“Nature Abhors a Category”

Published in: January-February 2008 issue.


JOAN ROUGHGARDEN threw down the gauntlet at the feet of the evolutionary biology establishment a few years ago when she published Evolution’s Rainbow: Diversity, Gender, and Sexuality in Nature and People (UC Press, 2004). The book challenged the widely held Darwinian dogma that some traits—especially those that appear maladaptive for survival, such as the peacock’s feathers—come into existence through competitive “sexual selection” rather than a cooperative form of classical natural selection. Such traits were thought to survive because they’re favored by the opposite sex—with females doing most of the selecting—which interprets them as an indicator of genetic fitness. One of Roughgarden’s main examples is the prevalence of homosexual behavior among animals—she documented some 300 such cases—which cannot be explained with recourse to sexual selection, which envisions a competitive struggle among members of the same sex. Instead, homosexual behavior among both males and females suggests a larger survival strategy based on group cooperation and teamwork, which in turn are promoted by physical intimacy.

Dr. Roughgarden is a professor in the Department of Biological Sciences at Stanford. Her latest book is Evolution and Christian Faith (Island Press, 2006). This interview was conducted by phone in November 2007.


G&LR: I wanted to ask about your book, Evolution’s Rainbow, which got a lot of interesting publicity when it came out a few years ago. You take a different approach to Darwinism and specifically to his theory of sexual selection, which you have challenged. You bring in hundreds of cases of species that exhibit traits and behaviors in support of your argument—including many examples of homosexual behavior. Perhaps a good way to begin would be with some of the evidence from other species that you cite—which is amazing and even weird at times.

Joan Roughgarden: Well, all the large charismatic mammals have homosexuality. But of course the bonobo are the ones of greatest interest because they’re one of our closest relatives. Male and female bonobo are often bipedal so they look quite humanoid. They’re four feet tall, so a very short human being would be the size of a bonobo. So it’s very easy to see ourselves in the way bonobo live. And chimpanzees are very well known for being very intelligent. Of the two chimpanzee species that are our closest relatives, one is the bonobo or pigmy chimpanzee, which is a rainforest animal that has not received as much attention as the so-called common chimpanzee, a savannah animal that is more conspicuous and more easily studied than the bonobo. The behavior of the common chimpanzee has more to do with coalitions and fighting and that sort of stuff, whereas a bonobo has a social system that involves friendship and a great deal of sexuality to mediate friendship. Humans, in some sense, split the difference. Many people in the LGBT community by now have heard of the bonobo, and they will always be the most exemplary species from our standpoint.

All sorts of species have homosexuality, including giraffes. Bruce Bagemihl’s book [Biological Exuberance, 1999], I believe, has pictures of giraffes and gorillas mounting. Elephants have been reported too. There are also species in which it hasn’t been formally reported. For example, it’s well known that penguins have homosexual pair bondings, but there’s no citation in the primary literature of penguins as far as I’m aware. There are lots of lizard species where people working on them see it but don’t write it up. We know that the tabulation in Bagemihl’s book is on the low side. What’s more, there’s no digesting of the information in his book. The most valuable part is his extended tabulation of the references.


G&LR: Your book, on the other hand, offers an overarching theory, one that puts you at odds with the evolutionary biology establishment, which adheres to sexual selection as a way to explain a lot of anomalies of species. So maybe you could tell us what sexual selection is and how your approach differs from a classic Darwinian approach with respect to sexual selection.

JR: Well, sexual selection is basically a biological theory of normal sex roles. It’s heterosexist in its framing. It’s an assertion that all males do certain things and all females do certain things: all males are supposed to be passionate and all females are supposed to be coy. And in all species, so Darwin is enunciating normative behavior throughout the animal kingdom. The rationale for females being coy is that they’re supposed to have expensive eggs and males are supposed to have cheap sperm so they can go around fertilizing any female they can find. So it becomes a theory to naturalize male promiscuity. One issue for sexual selection is whether Darwin’s claim about its universality is true or not. If you pick up a random bird or bee or snail or fish, is it true that the males are passionate and the females coy? The answer is frequently no—the data aren’t there. We don’t have survey articles, for example, of 10,000 species showing that ninety percent of them have passionate males and coy females. In fact, it’s the other way around. The harder you look at just about any species, the less and less accurate the templates appear to be. So one of the big arguments that I’m involved with is just getting people to face up to the facts and to realize that the norms they’ve claimed that just don’t really exist. But once you realize this, then every species that departs from the Darwinian template requires a special explanation. One of the main issues I’ve tried to get people to realize is that you can’t define these various expressions of gender sexuality as exceptional when the norms don’t exist.

