No. 5
Critique of Hamer’s Research  
Hamer and his team had recruited a group of 76 homosexual men from an AIDS treatment program. They all claimed to have at least one homosexual brother and a strong pattern of homosexual orientation among their maternal uncles but not among their paternal uncles. Hamer’s team hypothesized that this ought to be reflected on some gene on the X chromosome. A man gets his X chromosome from one of his mother’s two X chromosomes, and his Y chromosome from his father. Since the mothers were not homosexuals it was speculated that it was only one of her two X chromosomes that carried the gay gene. So, in a general population, about half of the male children would end up with the X chromosome carrying the gay gene and half would not. But in the sample of 40 pairs of homosexual brothers, not only half of them (i.e. 20) but a full 33 of them had an X chromosome that had a variation on the q28 gene that was atypical of the normal banding pattern. Since this number (33) was well over the predicted (random) 50% they assumed that this particular gene carried the male homosexual orientation. However, there were still 7 pairs of homosexual men without this “marking” on the gene. If this finding were true and honest and thus could be reproduced in subsequent studies, the conclusion that could be drawn would still be limited to this: This particular chromosomal pattern is neither necessary, nor sufficient to cause homosexuality. It is not necessary since 7 of the 40 homosexual pairs did not have this pattern. And it was not sufficient because a subsequent study by the Hamer team (including non-homosexual brothers with the same background) showed that some of these heterosexual brothers had the same gene marking on q28. Such a gene marking and link is hardly an acceptable definition of a “gay gene”. But (and again only if the research were honest) it could be argued that there may be some other characteristic associated with this particular gene marking that links to another family characteristic that predisposes the individual to be more vulnerable to becoming a homosexual. For example, an individual with that particular gene marking may have a genetic predisposition toward novelty-seeking behavior or whatever.  Who knows what it could be?