^Umm, I think you misunderstood the question. It wasn't about the abundance of actual
Homo sapiens from Earth, but about why so many humanoid aliens happen to look just like humans or nearly so, rather than just like Klingons or just like Cardassians or what-have-you.
Although, thanks to the wonders of recycled prosthetics, we have seen
some alien species that resembled each other.