The Evolutionary Arms Race: "Survival of the fittest." Raw competition? Or, a level of cooperation indispensable to life? Evolution tells us that both are important. We explore our own spiraling arms race with microorganisms, the only entities that can pose a threat to our existence. We follow the struggles of medical detectives uncovering the roots of epidemics and trace the alarming spread of resistance among pathogens that cause disease, like the new virulent tuberculosis nicknamed "Ebola with wings." Interactions between species are among the most powerful evolutionary forces on earth, and understanding them may be key to our own survival.

Why Sex?: In evolutionary terms, sex is more important than life itself without progeny, we are evolutionary losers. Sex fuels evolutionary change, by adding variation to the gene pool and eliminating unsatisfactory traits. We look at the endless variety of sexual expression and the powerful hold sex exerts over almost all living things. And we explore how the need to pass on our genes has shaped our own bodies, minds, and lives. Some scientists believe that art, literature, music in fact all of human culture may be the ultimate result of our sexual drives.