I also recommend Bruce Bagemihl's Biological Exuberance, an extensive catalog of diverse sexual development and behavior. Their work challenges those who claim that non-procreative sexual behaviors are "maladaptive evolution" because they don't allow the individual to leave more offspring, but it's clear from many of our closest genetic relatives (especially bonobos) that sex is not just about reproduction. It is often about strengthening social bonds within groups, and that same-sex activity is an important part of that.
Joan has also been critical of Richard Dawkins' concept of the "The Selfish Gene." Her book The Genial Gene: Deconstructing Darwinian Selfishness examines the assumptions behind this conept.
Evolution's Rainbow: Diversity, Gender, and Sexuality in Nature and People (Joan Roughgarden)
The Genial Gene: Deconstructing Darwinian Selfishness (Joan Roughgarden)
Biological Exuberance: Animal Homosexuality and Natural Diversity (Bruce Bagemihl)
Andrea James is a writer, director, producer and activist based in Los Angeles. Her work often focuses on consumer activism, the free culture movement, exogenous mysticism, humor, and LGBT rights.