> There isn't believed to be anyone left in the Americas or Tasmania who does not have any European ancestry from the last 500 years.

OK, but take the Andean's great-to-the-nth grandmother from 7300 years ago (one of the ones who lived in the same region all those centuries ago). Is that grandmother also an ancestor of the teacher in Somerset? And of some villager in a remote village in Tibet?

> At some point 7,300 to 5,300 years ago if someone had a living descendant, then all of humanity is their descendant.

Weren't, for example, Native Americans, isolated from Europe for more than 7,300 years?

So if you consider someone living in the Andes with pure Native American ancestry, how are they descended from Cheddar Man?

Just ask them to borrow, but don't return it. ;)