One final thought from me for today: In the original closed thread, Юрка mentioned such strange natural phenomena as the "penis" of female hyenas.* If one is generally interested in sexual behavior among non-human animals, I would strongly recommend Olivia Johnson's book "Dr. Tatiana's Sex Advice to All Creation" -- in my opinion, it's absolutely the best English-language book if you want a discussion of "the evolution of sex" на уровне, доступном к чайникам.

She talks about hyena genitals, the widespread "adultery" among monogamous birds, hermaphroditism in sea-snails, virgin-births in lizards, male bats that produce breast-milk, insects that copulate for several weeks, the effects of testosterone on the fetal brain-tissue of a "little girl mouse" before birth, female spiders that cannibalize their males, and, yes, a little about homosexuality (though this last topic only gets 5 or 6 pages, mostly on the topic of animal bisexuality -- she admits that "exclusive homosexuality" is quite mysterious).

And it's also very funny, since she writes in the style of a "Love-Advice Column for Lonely Hearts". For instance:

Dear Dr. Tatiana: I'm a male purple-spotted Madagascar tree-beetle. Last week I had a "lady friend" over to my house for a romantic evening -- dinner, aromatic candles, some wine, hot jazz playing on the radio. Suddenly, she bit off one of my eight testicles and flew away with it! Should I be worried? And I really liked her... do you think she'll want another date?

Dear Purple: In your species, it's considered very good manners for a lady to steal a gentleman's testicle -- that's why you have seven more of them. In fact, testicle-theft is an evolutionary advantage both for your girlfriend and for you yourself. Let me explain further...
And after an introduction in that style, she explains in detail (but on a non-specialist's level) the evolutionary science behind this seemingly strange behavior.

Unfortunately, although it has been translated into almost 20 languages, Russian is not among them yet. But I highly recommend it!

*To be more exact, female "penises" are the norm only in the Spotted Hyena (species Crocuta crocuta), but not found in any of the related hyena species.