古老頭骨把人類演化史往前推
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.
在南非一個洞穴裡找到的一小塊頭骨顯示，人類的一位近親出現的時間，比科學家原本以為的還要早。
這塊化石屬於一個成年的直立人。直立人能直立行走，一般認為是現代人類的直系祖先。化石出土於德里莫倫，那裡位在離約翰尼斯堡不遠、被稱為「人類搖籃」的地區。
這塊頭骨碎片大約有 200 萬年的歷史，比在高加索地區的喬治亞找到的成年直立人化石還早了約 20 萬年。長久以來，喬治亞的那些化石一直被當成這個物種最早的例子之一。
澳洲拉籌伯大學的研究人員和南非、美國的同行合作，他們認為，這項發現支持直立人最早出現在非洲南部的說法。同一個地點先前出土的一塊兒童頭骨已經透露了這個可能，而這塊新化石第一次讓人看到成年直立人的樣子。
在德里莫倫，直立人並不孤單。他們和另一種人類近親——粗壯傍人——生活在同一片土地上。粗壯傍人有巨大的牙齒和強壯的下顎，專門用來咀嚼堅硬的植物。令人意外的是，化石顯示，當地粗壯傍人的數量是直立人的十倍以上。