From: dkelly@bio5.acpub.duke.edu (Diane Kelly)
Subject: Re: women living together and concurrent cycles
Date: 8 Oct 93 17:48:19 GMT
> In article v140pxgt@ubvms.cc.buffalo.edu
(Daniel B Case) writes about menstrual synchrony:
|> >There was long a lot of anecdotal evidence attesting to this, and
|> finally some researchers at the U of Penn checked it out by attempting to
|> induce it artificially. They had one control woman wear "sweat pads" in her
|> armpits (the assumption was that some sort of pheromone had something to do
|> with it) then got the sweat out and mixed it with alcohol, and daubed it
|> under the noses of the participating women (none of whom knew or
|> associated with the control woman) at regular intervals. In time all
|> the studied women came to match the control woman's cycle. There's
|> still some controversy about this, but there's at least been some
|> research done on it.
I imagine at least some of y'all have been wondering why I haven't
already thrown my two cents in -- after all, I'm a biologist, I study
reproductive physiology, and I'm a woman. Well, it took me a little
time to search through the library for some real references...
OK, here goes. The first scientific evidence confirming human menstrual
synchrony appears in a 1971 paper by Martha McClintock. She interviewed 137
members of her (all women's) dorm several times during a school year,
and ended up with the onset date for every woman's period between late
September and April. She compared data for roomates, close friends, and
the living group as a whole, and found that in each case the mean
difference in onset dates decreased as the year progressed. In short,
women who spent a lot of time together had their periods start closer
and closer together as the school year went on. The experiment also
turned out to be repeatable (Graham and McGrew, 1980; Quadagno _et al._, 1981).
McClintock suggested that menstrual synchrony might be caused by some
sort of pheromone, but also pointed out that it could be any number of
other things -- after all, these women lived together, ate the same food
(it's a dormitory, remember?), and came in contact with many of the same
random influences... in short, the environment was really too
uncontrollable to determine an exact cause.
But just because McClintock was cautious when suggesting possible
causes for menstrual synchrony didn't mean that others wouldn't go
looking for that holy grail of a pheromone. That study Daniel mentions
above (Russell, _et al._, 1980) grabbed onto the idea that the axillary
sweat glands (the ones in your armpits) may be putting out scents that
are involved in unconscious human communication, and tried to apply it
to menstruation.
Now, although many people seem to think that the very idea of us human
types putting out scent-messages to each other is ridiculous, there is a
fair amount of indirect evidence to back it up. Humans have a
specialized type of sweat gland (apocrine sweat glands) located
primarily in the axillae (AKA armpits), the anogential region, on the
areole of the breast, and in the face and scalp. They secrete steroids
related to the sex hormones: notably androsterone and androsterol.
Bacteria on our skin break these compounds down into odiferous
substances. The secretions from these glands are similar to compounds
that are believed to influence behavior in non-human mammals. And the
glands are only active after puberty, and become inactive in
post-menopausal women (Doty, 1981). It's no surprise that when faced
with evidence supporting the existence of human menstrual synchrony,
scientists went looking for armpit pheromones.
Russell, et al. (1980) did get results suggesting that something
secreted in sweat might have an effect on menstruation onset. But some
of his methods have been criticized: (1) the sweat donor was one of the
scientists doing the experiment, and had contact with the test subjects
-- possibly adding an additional influence to her sweat-soaked pads. (2)
The sweat donor was a "known inducer" -- she had a history of making
other women's cycles conform to her own. Although the experiment had a
'no sweat' control, it did not have a 'sweat from a non-inducing woman'
control, which may have skewed the results.
In short, then -- menstrual synchrony does happen in humans, there's
some evidence that it may be pheromonally influenced, but no one has
isolated the compound. Now, since menstrual synchrony is just the
outward sign of _ovulatory_ synchrony, the really interesting
question is _why_ a bunch of women would start to ovulate at around the
same time...
Diane Kelly
Duke Zoology
Literature cited:
Doty, R. L. 1981. Olfactory communication in humans. Chem. Senses 6:351-75.
Graham, C. A. and W. C. McGrew 1980. Menstrual synchrony in female
undergraduates living on a coeducational campus.
Psychoneuroendocrinology 5: 245-252.
McClintock, M. K. 1971. Menstrual synchrony and suppression. Nature
229:244-245.
Quadagno, D. M., H. E. Shubeita, J. Deck, and D. Francoeur 1981.
Influence of male social contacts, exercise, and all-female living
conditions on the menstrual cycle. Psychoneuroendocrinology 6: 239-244.
Russell, M. J., G. M. Switz, and K. Thompson 1980. Olfactory influences
on the human menstrual cycle. Pharmacol. Biochem. Behav. 13: 737-739.
