The researchers started looking at bits of the Y chromosome known as the Alu family of retrotransposons.
"We found lots of Y-chromosome variations that people didn't know exist," Wilder said.
The new technique revealed that Y-chromosome DNA and mitochondrial DNA differ to the same degree among populations.
Hammer said, "That alone wouldn't say the Y chromosome is migrating more, but if just half as many males are getting their genes into the next generation on average as are females, then it implies more males are migrating to do that."
The pattern the researchers see in our genes doesn't require mass migrations of people across continents. The sailors with a girl in every port could have done it. Or it may be that village women snuck out for trysts with tall, dark strangers. Either way, Y chromosomes got around.