Working in East Africa in the 1950s, Tony Allison was the first researcher to find a connection between the infectious parasitic disease malaria and the genetic disease sickle cell anemia. His discovery is among the first and best-understood examples of natural selection, where the selective agent, adaptive mutation, and critical molecules involved are known--and all in humans. 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.