Earliest evidence of humans outside Africa

Scientists say they've found the earliest evidence of a human presence outside Africa.

Ancient tools discovered in China suggest primitive humans were in the region as early as 2.12 million years ago.

They are about 270,000 years older than the previous earliest evidence, which consists of bones and stone tools from Dmanisi in Georgia.

The research, by a Chinese-British team, appears in the journal Nature.

The stone artefacts were discovered at Shangchen on a plateau in northern China.

They comprise different types of stone tools constructed for a variety of purposes. All show signs of having been used.

Most were made of quartzite and quartz rock that probably came from the foothills of the Qinling Mountains, five to 10 km to the south of the dig site.

But we don't know which human species made them.

Why does it matter?

Humans left Africa at many times during their history. Living people outside Africa, for example, trace their origins to an exodus that occurred 60,000 years ago.

But there had been no evidence of human occupation in Eurasia until the Dmanisi evidence at 1.8 million years ago.

Co-author Prof Robin Dennell, from the University of Exeter, UK, said: "Our discovery means it is necessary now to reconsider the timing of when early humans left Africa."

Africa has traditionally been seen as the engine of human evolution - where key species arose before spreading out through the rest of the world.

However, some scientists have proposed a more important role in this story for Asia. With these new finds, some researchers will wonder how much further back the human story goes in Asia.

Sites where evidence of human presence has been found

Changing climate

Writing in Nature, palaeoanthropologist John Kappelman, who was not one of the authors on the new study, commented: "The roughly 14,000-kilometre trek from eastern Africa to eastern Asia represents a range expansion of dramatic proportions.

"The dispersal of hominins was probably facilitated by population increases as they moved into new territories and filled empty niches."

Some 80 artefacts were found in fossil soil that developed in a warm and wet climate. A further 16 tools were found in fossil soil that came from times when it was colder and drier.

The discovery shows that early forms of human were able to survive on the Loess Plateau in northern China under a variety of climatic conditions.

Dr Kappelman, from the University of Texas, Austin, explained: "The hominin dispersal probably occurred under the variable climates of the Pleistocene ice age. Does a migration to higher latitudes suggest the evolution of behavioural adaptations to colder climates? Perhaps.

"Rather than maintaining a continuous occupation of the Loess Plateau, the hominin population might have increased or dwindled, depending on the climate."