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Evolution and Homosexuality

cr88's picture

The Story of Evolution and the Evolution of Stories


Krishnan Raghavan


Reconciling Evolution with the Existence of Homosexuality


            Charles Darwin does not hesitate to admit that the theory of evolution through natural selection he posits in his Origin of Species could be challenged in a number of ways.  “That many and grave objections may be advanced against the theory of descent with modification through natural selection, I do not deny,” writes Darwin (379). “I have endeavored to give to them their full-force.” Darwin attempts to defend the validity of his basic argument against such potential refutations as the fact “that the more complex organs and instincts should have been perfected…by the accumulation of innumerable slight variations,” the absence of “fossil remains [that] afford plain evidence of the gradation and mutation of the forms of life,” and the fact that “all the individuals of the same species…must have descended from common parents” despite the fact that individuals of certain species may now be found in “ever distant and isolated parts of the world” (379-81). Another apparent piece of counterevidence for Darwin’s theory that Darwin does not specifically address (understandably so, given the era in which he lived) is the existence of homosexuality. Given that success in Darwin’s “Struggle for Existence” is predicated on the ability of “dominant species…to give birth to new and dominant forms” until these groups eventually “beat the less dominant,” the continued existence of a trait such as same-sex attraction that, while not rendering an individual incapable of reproduction certainly reduces the odds that he or she will do so, seems problematic (386). However, rather than contradicting Darwin’s theory of evolution, the surprising evolutionary benefits homosexuality may confer upon a species serve as a testament to the diversity and subtlety of means through which a species can remain evolutionarily competitive.

            Darwin’s theory of natural selection allow for the possibility that certain traits may work towards the success of a group’s survival at the expense of an individual’s genetic continuity. While Darwin does not, understandably, specifically address the issue of same-sex attraction in humans or other species, he does discuss the case of certain insect colonies in which a similarly paradoxical phenomenon takes place. The presence of neuters, or sterile females within insect colonies posed what Darwin initially thought of as “fatal difficulty” to the theory of evolution through natural selection. Such neuters are not only incapable of reproduction, but also “differ widely in instinct and structure from both the males and fertile females” despite the fact that “from being sterile, they cannot propagate their kind” (243).  The problem these insects pose with regards to Darwin’s theory is thus doubly parallel to the problem homosexuality poses, as homosexuality both reduces the chances an individual will pass on his or her own genes and is also a non-hereditary trait, despite claims to the contrary by certain fringe groups.  Returning to these insect-colonies, Darwin suggests that the insects’ sterility is the easier of these two apparent contradictions to his theory to explain, for “if such insects had been social, and it had been profitable to the community that a certain number should have been annually born capable of work but incapable of procreation” the insects’ sterility would be less evolutionarily problematic (243). Given that insects within a colony are all members of the same family, it is conceivable by the same logic that homosexual individuals who are less likely to reproduce may contribute to the genetic success of their families in ways other than perpetuating their own genes.

More difficult to explain for Darwin regarding the insects is the fact that the neuter worker insect’s “differing greatly from both parents [although] it could never have transmitted successively acquired modifications of structure or instinct” due to its inability to reproduce. However, Darwin posits that if the gene or genes that code for sterility also coded for the traits and instincts peculiar to the sterile “castes” that contribute to the overall fitness of their familial colonies, these genes might still be subject to the influence of natural selection within the fertile parents. “A slight modification of structure, or instinct, correlated with the sterile condition of certain members of the community, [if[ advantageous to the community” argues Darwin, would lead to the fertile members of the community flourishing and transmitting “to their fertile offspring, a tendency to produce sterile members having the same modification” (244). Returning to the question of homosexuality, if the particular “instinct” common to homosexual individuals (same-sex attraction) could be shown to contribute towards the overall fitness of the families of homosexual individuals, homosexuality would no longer contradict Darwin’s theory of evolution through natural selection.

