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What about sexual selection and homosexuality?
Homosexuality is the other problem with sexual selection. According to Darwin, the only purpose for sex is the transfer of sperm. And if hes right, then homosexuality is a biological dead end. But he isnt right. Most mating takes place without chance of conception. Humans have sex all the time, but produce very few offspring during their lives. A typical couple has sex once a week for 50 years, but has only two offspring. If the only goal of sex is the transfer of sperm, then its a very inefficient method for doing so. One of the other things Darwins theory teaches us is that when a species exhibits a trait that is inefficient, it is selected against. So, unless evolution has somehow overlooked sex, making it inefficient in contrast to all the other, wonderfully adapted traits that have evolved, then mating must really be serving multiple functions of which one is the occasional transfer of sperm.
So what is the purpose of sex in nature?
Its an incredibly effective form of tactile communication. It keeps animals in touch. Its very up close and personal. It also helps explain why animals have so many different parts of their brain, so many neurons, that confer pleasure. In most species, especially social species like mammals and birds, mating takes place as a way to form and manage relationships. And if you look at sex as an incredibly effective form of communication, it helps explain a lot of things in nature like homosexuality that have puzzled biologists for years. In bonobos (a primate very similar to a chimp), homosexual contact takes place as often as heterosexual contact. And bonobos are incredibly sexual. Genital contact is how they say hello; its how they communicate. It provides a sense of group security and access to food that the animals need to survive and to raise their young.
What do you think should replace his theory?
A theory that fits the data. I have replaced sexual selection with social selection. In social selection, animals are organized differently. Their organization is arranged to control access to reproductive opportunity, which includes everything they need to reproduce: food, nesting sites, mates. Animals use their resources as bartering chips to buy help from others. Sometimes this leads to cooperation and sometimes to competition. And this creates all kinds of familial relationships. Under certain circumstances, that means monogamy, but under others, that means polygamy and polyandry. Not only are there many types of family organizations, there may even be more than two genders.
In bluegill sunfish, one gender of male is a controller, a sort of alpha male, who first sets up a large territory and then solicits the help of another male gender through a same-sex courtship. The male pair bond together and then solicit females to lay eggs in their shared territory. Many species have multiple types of males, each type with a characteristic size, color and life history. In some of these, like the bluegill sunfish, one of the male types is even patterned like a female, leading to what we might think of as a cross-gender presentation. Gender variation and same-sex sexuality call for viewing the act of mating as a way of promoting various types of social relationships, and not solely as a mechanism for transferring sperm. Social selection is about evolution that promotes and manages social relationships.
It seems fortuitous that your book is coming out as the rest of the nation is discussing gay marriage how do you think it will affect the debate?
I dont know if my book can have any impact on the gay-marriage debate in this country. I hope so. It depends in part how many people have already made up their mind versus how many people are still looking into the matter. My book does show that many of the claims from the anti-gay agenda are simply mistaken that homosexuality is unnatural or that homosexuality is recent. My book also considers both gender and sexuality expression in the Bible, and shows how affirming the Bible is for variation in these human dimensions. The belief that the Bible somehow condemns homosexuality across the board is simply false, and the Bible positively affirms transgender expression, in both Hebrew and Christian testaments. So, if people are interested in learning more, then the book has lots to offer. I hope reading the book is a liberating and empowering experience for each reader, and that this experience translates into better social policy than we now have.
Evolutions Rainbow: Diversity, Gender and Sexuality in Nature and People | By Joan Roughgarden | University of California Press | 472 pages | $27.50, hardcover