Gotham Central wrote:
Hell even the Kelvans from the Andromeda galaxy looked totally human.
No, they transformed themselves into a human shape so they could operate a spaceship designed for humanoids. Spock got a telepathic impression of their true form as "immense beings" with "a hundred limbs that resemble tentacles." It was a vital story point that the Kelvans had trouble adjusting to the human forms they'd adopted, and that Kirk & crew defeated them by exploiting their unfamiliarity with human emotions and appetites.
On the other hand, the Mudd's Planet androids did say that their creators from the Andromeda Galaxy were "quite humanoid." Implicitly the androids were made in those Andromedans' image. Although I prefer to think that they were more approximately humanoid and that Harry had the androids remodel their appearance to a more human one.
The race that we see in "The Chase" does not fully explain this since they, while humanoid, were not human...and their genetic sequence leads to the Romulans/Vulcans, Klingons and Cardassians as well. So why would you get more humans than anything else?
I like to use neoteny as an excuse. Lots of species' evolutionary processes tend toward neoteny -- that is, species evolving to retain formerly juvenile traits into adulthood. It's been said that humans are basically neotenous chimpanzees -- we retain the large heads, small muzzles, neuroplasticity, and so forth that chimps only have in their youth. And if you look at the various Trek-universe infants we've seen, most humanoid babies tend to look more human than their adult forms, with the more elaborate ridges and other anatomical features growing in later (which is, of course, because it wouldn't be practical or humane to subject a live infant to an arduous prosthetic makeup process -- although by "Demons"/'Terra Prime" they were able to do pointed ears with CGI). So if Trekverse humanoids tended toward neoteny in their evolution, they would often become increasingly humanlike as well.