The Incredible Human Journey (13 page)

When you’ve got information coming in from so many different areas of science, from archaeology, from studies of skull shape, from reconstruction of ancient environments and from genetics, perhaps it’s not surprising that there are different views, and it may take a long time for a consensus to be reached. But each new bit of evidence adds to the picture and helps to make it clearer. There are still missing pieces in this puzzle, and it seems that the debate about routes out of Africa won’t be settled until more hard, archaeological and fossil evidence emerges from North Africa and the Levant, and from what, at the moment, is a mysterious, big black hole: Arabia.

An Arabian Mystery: Oman

Political unrest in South Arabia has meant that Palaeolithic archaeology has been very low on the agenda in the countries that form a potential ‘Arabian Corridor’, from Bab al Mandab, along the coast between the Red Sea and the Persian Gulf.
¹
Yemen, in the west, was embroiled in civil war until the mid-nineties, and Oman, to the west, only opened its doors to outsiders in 1970.

One of those outsiders who had recently been tramping around the dry, desert landscape of Oman looking for traces of early human occupation was archaeologist Jeff Rose. I flew into Muscat and then on, across a vast, rocky, desert plain, to Salalah, in the Dhofar region, and there I met Jeff. He was fascinated by Arabia and the Gulf region. His obsession with Sumerian legends was evident, not only from his conversation, but by the fact that he appeared to be liberally covered in them, in the form of colourful tattoos. But it was prehistory that had drawn him to Oman. The scarcity of well-dated evidence from the Middle Palaeolithic of South Arabia, and its crucial position and relevance to the debate about routes out of Africa, made it irresistible to Jeff .

As far as modern human fossils are concerned, there are none at all in Arabia, and the earliest ones from the Indian subcontinent date to later than the colonisation of Australia. There
are
collections of Middle Palaeolithic tools from Arabia, but the dating of these is uncertain and there’s nothing to mark them out as modern human. These tools could have been made by
Homo sapiens
, but, equally, they might have been manufactured by previous, archaic species.
²
To make things even more difficult, many of these collections of stone tools have been discovered lying on the surface of the ground, and so they are practically impossible to date.

Jeff and I drove north from Salalah, up into the rocky desert of Djebel al-Qara. Turning off the road, we headed into the desert landscape, dotted with rocky outcrops and frankincense trees. Jeff spotted a darkish area on one raised area of rock and we alighted and climbed up it to investigate. The ground was littered with angular, dark brown stones. And they weren’t just any old stones. Most of those I stooped to examine had been flaked and shaped, not by natural processes but by humans. It seemed amazing to me to have driven into what seemed like the middle of nowhere, into a dry and unwelcoming landscape, and find this evidence of early human activity just lying there, on the surface of the ground. ‘Pretty much anything you pick up here has been created by humans in the past,’ said Jeff, reaching for what looked just like any old stone from a distance, but, on closer inspection, proved to be yet another lithic. ‘Look at this, for instance. You can see where it’s been flaked. It’s a burin – like a chisel – for working softer materials like wood, hide or bone.’

Then he spotted a larger, more angular pebble. ‘This one’s a core – and they would have struck it like this to remove slivers of stone.’ He held the core and imitated the action, without actually hitting the stone. ‘Cores are important because they show us how they made their stone tools. And this technique is very distinctive. This is a blade core: it’s been used to make long, thin blades.’ We went on, scanning the ground for stones. It seemed every other stone was worked. I found one of the thin blades that had been made from a core like Jeff had showed me.

I asked Jeff how old he thought these tools might be. ‘It’s hard to say. It’s a surface site so it’s impossible to be specific about dates. But based on the type of technology, it could be anywhere from 12,000 to 70,000 years old, maybe even older. There was a site found recently on the coast of Yemen, with similar technology, that was dated to 70,000 years ago.’

It is very difficult to argue for the presence of modern humans based on the style of undated stone tools, but archaeological deposits in caves and filled-in basins have been reported in Arabia, if not in detail, and this made Jeff hope that there was good, datable archaeology to be found in Oman.
³

It was hard to believe that people could have survived in the desert, though. Today, most of southern Arabia is desert, with the vast Rub’ al-Khali sand sea filling the interior. But Jeff was very keen to show me that not all of Oman was dry, all of the time, even today. We drove east from Salalah and headed inland to the Wadi Darbat. As we drove, the landscape suddenly changed, from rocky desert … to a verdant oasis. We were there at the end of the rainy season, and the monsoon had filled the wadi with a turquoise river, fringed by lush grassy meadows, framed by green, wooded slopes. Herds of cows and camels shared the pasture and the cool waters. But this was temporary; during the dry season, the greenness would fade back to desert, and plants would lie dormant, waiting for the next summer’s rains.

The verdant green valley of Wadi Darbat reminded me of south-west France. It seemed as though I’d been magically transported away from the hot and unforgiving desert that characterises most of Oman, even during the rainy season, to an idyllic valley full of plant and animal life. The desert had been almost silent. But here the air was full of the sound of birdsong. Life abounded. And it all came down to the presence of water.