But only one part of it is the enunciation of norms, of gendered behavior—heterosexual gendered behavior. The second part of Darwin’s theory has to do with the attribution of intentions. According to Darwin, what the females are doing is, they’re choosing mates and they’re selecting males for the best genes, and they use certain traits as indicators of who’s got the best genes. They look at ornaments and the like to identify the males who have the best genes all around. Or it could be something like antlers, which tell the female, well, there’s a powerful strong warrior. And females supposedly observe the males fighting and then copulate with the winner. And so the whole idea is that among the males there’s a hierarchy of genetic quality for males, and the females are all trying to ascertain who the best males are in terms of their genes so that their own sons will inherit those genes. So this in turn is part two. So part one of sexual selection is the assertion of norms. Part two is the assertion of intention in females to select males for the best genes.

To be sure, some males will sire more young than the others, but not because of their genes and any genetic tie to reproductive success. The females have already weeded out all the bad genes, and all the males that reach maturity are “good.” And so this whole myth—this whole notion of being able to rank males by their genetic quality is a mistake. And I’m also trying to get biologists to acknowledge their own data so that the field of evolutionary behavioral ecology can take it into account. Some people think I’m being critical of the whole discipline, which is not the case. I’m being critical of their unwillingness to draw the conclusions from the data. It’s dishonest to keep pretending that sexual selection is, in fact, even a valid theory in light of their own data.


G&LR: Where does homosexual behavior come into play?

JR: Well, homosexuality is a small piece of the issue here. It’s almost always the entrée for people who want to interview me, because there’s so much interest in homosexuality and gay animals, but this is just the tip of the iceberg. If the only problem were just the underreporting of homosexuality, I would be very comfortable with some special explanation of it. But that’s not the problem. That’s a small issue.

I’ll get back to this in a second. I just wanted to finish answering your first question about the sexual selection theory. There are several studies of this, but one study of a flycatcher in Northern Europe was just published in Nature last year—the collared flycatcher. It’s a forest bird, it’s supposed to be a perfect exemplar of sexual selection theory, but after 24 years of study and 8,500 marked specimens they showed zero heritability in fitness, which is the statistic used for male reproductive success. So that means some males sire lots of young and others don’t, but the sons of those who sired lots of young themselves may or may not sire a lot. It’s the luck of the draw, genes and circumstance, and a lot of it is culturally inherited, because the owner of a good territory can let his sons have a good territory, but it’s not genetic when that kind of thing happens. It’s a waste of time for a female to try to choose her mate on the basis of his genetic quality.


G&LR: So it really is based on life experience and the kinds of social interactions and networks that develop. You talk a lot about friendship patterns and associations, especially among females.

JR: Of homosexuality, specifically. In addition to sexual selection, the other main issue raised by homosexuality is the notion of friendship, and according to typical Darwinian theory, it’s survival of the fittest, and there’s no place for friendships. Males are supposed to be fighting one another all the time to earn the favor of females. And so if we start seeing friendships among males, then that, in and of itself, is problematic. When I look at homosexuality, I don’t make an issue of that as such, because I lump it in with all sorts of expressions of physical intimacy—like bats that kiss by rubbing their tongues together. Mammals, for example, frequently groom each other, searching around for little bugs, and birds preen each other. I just took a picture of some parrots preening each other in Hawaii last week. And of course they call back and forth to each other all the time, in a clearly friendly way, so it’s pleasurable for both parties. It’s communicating friendship and it’s not communicating hostility.


G&LR: Whatever helps to smooth the activities of a community or a tribe, or a herd, or pod or whatever kind of social structure they have.

JR: In the article I had in Science [2/17/06] a couple of years ago, which was very controversial, I looked at the data that talks about team play and team work, how animals work together. And that’s where friendship is important. There are two elements to teamwork. One is coordinated activity and the other is working toward a shared goal. Friendship and the physical intimacy of friendship—not just general acquaintance but the physical intimacy part, which often involves homosexuality—accomplishes both of these. When you see football or basketball players—they’re touching all the time in order to coordinate and get on the same page. But also they experience pleasure in each other’s welfare. And the value of this friendship is the actual feeling of pleasure in it, in another’s welfare. And in getting a basket together—it’s not just a basket; you get to smile together. It’s a joint accomplishment. And so my notion of homosexuality is that it’s a mechanism that achieves teamwork. The sharing of a goal has to be built into the pleasure system; they’re not rationally figuring out what will keep the team together.


G&LR: It has spilled over into homosexuality as a logical extension of physical intimacy. We probably make too much of the purely sexual aspect of these kinds of relationships.

JR: I think just about every biologist would agree with that. It’s almost a social fetish, if you will, to focus on the sexual aspects of homosexuality, but that’s the society we live in. But from a biologist’s point of view, we always see millions of different ways of accomplishing the same thing, and we don’t tend to focus on a species’ particularities. It’s obvious that homosexuality would be good way to achieve this kind of reciprocally pleasurable, tactile contact.


G&LR: One implication of this is that your approach challenges or even refutes the idea of a fixed gay identity.

JR: My work would certainly refute that, but it has already been refuted by anthropological studies and historical studies.


G&LR: What about species, such as penguins, famously, in which two males or two females form a pair bond and carry on as if they were an ordinary couple?

JR: The question of whether that’s a “category” is another matter. If you were to take all penguins and look at the bell curve, sure, you’d find some that were, I suppose you would say, exclusively homosexual. But if we look at the gay and lesbian populations even among humans, it wouldn’t be true of the people who identify as gay or lesbian or trans, that they’re exclusively.


G&LR: I see what you’re saying. It’s a continuum and it forms a bell curve.

JR: Yes. It’s a bell curve. Nature abhors a category. There may be an archetypal “gay” and an archetypal “straight,” and that’s been a long discussion over the last sixty years—the existence of sex categories. The biological approach to categories was initially thought out with the notion of a species, and the old approach back from Linnaeus’ time was to identify type specimens—definitional specimens of a robin or a blue jay—and put those in the museum and that’s that. But then it became clear that this was a fallacious notion of how to define a species. Then it was necessary to have a species as represented by a sample from the population, so all of a sudden instead of one robin specimen you have a spectrum representing what “robinhood” is like. The same thing would be true for any other category within a species. So if you take gayness as representative—how would you represent gayness? Well you’d have several dozen gay men, let’s say, and you’d have a spectrum of childhood experiences, when they came out, and the intensity of their sexual arousal, the direction of their sexual arousal, and you get a distribution.

One of the biggest problems with the original sexual selection notion is that all males have to line up one way, and all females have to line up another way. Darwin may have gotten the templates wrong. He also got the number of templates wrong, because in a lot of species, there are three kinds of males—really different, not just small personality differences: different colors, different sizes, different lifespans. One will have black feathers around its neck, the second white feathers, and the third no feathers at all—this is in a very well-studied bird in Europe. So the gender spectrum is not bimodal but multimodal.


G&LR: One objection to your emphasis on cooperative behavior as opposed to Darwinian competition is that natural selection necessarily operates at the level of the individual and not the group. Doesn’t Darwinism presuppose individual competition for the right to pass on one’s genes?

JR: Definitely not. First of all, my social selection or cooperative selection is definitely natural selection at the level of the individual. The problem is that Richard Dawkins [author of The Selfish Gene], for example, and others in the sexual selection and sexual conflict arena, equate evolutionary success with selfishness, and that’s just a non sequitor. We all agree that evolution proceeds by genes increasing in the gene pool from one generation to the next, but the question is how do they do that. What do genes do to get ahead, so to speak? Do they cooperate with one another or compete? This business of team play is definitely an individual selection process. Think of a baseball team. You come home with a bigger paycheck if your team wins. It’s your paycheck and you’ve also helped your teammates.


G&LR: Dawkins would say, that’s fine as long as they’re your relatives. You’ll help them because you share DNA with them. But if they’re not relatives, then you have no interest in helping them from an evolutionary standpoint.

JR: No, you’re not related. If you were playing right field, you’re not related to the pitcher. You and the members of the team are benefiting individually when the team wins, and that’s the social root to evolutionary success at the individual level through teamwork.


G&LR: Dawkins would argue that you have an interest in preventing someone with different genes from succeeding, even if temporarily. You might use them for your own benefit, but in the long run they’re ultimately your rival and you want to squash them, so that your genes are the ones that can get passed on to the next generation.

JR: That would be an assertion on his part. That’s far from clear. You might very well in perpetuity do better by working in a team. For example, if you’re a wolf and you have to catch food, you’re in a pack, and in order to bring down an elk, it will be true in perpetuity that you’re not going to catch anything outside the pack. You win only if your pack wins.


G&LR: What are the implications for the LGBT rights movement and the whole concept of gay identity? I think the movement has abandoned Kinsey’s idea of a spectrum in favor of a binary notion of sexual orientation.

JR: Well, I have my opinion about the political implications. I think it’s in our interest to know more about the biology—the natural biology of homosexuality. But also to understand the Bible better. It’s only then that we can address the curricula where people are taught to be prejudiced. I think political activism on behalf of gay rights is stalling a bit because we’re up against people who actually think that we don’t have rights. Or that there actually is something wrong or sinful about us collectively. And they think that for reasons that they learn in school or in church. And I don’t think we will get much farther than we have without addressing the substance of the basis for the prejudice we’re seeing.

It’s not enough just to claim that we deserve our rights just because we’re human beings, because they then can say, “Well, pedophiles are human beings but don’t deserve rights.” We have to be able to say that it’s not like pedophilia; it is not a disease. There is no moral character to being gay that goes across cultures. Homosexuality is common in the natural world, as is variation in gender and sexuality. But no one talks about this. Instead, you get the party line of sexual selection and gendered sexuality.



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