In the last four decades, however, many new evolutionary theories have been created and revised. The "Out of Africa" theory, for example, maintains that humans emerged rapidly in one small part of Africa and then spread to replace all other humans within and outside the continent. Chris Stringer has a theory of his own. His new book, "Lone Survivors: How We Came to be The Only Humans on Earth" suggests that distinct humans coexisted and competed across the African continent, exchanging genes, tools and behavioral strategies.
Chris Stringer, author of Lone Survivors: How We Came to be the Only Humans on Earth, discusses his new book laying out his controversial theory on the evolutionary origins of modern humanity.