ABSTRACT
Humans from different parts of the world form regional populations—often incorrectly classified as separate human “races”—that are linked into a single worldwide species. No regional population is completely isolated from the others, and all of them share a common human biology. Local variations in regional populations can be produced by environmental differences, geographic or cultural restrictions to intermarriage, or even natural or geopolitical events. However, no human population is completely isolated and completely disconnected from any other. Human: the one human species to which we all belong covers the Earth, every region’s population exhibiting some minor distinguishing traits grading into adjacent populations.
