The Pathogen Hypothesis For Male Homosexuality

There are known examples of similar phenomena that occur in the wild. A parasite called Sacculina infects a male crab by attaching to its genitals and giving it hormones to make it behave like a female crab. It then causes the male crab to nurse the Sacculina’s eggs. The parasite reproduces and the cycle continues. A more commonly known example is Toxoplasma Gondii. These parasites reproduce in the intestines of cats and lay eggs in the cat’s feces. They then spread to other intermediary hosts such as rodents. The parasite infects and modifies the behavior of rodents to make them attracted to cats, rather than fearful of them. The cat then eats the infected rodent, and Toxoplasma Gondii is able to reproduce again. These are well established examples of parasites exploiting another organism’s form for their own benefit.

All STDs are caused by pathogens. Virtually every STD is orders of magnitude more prevalent among Men Who Have Sex with Men (MSM) than it is among the general population. We’re not claiming that there are known STDs that make people gay, but this does demonstrate that pathogens do spread better among homosexual men than other populations.

Furthermore, most people are disgusted by homosexual intercourse and sexual promiscuity. This instinct (commonly labeled “homophobia”) is part of the immune system, and is usually reserved towards disease and infection vectors that humans have been exposed to for millennia, such as decaying organisms, insects, arachnids, fecal matter, etc. This natural instinct is so strong that cultures and religions have evolved explicit values and policies against homosexuality (e.g. Islam and Christianity). Similar religious policies include the banning of certain kinds of food, or unsafe preparation methods to limit the spread of disease. In homosexuals, the disgust response towards homosexual intercourse is gone, despite the high risk of catching a multitude of diseases that reside in fecal matter and may be transmitted via anal sex.

Additionally, homosexual men tend to be more sexually promiscuous relative to normal people. They tend to have sex more often and with far more partners. These facts are consistent with the pathogen hypothesis because an intestinal pathogen would be able to spread itself to more hosts if its current hosts engage in frequent anal sex. These behavior patterns are also consistent with the disgust response in homosexuals being suppressed by something. It could be that this specific yet simple behavioral effect happens to be good at propagating pathogens.

Pedophilia is another behavior that is more common among the homosexual population than the heterosexual population. “A study in the Journal of Sex Research found that although heterosexuals outnumber homosexuals by a ratio of at least 20 to 1, homosexual pedophiles commit about one-third of the total number of child sex offenses” (Dailey)⁶. This disparity fits the hypothesis, because it would be advantageous for pathogens to infect their hosts as early as possible if they rely on psychologically modifying their hosts. The younger the host, the more plastic the brain will be. Pathogens are thus motivated to cause their hosts to engage in sexual intercourse with young children and younger men. Some research also suggests that male victims of child sexual abuse are more likely to become victimizers themselves.⁷

Above all, the primary evidence for the pathogen hypothesis is homosexuality itself. Over 75% of homosexual couples don’t raise any children at all. Since homosexuals don’t reproduce nearly as much as heterosexuals, the condition is unlikely to be hereditary. If it were, then it would select against itself and be an evolutionary dead end. Instead, the condition is present in more than 1% of the male human population. This implies that most cases of homosexuality are caused by environmental factors, not genes. It’s thus the prevalence of homosexuality that requires explanation. We have yet to find any precise causal pathway to explain homosexuality, so we should prioritize investigating theories that could explain a prevalent maladaptive behavioral pattern. If a reproducing machine is doing something other than reproducing, we should suspect the involvement of a pathogen that has captured the machine.

Just because we evolved to have particular functions, that doesn’t mean that these functions can’t be heavily changed by environment. For example, we evolve to walk upright. We are descendants of homo erectus, or upright man. In spite of this however, there are instances of feral children for example who were raised in wolf packs and other unnatural, atypical environments who instinctively walk on all fours. It’s what feels natural for them, since it’s what they were taught at a young age. They struggle for the rest of their lives to walk upright when they enter human society, and when people attempt to teach them to walk upright. This does not negate the fact that human beings are meant to walk upright, as it’s what we evolve to do.

The same can be said for how sexuality. Heterosexuality is an innate aspect to human beings that we evolved to have. Just as humans evolved to walk upright, humans evolved to be heterosexual. If homosexuality is an environmentally-caused behavior, then it ought to be corrected.

– Commander Waldo, The Alternative View on Homosexuality.

None of the other theoretical causes of male homosexuality have any evolutionary reasoning to back them up or explain why homosexuality has continued to exist despite being maladaptive, which makes all of them unlikely. Since homosexuality is maladaptive, anything that causes it would be selected against by evolution, unless the cause is another reproducer of some sort. The pathogen hypothesis proposes that a pathogen evolved to cause male homosexuality, so it’s the only hypothesis that is compatible with evolutionary theory.

