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From: PAPAI@kcgl1.eng.ohio-state.edu (Jonathan Papai)
Newsgroups: alt.folklore.urban
Subject: more info on genetalia size, etc.
Date: 2 Feb 1994 19:27:18 GMT

Some time ago, discussion turned to size of penises. I made the assertion that testis size was related to ethnic group, and also to the frequency of twins being born. I found the source of my assertions:

_Discover Magazine_ ISSN 0274-7529, August, 1988, p. 64

Title:          Double Trouble
Author:         Jared Diamond, (UCLA Prof. of physiology and
                something else and MacArthur Genius Award winner, etc.)

Data from article says Monozygotic (identical) twins 4 per 1000 births.

Dizygotic (fraternal twins) frequency varies among populations.

Diamond goes into one of his usual analogy-filled discussions of why twins are rare among humans, noting that if twins were to become the norm, several changes in human physiology would be necessary, in addition to increased ovulation.

1. Women would need four breasts. Among mammals, the number of tits correlates well to twice the average brood size. [obvious exceptions prove the rule.]
2. Women would have to be about twice as big, (250 lbs instead of 125.) Twins are born on average 5.5 lbs, with singletons at 7.5 lbs. Birth weight is a strong determinant of survival and health. Enlarged women would have larger babies, and would be able to produce more milk for them.
3. Men would have bigger testis.

Diamond says:

        "..empirical fact that when animal breeders select female
        sheep or mice to have bigger broods, the offspring males
        have larger testis."

Diamond posits a hormonal connection I don't understand.

In any case, the rate of dizygotic twins is:

4 per 1000 in Asians
40-50 per 1000 among Yoruba in Africa
16-19 per 1000 in two other African porulations

8 per 1000 in Caucasians.

Diamond then looks for a correlation between testis size and these observations.

        "Astonishingly, for all the obsessive interest that men
        harbor in the size of their own and other men's
        genetalia, few actual measurements of average testis size
        in human populations are available.  The most accurate
        measurements are based on testis weight at autopsy, which
        average about 8-10 grams per testis in two series
        totalling 209 Chinese cadavers, and 20-22 grams in a
        series of 140 Danish cadavers.  Cruder estimates of
        testis size in living men suggest that two other Asian
        populations, Japanese and Koreans, also tend to have
        smaller testis than Caucasians.  These population
        differences are much greater than would be expected as a
        by-product of body size and do not appear to be related
        with differences in copulatory frequency.

So , the following is likely:

Tb. Men are obsessed with their and their neighbors genetalia size. T. But not obsessed enough to do a whole lot of research on it. T. Dizygotic twins are most common among Africans, less so among

Caucasians, and least so among Asians. Tb. Probably at least partially because Caucasians have bigger

testis than Asians, (at least dead ones.)

.......

Another assertion I previously made, (and still believe), is that identical twins are more frequent now than they used to be, and that is related to women delaying childbirth to later in life. I have not yet found information related to this, but will keep looking.

None of the above is related in any way to crystallographic twinning.

Jon "abcabcabcacbacbacba" Papai