Subject: Twin studies
From: [email-masked]
To: [email-masked]
Date: Mon, 16 Dec 1991 13:38 EST

Pinched from soc.motss:
_______________________________________________________________________________

From: [email-masked] (Geoffrey Scott Puterbaugh)
Date: 16-DEC-1991 03:27:30
Description: New Publication: Twins and Homosexuality

Big news day in the "Twins and Homosexuality" world. You
may have heard about this on the news Saturday night.
 
Reference: J. Michael Bailey and Richard C. Pillard: "A Genetic
   Study of Male Sexual Orientation," Archives of General
   Psychiatry, v. 48, 1991 (December), pp. 1089-1095.
 
ABSTRACT: Homosexual male probands with monozygotic cotwins,
dizygotic cotwins, or adoptive brothers were recruited using
homophile publications.  Sexual orientation of relatives was
assessed either by asking relatives directly, or when this was
impossible, asking the probands.  Of the relatives whose sexual
orientation could be rated, 52% (29/56) of monozygotic cotwins,
22% (12/54) of dizygotic cotwins, and 11% (6/57) of adoptive
brothers were homosexual.  Heritabilities were substantial
under a wide range of assumptions about the population base rate
of homosexuality and ascertainment bias.  However, the rate
of homosexuality among nontwin biological siblings, as reported
by probands, 9.2% (13/142) was significantly lower than would
be predicted by a simple genetic hypothesis and other
published reports.  A proband's self-reported history of
childhood gender nonconformity did not predict homosexuality
in relatives in any of the three subsamples.  Thus, childhood
gender nonconformity does not appear to be an indicator of
genetic loading for homosexuality.  Cotwins from concordant
monozygotic pairs were very similar for childhood gender
nonconformity.
 
End of abstract.  Speculations in another append, perhaps.
 
Best regards,
 
Geoff