I suspect that we will find out modern man is very similar to ancient man and a lot of scientific suppositions about ancient history is hogwash...
No "suspect" about it, we know for certain that moderns humans and, for example, Neanderthals shared 99% identical DNA.
We also can see where they did occasionally interbreed, making us, by definition, the same species.
Other pre-human creatures were also doubtless closely related to us, though certainly not as close as Neanderthals.
Indeed, despite 8 million years of evolution separating humans from ancestors of chimpanzees, we still share something like 96% similar DNA with modern chimps.
Finally, words like "hogwash" are inappropriate here.
"Mistaken" is entirely adequate, if it indeed applies.