A review by somestuff
Why Is Sex Fun?: The Evolution of Human Sexuality by Jared Diamond

2.0

interesting short and sweet 
i love comparative physiology for evolutionary studies so those portions of this were really fun but as with most pop science on evolution there was a bit too much focus on current day trends ignoring the vast cultural differences in our evolutionary ancestors as well as too much focus on people wanting to “support people with their genes” as if this is something early humans  would have articulated. ignores the group social aspects of humans in favor of supporting each other for survival of everyone in the group to just wanting those with your genes to survive. And in this way also greatly ignores any homosexual/bisexual tendencies which in a book about why sex is fun should probably be addressed.
also doesn’t actually answer the question in the title. not that we cannot easily guess the reason for why evolutionarily sex is enjoyable but this has chapters devoted to male lactation and why humans have unknown estrous cycles seems like a bit more should have been included about the purpose of enjoyment of sex. And as for the estrous cycle question diamond ignores the evolutionary theory for why we could have developed  this characteristic of humans having sex All the time bc it was enjoyable led to more offspring than a trackable easily seen estrous cycle like… interesting how throughout the book actual enjoyment of sex wasn’t ever brought up beyond a sentence in the chapter abt penis size. quite prude for a book about sex lmao. And in a book that actually does mention comparative physiology in production of offspring— it’s very rigid in descriptions of gender and sexuality. Like you’re discussing lizards that can change sex and frogs where children develop in the body of the ‘male’ frog like clearly there’s some breakdown in rigid mother/father descriptions that should be addressed here. Strange how it’s ignored.