The DNA of Albert Perry may change the story of human origins. Perry, an African-American, approached a DNA testing company to find out more about his ancestry. The results would have come as quite a surprise (had he lived to see them), and have raised questions for geneticists around the world.

It turns out that Perry carried a very different type of Y chromosome, never seen before. Every male has a Y chromosome, which is a piece of DNA inherited by sons from their fathers. But, unlike most DNA, the Y chromosome is not shuffled as it is passed down, and changes only slowly through mutation. Tracking these mutations allows scientists to create a genetic tree of fathers and sons going back through time.

As a man may have several sons or none, some branches of the genetic tree die out each generation, while others become more common. Going back through time it is therefore inevitable that all modern Y chromosomes must descend from from one man at some point in the past. He has become known as “Y-chromosomal Adam”....