I came across this article at Seed Magazine about the work of Joan Roughgarden, author of Evolution’s Rainbow. It’s a good read for people who might not realize just how prevalent in the natural world, homosexuality actually is:

Joan Roughgarden thinks Charles Darwin made a terrible mistake. Not about natural selection—she’s no bible-toting creationist—but about his other great theory of evolution: sexual selection. According to Roughgarden, sexual selection can’t explain the homosexuality that’s been documented in over 450 different vertebrate species. This means that same-sex sexuality—long disparaged as a quirk of human culture—is a normal, and probably necessary, fact of life. By neglecting all those gay animals, she says, Darwin misunderstood the basic nature of heterosexuality.

Male big horn sheep live in what are often called "homosexual societies." They bond through genital licking and anal intercourse, which often ends in ejaculation. If a male sheep chooses to not have gay sex, it becomes a social outcast. Ironically, scientists call such straight-laced males "effeminate."

Giraffes have all-male orgies. So do bottlenose dolphins, killer whales, gray whales, and West Indian manatees. Japanese macaques, on the other hand, are ardent lesbians; the females enthusiastically mount each other. Bonobos, one of our closest primate relatives, are similar, except that their lesbian sexual encounters occur every two hours. Male bonobos engage in "penis fencing," which leads, surprisingly enough, to ejaculation. They also give each other genital massages.

As this list of activities suggests, having homosexual sex is the biological equivalent of apple pie: Everybody likes it. At last count, over 450 different vertebrate species could be beheaded in Saudi Arabia. You name it, there’s a vertebrate out there that does it. Nevertheless, most biologists continue to regard homosexuality as a sexual outlier. According to evolutionary theory, being gay is little more than a maladaptive behavior.

Roughgarden has a particular bone to pick with Peacocks…

Darwin’s theory of sex began with an observation about peacocks. For a man who liked to see the world in terms of functional adaptations, the tails of male peacocks seemed like a useless absurdity. Why would nature invest in such a baroque display of feathers? Did male peacocks want to be eaten by predators?

Darwin’s hypothesis was typically brilliant: The peacocks did it for the sake of reproduction. The male’s fancy tail entranced the staid peahen. Darwin used this idea to explain the biological quirks that natural selection couldn’t explain. If a trait wasn’t in the service of survival, then it was probably in the service of seduction. Furthermore, the mechanics of sex helped explain why the genders were so different. Because eggs are expensive and sperm are cheap, "Males of almost all animals have stronger passions than females," Darwin wrote. "The female…with the rarest of exceptions is less eager than the male…she is coy." Darwin is telling the familiar Mars and Venus story: Men want sex while women want to cuddle. Females, by choosing who to bed, impose sexual selection onto the species.

Darwin’s theory of sex has been biological dogma ever since he postulated why peacocks flirt. His gendered view of life has become a centerpiece of evolution, one of his great scientific legacies. The culture wars over evolution and common descent notwithstanding, Darwin’s theory of sexual selection has been thoroughly assimilated into mass culture. From sitcoms to beer ads, our coital "instincts" are constantly reaffirmed. Females are wary, and males are horny. Sex is this simple. Or is it?

Indeed, biology now knows better. Nobody is hornier than a female macaque or bonobo (which mount the males because the males are too exhausted to continue the fornication). Peacocks are actually the exception, not the rule.

Roughgarden first began thinking Darwin may have been in error after she attended the 1997 gay pride parade in San Francisco, where she had gone to walk alongside a float in support of transgendered people. Although she had lived her first 52 years as a man, Roughgarden was about to become a woman. The decision hadn’t been easy. For one thing, she was worried about losing her job as a tenured professor of biology at Stanford. (The fear turned out to be unfounded.)

