Thursday, May 15, 2008

Menarch and Altitude

Here is an odd tidbit I came across in The Power of Place, by Winifred Gallagher: "Because menarch occurs about three months later per thousand feet [of altitude], [Tibetan] girls don't menstruate until sixteen to eighteen, instead of ten to twelve." That would mean that girls who grow up in Bozeman should start menstruation about 15 months later than girls who grow up at sea level; I wonder if they do?

In another place, Gallagher mentions that female rats who are raised with brothers start menstruation earlier than females who are raised with only other females. Which I guess makes sense evolutionarily: if there aren't any males around, why use up the energy needed for menstruation?

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