"Tens of thousands of years ago, the rise of humanity as we know it began. Modern humans spread from Africa to Europe and Asia, which were already populated by older Neanderthal cultures. The two groups interbred, adding some Neanderthal DNA to our present-day genes. The relatively sophisticated humans flourished, while their Neanderthal counterparts disappeared, going extinct in Europe somewhere between 39,000 to 41,000 years ago. But the timeline, in many places, is still foggy. By identifying a pair of ancient teeth as conclusively human, a team of scientists think they've managed to clear things up a little — and helped settle a debate about how different human and Neanderthal cultures might have been."