            Given the parallels between the difficulties sterile worker castes in insect colonies pose to Darwin’s theory and those posed by the existence of homosexual individuals, there would need to be evidence in support of homosexual individuals compensating for their decreased likelihood of procreation by contributing towards their familial gene pool’s perpetuation in some other fashion for the existence of homosexuality not to contradict Darwin’s theory of evolution.  However, a recent article in the New York Times studying the phenomena of homosexual behavior in the animal kingdom found that such behavior, precisely because it is not directly related to an individual’s procreation or survival, may actually only be superficially similar in distinct species. “Within the logic of each species, or group of species,” writes author Jon Mooallem, “many of these behaviors appear to have their own causes and consequences – their own evolutionary meanings.” To illustrate this point, Mooallem contrasts the causes of male homosexual behavior in dung flies to those of homosexual behavior in young bottlenose dolphins; the former “mount other males to tire them out, knocking them out of competition for available females” while the latter “mount one another simply to establish trust and form bonds…[which] actually turn out to be critical to reproduction, since when males mature, they work in groups to cooperatively gain access to females.” These examples also illustrate another difficulty of explaining homosexual behavior in the animal kingdom using Darwin’s arguments about sterile worker castes in insect colonies; namely, that while the sterility of these castes is absolute, homosexual copulation is rarely an exclusive behavior in the animal kingdom and thus cannot be fully explained using Darwin’s arguments about the ways in which workers unable to reproduce may help perpetuate their genes alternatively by aiding the reproductive success of their fertile relatives. However, studies of one species in which individuals who engage in homosexual behaviors are often exclusively homosexual offer evolutionary justifications of homosexuality that are intriguingly similar to those put forth by Darwin regarding sterile worker castes. The species is none other than homo sapiens sapiens, and two studies in particular offer explanations of human homosexuality that are strikingly similar to Darwin’s explanations of sterility in insect worker castes. A study conducted by evolutionary psychologists Paul Vasey and Doug VanderLaan of the fa’afafine, a people considered a third gender in Samoa that are born biological male and “tend to be effeminate and attracted exclusively to adult men as sexual partners” concluded that the fa’afafine contribute to the evolutionary success of their families in a surprising way (Vasey). The fa’afafine are “much more altruistically inclined towards their nieces and nephews than either Samoan women or heterosexual men” and will “babysit a lot, tutor their nieces and nephews in art and music, and help out financially.” Interestingly, this altruism extends only towards the fa’afafine’s own nieces and nephews; fa’afafine are not particularly more likely to exhibit a general altruism towards children. Another study, conducted by researchers at the University of Padua in Italy showed that female relatives of gay men are likely to be more fertile than average, suggesting that certain genes that lead to increased fertility in women may lead to homosexuality in men (Henderson). These two studies taken in tandem not only offer an explanation of how homosexual individuals may help their genetic pool to survive as well as how genes causing homosexuality might endure in spite of their apparent evolutionary inutility but also offer an interesting unified explanation of the evolutionary potency of homosexuality. Not only are more descendants produced through increased fertility, but a greater ratio of caregivers to offspring now exists to ensure the continued success of these offspring.

            Darwin’s theory of evolution through natural selection and the existence of homosexuality are thus not mutually exclusive.  Darwin himself allows for the possibility of indirect evolutionary pathways which while apparently requiring some individuals not to reproduce, contribute to the perpetuation of a familial gene pool. While homosexuality is difficult to analyze in the animal kingdom, the example of human beings suggests that homosexuality may despite appearances work not only to increase the number of offspring produced but may also work towards raising the quality of life enjoyed by those offspring. Such a reconciliation of Darwin’s theory with a phenomenon that seems to so starkly contradict the theory’s presuppositions demonstrates the dynamic and vital nature of Darwin’s theory of evolution through natural selection.  Evolution, like the Lord some imagine it to have supplanted, works in mysterious ways.


Works Cited


Darwin, Charles. On the Origin of Species by Means of Natural Selection. Ed. Joseph Carroll. Peterborough, Ont.: Broadview, 2003. Print




Paul Grobstein's picture

Evolution and homosexuality

 "Darwin’s theory of evolution through natural selection and the existence of homosexuality are thus not mutually exclusive."

To which I might add a couple of additional points.  One is that Darwin was probably overlying concerned about "dominant forms ... that beat the less dominant."  While this may occur in an equilibrium over long periods of time, I seriously doubt that most of evolution fits this description.  What is "dominant" is more often constantly changing because of both environmental change and ongoing random change in the populations involved.  Under these circumstances, traits may persist in populations for extended periods of time regardless of their comparative average reproductive capabilities.

At least as important is that Darwin left open the issue of the role of both individual choice and culture in evolutionary change, and that issue still needs attention (in part through this course).  Culture does not follow directly from biological evolution but instead, as with scientific stories,  a given gene pool may give rise to many different cultures.  These in turn influence the reproductive success of individuals.  If non-reproducing individuals significantly influence culture (which they obviously do in the case of humans) then the exert not only a significant influence on the course of human evolution not only at cultural levels but at the level of gene pools as well.