In some parts of the world, there is an intimate connection between the infectious parasitic disease "malaria" and the genetic disease "sickle-cell anemia." A keenly observant young man named Tony Allison, working in East Africa in the 1950s, first noticed the connection and assembled the pieces of the puzzle. His story stands as the first and one of the best understood examples of natural selection, where the selective agent, adaptive mutation, and molecule involved are known-and this is in humans to boot. The protection against malaria by the sickle-cell mutation shows how evolution does not necessarily result in the best solution imaginable but proceeds by whatever means are available.