Defining when a population has diverged enough to be called a separate species is not a dividing line but a continuum.
A swamp dries up and becomes a forest over a hundred years. It was obviously a swamp one hundred years ago, and it is obviously a forest now. At what point did the swamp become a forest? Was there a particular second when it happened? One location that was obviously forest first?
We aren’t talking about a forest or arbitrary categories, we are talking genetics. Surely there was a time there was no such thing as a genetic human, and then there was, and according to evolution this happens because of mutation and natural selection.
So when and to whom did this mutation happen to?