For Janet Mann, a professor of biology and psychology at Georgetown University, who has studied same-sex behavior in dolphin calves, their homosexuality "is about bond formation," she said, "not about being sexual for life."
She said that studies showed that adult male dolphins formed long-term alliances, sometimes in large groups. As adults, they cooperate to entice a single female and keep other males from her. Sometimes they share the female, or they may cooperate to help one male. "Male-male cooperation is extremely important," Mann said. The homosexual behavior of the young calves "could be practicing" for that later, crucial adult period, she added.
But, scientists say, just because homosexuality is observed in animals doesn't mean that it is only genetically based. "Homosexuality is extraordinarily complex and variable," Bagemihl said. "We look at animals as pure biology and pure genetics, and they are not." He noted that "the occurrence of same-sex behavior in animals provides support for the nurture side as well." He cited as an example the ruff, a type of Arctic sandpiper. There are four different classes of male ruffs, each differing from the others genetically. The two that differ most from each other are most similar in their homosexual behaviors.
Zuk said, "You have inclinations that are more or less supported by our genes and in some environmental circumstances get expressed." She used the analogy of right- or left-handedness, thought to be genetically based. "But you can teach naturally left-handed children to use their right hand," she pointed out.
Still, scientists warn about drawing conclusions about humans. "For some people, what animals do is a yardstick of what is and isn't natural," Vasey said. "They make a leap from saying if it's natural, it's morally and ethically desirable."
But he added: "Infanticide is widespread in the animal kingdom. To jump from that to say it is desirable makes no sense. We shouldn't be using animals to craft moral and social policies for the kinds of human societies we want to live in. Animals don't take care of the elderly. I don't particularly think that should be a platform for closing down nursing homes."
Bagemihl is also wary of extrapolating. "In Nazi Germany, one very common interpretation of homosexuality was that it was animalistic behavior, subhuman," he said.
What the animal studies do show, Zuk observed, is that "sexuality is a lot broader term than people want to think."
"You have this idea that the animal kingdom is strict, old-fashioned Roman Catholic," she said, "that they have sex just to procreate."
In bonobos, she noted: "you see expressions of sex outside the period when females are fertile. Suddenly you are beginning to see that sex is not necessarily about reproduction."
"Sexual expression means more than making babies," Zuk said. "Why are we surprised? People are animals."
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