Banana Slugs are hermaphrodites, which means they are an animal that has both female and male reproductive parts

Forty and Fabulous is the theme for Pride this year. San Francisco’s Pride Celebration and Parade has been going strong since 1970. Pride recognizes and celebrates the diversity that has put San Francisco on the map. NightLife at the California Academy of Sciences kicked off the Pride weekend with some help from Juanita MORE, Verasphere, SF Cheer and Jane Tollini. In prepping for the festivities and specifically Jane Tollini’s talk – “How Animals Get Down”, I had to research a specific Academy animal and its claim to fame.

Below are a few of the tidbits I’ve learned about in my tenure at the Academy which prove equally intriguing:

The most popular docent cart at NightLife is the baculum cart. Baculums are penis bones that are found in most mammals. They range in sizes depending on the mammal and aid in sexual intercourse. One of the largest Baculums belong to the walrus and Alaskan native Americans would polish and carve these baculums for clubs or knife handles. They are known is there culture as Oosik.

Banana Slugs are hermaphrodites, which means they are an animal that has both female and male reproductive parts. In some cases of mating, a male reproductive member will become stuck; if this happens it is chewed off and discarded; thus making the slug a female.

There is a species of Cichlids called the Cross Dressing Cichlids. In this species there are three sexes – a dominant male, a non-dominant male and a female. The beta male resembles the female and when the alpha male is protecting his female harem the beta male will mate with the females. It is also interesting to note males can change between dominant and non-dominant.

Clownfish live in small groups in a single anemone. They are one of only a few species of fish that are immune to the anemone’s toxicity. Within a group of Clownfish there is a breeding pair that cohabitate with smaller non-breeding males. When the female dies, the dominant male changes sex and becomes the female. This strategy is defined as sequential hermaphroditism.

Penguins like most birds, reptiles and amphibians reproduce by what’s known as a cloacal kiss. The cloaca is a single orifice that is used for many functions; namely, urinating, defecating and mating. Thus, both male and female penguins have cloacas. Mating is achieved by bringing the cloacas together to touch.

Often it is very difficult to sex a snake as all the reproductive parts are internal. Biologists will use a special probe to determine the sex of a snake in captivity. Males have two members that protrude during mating calling hemepenes. Other than during mating, it is hard to tell the difference between a male and female. I learned this the hard way when I went to pull out a Ball Python for an outreach program. It was curled around its cage mate and I realized too late that they were mating when I interrupted!

I have often heard that homosexuality is not natural. Yet is has been observed, researched, and documented in many species – so has sex changes, several sexes in one species, hermaphrodites, harems, polygamy and sexual cannibalism. An interesting article was written up in the New York Times entitled, "Can Animals Be Gay?" If you are interested in learning more about the diversity of reproduction methods in the animal kingdom and why this diversity is needed; these two books are great:

Dr. Tatiana's Sex Advice to All Creation: The Definitive Guide to the Evolutionary Biology of Sex by Olivia Judson

Evolution's Rainbow: Diversity, Gender, and Sexuality in Nature and People by Joan Roughgarden

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Last blog I talked about some studies that link homosexuality and genes. The most powerful studies are those that compare identical twins to fraternal twins. These studies show that both twins in an identical pair are more likely to be gay than are both twins in a fraternal pair. Since identical twins have the same DNA, this suggests that something genetic is going on.

But no study showed that if one identical twin was gay, then the other one was always gay as well. We'd expect both twins in an identical twin pair to share a purely genetic trait 100% of the time. Because they don't, the environment definitely plays a role. But not like you might think.

By environment I don't mean certain family situations (although these sorts of factors probably contribute as well). What I am referring to are environmental factors that can affect brain development. Factors like viruses, hormones, or maybe even antibodies.

We know, for example, that the more older brothers a man has, the more likely he is to be gay. Even if he doesn't live with the older brothers.

This suggests that something biological is going on. It is as if the mother's body remembers how many sons she has had. One way this might happen is through her immune system.

Perhaps when a mother has a son, she makes antibodies to something having to do with carrying a male child. The more sons she has, the more antibodies she makes. At some point, she makes enough antibodies to affect brain development and the younger son is now gay.

Of course, not every youngest son is gay– he is just more likely to be homosexual. Other factors have been reported to increase the chances that someone is gay too. These include being left handed, having a counter-clockwise hair whorl and maybe even different finger lengths. All of these traits are associated with differences in brain development.

There are apparently many paths to a homosexual brain. This isn't surprising as human sexuality is much too complex to be due to a single gene or environmental factor. Most likely, it is the result of many factors all working together.

Some gay men may have inherited genes that made environmental factors more likely to affect their sexuality. And some gay men may have been exposed to multiple environmental effects that affected their sexuality despite their genes.

I think you can appreciate how these kinds of complex interactions can make finding "gay" genes incredibly complicated. And why it is hard to pinpoint the environmental effects that contribute to becoming homosexual as well.

Dr. Barry Starr is a Geneticist-in-Residence at The Tech Museum of Innovation in San Jose, CA.

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