I’m surprised at the number of people I talk to about animal behavior that are shocked at how common homosexual behavior is in the animal kingdom. I often point gay animal skeptics to Biological Exuberance by Bruce Bagemihl—a 1999 book detailing more than 300 different animal species that engage in a diverse array of behaviors that fall under the umbrella of homosexuality. Everything from same-sex sex, affection, pair bonds, and parenting. It might seem odd that homosexuality should be so widespread given that evolution is based on the need for animals to produce offspring. This is often a topic broached by anti-gay groups hoping to (misguidedly) show that same-sex behavior is not “natural.” But the literature on animal homosexuality shows that same-sex sexual behavior in a given species does not negatively impact a species’ reproductive rates, so it’s a non-issue.
Take the example of the Laysan albatross. This species of giant bird forms lifelong pair bonds—where two individuals stay together for life, mating and raising offspring together over the course of many decades. Some of these lifelong pair bonds are between same-sex couples. In one study of Laysan albatrosses living on Oahu, one-third of the lifelong pairs were female same-sex couples. In many of these cases, however, one or both females would mate with a male at some point, resulting in fertilized eggs that the female pairs raised together. Many of the cases of homosexuality in the animal kingdom work like this, where same-sex behaviors are just part of an individual’s typical behavioral repertoire, and reproduction still occurs to ensure species survival. Bonobos are perhaps the best example: Individuals engage in sex between same- and opposite-sex partners on a regular basis, resulting in lots of gayness, but also lots of babies.
Exclusive attraction to members of the same sex is rarer, but not unheard of. In domestic sheep, it’s estimated that 10 percent of rams (the males) are only interested in mating with other rams. Researchers studying this phenomenon found that these gay rams had differences in their brains—a thicker cluster of neurons in part of their hypothalamus—when compared to straight sheep. The reason for the differences being the relative amount of estrogen levels that the developing ram was exposed to before birth. In other words, as Balthazart argues in his book, these rams were born gay. All this to say that there’s nothing particularly unusual or controversial about (inborn) gayness in the animal kingdom. [Continue reading…]