Adam Rutherford writes at the Guardian that he's a direct descendant of Charlemagne. Then again, he adds, basically everyone of European descent can claim Charlemagne — who had at least 18 children — as an ancestor. And this, he notes, is something he can determine without analyzing a vial of spit or a drop of blood.
"This is merely a numbers game," he says. People have two parents, four grandparents, eight great-grandparents, and so forth, he says, but rather than expanding out to billions of ancestors at the time of Charlemagne — which would be more than the number of people alive then — family trees begin to fold in on themselves. All Europeans, he adds, are descended from the same people.
Done properly, Rutherford writes that genetic genealogy be a powerful tool to study families and human migrations. At the same time, some companies use it to make "outlandish claims" about ancestry, he adds. One company, he notes, says it can pinpoint the village where its customers' ancestors lived 1,000 years ago, even though that far back, people have thousands of ancestors.
"A secret history is hidden in the mosaics of our genomes, but caveat emptor. If you want to spend your cash on someone in a white coat telling you that you're descended from Vikings or Saxons or Charlemagne or even Drogo of Metz, help yourself," he adds. "I, or hundreds of geneticists around the world, will shrug and do it for free, and you don't even need to spit in a tube."