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PALAEOANTHROPOLOGY
Re-evaluation of the age of Zhoukoudian, a prominent site of Homo erectus occupation in China, prompts a rethink of the species' distribution in both the temperate north and the equatorial south of east Asia.
The Zhoukoudian cave system, discovered in 1918 near the outskirts of modern-day Beijing, is one of the prize sites in palaeoanthropology (Fig. 1). It has produced a long sequence of well-preserved Homo erectus fossils and stone tools, unique in northeast Asia, that have been dated variously to between 0.4 million and 0.6 million years (Myr) ago. In their report on page 198 of this issue, Shen and colleagues1 push back the age of Zhoukoudian's lowest occupation level to 0.78 Myr ago. The new age estimate is consistent with the cold-climate fauna found within the locality's lowest levels, and it also correlates with revisions in the regional chronology of H. erectus sites2-6. Overall, the recent studies suggest that the onset of glacial cycles brought the open-land habitats in which H. erectus thrived.
The first fossils of H. erectus were found at Trinil in Java, Indonesia, in 1892 by Eugène Dubois. It was Dubois who coined the name 'erectus', based on a thigh bone that indicated upright posture7. Homo erectus had a heavily armoured and thickened skull, with an adult brain size in the 650-1,250-cm^sup 3^ range8 - the equivalent value for modern humans (H. sapiens) is 1,100-1,800 cm^sup 3^. Homo erectus stood 145-180 cm tall9, walked fully upright with a modern-like human footprint10, and used stone tools. The species is easily distinguished from H. sapiens by its distinctive torso, which was much more barrel-shaped and larger in volume11.
Fossil evidence now points to an origin of H. erectus about 2.0 Myr ago in equatorial Africa, followed by dispersal northwards and eastwards into Eurasia8. Incontestable evidence of that dispersal comes from the site of Dmanisi (Trans caucasia, Republic of Georgia) at 1.75 Myr ago and from southeast Asia (Java) by 1.6 Myr ago. Homo erectus survived to as late as 0.35 Myr ago in continental east Asia, and isolated populations persisted longer on the Indonesian archipelago. One group on Java, commonly known as 'Solo Man', may have survived until 50,000 years ago12.
As far as east Asia is concerned, Zhoukoudian has...