Most of the book is about heterosexual sex, and a lot of it is about female instinctual programming directed at getting the best sperm and the best chance of raising the child to reproductive age. Most of the rest is about the possible counterpart strategies for male programming. (Of course, all this is overlaid nowadays with some rules and morals. It's not like this programming is all of what's going on. But the effect of the programming is possibly quite a bit more than we like to think.)
There's an astounding amount of detail about all the different kinds of sperm, all the stuff that the female body does to get the sperm it wants, and all the complex strategies that our bodies are doing without our (usually) noticing.
He touches on homosexuality too though. His theory is that same-sex play between young males benefits their genes' evolutionary chances by giving them experience that stands them in good stead when they get a chance to have sex with a fertile woman. Because although some parts of attraction may be programmed in, "how to do sex" has to be learned.
I'm not convinced that proves anything about whether homosexuality is genetic - that theory works just as well if everyone's "potentially" bisexual and the outcome's determined by upbringing or chance. And I think he missed a few tricks, particularly talking about the evolutionary benefit to female/female couples. But overall, not specially homophobic, and not completely implausible to me. And sheds a whole new light on polyamory.
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