[mmooss]

I wonder if the authors of the paper thought about that issue. How is "nearest common ancestor" defined?

[zamadatix]

The paper uses the proper term "most recent common ancestor" (commonly abbreviated MRCA) which specifically means the most recent individual from which all individuals of a set (such as "all humans") are genetically descended from (i.e. if you traced everyone's lineage at least one branch up the tree would always hit this person, not that this person was the only source of genetic information from that time).

[zamadatix]

Clarity: it should have read "if you traced everyone's lineage _then_ at least one branch _somewhere_ up the tree would...".

I realized the way it was written could be ambiguously read as "if you traced everyone's lineage _by_ one branch up" after the edit window had passed.