The 2013 book My Genes Made Me Do It! Homosexuality and the Scientific Evidence (text) argues that homosexuality is, at most, only weakly and indirectly genetically based, and that conversion therapies are effective.

As part of this argument, it claims that homosexuality decreases in men as they age, using old Kinsey data to support it: (from page 49-50)

Although the Kinsey surveys of 1948 and 1953 greatly exaggerated homosexual and bisexual numbers, they showed one interesting trend, also borne out by subsequent studies—a steady decline in homosexual fantasy and activity with increasing age compared with heterosexuals

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Is there good evidence that, as men get older, there is a decline in their homosexuality (both fantasy and activity) at a faster rate than their heterosexuality.

Related question which did not receive a useful answer; the only answer explained how survey answers were of limited reliability.

  • I made a major edit to remove the speculation and focus on the claim. – Oddthinking Jan 5 at 1:16
  • Comments are not for extended discussion; this conversation has been moved to chat. – Oddthinking Jan 5 at 14:05

Properly conducted longitudinal studies have found that, if anything, the trend is in the opposite direction.

Only two longitudinal and prospective studies have examined changes in sexual identity over time, both of which were conducted among young women (Diamond, 2000; 2003; Sophie, 1986). Although no comparable studies exist on the sexual identity development of males, three longitudinal studies of young men have examined changes in sexual attractions (Dickson, Paul, & Herbison, 2003; Stokes, Damon, & McKirnan, 1997; Stokes, McKirnan, & Burzette, 1993). Taken together, the studies have found considerable consistency, as well as change, in sexual self-identification and attractions over time. For example, among 80 female youths (65% college students, and over sampled for youths who did not self-identify as lesbian, bisexual, or straight), Diamond (2000; 2003) found that 70% were consistent in their self-identification as lesbian, bisexual or unlabeled after two years and 50% were consistent after five years. An additional 15% transited to a lesbian or bisexual identity after two years, as did 14% after five years. Few youths transited from a lesbian, bisexual, or unlabeled identity to a straight identity. Among 216 behaviorally bisexual men (ages 18 – 30 years), Stokes and colleagues (1997) found that over the course of one year, 49% reported no changes in sexual orientation, 34% became more homosexually oriented, and 17% more heterosexually oriented. Clearly, the consistency and change documented by these various research studies must now be understood.

Regarding the quoted graph, Kinsey's report was based on self-selected interviewees and no attempt was made to obtain a representative sample. At the time this was ground-breaking research because merely talking about the subject was considered taboo, but you cannot trust any statistics derived from these interviews because of the number of potential confounding factors.

In particular, the graph shows a huge hump in category #6 at ages 13-15 and the smaller one for category #3, but nothing at that age in categories #4 and #5. This lack of correlation between the different categories strongly suggests some kind of sampling artefact.

Two possible explanations that occur to me are:

  • This data may have come from Kinsey's interviews with paedophiles, who cannot be considered to have valid opinions on their victim's sexuality.

  • At the time there was widespread ignorance about all aspects of sex, and sex education beyond a "birds and bees" talk from a parent was very rare. Some of Kinsey's interview subjects may have had homosexual attraction or experiences during adolescence and only later found out that what they were doing was considered taboo. They would then repress any homosexual tendency and report that they had since become straight.

I can't prove either of these theories, but they explain the graph shown at least as well as the theory that homosexuals turn straight as they get older.

Lastly, even if sexual orientation does tend to turn straight with age, this is not evidence against a genetic component because ageing in general has a genetic component.

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    The Kinsey survey has an eve more glaring flaw. Because he didn't do a longitudinal study following specific people over time, the data is strongly confounded by the environment that existed when the surveyed people were young. Eg 50 year olds were young at a time when attitudes to homosexuality were (possibly) far more intolerant. So the sample might be strongly influenced by historic changes in tolerance not individual changes in inherent preferences. – matt_black Jan 5 at 13:58
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    @matt_black Yes I thought about that, but AIUI attitudes throughout the early 20th century were uniformly negative, so it seemed less likely. Of course we could carry on spinning just-so stories forever. I just wanted to show that there are alternative explanations. – Paul Johnson Jan 5 at 22:47
  • The quote claims a decline in homosexual activity and fantasys, not a decline in number that identify themselves as homosexual. Since sexual activity in general likely decreases in upper age it is possible that the number identifying as homosexual (as they become confident of their attraction) can go up even as homosexual activity goes down due to lack general lowered sexual activity as one ages. – dsollen Jan 7 at 15:41
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    @dsollen The Kinsey scale is about the relative frequency of homosexual and heterosexual activity and desire, not the absolute amount. – Paul Johnson Jan 7 at 16:47

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