It wasn’t just the greenery that reminded me of the Dordogne. Up on those wooded slopes were huge rockshelters. They looked like good places to start looking for traces of human habitation. Jeff knew that stone tools had been found in some of them, and they were exactly the type of site where ‘good archaeology’, sealed in layers of sediment and datable, might be discovered. I could see why Jeff found Oman so exciting: there was so much promise here, and the chance to find the answers to so many open questions.

The transmutation of desert to a green Eden is a seasonal occurrence in Wadi Darbat. But just such a transformation, across vast swathes of South Arabia, has happened at various times in the deep past. Looking back into the Pleistocene, the environmental state of the region has fluctuated, depending on the intensity of the monsoon rains. Marine cores from the ocean around Arabia show that monsoons became heavier at the onset of interglacials, as ice sheets retreated and ocean surface temperatures increased. At the beginning of the last interglacial, about 130,000 years ago, there was a dramatic increase in the amount of rain falling on South Arabia, lasting for about 10,000 years. There was another peak in rainfall at the end of OIS 5, between 78,000 and 82,000 years ago.
^4
,
5
And at those times, South Arabia would have become a very agreeable place in which to live.

Sites like the one we had visited in the desert were difficult to understand until I started to think about how much the environment had changed over time. In Oman, there are a number of sites where scatters of stone tools have been found on what is now a bone-dry landscape, but which would have been well watered during interglacials. Many sites are close to ancient, but now dry, wadis or river channels, and relict lakes, which would have been full of water during interglacials.
^3
,
6

Many of the Arabian Middle Palaeolithic stone tools are small oval or leaf-shaped bifaces, which look as though they have been flaked using a soft hammer. Oxygen isotope stage 6 would have been too dry for any humans, archaic or modern, to survive in Arabia, so when conditions improved in OIS 5, the biface-makers must have moved into the region from a neighbouring area: from refugia in the Levant, in East Africa, or in the Zagros Mountains. The closest technological link is to East Africa; there are no tools anything like the Omani ones in collections of Mousterian tools from the Levant or Zagros Mountains.
⁶

The fauna of southern Arabia shows links with Iran and Pakistan to the east, and with Africa to the west. Baboons, indigenous to the arid uplands of Ethiopia and Somalia, are also found in Yemen. Baboon mtDNA lineages suggest that they originated in East Africa between 50,000 and 150,000 years ago, and later migrated into Arabia.
^1
,
4
(So baboons appear to have migrated via the southern route, without boats, presumably making their way around the coast of the Red Sea.)

Many sites around South Arabia may lie beneath seas: either under the Rub’ al-Khali sand sea inland, or submerged under the Arabian Sea as the oceans have risen. Jeff was particularly interested in the idea of a submerged coastal plain where humans could have lived. Yemen and Oman may have been liberally doused with monsoon rain when interglacials arrived, but even during glacial periods it seems that there may have been enough water for humans (alongside other flora and fauna) to exist, along the coast. Because underwater, but close to the coast of the Arabian Sea and the Persian Gulf, there are submerged freshwater springs. ‘One of the strangest things about Arabia is that we have this completely arid landscape, and yet beneath the surface there’s heaps of fresh water, running towards the coast and coming up under the sea,’ Jeff explained. ‘If you were to dive down with a canteen you could fill it up with fresh water and have a drink.’

When sea levels were lower during glacial periods, these springs would have watered the exposed coastal plains, creating a long oasis stretching along the southern coast of Arabia from Yemen to the Gulf.
⁴
This means that when sea levels dropped, reducing the Bab al Mandab gap to some 11km, there would have been this coastal oasis on the other side. So, for Jeff, the Red Sea was not a barrier to human migrations but a conduit between Africa and Arabia. And, indeed, Middle Palaeolithic tools have been found at sites along the eastern coast of the Red Sea.
³

The Arabian oasis ran right along the southern coast and up into the large plain that is now the Persian Gulf. ‘It’s the shallowest inland sea in the world, just 40 metres deep, so when the sea level was lower the entire area was an exposed flood plain – a beautiful verdant paradise,’ Jeff enthused. ‘It sounds idyllic,’ I said. ‘Well – the Sumerians called it “Eden”,’ he replied.

The Gulf Basin would have received water from underground aquifers, welling up as springs, from the Tigris and Euphrates rivers, and from rivers flowing down from the Zagros Mountains to the east. All this water would have flowed into a great river which ran down the length of the Gulf Basin; topographical studies of the seabed, or bathymetry, have shown the wide, deep groove created by this ancient waterway. So Jeff argued that, between 115,000 and 6000 years ago, the Gulf Plain would have formed a refugium where humans and other animals could have survived, even while harsh and arid conditions prevailed elsewhere.
⁴

Studies of the palaeoenvironment of Arabia are fascinating. It seems that there would have been favourable habitats for humans to exploit there during both interglacials, with the monsoon rains greening the Arabian deserts, and, at the height of glacials, where the interior would have been incredibly arid, the exposed coastal plains would have been kept oasis-like by freshwater springs.

But none of this means that the southern route and the Arabian Corridor
were
used as the main or only route out of Africa for modern humans. The Middle Palaeolithic archaeology of Arabia shows someone was there, but it really is impossible to pin down whether it was
Homo
sapiens
,
heidelbergensis
or
neanderthalensis
on the basis of the currently available evidence.
³
It seemed that Jeff had his work cut out for him.