Why do women livivng together in groups(e.g.Hostels) tend to have there period at the same time?

Answer 1

the body secrets a hormone related to the menustral cycle that cannot be detected by human, thus triggering all menustrating women living together to start closely together.weird huh.

Answer 2

It's known as menstrual synchrony

This article gives an evolutionary basis for the phenomenon:

"Why synchrony occurs is pretty much a total mystery. The only published theory I've seen treats it as an evolutionary holdover from prehistoric times, when it was common for men to take multiple mates and efficient reproduction was essential to the survival of the species. The author of this theory assumes that women in their brief monthly phase of peak fertility give off some pheromonic signal that drives men wild."

Answer 3

Easiest answer: pheromones. Over time, the reception of the pheromones generated by menstruating women will tend to time all their periods to approximately the same cycle. Probably intended to reduce stress levels in co-habiting females.
Did you know that in men living to expended periods of time with one or more women, there is a demonstrable drop in sex-drive? Just a curious fact. This would also tend to reduce stress levels. LOL

Answer 4

its called Cycling. Everyone gets on the same cycle because of all the hormones of each other. my mom and my sister and i all did the same thing when we lived together.

Answer 5

That is such a good question....lol That's true because girls I work with have it the same time like me to...weird huh.

Answer 6

maybe because there are a lot of them, so it seems that a group of them are always having their period.

Answer 7

http://www.teenwire.com/ask/2000/as-20000914p080.php

Answer 8

I never understood this myself but it happens.

Answer 9

cycling, hormones, who knows, but the girls I work, ours all follow each other.

Answer 10

Do they?

First I've heard of that.