Homo Mysterious: Evolutionary Puzzles of Human Nature (15 page)

But Haldane’s demonstration is nevertheless convincing, and relevant: Just a small difference in fitness is capable of driving huge differences in ultimate success, and it seems more than likely that someone who is bisexual, who occupies any of the intermediate points in the Kinsey scale, would be at least somewhat less fit than another person whose romantic time and effort is devoted exclusively to the opposite sex. Remember, a difference of merely one part in a thousand is sufficient to cause a monumental difference in outcome, such that anything less than a full commitment to opposite-sex preference would have to be strongly selected against. Not only that, but it is also true that some people, at least, are pretty much entirely “sheep” or “goats”; that is, they are exclusively homosexual in their preferences. Indeed, numerous studies have confirmed the common-sense assumption that homosexuals have lower lifetime reproductive success than do heterosexuals.
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A basic bio-economic model shows that the puzzle is more puzzling yet. Thus, every behavioral or physical trait can be associated with an average benefit—its positive contribution to reproductive payoff—as well as a cost, its negative effect. Obtaining food thus conveys a benefit in terms of calories added, as well as a cost, measurable, for example, as time, energy, and risk expended while foraging or hunting. Natural selection works to adjust such traits so as to generate the largest possible ultimate fitness payoff, which economists would describe as maximizing “utility” by favoring the largest difference between benefits and costs.

Clearly, heterosexual reproduction is costly, requiring time and energy in courtship as well as the act of mating itself. But although evolutionary biologists have long wondered about the adaptive
value of sexual reproduction as opposed to its asexual alternative,
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no one seriously questions that once a lineage has opted for sexual reproduction, the actual costs of heterosexual behavior are more than compensated by its fitness benefits. Although sex itself remains an evolutionary mystery (compared to reproducing asexu-ally, which generates twice the genetic payoff per parent), it is nonetheless clear that among individuals already specialized for sexual reproduction, the balance sheet is positive. That is, the accumulated evolutionary benefits of interacting with an opposite-sex partner on balance exceeds the sum total of costs.

What about homosexual interactions? They, too, are costly, even if measured strictly in terms of time and energy.
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Economists would have to conclude that at a minimum, same-sex courtship and consummation impose an above-zero “opportunity cost” on the participants, if only in that time and energy budgets are finite, and whatever is expended on homosexual relationships cannot be available for direct, heterosexual reproduction or simply for self-maintenance. The problem, therefore, isn’t merely one of sexual preference, but also time and energy.

The plot thickens.

On the other hand, it is still possible to negate much of the evolutionary mystery if it can be argued that homosexuality is disconnected from genetics—which turns out to be a very difficult case to make. One possible route, however, would be to emphasize the uncertainty of the designation “homosexual.” It could be pointed out, for example, that for some people, bisexuality is a stable state, whereas for others, it is part of a life-course transition from one preference to another.
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Moreover, what sorts of acts are necessary to qualify as homosexual? Holding hands? Back or shoulder rubs? Kissing? Fondling genitals? Mutual masturbation? Oral sex? Anal sex? Dildos? Even more confounding: What about people who
acknowledge having occasional same-sex hankerings but who do not actually
do
anything? And what of those cases—notably, from same-sex prisons—in which the overt behaviors are clearly within the range of “traditional” homosexual acts, but whose participants often maintain that they are not in fact homosexual, but rather, are simply acting out of social dominance, subordination, or loneliness, combined with a dearth of heterosexual partners? Moreover, among many nonincarcerated men in a wide range of societies, those who take an active, mounting, inserting role relative to other men are typically considered fully masculine. In short, where do we draw the line?

One way of dealing with the definitional dilemma is to speak about “men who have sex with other men” and “women who have sex with other women,” which neatly gets around the difficulty of nonexclusivity. After all, a man who has sex with other men doesn’t necessarily refrain from sex with women, on occasion. But this simply introduces yet another problem: namely, the meaning of “have sex.” And in truth, this definitional folderol is largely besides the point, tantamount to a squid or octopus emitting lots of ink in an effort to confuse its pursuers.

In the pages to come, I’ll refrain from drawing any lines or squirting excessive ink, but I will focus on the agreed fact that homosexuality exists, that in its various manifestations it differs from exclusive heterosexuality, that it is present in nontrivial frequency, and that, regardless of the precise details, it therefore requires some sort of evolutionary explanation. Or maybe not.

Thus, we must consider the possibility that homosexuality is entirely a function of proximate causes, devoid of evolutionary substructure. Homosexuality could conceivably be an illness, as argued in 1886 by the sexologist and psychiatrist Richard von Krafft-Ebing in his highly influential book,
Psychopathia Sexualis
.
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Astoundingly, reverberations of this view persisted in the
Diagnostic and Statistic Manual of Mental Disorders
(DSM) of the American Psychiatric Association until 1974, when the DSM no longer classified homosexuality as a mental disorder. Aside from its hurtful social impacts, the perception of homosexuality as an illness flies
in the face of the high and persistent cross-cultural existence of same-sex preference.
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There is actually an early history of categorizing homoeroticism as nonpathological, beginning, not surprisingly, among the ancient Greeks. Perhaps the best known “hypothesis” for the origin of same-sex preference occurs in Plato’s
Symposium
, where it is enunciated by the comic playwright Aristophanes. According to this story—clearly intended as myth rather than a serious explanation—the founding human beings were remarkable creatures known as Androgynes, who sported four arms and four legs, as well as the sexual apparatus of both male and female. Great was their power and glory, but they grew insolent. Zeus responded—as was his habit—with thunderbolts, splitting each offending creature into two, each one equipped with what we now take to be the traditional two arms, two legs, and one paltry set of genitals, either male or female. (Fortunately, the Androgynes abated their insolence at this point, for if they had not, Zeus was apparently prepared to split them yet again, which would have resulted in beings who hopped about on one leg … and with sex organs that can scarcely be imagined.)

