The popular idea that women who they live Together or close contact have a synchronized menstrual cycle, in reality it is one false belief. Born in the 1960s after a study on the students of an American college, the research had such a success that menstrual synchrony even took the author’s name: it is known as “McClinTock effect“. The study, based on 8 months of self-relevant data by the participants, showed that the” narrow friends “actually had the menstrual cycles that aligned over time. The subsequent searches were unable to replicate these results and it original study was discreditedas well as the theories used to explain the phenomenon, from a phantom action of the dumped to an evolutionary coupling strategy. In reality, it is precisely the variability of the menstrual cycle to make synchronization impossible and if we realize that among our friends we have menstruation at the same time, it is simply one coincidence.
The study on menstrual synchrony that gave rise to the false myth
In 1971 the prestigious magazine Nature Publish an article that made history: “Menstral Synchrony and Supprecess” by Dr. Martha McClinTock. The research was based on the data collected by 135 girls between 17 and 22 years old who lived in same dormitory to college and stated that in women who they live together or in close contact (roommate companions, close or more assiduous friends) the menstrual cycle It tends to synchronize, appearing in the same period.
The participants indicated their “narrow friends” and recorded the dates of the menstruation (the moment when the menstrual flow appears) for 8 months And the McClinTock found that at the end of the study, the “narrow friends” actually had menstruation in the same period.
Ferormoni and evolutionary strategy
The McClintock hypothesized that it was due to the release of pheromoni feminine able to stimulate or inhibit the beginning of menstruation in nearby women. According to another theory, however, the synchronization of the menstrual cycle was one evolutionary strategy inherited from animals to escape the sexual dominance of a single dominant male, which in fact would have less control over coupling and reproduction If all the guard females go into heat at the same time. For females, there would in fact be more likely to mate with other males too. In reality, both theories have been discredited.
First of all, There are no studies that confirm the Ferormoni theory in humans, but doubts have also been raised about evolutionary strategy theory to increase mating chances. In fact there are animal effects that reproduce second seasonality and therefore they go into heat in specific periods and by force synchronized. But, according to a 2004 research, it seems that even in the animal world, in the case of animals that do not reproduce according to seasonality, if the females went into heat at different times (therefore in asynchrony) could be more likely to mate with the male with the best genetic heritage.
Also, studying and recording when our close relatives of the animal kingdom went into heat, i dadof the researchers have conceived two mathematical models To explain any synchronizations: one with the theory of evolutionary strategy and the other based on the case. Comparing them both with what is recorded (for well 6 years!) During the study, the model based on the case It was the one that most adapted to the collected data.
A false myth born from wrong assumptions
In the 70s, “the McClinTock effect” had an amazing success, so much so that it was still debated today, but none of the subsequent research has managed to reproduce the same results (and those who did it, present the same mistakes of the original study). Wider and more lasting studies have shown that the appearance of menstruation in the same period in women falls within the realm of the random coincidences.
Criticism concerning the analysis method, the scarcity of data collected and not least the design of the study of ’71 have also been accumulated. McClinTock took into consideration Only the start date of menstruationwithout calculating theovulation or other factors of the menstrual cycle. In addition, I will consider a 28 -day fixed cycle, while the duration of the menstrual cycle is variable. Finally, the study included few students and in a too short period of time.
The variability of the female menstrual cycle makes synchronization impossible
If we seem to have the synchronized cycle with the women of our life, it is therefore simple perception. The menstrual cycle has a duration average 28 days, but the key to everything lies in the word “media”. In fact it can vary from woman to women: a cycle is also considered normal shorter (23-26 days) or longer, 35-40 days. Let’s assume that the woman TO has a 30 -day cycle and the woman B of 26: during the year there will be periods in which the menstruation of the two overlap.
But that’s not all: the menstrual cycle is also variable For the same woman from month to monthanticipating or delaying a few days. So any synchronization between two women is simply one coincidencehowever, which we pay more attention.
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