We find ourselves in a time of great social upheaval. People are testing the boundaries of just about everything related to sex and gender. Biological sex, long thought to be a simple binary, is now being understood as a spectrum. Gender is being uncoupled from sex and expanded to an astounding range of diversity. The traditional categories of sexual attraction are being supplanted by more creative labels. Where is this shift coming from? The answer may surprise you. Diverse sexual behaviour is not a new development, or even a human one. It didn't emerge from recent progressive culture, it's the product of billions of years of experimentation throughout the animal kingdom.

Evolutionary biologist Nathan H. Lents takes readers on a journey from silent crickets to lesbian albatrosses to bonobos who kiss, revealing what this incredible array of sexual diversity can teach us about our own. Amusing, enlightening and meticulously researched, Lents convincingly shows that diverse genders and sexuality have evolutionary functions far beyond procreation. The Sexual Evolution is a perspective-altering book that advocates understanding and demolishes biases held by even the most open-minded among us.