The paradox of inherited homosexuality

© May 2014 Paul Cooijmans


The sole purpose of this article is truth-seeking. The article should by no means be understood as promoting or approving of homosexuality, or denying the possible danger it poses to the predominantly Christian fabric of Western society.

Introduction to the paradox

In the context of evolution, a paradoxical finding is the apparent hereditary nature of homosexuality. Studies of one-egged twins have shown remarkable concordances on sexual orientation, varying from about 8 % to over 50 % (in one early study even 100 %), and concordance among one-egged twins has been found to be higher than among two-egged twins.

Given that one-egged twins have virtually 100 % of their genomes in common (and two-egged twins only about 50 %) this suggests a genetic component among the causes of homosexuality. It also implies that many or most who carry the gene variants (alleles) that seem to lead to homosexuality in some individuals are heterosexual, and leaves room for other, non-genetic, factors contributing to sexual orientation next to the hereditary component. Apart from twin studies, there is some other (anecdotal and scientific) evidence that homosexuality "runs in families". There are, however, also twin studies that do not show a concordance significantly higher than what could be expected if there were no genetic component.

Realistically assuming that homosexuals are less likely to procreate than heterosexuals, the existence of gene variants that contribute to homosexuality forms a paradox, even if many who carry them do have children. If those genes prevent even a small proportion of those who have them from multiplying, they will reduce fitness such that, over many generations, they vanish from the gene pool almost entirely. That is not the case though: homosexuality rates in current populations are estimated to be in the order of several percent (averaging close to 4 %). Assuming a heritability of somewhat under 50 %, this means that around 10 % of the population must be carrying the pertinent alleles.

In the event that the partly hereditary nature of homosexuality is disproven at some point in the future, the paradox disappears, rendering the rest of this article superfluous. Until then, read on.

Solutions that have been proposed

A possible explanation of this paradox is that the gene variants that cause some to become homosexual also offer a fitness advantage (to heterosexuals carrying them) by contributing to some adaptive trait, thus offsetting the deleterious effect of those alleles in exclusive homosexuals. For example, it has been suggested that heterosexual men with these genes might be more attractive to females as a result of supposed female or feminine traits in such men. A number of theories along those lines exist, all feasible but none convincing, and it is probably up to geneticists to eventually resolve the matter.

Introduction of the solution to be discussed

A possibility that might be worth looking into is that the genetic component of homosexuality may at the same time contribute to personality features leading to creativity and achievement, thus providing an evolutionary advantage to the (heterosexual) carrier. In particular, mental ability — intelligence — seems a candidate, being the most adaptive trait of all. It is not suggested that this is indeed the case, but there are interesting arguments for, as well as against it. The taboo or politically incorrect nature of some of these arguments may explain why this possible solution of the paradox is so rarely discussed, even though the possibility is self-obvious once one sees the pattern.

Below are a number of arguments and counterarguments. The goal is not to plead for or against, but rather to acquaint the reader with the discussion. Keep in mind that the idea is not that homosexuality as such is adaptive, but that its possible genetic component is adaptive in heterosexual carriers.

Arguments and counterarguments

Once a philosopher, twice a pervert

The friendly maxim Once a philosopher, twice a pervert suggests an informal awareness among the public that high intelligence tends to go with sexual deviance.

Over-representation in creativity

There is a persistent notion that homosexuals are over-represented in fields requiring creativity. Upon closer inspection, this is the most obvious in the performing arts, and might plausibly be true for other types of visual art. It may or may not be true for music, literature, the humanities, and exact science. Intelligence is an important component of creative achievement, and this over-representation, if true, would positively support the solution being discussed.

Problems are the lack of hard statistics about the occurrence frequencies of homosexuals in various groups, and the possible bias in self-reported data from questionnaires (in "liberal" societies and communities, people may be more inclined to identify as or admit to being homosexual, one says).

Educational achievement and income

There is fairly abundant evidence that homosexuals achieve higher educational levels than do heterosexuals. Considering the well-established positive and causal correlation between I.Q. and educational level, this indicates that homosexuals may have higher average I.Q.'s. On the other hand, it may be that persons of higher educational level are just more likely to admit to being homosexual. Roughly the same can be said about income, which is closely related to educational level.

