There are several known major Earth colonies, and perhaps dozens (or more) colonies of humans who were not officially affiliated with Earth. There are probably tens of thousands of Starfleet vesselstens of thousands of Starfleet vessels, and if what we've seen is any guide, the vast majority of the individuals serving are Human.
So roughly how many humans, are there, total, in the Star Trek universe? (Yes, I know the Star Trek universe covers several hundred years.) Tens of billions? Hundreds? Trillions?