heritage. I thought about a recent conversation (thanks @patrickrhone ) on “race” & “heritage” when I read this in Randall Munroe’s wonderful What If? 2:
Each of your ancestors represents the merger of two family trees, so more and more people are included as you move further back… If you follow it back far enough, the relentless doubling means that eventually you’ll reach a date at which all surviving lineages have been absorbed into your family tree. At that point, all the people who left descendants are your ancestors, and you and everyone else have the same set of ancestors.
A 2004 simulation by Douglas L. T. Rohde and colleagus estimates that the identical ancestors point is likely somewhere between 5000 & 2000 BCE. At that date, anyone who left descendants at all is an ancestor of everyone. Each lineage from that date has either died out or expanded to include all living humans, and so all living humans share the same set of ancestors from that point backward.