古い頭骨が示す人類進化の新たな年代

A small piece of skull found in a cave in South Africa suggests that one of our closest ancestors appeared earlier than scientists had thought. The fossil belongs to an adult Homo erectus, a species that walked upright and is widely believed to be a direct ancestor of modern humans. It was discovered at Drimolen, a site in the area known as the Cradle of Humankind, not far from Johannesburg. The skull fragment is about two million years old. That makes it around 200,000 years older than the adult Homo erectus fossils found in Georgia, in the Caucasus region, which had long been seen as some of the earliest examples of the species. Researchers from La Trobe University in Australia, working with colleagues in South Africa and the United States, say the find supports the idea that Homo erectus first appeared in southern Africa. A child's skull from the same site had already hinted at this, but the new fossil shows for the first time what the adults looked like. Homo erectus was not alone at Drimolen. It shared the landscape with another human relative, Paranthropus robustus, which had huge teeth and powerful jaws for chewing tough plants. Surprisingly, the fossils show that Paranthropus outnumbered Homo erectus at the site by more than ten to one.