DarkFather said:

Scandanavians and Aborigines have been genetically seperated for more than 2000 years, and they're still the same species.

Fascinating. And are the Scandanavians from the planet Scandanav, or have they been on the earth those whole 2,000 years just as the Aborigines?

DF makes a very valid point here. Scandinavians and Aborigines look about as different from one another as possible, while living on the same planet only separate climates. Imagine the differences there might be had they lived on two separate planets, with very different climates, atmospheres, conditions, resources, foods.

I agree they would be the same species (in fact, I have a really hard time buying into the idea of cross species evolution, but that is a whole different discussion), but they would be quite different. 2000 years is a rather short amount of time for any biological changes to take place. But then again, the vast majority of aliens in Star Trek seem to be biologically identical anyway. Silly science fiction stories! So unrealistic I can barely stand it! ;)