able to detect them involuntarily and without giving us any notice.
This causes us to feel more attracted or less by someone simply because of the pheromones that they releases and our organism has detected. In the case of women who live together (leaving aside any sexual and / or sentimental component), pheromones make them empathize with each other, getting their menstrual cycles regulated in such a way that they make them coincide. Of course, this synchronization requires a time of coexistence and a close relationship between these females, predominating the ovulatory cycle of one over the others.
It should be noted that, despite the years that have elapsed and the number of studies conducted on the subject, it has not been possible to give an explanation of why pheromones influence this synchronization.
The importance of the study carried out by Martha McClintock helped that an important part of the scientific world accepted the existence of pheromones in human beings, something that until then was believed that only existed in animals, although at the moment it is still not known with certainty how they are produced or what glands are responsible for producing them.
Evidently there are voices discordant with McClintock conclusions and place the fact of menstrual synchronization closer to the so-called “urban legends”. If caused by some type of hormone would be by those that are released through the hypothalamus, an endocrine gland which is the part of the brain responsible for regulating menstrual cycles (among other things). Possible causes of synchronization (if any) include a shared environment, number of hours of light received and the same ambient temperature.
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