Biogeography primarily investigates what elements?

Biogeography primarily focuses on the abundance and distribution of living organisms across various geographical areas. This field examines how organisms are distributed in space and time, as well as the factors that influence these patterns, including environmental conditions, historical events, and evolutionary processes. By studying the geographical distribution, biogeographers gain insights into how ecosystems function and how species adapt to their environments.

The other choices, while relevant to different aspects of biological and anthropological studies, do not encapsulate the essence of biogeography. The evolutionary history of human species pertains more to paleoanthropology and human evolution, health outcomes are generally studied through the lens of public health and epidemiology, and genetic variation is a focus of population genetics. Each of these fields has its own specific methodologies and areas of inquiry, distinct from the overarching themes of biogeography.