In 1972, Harvard psychologist Martha McClintock published research on menstrual synchronization, the first of its kind. The data pointed to a curious phenomenon – a group of women living together began to experience a delay or postponement of their monthly cycle until it harmonized in time to coincide with the monthly cycles of the other women in the group. This was the first scientifically supported study suggesting that social interactions have a strong effect on the menstrual cycle, and the first substantiated theory of how pheromones might influence human behavior. Over the last 40 years of research, many more similar developments have emerged, but the scientific world is divided into two camps – one accepts the assumption as fact, and the other completely rejects it. Both sides have their arguments. Opponents of the idea believe that even if synchronization occurs, it has no biological function and is most likely a rudimentary (obsolete, no longer needed) adaptive mechanism left in our genes from the time when human ancestors needed it. It is believed to have been useful in making it easier to raise new generations from a cohesive social group. NEWS_MORE_BOX Proponents of the theory, on the other hand, rely on research demonstrating the effect of the phenomenon, but cannot name a clear cause for it. It is a common observation that in a close-knit group of women who spend a significant amount of time together, the ovulation period of the entire group aligns with that of the most popular, most sociable, and most dominant of them all—the alpha female. On the principle of pheromone communication, the ovulation of everyone else gradually approaches that of the leader of the group, even if she is only subconsciously perceived as such. Categorical evidence to accept or reject this theory does not yet exist, but the combination of documented manifestations of synchronization and lack of evidence make the question particularly popular in modern science. For more information, view the following video: