The sites main flaw is putting everyone into one catagory as if the human body is the same throughout the world. thats not true, biological life is very adaptable and it does not take thousands of years.
Eskimos have adapted big time to their diets of raw fish, extreme cold, and darkness for half the year. fundamental processes of the body have changed in them, such as their blood not rushing away from extremties like hands and feet, during the cold. This is a major change, and they adapted in just a few generations maybe even less.