New Delhi:
From the foothills of the mountains to the flowing streams, there are ancient signs that humans arrived in Asia earlier than thought, a new study by archaeologists in China says.
Ancient tools and bones were recently discovered in China by a research team of archaeologists which suggest that our earliest human ancestors left Africa and colonised Asia over two million years ago.
“Our discovery means it is necessary now to reconsider the timing of when early humans left Africa,” said Professor Robin Dennell from the University of Exeter in the UK, who was involved in the study.
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The research team was led by Professor Zhaoyu Zhu from the Chinese Academy of Sciences at a locality called Shangchen in the southern Chinese Loess Plateau.
They found that the oldest artefacts are 2.12 million years old and are 270,000 years older than the 1.85 million-year-old skeletal remains and stone tools from Dmanisi, Georgia, which were previously the earliest evidence of humanity outside Africa.
The artefacts, including a notch, scrapers, cobble, hammer stones and pointed pieces, show signs of use - the stone had been intentionally flaked. Most were made of quartzite and quartz that probably came from the foothills of the Qinling Mountains 5 to 10 kilometres to the south of the site, and the streams flowing from them.
Fragments of animal bones 2.12 million years old were also found.
The Chinese Loess Plateau covers about 270,000 square kilometres, and during the past 2.6 million years between 100 and 300 metres of wind-blown dust - known as loess - has been deposited in the area.
The 80 stone artefacts were found predominantly in 11 different layers of fossil soils which developed in a warm and wet climate.
A further 16 items were found in six layers of loess that developed under colder and drier conditions. These 17 different layers of loess and fossil soils were formed during a period spanning almost a million years.
This shows that early types of humans occupied the Chinese Loess Plateau under different climatic conditions between 1.2 and 2.12 million years ago.
The layers containing these stone tools were dated by linking the magnetic properties of the layers to known and dated changes in the Earth’s magnetic field.
The study was published in the journal Nature.
How humans migrated out of Africa about 60,000 years ago
Our ancestors, according to previous studies, migrated out of Africa about 60,000 years ago as the climate changed from wet to very dry.
Genetic research shows people migrated from Africa to Eurasia between 70,000 and 55,000 years ago.
Previous studies suggested that the climate must have been wetter than it is now for people to migrate to Eurasia by crossing the Horn of Africa and the Middle East.
"There has always been a question about whether climate change had any influence on when our species left Africa," said Jessica Tierney, associate professor of at the University of Arizona in the US.
"Our data suggest that when most of our species left Africa, it was dry and not wet in northeast Africa," said Tierney.
Researchers found that around 70,000 years ago, the climate in the Horn of Africa shifted from a wet phase called "green Sahara" to even drier than the region is now. The region also became colder.
They traced the Horn of Africa's climate 200,000 years into the past by analysing a core of ocean sediment taken in the western end of the Gulf of Aden.
The study was published in the journal Geology.
With inputs from agencies
