And the differences people can see are due to environmental factors and survival of the fittest causing people in one are for a long time to adapt over many, many generations. If your ancestors were in a different environment you could easily look quite different and be a different, "race" according to how most people use the term. And your offspring down the line may not look like you even if you procreated with someone who looks exactly like you. Now since we have "conquered" the earth and live indoors etc, those changes may be more minimal. But here it is explained for everyone.


And if isolated for long enough under the right conditons eventually a new race could develop, but again I doubt it ever will amonsgt humans now due to the lack of isolation. But again, please understand the term if you want to use it, use it properly and educatedly.