थॉम्पसन तथा नोटेस्टीन ने जनांकिकी संक्रमण की मूलतः कितनी अवस्थाओं के होने का सुझाव दिया था?

In traditional anthropological classification of human races, which racial group was characterized as 'yellow-skinned'?

What is the approximate estimated proportion of ecumene (habitable) and non-ecumene (uninhabitable/sparsely inhabited) areas on the Earth's surface?