Anyhow. This is one of her choices: "Not that we’re some woo-woo skeptics, but it is curious what happened about four to five thousand years ago: Europeans changed. More specifically, their genetics changed completely, and no one’s really sure why."
"The genetic markers of this first pan-European culture, which was clearly very successful, were then suddenly replaced around 4500 years ago, and we don’t know why,” Adelaide professor Alan Cooper, the Centre’s director, said in a statement. What bizarre event precluded this change is unknown (although assuredly the answer is not a Doctor Who-style invasion), but we do know we’re ready for historians and archaeologists to team up and crack the case.
The reference to Doctor Who should provide an obvious clue, but perhaps Jamie and Alan don't read much history.