Is male homosexuality maternally linked?

Abstract

Is male homosexuality maternally linked? In 1993 Hamer et al. noted a preponderance of male relatives in the maternal lines of gay men relative to heterosexual controls, and then reported a possible X-chromosome linkage to male homosexuality. This paper is the first notice of an ongoing investigation measuring whether this is a maternal inheritance effect or a general fecundity effect through the female line. The test of Hamer's proposition is, first, in finding a difference in the numbers of gay uncles and male cousins between maternal and paternal parental lines; then, in finding a difference in the numbers of gay male cousins between the male and female maternal lines; and last, in finding an increased reproductive rate for maternal line relatives, particularly female ones. A genetic pedigree was taken of a matched sample of 60 straight and 60 homosexual men drawn from the gay population of Sydney, Australia, and the first two tests were not supported and only partial support was found for the third pr...