According to Aristophanes, the human search for emotional and carnal union ever since is simply a continuing attempt to re-establish our species’ prior, androgynous wholeness, each person seeking to reunite with his or her missing half. Since there were originally three kinds of Androgynes—male–female, male–male, and female–female—this story conveniently explains not only the origin of men and women, as two distinct sexes, but also the source of male and female homosexuality as well.

It appears that the first effort at a scientific explanation for same-sex preference was by Karl Heinrich Ulrichs (1825–1895), considered by many the first gay rights activist. He suggested that male homosexuals were actually
anima muliebris virili corpore inclusa
(“a woman’s psyche trapped in a man’s body”) and that lesbians were the inverse. In 1870, Ulrichs gestured toward likely biological underpinnings of homosexuality as an argument for gay rights, arguing that a male homosexual has inalienable rights. His sexual
orientation is a right established by nature. Legislators have no right to veto nature, no right to persecute nature in the course of its work, and no right to torture living creatures who are subject to those drives nature gave them.
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However, since this “inversion model” claims that homosexuality derives from a mismatch between sexual anatomy and sexual preference, it nonetheless implies that homosexuality is pathological. It found favor with many early sex theorists, including Freud, von Krafft-Ebing, and Henry Havelock Ellis. Yet the picture is muddled. A historical overview of the psychoanalytic perception of homosexuality begins as follows:

As the founder of psychoanalysis, Freud entertained complex and inconsistent views about homosexuality. In a famous letter to the mother of a homosexual, he stated that homosexuality is neither a vice nor an illness. He spoke out against persecution of homosexual people and pointed out that many great men, among them Plato, Michelangelo, and Leonardo Da Vinci, were homosexual. He also observed that it was generally not possible to change sexual orientation with psychoanalysis. In a letter to Ernest Jones, Freud affirmed the right of homosexual people to become psychoanalysts.
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At the same time, Freud believed that the Oedipus complex was both biologically determined and normal, which led many analysts to question how a man could in his youth be sexually attracted to his mother, then become attracted to men as an adult and yet all the while be “normal.” And for a truly stunning example of seeming to embrace simultaneously a pathologized as well as a normalizing view of homosexuality, consider this observation by Freud:

By studying sexual excitations other than those that are manifestly displayed, it has been found that all human beings are capable of making a homosexual object choice and in fact have made one in their unconscious. Indeed libidinal attachments to persons of the same sex play no less a part as factors in normal mental life, and
a greater part as a motive force for illness,
[my emphasis] than do similar attachments to the opposite sex.
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So, everyone is constitutionally bisexual, capable of homoerotic no less than heteroerotic unconscious choices, of which the former are as consequential as are heterosexual preferences in normal life … but even more important when it comes to mental illness!
Comparable foolishness is found in a hypothesized identification with the opposite-sex parent, rage toward same-sex siblings, castration anxiety, an unconscious fear of heterosexuality, a faulty sense of gender identity, and so forth—all emphasizing early developmental experiences and more or less based on the assumption that
normal
development leads to heterosexuality.

The view that homosexuality is pathological is currently held almost exclusively by right-wing ideologues and religious fundamentalists; at present, it is the overwhelming view of unbiased scientists that same-sex preference, when it occurs, is no less “natural” than its opposite-sex counterpart. Some of the evidence for this comes from the widespread distribution of homosexuality among animals. Once a species is observed long enough, nearly always it eventually reveals instances of homoeroticism, usually via male–male and/or female–female mountings, often with genital contact and pelvic thrusting. In most cases, these interactions take place in the context of bisexuality, typically by juveniles.

What is uniquely human, or nearly so, is the existence of at least some individuals for whom homosexuality is an
exclusive preference
, that is, individuals occupying the far end of Kinsey and colleagues’ 7-point scale. To my knowledge, the only other mammal species of which this is true are domestic sheep,
Ovis aries
, among whom some rams appear to be homosexual exclusivists, regularly ignoring ewes in heat and preferring to mount other rams.
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Some rams are heterosexual (55–75%, depending on the study), some bisexual (18–22%), some exclusively homosexual (7–10%), and some asexual (12–19%). The homosexual rams, interestingly, are masculinized; that is, they are the mounters rather than the ones mounted. It seems plausible that these individuals have experienced intrauterine influences upon their sensory receptors and/or brain mechanisms, rendering them sensitive to male pheromones rather than female.
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It is difficult to identify what might be uniquely shared by domestic sheep and human beings, such that they, alone among other animals, exhibit exclusive homosexuality. Dominant male baboons will on occasion accept what appear to be sexual advances from subordinate males, but I do not know any instances in which male–male pairs establish a close social and sexual relationship while ignoring nearby fertile females. There is, of course, no reason
to believe that such examples won’t eventually be identified, among mammals in general, or primates in particular. If current speculation proves correct, they would likely correlate with a complex cascade of hormonal events. Thus, it is generally accepted that hormones, especially circulating sex hormones, can activate existing neural patterns and predispositions. It was thought for a time that gay men were “that way” because their testosterone levels were lower than that of heterosexuals, with bisexuals in between, just as lesbians were supposed to be “androgenized” relative to straight women. Such “findings” were never confirmed, but nonetheless penetrated into much popular consciousness.
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What is somewhat newer, however, and for our purposes more important, is the idea that in addition to being
activational
, hormones also have an
organizational
role, influencing the establishment of brain systems and structures beginning early in embryology. Even here, however, some sort of genetic involvement seems necessary, even if merely permissive rather than directly causative.