Again. Nobody is saying there is a definitive starting point of “In the year 0 ICBA, the first homo sapien was born”. There fundamentally cannot be.

But… there was. Or, to be less precise, there were probably multiple definitive starting points before one took hold.

You can have an individual born that appeared strikingly like a modern human, but if their population hasn’t genetically changed enough their offspring go right back to looking just like any other precursor to modern humans.

Yes. The individual was, potentially, “evolved”. But the population “reverted” back. That doesn’t change the fact that there was an individual who had reached the next stage. Because… a mutation/defect is isolated until it isn’t.

But for the purposes of a thought experiment/“shower thought”? Yeah, there was very much a point where a single human existed. We just will never know beyond “it probably happened in this very large span of time”.