जनसांख्यिकीय संक्रमण सिद्धान्त का प्रतिपादन सर्वप्रथम किसने 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?