After living for a year in Santa Barbara while undergoing the "physical aspects of the transition," Roughgarden returned to Stanford in the spring of 1999 and decided to write a book about the biology of sexual diversity. In particular, she wanted to answer the question that had first surfaced in her mind back in 1997. "When I was at that gay pride parade," Roughgarden remembers, "I was just stunned by the sheer magnitude of the LGBT [Lesbian, Gay, Bisexual, Transgender] population. Because I’m a biologist, I started asking myself some difficult questions. My discipline teaches that homosexuality is some sort of anomaly. But if the purpose of sexual contact is just reproduction, as Darwin believed, then why do all these gay people exist? A lot of biologists assume that they are somehow defective, that some developmental error or environmental influence has misdirected their sexual orientation. If so, gay and lesbian people are a mistake that should have been corrected a long time ago. But this hasn’t happened. That’s when I had my epiphany. When scientific theory says something’s wrong with so many people, perhaps the theory is wrong, not the people."

Like Roughgarden, my own sexuality has forced me to think about Darwin and natural selection, and why homosexuality exists. I think most gay people go through this process of questioning our existence, in part because the culture we grow up and live in keeps telling us that at best we’re some sort of very strange anomaly that needs explaining, if not some kind of curse on civilization that needs wholesale eradicating. Mary Renault’s wonderful same sex romance, The Charioteer, set in England during world war II, contains a scene where a group of gay British soldiers ponder the question in ways that were typical of those times. One of them says…

"In the first place I didn’t choose to be what I am, it was determined when I wasn’t in a position to exercise any choice and without my knowing what was happening. I’ve submitted to psychoanalysis; it cured my stutter for me, which was useful as far as it went. All right. I might still be a social menace, like a child-killer, and have be be dealt with whether I was responsible or not. But I don’t admit that I’m a social menace. I think that probably we’re all part of nature’s remedy for a state of gross overpopulation and I don’t see how we’re a worse remedy then modern war, which from all I hear in certain quarters has hardly begun."

The overpopulation theory of homosexuality was popular back in the middle 20th century. It seemed to become ingrained in the popular culture after someone did a study of overpopulation in rats which seemed to reinforce the notion that it was packing huge numbers of people together in close quarters that caused all the ills of modern city life…crime, violence, and homosexuality. It was an explanation that explained nothing. If city life caused such maladaptive behavior in humans, then why do humans persist in bunching themselves together all the same? And if homosexuality is a side effect of squalid urban living, then why do homosexuals exist at all in rural communities? Ask gay people in the trendy urban gay zones where they came from, and a lot of them will tell you they fled to the city from the sticks.

But the heterosexual premise is hard to get past.  Everyone is heterosexual by default… For years scientists have simply ignored evidence that homosexuality is both common and natural in species. The thinking has always been that it needs some kind of special explanation, that it exists apart from the natural world in some way, because it is maladaptive on its face.

Roughgarden’s first order of business was proving that homosexuality isn’t a maladaptive trait. At first glance, this seems like a futile endeavor. Being gay clearly makes individuals less likely to pass on their genes, a major biological faux pas. From the perspective of evolution, homosexual behavior has always been a genetic dead end, something that has to be explained away.

But Roughgarden believes that biologists have it backwards. Given the pervasive presence of homosexuality throughout the animal kingdom, same-sex partnering must be an adaptive trait that’s been carefully preserved by natural selection. As Roughgarden points out, "a ‘common genetic disease’ is a contradiction in terms, and homosexuality is three to four orders of magnitude more common than true genetic diseases such as Huntington’s disease."

For Roughgarden, homosexuality exists to re-enforce bonds between members of a group. I’m with her there, but I think there is more to it. We are a sexual species…that is, we reproduce sexually. So that dating and mating urge is hard wired into us at a very low, a very ancient and primative level. And for creatures such as we, whose offspring have very long childhoods, sex is plainly not only for producing children, but also for reinforcing the intimate bond between a couple. But why would natural selection care that couples who can bear no children, also experience this sexual gratification?  And yes, nature patently does care that they do.

Consider the humble prostate gland. You can bring a human male to orgasm by massaging it, which is what happens during a certain kind of male to male sex. Tell me what other glands in the human body produce a sensation of pleasure when you to that to them. Rubbing most of them I think, will produce pain not pleasure. But that one particular gland, located in that one particular spot in the male anatomy, is very different in that regard. Why? That’s a question I think biologists need to look at carefully, because it isn’t overpopulation that did that, nor loose sexual mores nor rampant godlessness. It was millions of years of adaptive evolution that gave that to human males, even the ones who have utterly no use for it at all. So clearly there is something that makes same sex coupling worthwhile enough, that nature has given all human males a special adaptation to make it pleasureable for them, whether or not any given individual male actually makes use of it.

Homosexuality is certainly not harmful to the individual, nor is it necessarily harmful to the species. In the first place, homosexuality does not equal sterility. But more importantly, survival of the species involves just a tad more then reproduction. Giving birth to a zillion offspring isn’t going to help the species survive, if they all die before they mature. You see in species all the time, that some individuals will forgo reproduction in favor of helping the rest survive. In fact, in some species of insects, like honey bees, nearly none of the individuals in the group reproduce. Most of them work to insure the survival of the whole. Most honey bees don’t have sex at all in their lifetimes, yet honey bees are a very successful form of life on earth. You would expect people comfortable with the concept of evolution to acknowledge that simple staringly obvious fact. Reproduction alone isn’t everything.

Humans can’t win the battle of survival, or even hope to stack the deck, by reproducing like insects. Human individuals just aren’t capable of having that many children, and human offspring have a long childhood, during which they need a lot of attention. So the mating game for humans can not be merely single minded gene shopping. It must also be about looking for families and tribes that can best raise and care for our young, and ourselves. Your family, your tribe, can make you a lot more desirable then you all by yourself are. Evolutionists have a term for this. They call it "Kin Selection".

This isn’t rocket science. Let’s say we have two eligible human male bachelors in their physical prime. Bachelor ‘A’ is a perfect genetic specimen. Tall, muscular, and beautiful. You take one look at this guy and you know he’s never going to be sick a day in his life. Bachelor ‘B’ on the other hand, isn’t horribly ugly…he’s just not dazzlingly attractive either. He’s an average Joe. Not very well muscled, but not sickly. A little flab around the gut, but not too much. A weak jaw, but a good back. He’s already starting to loose a little of his hair. Seems obvious which one of the two will get the most dates, right? But add another set of facts into the mix. Bachelor ‘A’s family are dirt poor. Bachelor ‘B’s are billionaires. Now who gets the most dates?

It seems cynical, but there’s something else at work there besides pure greed…something very, very old. You see it at work over and over again in the natural world. Mates are selected not only for their own desirability, but for their family’s, or their tribe’s.

And here’s where the peacocks come back into the picture…

Why Do Peacocks Stick Together in Avian `Singles Bar’?

By MATTHEW FORDAHL, AP Science Writer
Copyright ©1999 Associated Press

Groups of peacocks strut their stuff in hopes of attracting the finest peahens, but only a few lucky guys will find a willing mate in the wild kingdom’s equivalent of a singles bar.

Scientists have long wondered why the unsuccessful peacocks stick around the same group year after year when the hens tend to select the same few males each breeding season.

Research published Thursday in the journal Nature suggests a sound evolutionary reason: Many of the bird buddies within individual groups are brothers. By working together, the brothers are increasing the odds that their genes will be passed to another generation.

"By helping your relatives to attract mates, your genes are spread," said Marion Petrie, a researcher at Britain’s University of Newcastle, Newcastle-upon-Tyne.

The research sheds light on why some peacocks seem unconcerned with sex and are content to be hangers-on in the animal singles scene: Larger groups of peacocks attract more females, so some of the peacocks are there just to make the group bigger.

"The benefits of helping closely related dominants to attract more females may outweigh the subordinate males’ own meager mating opportunities," said Cornell University researcher Paul Sherman in an accompanying Nature commentary.

Petrie and her colleagues studied about 200 free-ranging peafowl in Whipsnade Park north of London. Using DNA fingerprinting, the researchers found birds inside the strutting groups are more likely to be related to each other than those outside the group.

But how do the related birds find each other? That’s unclear, but it is not because the peacock brothers grew up together.

In fact, the researchers found that when peacock brothers were separated before hatching, and then were released into Whipsnade Park when they were yearlings, the brothers still tended to group together.

The mechanism by which the birds found their relatives is unclear. It could be by odor, feather patterns or the sounds the birds make.

"There is some way in which kin can be associated, which doesn’t require learning or environmental clues," Petrie said. "They didn’t know their fathers or mothers. They could not possibly learn who their brothers were. They had no reference points to where they were born, but they still found each other."

If you don’t pass on your genes, but you help your siblings pass on theirs, your family genes get passed on, and that’s good enough as far as natural selection is concerned. If you help make your family, or your tribe look desirable, then the genes in that pool, which likely include a good many of yours too, get to go a few more rounds. If a trait is recessive, not everyone in the group needs to express it, for it to get passed along too, with all the others.

How do Gay people fit into this? Well again it isn’t rocket science. Our child bearing years are also the years of our physical prime, for fairly obvious reasons. Let’s say you have two groups of humans, one in which all the members in their physical prime are preoccupied with caring for their own offspring, and one in which a small minority isn’t. And if that small minority is welcomed and accepted by the rest, their nurturing and protective instincts can become attached not to their own offspring, since they don’t have any, but to the group as a whole. So here is a small group out of the whole, who are in their physical prime, intimately bonded to one another, looking after, and taking care of the needs of the whole.  (You can make a case that the narcissism gay people are often accused of today, happens when they are not accepted by their families, and their community and those nurturing instincts turn inwards.)

Question: which group of humans is going to have more resources to take care of its members during times of stress? Which tribe has the better resources to take care of its old? In preliterate times, your old people are your history books. They know where the game went when the last big drought came, and where the water could be found. They know how the tribe over the hill was defeated the last time they came to raid your territory. They know how sickness was cured, how disease was avoided. Who can be there to look after them while the others are caring for their young? Which tribe can better care for its and sick, and provide for the orphaned? Who can spend the most time manning the defenses, watching for predators, or predatory humans, without also having to worry about their own young? Which tribe, over the long haul, be better able to weather bad times, and prosper in good times? Whose members then, will look the most desirable?

For social animals, homosexual members of the group provide a survival edge for the group as a whole.  It may not be a big one.  But it is enough of one that the trait, far from being selected out, has been adapted for.  And you see it everywhere in the animal kingdom.  The trait survives today in nearly all animal species that reproduce sexually, and live and raise their young in groups.  It is present today in the human family, as it almost certainly was in the families of our pre-human ancestors.  They would have needed it more.  The African plains of our birth were I am told, not a very friendly place for the human line.  There were times we almost didn’t make it.

Agriculture and industrialization sweep the demands of our tribal past away…a person can now take care of both their own young, and the needs of the whole without having to choose between them most of the time. You can become a policeman or a fireman or a doctor or a scientist. Civilization gives us the means to take care of our community and our families both without overgreat burden. Yet that tribal past is where we came from. It made us what we are. For good and for ill, as when our tribal instincts cause us to separate each other into groups of ‘us’ verses ‘them’, that tribal past is the bedrock upon which we make our modern lives. We live in the twenty-first century, but we were born in a prehistoric past, long gone over our horizon. It made us what we are. To understand ourselves, we must look to those ancient times from which our kind began its walk to the present.

Natural selection not only allows for a homosexual minority in human societies, you can make a good case that it actually predicts one.

[Edited a tad…]