That estimate matches prior DNA studies, putting a date to the time when human beings first emerged on the planet. But would these first humans have been anatomically just like us? Probably not, suggests lead author Timothy Weaver, an anthropologist at the University of California at Davis.

"Early fossils along this lineage are quite different from later ones," he told Discovery News.

Fast evolution, in fact, probably drove the initial Neanderthal/human divergence, which likely began as genetic drift -- random changes in DNA. As the two groups parted ways, their changing environments likely drove more substantial changes in body shape and size, in response to differing needs.