There are other documented and proposed causes of homosexuality, and there is a consensus that hormones are involved in sexuality. Homosexuality is known to be associated with abnormal prenatal hormone levels during crucial neurological development periods (Sheppard)⁸ and (Wilson)⁹. This may be a separate cause of male homosexuality, but if so, then it’s assuming that a key human reproductive function has been causing 2 to 5% of males to have significantly less offspring without it being selected out.

No one claims that evolutionary theory alone is sufficient to explain everything about human behavior or disorders, but evolutionary theory constrains any such explanation. If a proposed mechanism assumes natural selection somehow stopped acting with respect to this trait for hundreds of generations, then it is probably false. The hormonal imbalance hypothesis also cherry-picks its own evidence, since it ignores research about how homeostasis is hard to knock out of equilibrium in key reproductive functions. The hormonal imbalance hypothesis is thus not a solid explanation for male homosexuality because its premises are not consistent with evolutionary theory or physiology.

It’s also possible that the hormonal imbalance hypothesis could be connected to the pathogen hypothesis, since there are known pathogens that control sexual development by secreting hormones (e.g. Sacculina), and also since people typically inherit their gut flora from their mothers during birth. Gut flora could affect the prenatal environment, the mother’s immune system, or hormones in the mother’s blood. If there is a connection between these two hypotheses, then the hormonal imbalance hypothesis would be consistent with evolutionary theory.

Another possible cause is having multiple older brothers, which can cause an immune response or an allergic reaction in the womb that turns male fetuses homosexual. The mechanism is thought to be a maternal immune response to male fetuses, whereby antibodies neutralize male Y-proteins that are thought to play a role in sexual differentiation during development.¹⁰ Some estimates say that fraternal birth order causes homosexuality in at least one-sixth of all homosexual men. But once again, this hypothesis also fails to explain why homosexuality has persisted without its causes being selected out of the gene pool, i.e. genetic factors that contribute to the immune response in the mother’s womb.

The validity of the Gay Uncle Hypothesis depends on the validity of kin selection theory. While it is true that some homosexuals do adopt children, the 2010 US Census shows that about ~80% of children raised by homosexuals are the biological offspring of one of the homosexual partners. Homosexual men are also far less likely to have biological children than homosexual women. There’s also no widespread evidence of gay uncles caring for their nieces and nephews, among humans or in nature. More generally, Kin selection theory is based on fallacious reasoning, so it should be rejected in favor of the phenocentric theory of biological purpose. And even if kin selection theory were true, it’d make more sense for homosexuals to be asexual instead, since investing in a relationship would take away time and resources that could instead be invested towards nieces and nephews. We can thus reject the Gay Uncle Hypothesis since there is no sound reasoning to support it.

George Francis has written an article arguing that data from Genome-Wide Association (GWA) studies suggests that antagonistic pleiotropy is a more likely cause of homosexuality. It’s worth reading, and it seems to be more likely than the other proposed causes.

Cultural factors may also have some impact on people’s sexualities. George Francis has written another article investigating this topic. Historically, left-handedness used to be considered taboo and superstitious. Left-handed people would often be violently punished if they used their left hand to write or whatever, so they learned to use their right hand. “Real” left-handedness, was seen as extremely rare and a minor thing that wasn’t significant at all. When it became socially acceptable to be left-handed, the rate of left-handedness skyrocketed. This is similar to how the rate of homosexuality skyrocketed as it became more acceptable. With this considered, it could be that there’s a large segment of the population that is homosexual and/or bisexual to some degree, and that it has only been suppressed by strong social pressure. In which case, only those who were the most unavoidably non-hetero actually acted on it, since the consequences were so severe. As society changes and adjusts, it becomes more and more acceptable, and the degree to which someone has to be non-hetero to embrace their sexuality goes down. A feedback loop of acceptance and normalization then occurs.

If we know that there are multiple causes of male homosexuality, then homosexuals could be separated into two groups if the pathogen hypothesis is true: 1. those who have been infected with pathogens, and 2. those who have not. If a large fraction of homosexuals are not affected by the pathogen, then future research could investigate the ratio of pathogen-infected homosexuals who did pedophilia vs non-pathogen-infected homosexuals who did pedophilia, and that could reveal more information about the strong correlation between homosexuality and pedophilia.

Some people may say that the pathogen hypothesis is too unlikely to have any possibility of being true. But given all the facts that we have stated about homosexuality and how humanity has been so unable to figure out all the factors and contributing causes to homosexuality, is the pathogen hypothesis really any more unlikely than the other proposed explanations, especially when they all fail to explain why homosexuality is so unexpectedly common in the first place?