'प्रवासन के नियम' (Laws of Migration) को सबसे पहले किसने व्यवस्थित रूप से प्रतिपादित किया 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?