Green Arabia's key role in human evolution

By Sylvia Smith
BBC News, Saudi Arabia

image copyrightAFP
image captionWhilst the interior of the Arabian Peninsula is dry today, it was once lush and green

Scientists have been illuminating the vital role played by the Arabian Peninsula in humankind's exodus from Africa. Far from being a desert, the region was once covered by lush vegetation and criss-crossed by rivers, providing rich hunting grounds for our ancestors.

As the sun rises over a vast sand sea in the Arabian Peninsula its first rays illuminate a number of hand axes scattered over the surface of the arid desert.

Nearby, a team of international experts start their day's work picking up and examining remains that are putting a new gloss on the history of human occupation in the area and challenging previously-held theories.

For the first time, the technical expertise of scientists in varied disciplines including palaeontology, geochronology and mapping is being combined to take a holistic look at the role played by Saudi Arabia in the African exodus.

Recent finds are overturning long-held theories by moving it from the periphery right to the centre.

According to Prince Sultan bin Salman bin Abdulaziz, the first Arab to go into space and currently head of the Saudi Commission for Tourism and National Heritage, the multidisciplinary team have uncovered evidence that our human ancestors' first steps out of Africa were made 50,000 years earlier than was commonly believed.

"The Arabian Peninsula has witnessed dramatic changes in climate," he says.

"In the middle Pleistocene this encouraged early man to make for the then-green peninsula as his destination."

image copyrightCrassard et al. 2013
image captionScientists have mapped the ancient river systems that criss-crossed what is now desert

Wet environment

New research by the international team of experts shows that the Peninsula had human settlements for long periods of time and was not merely a transit point, as was previously thought.

The teams have uncovered several settled periods of wet weather with numerous shifts in environments over the last million years.

One advantage of marrying diverse disciplines under one umbrella is that the various strands can be woven in to a comprehensive common story about the mutating Arabian environment and human history.

What appear to be large dried-up water courses when seen from the ground become major palaeo-rivers viewed from space.

Michael Petraglia, who heads the group and is professor of human evolution and prehistory at the School of Archaeology, Oxford University, says the multidisciplinary approach is paying off.

"Innovative space shuttle technology has allowed the mapping of over 10,000 lakes across Arabia including the now barren Nafud desert," he says.

"This finding links directly with the discovery of the remains of elephants, hippos, crocodile and molluscs at a couple of our sites in the Kingdom."

image copyrightRichard Duebel
image captionProf Michael Petraglia is uncovering a rich history of settlement by early modern humans

Exit plan

Indications are that the earliest lakes had fresh, potable water and were in some cases interconnected. The 50-strong team now believe that there were real routes for animals and humans to follow.

While the main routes into Arabia were from the Horn of Africa into south-west Arabia, the other was across the Sinai. From those two points it is believed that humans were following rivers into the interior.

Ali Ibrahim Al Ghabban, deputy director of the Saudi Commission on Tourism and National Heritage says that with no human skeletal remains in Arabia from the time ranges in question, human history depends on other evidence.

image copyrightRichard Duebel

"[It is assessed] on the basis of similarities in stone technology between finds in Arabia and Africa," he says.

"It is reasonable to suppose that anatomically modern humans have been present in Arabia for at least 125,000 years, and possibly a little longer."

Most of the early sites consist of little more than stone tool scatters, and Prof Petraglia's team have unearthed hundreds of these implements fashioned for activities associated with hunting such as scraping skins.

This is a significant stage in human evolution with our forebears showing the ability to think ahead.

"It means that at this stage we are able to kill our prey more easily," says Prof Petraglia. "Working stone in this way indicates forethought and planning. It is also what we see in East Africa."

Among the group of experts are rock art specialists whose work, according to Ali Ibrahim Ghabban may well lead to yet more interesting results.

Rock art sites occur in central Saudi Arabia at the Jubbah palaeolake in the Hail region, where there is excellent evidence for Middle Palaeolithic sites along lake shores.

"These sites are of global importance," Ghabban says.

"They are the signatures of modern humans moving out of Africa."

Other field expeditions are looking into world-rated rock art sites in Jubbah, Shuwaymis, and Nejran, with finds examined in multiple laboratory studies.