Out of Africa, into China
Tools discovery pushes back hominin migration, calling current theories into question. Andrew Masterson reports.
The timing of hominin dispersal out of Africa needs to be re-examined, according to a team of Chinese archaeologists who present evidence that human ancestors reached China much earlier than thought.
In a paper published in the journal Nature, Zhaoyu Zhu from the Chinese Academy of Sciences and colleagues reveal more than 100 artefacts unearthed from 17 sediment layers at a location known as Shangchen on the southern Chinese Loess Plateau. The oldest of these dates to 2.12 million years ago – making it the earliest hominin find outside Africa by more than a quarter of a million years.
Until this find, the earliest evidence for hominin presence beyond Africa came from Dmanisi in Georgia, where in 2011 bones and stone tools including flakes and choppers were dated to just after 1.85 million years ago.
The next two earliest finds were both discovered in southern China, in the same broad area as the new artefacts. They comprised two teeth, tentatively identified as coming from Homo erectus, and a skull, conclusively identified as belonging to the same species. They dated from 1.7 and 1.63 million years ago, respectively.
The latest finds comprise 88 stone flakes and another 20 unmodified stones, all thought to have been used as tools. They include scrapers, points, borers and possible hammers.
The 17 sediment layers account for two quite different types of climate-determined environments. Most of them formed during warm and wet periods, while six were classified as “loess”, a type of sediment that forms from accumulated wind-blown dust indicative of colder and drier environments. The artefacts were much more common in the former than the latter.
Altogether, the evidence suggests that Shangchen was occupied by hominins repeatedly – although not necessarily continuously – for about 850,000 years.
Zhu and colleagues say that the finds imply that members of the genus Homo “had left Africa before the date suggested by the earliest evidence from Dmanisi”.
They conclude: “This makes it necessary to reconsider the timing of initial dispersal of early hominins in the Old World.”
In a commentary included in the same issue of Nature, anthropologist John Kappelman from the University of Texas at Austin, US, says that the journey of hominins across 14,000 kilometres from Africa to Asia “represents a range expansion of dramatic proportions”.
However, he adds, even at a dispersal rate of just five to 15 kilometres a year – “a value well inside the daily foraging range of modern hunter-gatherers” – the distance could have been covered in as little as 1000 years.
Zhu and his colleagues have made a valuable addition to the tale, he says, but the current archaeological record and the dating techniques currently available “are not sufficient to resolve a dispersal event of such potential speed”.