Sex is a subject as fascinating to scientists as it is to the rest of us. From the contentious problem of why the wasteful reproductive process exists at all, to questions of how individuals choose their mates and what traits they find attractive and why, research into the nature of sex has given rise to a vast range of findings. This book explores these findings, and their implications for the sexual behaviour of our own species, putting forward the metaphor of the red queen (from "Alice in Wonderland"), who has to run at full speed to stay where she is as a highly effective metaphor for a whole range of sexual behaviours. The book was shortlisted for the 1994 Rhone-Poulenc Prize for Science Books.