The Ancestor's Tale: A Pilgrimage to the Dawn of Evolution

by Richard Dawkins

There’s a telling difference between ‘gene trees’ and ‘people trees’. Unlike a person who is descended from two parents, a gene has one parent only. Each one of your genes must have come from either your mother or your father, from one and only one of your four grandparents, from one and only one of your eight great-grandparents, and so on. But when whole people trace their ancestors in the conventional way, they descend equally from two parents, four grandparents, eight great-grandparents and so on. This means that a ‘people genealogy’ is much more mixed up than a ‘gene genealogy’. In a sense, a gene takes a single path chosen from the maze of crisscrossing routes mapped by the (people) family tree. Surnames behave like genes, not like people. Your surname picks out a thin line through your full family tree. It highlights your male to male to male ancestry. DNA, with two notable exceptions which I shall come to later, is not so sexist as a surname: genes trace their ancestry through males and females with equal likelihood.