Overview: Paleoanthropologists, linguists, archeologists and other scientists offer the latest interpretations of fossil findings and genetic studies and posit intriguing theories on how Homo sapiens became the only existing human species. Did we kill off our cousins, interbreed and merge with them, or did they just die out? It took five million years for an upright ape to evolve into an agile, quick-thinking and inventive human being. But once our ancestors emerged in Africa, were we destined to dominate the globe?