The Evidence That Human Pheromones Exist

In the most general sense, pheromones are chemicals released by animals and insects to communicate with each other. But more intriguingly, pheromones also are supposed to allow one animal to influence the physiological state of another animal.

The evidence that pheromones exist in the animal kingdom is abundant and beyond doubt. However, do humans communicate by pheromones? More specifically, do we secrete any chemicals that, if someone else smells them, will create sexual arousal, anger, or fear? Can we spray on a cologne, as some claim, and make the opposite gender attracted to us? Can another person's sweat influence your emotional state?

About Human Pheromones

Human pheromones are said to exist in human sweat. But before we go looking for pheromones, we should ask whether the effects human pheromones are supposed to actually exist. I’ve heard they are supposed to be the cause of:

• Menstrual synchrony: women that live together get their periods at the same time
• MHC dependent mating: women rate smelly shirts (or sweat) from men with different MHC genes than themselves as more appealing than the sweat from men with similar MHC genes
• Pheromone colognes influencing the people around you: various people report that colognes containing putative human pheromones can be used to attract members of the opposite sex and produce all sorts of social effects according to http://astrobiosociety.org

The Vomeronsal Organ

Let's take each of these in turn. But before we start, we have to talk about the vomeronasal organ. The evidence that animals communicate via pheromones is abundant, and when animals communicate via pheromones the signal is processed in an area of their brain called the vomeronasal organ. Humans do not have a functional vomeronasal organ, so they do not process pheromones in this way.

However, this does not by itself mean that human pheromones do not exist, and some recent evidence indicates signals from human pheromones may be processed in other areas of the brain. So while the absence of the vomeronasal organ in humans does not bode well for the existence of human pheromones, it does not by itself prove that they do not exist. In short, ignore all discussion of the vomeronasal organ.

Menstrual Synchrony

Whenever people talk about pheromones they always bring up the McClintock study. In a nutshell, the McClintock study claimed to show that pheromones cause the menstrual cycles of women living together to synchronize. However, the story is actually much more complicated than this. The original McClintock study was done a long time ago, in 1971. And attempts have been made since to replicate the study. Learn more at http://pheromones-work.weebly.com

About half of the new studies have supported menstrual synchrony and half have not. This is a problem itself, but there are also many reasons to think that the studies supporting menstrual synchrony do not demonstrate sufficient evidence to support the idea.

First, what exactly is menstrual synchrony? Starting your period at the same time, ending your period at the same time, or having your period at the same time? If it's having your period at the same time, how many days do you have to overlap?

The point is that menstrual synchrony has varying definitions and the definition matters. If menstrual synchrony meant starting your period at the same time that would be very interesting, but it often just means having overlapping periods. And if that is the case, then the overlap is statically very likely. Learn more at http://pheromones-4u.com

Conclusion

The menstrual cycle can vary from 21 days to 35 days, and the period itself can last from 3-5 days. The menstrual cycle can be affected by a woman's stress level, a diet she's on, exercise, and birth control. Some women have regular cycles, some women have regular cycles some of the time, and some don't have regular cycles at all. With all of these factors combined, it would be strange if women living together did not have overlapping periods on occasion. And this doesn't even begin to take account of confirmation bias.

Simply put, women living together notice and remember when they are having their periods at the same time. But they don't notice if they don't. This means women will remember having periods with roommates more often than they really do.