The correlation of homosexuality with educational achievement and income may also be seen as supporting the more anecdotal notion that homosexuals (as well as other sexual deviants) are over-represented among high achievers in general.

Ancient Greece and Rome

Ancient Greece is a historical civilization associated with high intellectual and artistic achievement — and proverbially connected with the practice of homosexuality, which primarily took the form of pederasty. By way of counterargument, it could be pointed out that the adult men who engaged in this behaviour tended to have heterosexual relationships as well, pederasty being something "on the side", and that one did not have the concept of "sexual orientation" that we have. That is, one did not identify personally as heterosexual or homosexual, and homosexual behaviour was considered normal.

In ancient Rome, too, homosexuality was common. Some see homosexuality as one of the forms of decadence that occur in higher civilizations. Considering the causal relation between civilizational level and average I.Q., the association of homosexuality with civilization, if true, would make plausible a relation between homosexuality and intelligence.

Prevalence of hatred of homosexuals

Hatred of homosexuals, often mistakenly called "homophobia" and expressed in anti-homosexual violence and in laws that forbid homosexuality (even on pain of death), is most prevalent in countries and populations of low average I.Q. Assuming that people in general are attracted to who are familiar to them and dislike who are alien to them (genetic similarity theory), this suggests that homosexuality is rarest in the populations where hatred of homosexuals is greatest (id est, in low-I.Q. populations). Note that in this line of reasoning, homo-hatred results from the genetic dissimilarity between hater and hated, and is analogous to ethnocentric mechanisms like racism, nepotism, and discrimination.

However, psychoanalytic theory dictates that hatred of homosexuals is a result of "repressed" homosexuality in the person displaying that hatred, thus implying that homosexuality is abundant in populations with much homo-hatred. Then again, psychoanalysis is now almost universally considered a pseudoscience that is mostly or entirely mistaken, and the Freudian mechanism of "repression" may just be a fiction. Genetic similarity theory has a firm empirical basis, whereas psychoanalytic theory is a priori, lacks any empirical basis.

The "soft" nature of male homosexuals

Male homosexuals are reputed to be less aggressive than heterosexual males, and more often drawn to typically female, "caring" professions like nurse or hairdresser. While this does not necessarily keep them from going to war — think of Alexander the Great or Richard the Lionheart — lower aggression would be something they have in common with those of above-average I.Q. Aggression, lack of impulse control, violence, and crime are correlated negatively with intelligence and associated with below-average I.Q. This common trait might result from a common genetic component between homosexuality and intelligence. But then, it might have mainly to do with the levels of prenatal and post-pubescent testosterone. But then again, testosterone levels are coded for by genes, so this would not contradict the possibility of a genetic link.

The "masculine" nature of some female homosexuals

At least some female homosexuals have masculine traits, and presumably a more masculine brain than heterosexual females have. Such a brain results from higher prenatal testosterone levels, which in turn result from one's genetic code. Since men (who also tend to have masculine brains) have a wider spread of I.Q. and are therefore over-represented in the high range of mental ability, lesbians with more masculine brains than heterosexual females will also be over-represented in the high range of I.Q., and that will help them excel in creative achievement of any kind, including typically "male" fields.

(Note that "with more masculine brains than heterosexual females" is a restrictive relative clause, that is, defines a subset of lesbians. There is therefore no implication that all lesbians have masculine brains.)

If there is a genetic commonality between homosexuality and intelligence, it may be operating differently in males and females.

Differential incidence in ethnic groups, races, countries

Homosexuality has been found (by anthropologists) to be virtually absent and even unknown in hunter-gatherer societies, which are the most primitive human societies that have existed. Average I.Q.'s of such groups have been estimated to be in the 50s to 60s; even if those estimates are inaccurate, at least the tested I.Q.'s are the lowest of all ethnic groups. On the other hand, Jews, who have the highest average I.Q. of any ethnic group, are (self-)reported to have an unusually high incidence of homosexuality (around 10 %, which would also be about the highest of any ethnic group).

