Yes, it very much depends on the definition of Homo sapiens.

There is a strict genetic definition in which a set of defining genes constrain the species, in which case there was likely a first human, but there is every possibility that their first descendents didn’t meet that definition and it took a few generations of back and forthing and natural selection for a consistent line of humans to exist.

On the other hand you could define the species based on social behavior, in which case the “first human” only arose in context of at least one other member of the species, and “Adam and Eve” or “Annie and Eve” or “Adam and Steve” scenario.

Then you go to what most agricultrually minded people think of as a “species”, which is fetile interbreeding. In that case it seems like there never really was a separation between Homo sapiens and Homo erectus and Neanderthals, as there is now broadly accepted evidence of interbreeding long past the “differentiation” of the species, though social and territorial differences seem to have kept them from re-merging into a unified population.