Question

Do reproductive isolating mechanisms apply to humans? If so, why? If not, why?

Answer 1

At the present time, not so much. Global travel brings potential mates together.

In the past, Australia was pretty much geographically isolated.
There was also a period of millenia during which Asia was more or less geographically isolated from Europe and Africa.
You also have sexual selection in Asia, which is why there weren't any blond-haired Asians.

Answer 2

I would say not...lakotareid makes a very strong point