Human bones from Bulgaria suggest human beings first arrived in Europe thousands of years earlier than previous studies have shown. This means humans shared the continent with Neanderthals, our closest relative, much longer than experts had believed. Scientists studied four pieces of bone and a tooth. Detailed radiocarbon and genetic testing show they came from four Homo sapiens, the oldest of which is dated to about 46,000 years ago. Two separate reports on the study appear in the scientific publications Nature and Nature Ecology & Evolution.