We now know that at least part of the explanation is dilution. Ancient DNA from Europeans who lived before nine thousand years ago shows that pre-farming Europeans had just as much Neanderthal ancestry as East Asians do today.26 The reduction in Neanderthal ancestry in present-day Europeans is due to the fact that they harbor some of their ancestry from a group of people who separated from all other non-Africans prior to the mixture with Neanderthals (the story of this early-splitting group revealed by ancient DNA is told in part II of this book).
