If correctly dated, the find means that hominins – the group of humans and our extinct forefather species – left Africa earlier than archaeologists have been able to demonstrate thus far, a team reported in the scientific journal Nature.
“Our discovery means that it is necessary now to reconsider the timing of when early humans left Africa,” said study co-author Robin Dennell of Exeter University in England.
Hominins are believed to have emerged in Africa more than 6m years ago. They left the continent in several migration waves starting about 2m years ago.
The first migrants were likely members of the species Homo erectus (upright man) or Homo ergaster (working man) – extinct predecessors of our own group, Homo sapiens (wise man), which first emerged about 300,000 years ago.
The oldest known African fossil attributed to a member of the Homo family is a 2.8m-year-old jawbone from Ethiopia.
Previously, the oldest evidence for hominins in Asia came from Georgia in the form of fossilised skeleton bits and artefacts dated to between 1.77m and 1.85m years ago.
There have been other, unproven, claims of even older fossil discoveries, the study authors said.
The latest find of 96 stone tools, was extracted from 17 layers of sediment in the southern Chinese Loess plateau.
Dennell and a team used a field of science known as “palaeomagnetism” to date the sediment layers. These form when dust or mud settles before being capped by another new soil coat. Any artefact found within a layer would be the same age as the soil around it.
Dennell and a team measured the magnetic properties of minerals in the soil layers to determine when they were deposited.
This dated the tools, of a type known to have been manufactured by Homo species in Africa since at least 3.3m years ago.
The paper offers strong evidence for a hominin presence in Asia further back than we thought, Dennell said.
“There may be older evidence in places like India and Pakistan, but so far ... the evidence is not strong enough to convince most of the research community,” he said. “With this type of claim, for an early human presence in a region, the evidence has to be absolutely watertight and bombproof.”
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