Male homosexuality

Male homosexuality has long been regarded as being an evolutionary puzzle. Around 4 percent of men are homosexuals. They have on average five times fewer children than their heterosexual counterparts. Why doesn't the behavior die out? A common explanation is that "superwoman" genes spread through the female lineage, while inducing female behavior in males as a side effect. No doubt this explains some male homosexuality.

I previously discussed the possibility of parasites causing male homosexuality in my 2017 "ubiquitous parasites" article.

At the time I discussed culturally-induced homosexual behavior - giving the example of celibate priests and altar boys. However, the possibility of male homosexuality being induced by organic parasites is also of interest.

Homosexual men spend more time having sex and less time raising children. That's a situation favoring parasite transmission. Homosexual men famously have a high parasite burden. Male homosexuality correlates with HIV/AIDS, hepatitis A, B and C, gonorrhea, syphilis, toxoplasmosis - and probably many other infectious diseases. It is widely understood that male homosexual behavior causes parasite transmission. However it also seems possible that causation could run the other way around: parasites could favor the production of homosexual behavior - for example: by interfering with development during childhood.

Many parasites would "prefer" to sterilize their hosts, as a strategy to divert host resources away from producing offspring and towards spreading parasite genes. Male homosexuality is not sterilization, but it drastically reduces reproductive output - and so from the Point of view of parasites, it comes close. Many parasites would "like" to influence their hosts in this direction. Their influences may systematically add up.

Of course, it is not politically correct to say that male homosexuality could be (a symptom of) a disease. It took a long struggle by activists to get homosexuality out of the Diagnostic and Statistical Manual of Mental Disorders. However, science doesn't care about what is in fashion - so the hypothesis need to be on the table and the evidence needs to be examined.

I don't have a lot of new evidence to present here. Many lab experiments relating to the topic are probably unethical, so we may have to rely on an analysis of the results of "natural experiments". Epidemiology is an obvious place to look for evidence for infectious homosexuality. My understanding is that homosexuality is fairly evenly distributed in human populations. That doesn't favor the hypothesis the "infectious homosexuality" hypothesis, but it is at least consistent with it - if a widespread parasite is involved.

Regardless of whether "infectious homosexuality" is a thing, science and technology are likely to be able to detect and reverse tendencies towards homosexuality in childhood. However, "infectious homosexuality" might make this outcome happen faster. Then that time comes, it seems likely to be a new controversial dilemma for those involved.

References

INFECTIOUS CAUSATION OF DISEASE: AN EVOLUTIONARY PERSPECTIVE

Ubiquitous parasites