3 ms·

"The key is that the propagation of ancestry never stops, because ancestry doesn't round down to zero." I get your other points but this assumption seems obvio

• magicalhippo 6y ago
  But they would then not become an ancestor, and thus will not appear in a chain of ancestors.
• simonh 6y ago
  It only takes one single person to migrate and have surviving descendants for everyone to end up their descendant. So yes it's possible that people migrate and not have descendants, but that has to be true for every single one of them. In reality even over very long geographic distances we have evidence of hundreds or even thousands of people migrating. Marco Polo first visited China with his uncles who had been there before. He recoded that there were so many European traders in Beijing that the Italians, Spanish, etc each had their own districts. Even before that Rabban bar Sauma was an Armenian Christian monk born in the Armenian district of Beijing in about 1220, who travelled to Europe. He appears in the court records at the Vatican and in England. As for sub-Saharan Africa, Middle Eastern traders have been plying the seas of eastern Africa, and running caravans through central Africa for thousands of years. Their cultural and genetic fingerprint is all over Africa. There is a small, but persistent and measurable level of sub-Saharan African genetic markers in southern Europe dating to the Roman era.