Synchronised Menstrual Cycles- True or Not?

[bug_girl]

nature won't benefit, but individual females might. a totally PIDOMA explanation probably has to do with the group dynamics of primates.

menstrual synchrony might lead to birth synchrony, and reciprocal care of infants.

menstrual synchrony might also lead to confusion of paternity. Male infanticide is fairly common, apparently, in groups in which the dominance hiearchy changes.

human females don't have some of the obvious external changes that symbolize fertile periods (thank goodness!) in other primates. so that might be a factor somehow, although i'm not sure how.

the person doing the coolest work in this field is Sarah Hrdy--try looking up some of her recent work.

 

[peptoabysmal]

And how this is explained in terms of... Natural behavior. I don't know the right term so bare with me. All I want to ask is how and in what way Nature profits from this synchronization?

I'll take a wild guess and say that it probably had something to do with competition for mates, the same force that evolved breasts to be plump even when not necessary to provide nourishment and child bearing hips to attract males.

 

[epepke]

The Cecil Adams site brought up an interesting point. In order for "synchronization" to make any sense, the period of the period, so to speak, must be the same. Different women have different periods. There is no meaningful way to say that a woman with a 26-day cycle is synchronized with a woman with a 29-day cycle.

So, in order for synchronization to occur, the periods of the periods would also have to become the same.

Funny thing about synchronizing cycles with a pulse (even a long or gradual one, like emitting pheromones). The only practical way of doing it in a stable way is to have an oscillator going on with a certain period and have the pulse slightly advanced with a period slightly shorter than the period of the oscillator. When the pulse is retarded, or it is too advanced, what happens is chaotic fluctuations. Even biological systems do this. The sinus and AV nodes of the heart work like this; when it doesn't work right, you get the chaotic behavior known as fibrilation. People have circadian circadian on average about 25 hours, just enough to be brought up to speed with sunlight as a signal. A person with a circadian cycle shorter than 24 hours gets insomnia, and for even an ordinary person, exceeding the limits with travel causes jet lag. Chaotic behavior often spontaneously reverts to non-chaotic behavior, but it usually takes some time.

However, when a bunch of women get together, the long-period and short-period women are all giving out signals. Half of them, considered pairwise, would have to be in the chaos-promoting direction rather than the synchrony-promoting direction. So, for a time at least, one would expect irregular menstrual cycles. Is this reported as well?

 

[Cleopatra]

Originally posted by bug_girl ]
nature won't benefit, but individual females might. a totally PIDOMA explanation probably has to do with the group dynamics of primates.

menstrual synchrony might lead to birth synchrony, and reciprocal care of infants.

menstrual synchrony might also lead to confusion of paternity. Male infanticide is fairly common, apparently, in groups in which the dominance hiearchy changes.

human females don't have some of the obvious external changes that symbolize fertile periods (thank goodness!) in other primates. so that might be a factor somehow, although i'm not sure how.

the person doing the coolest work in this field is Sarah Hrdy--try looking up some of her recent work.

You know bug_girl social anthropologists have been based whole theories of on the phaenomenon of the syncronization. In fact the theory that in Eastern Mediterannean we had Matriarchal ( I would add Nazist totalitarian but you are new to the board to get the joke ) types of social organization is based on the fact you pointed above: "human females don't have some of the obvious external changes that symbolize fertile periods (thank goodness!) in other primates. so that might be a factor somehow, although i'm not sure how."

Plus the speculation that the ferormones must have caused synchronization of the menstrual cycles and therefore a thick mystery as to the paternity of the offsprings

Of course,from the moments that the males realized their contribution to the breeding of babies they demanded exclusivity in order to provide food and security.

I think though that those theories were in fashion during the 70ies and they have been debunked. I *think* that none believes in our Matriarchal Past anymore. I stopped following the issue because in the mean time I grew up and I realized what a distaster for our gender would be the revival of a matriarchal society