From the earliest days of life on earth, disease has evolved alongside us. And its presence isn't just natural but is also essential to our health. Drawing on the latest research, Zuk answers a fascinating range of questions about disease: Why do men die younger than women? Why are we attracted to our mates? Why does the average male bird not have a penis? Why do we--as well as insects, birds, pigs, cows, goats, and even plants--get STDs? Why do we have sex at all, rather than simply splitting off copies of ourselves like certain geckos? And how is our obsession with cleanliness making us sicker?

In this witty, engaging book, evolutionary biologist Zuk makes us rethink our instincts as she argues that disease is our partner, not our foe. Reconsider the fearsome parasite!