SHARJAH // Archaeologists have discovered ancient artefacts in Sharjah that may rewrite the history books on human migration.
Ancient stone tools excavated from a dig site in Jebel Faya suggest that early humans may have emerged from Africa around 50,000 years earlier than previously thought.
Until now it was believed humankind left Africa around 60,000-70,000 years ago. The new data, published yesterday in the US journal Science, pushes the departure date to around 125,000 years ago.
"These findings will stimulate a re-evaluation of the means by which modern humans became a global species," said Simon Armitage, co-author of the study and a lecturer in the department of geography at Royal Holloway, a college at the University of London.
"This is really quite spectacular," said Michael Petraglia of the University of Oxford, an archaeologist who also specialises in human migration. "It breaks the back of the current consensus view."
The findings are the conclusion of an eight-year excavation led by Hans-Peter Uerpmann, a professor from Tubingen University in Germany.
Researchers uncovered a series of Palaeolithic stone tools, such as small axeheads, scrapers and notched tools called denticulates.
The tools are similar to tools produced by early modern humans in east Africa but different from those made in the Levant and the mountains of Iran, leading scientists to believe our ancestors migrated directly into Arabia, rather than via the Nile Valley and the Near East, as is usually suggested.
"The big question this leaves is when did humans migrate out of Africa, and what caused them to make that move?" Dr Armitage said.
Dr Armitage dated the Jebel Faya tools using a technique called luminescence, which determines when materials were last exposed to light.
Most researchers believe modern humans left Africa no more than 70,000 years ago, but Armitage and Uerpmann said those conclusions, which are primarily based on genetic dating, are "fairly controversial" in the scientific community.
Anatomically modern humans are known to have evolved in Africa between 200,000 and 150,000 years ago. The "Out of Africa" theory hinges on the supposition that these humans then migrated across the world, replacing earlier human forms such as the Neanderthals.
The newly discovered stone tools, which were unearthed at Jebel Faya between 2003 and 2010, bolster a new theory on the migration of humans, because the tools are similar to the ones made in East Africa during that time period and are different from tools discovered further south on the Arabian Peninsula.
The proposed migration would have been possible only during a narrow time frame in history, experts said. About 130,000 years ago, sea levels were approximately 100 metres lower than they are today, and the Nejd Plateau was passable.
"There was a brief period where modern humans may have been able to use the direct route from east Africa to Jebel Faya," said Adrian Parker, a professor of geography at Oxford Brookes University.
Jebel Faya, now a 10-kilometre long limestone mountain outlier, at that time may have been a savanna, with water bodies and vegetation.
"Once humans had crossed into southern Arabia, this migrant population would have experienced decreased predation and competition for resources," Mr Uerpmann wrote in the study, entitled "The Southern Route 'Out of Africa': Evidence for an Early Expansion of Modern Humans into Arabia."
The researchers aren't sure where the population moved after inhabiting Jebel Faya, but the team believes they may have continued across the Arabian Gulf, via a land connection between southeastern Arabia and Iran, and on to India and Indonesia.
In September, Dr Petraglia theorised that modern humans may have emigrated from Africa more than 70,000 years ago, after he discovered tools in Saudi Arabia and India.
"It is a remarkable fact that, until now, nobody has looked at what I believe is the pivotal part Arabia played in the overland migration of humans," he said.
Most experts believe modern humans travelled up the Nile Valley before moving north to Asia and Europe about 60,000 years ago.
Remains found at the Skhul and Qafzeh caves in Israel date back to between 120,000 and 80,000 years ago.
But many experts believe these modern humans either died out or went back to Africa, because fossils found after this period are primarily Neanderthal.
More research will be done in this field, as Dr Petraglia leaves this month to continue work in Saudi Arabia, and "other archaeologists plan to comb Arabian caves and sands for signs that our ancestors passed this way", according to the journal Science.
Not everyone in the research community is convinced. Paul Mellars, an archaeologist at the University of Cambridge, told Science he believed the team's conclusions were flawed.
"I'm totally unpersuaded," Mr Mellars said. "There's not a scrap of evidence here that these were made by modern humans or that they came from Africa."