(Some deny that Jews are an ethnic group — "there is no Jewish gene" being a favourite catchphrase — however, D.N.A. studies have shown that current Jews, by their Y-chromosome, can be traced back to a small group that lived in the Middle East about 4000 years ago, thus demonstrating that bloodlines have been preserved with rigour and Jews are indeed an ethnic group.)

This raises the question whether a correlation exists between average I.Q. and rate of homosexuality across ethnic groups, races, or nationalities. A positive correlation would suggest a genetic link as one of its possible explanations, especially in combination with the correlation of homosexuality and educational achievement (and therefore probably I.Q.) within the groups. While I.Q. data for such groups are readily available and have been thoroughly studied and discussed, problems are again a lack of good statistics on homosexuality rates, possible cultural bias in self-reported data, as well as the anecdotal nature of much information on homosexual practices, such as observations by discoverers, missionaries and the like. For instance, in particular the homosexuality rates of countries in sub-Saharan Africa, which would be so very interesting and important to know, are controversial; different sources say rather different things. This question (a possible correlation between average I.Q. and rate of homosexuality across ethnic groups, races, or nationalities) may be inconclusive as yet, and a possible positive correlation need not result from a monotonous relation. When a positive correlation is found, it needs to be teased out whether it is intrinsic, or merely results from a more liberal atmosphere in higher-I.Q. populations that makes people more likely to identify as homosexual.

Some general remarks about homosexuality itself

What is meant by "homosexuality" in the present context

"Homosexuality" is having a sexual preference for the same sex that one has oneself. Notice that words like "lesbian" (female homosexual) and "gay" (male homosexual) are superfluous, and especially the latter needs to be avoided because of its confusion with "cheerful", which is the real meaning of the word. Bisexuals are both homosexual and heterosexual, therefore they are homosexual too. One might call bisexuals "inclusive homosexuals", and those who prefer only their own sex "exclusive homosexuals".

Transsexuals, nowadays also called transgenders, may or may not be homosexual, depending on whether one uses the sex perspective or the gender perspective. For instance, a transsexual with a male body but a female gender identity who has a sexual preference for males is technically homosexual, but is heterosexual relative to one's gender (realize that "gender" refers to one's identity, to "how you feel inside your head"). The same transsexual with a preference for females is technically heterosexual, but homosexual from the gender perspective.

The homosexual community has come to prefer the umbrella concept "L.G.B.T.", for lesbian/gay/bisexual/transgender, which is fine with respect to the topic of the present article, as long as one understands that the underlying biological causes of the various conditions may differ. Noteworthy is the absence of a "P" in "L.G.B.T.", even though paedophiles may be homosexual too; clearly, some sexual deviations are more equal than others.

For completeness, it is pointed out that asexuals, who have no sexual preference at all, are obviously not homosexual; also, that the concept of intersexuality (hermaphroditism) refers to a very rare physical condition and not to an orientation or identity. In the case of intersexuals, it seems logical to use the gender perspective to determine their sexual orientation.

The disorder/orientation distinction

The question whether homosexuality is a disorder is not relevant with regard to the topic of this article. It must be pointed out though that all other sexual deviations are still listed as disorders in the diagnostic manuals; again, there are political forces that want some deviations to be more equal than others.

The behaviour/orientation distinction

While homosexuality is now in the Western world considered an orientation, that is, an identity, a personality attribute that is likely unchangeable, there are also reports of homosexual behaviour unaccompanied by a sense of homosexual identity or orientation. This concerns situations where there is a long-term lack of persons of the opposite sex, such as prisons, armies at war, boarding schools, and monasteries, as well as observations from other than Western cultures. Apparently, homosexual behaviour does not imply a homosexual orientation. One could speculate that the actual homosexual orientation involves some compelling predisposition, genetic, biological-environmental and/or otherwise, and one might even speculate that cultural environment has a role in shaping the eventual identity. With regard to the idea presently discussed, it is the possible genetic component of the possible predisposition that is relevant, and the actual homosexual orientation is likely more relevant than homosexual behaviour without a sense of homosexual orientation.


These are some sources that in various ways touch on this topic: