Data from any single gene cannot really tell you anything so definitive. If you follow the mitochondrial DNA backwards, it will take you to a certain place - to an Ursula or Tara or whatever. But if you take any other bit of DNA, any gene at all, and trace it back, it will take you someplace else altogether.' It was a little, I gathered, like following a road randomly out of London and finding that eventually it ends at John O'Groats, and concluding from this that anyone in London must therefore have come from the north of Scotland.