Photograph by Scott DeGraw, NGS
High atop a dusty plateau on the Arabian Peninsula, archaeologist Jeffrey Rose picked up a rock, saw something surprising, and started asking questions that could change history. His unusual discoveries in southern Oman help shape new theories about when early humans may have exited Africa, who those pioneers were, and what route they took on the first stage of their journey to every corner of the Earth.
In the late 1990s geneticists identified mitochondrial DNA signatures suggesting that the first humans to leave Africa may have traveled through Ethiopia to Yemen and Oman. Scientists theorized they were beachcombers who followed the coastline. Rose arrived in the area, eager to test the theory that Arabia was the gateway out of Africa by searching for archaeological evidence. "We surveyed for years," he recalls. "Stone Age artifacts littered the landscape; virtually any place I stopped the car, I found a Paleolithic site. But none of it showed a connection to Africa; and along the coast we found no evidence of humans at all."
He and his international team of scientists returned to Oman in 2010, and on the final day of their surveying season, at the last site on their list, "we hit the jackpot." The find was a very specific stone tool technology used by the "Nubian Complex," nomadic hunters from Africa's Nile Valley. Nubian technology is a unique method of making spear points that was previously only known from North Africa. Rose's team ultimately discovered over a hundred workshop sites where these artifacts were manufactured en masse. "It was scientific euphoria," he describes.
The Nubian origin and inland location of the discovery were equally unexpected. "We had never considered the link to Africa would come from the Nile Valley, and that their route would be through the middle of the Arabian Peninsula rather than along the coast," Rose notes. "But that's what the scientific process is all about. If you haven't proven yourself wrong, you haven't made any progress. In hindsight, the Nubian connection makes perfect sense. The Nile Valley and Oman's Dhofar region are both limestone plateaus, heavily affected by perennial rivers. It's logical that people moved from an environment they knew to another one that mirrored it. At the time when I'm suggesting they expanded out of Africa, southern Arabia was fertile grassland. The Indian Ocean monsoon system activated rivers, and as sand dunes trapped water, it became a land of a thousand lakes. It was a paradise for early humans, whose livelihood depended upon hunting on the open savanna."
Accurately dating Rose's Nubian discovery was made possible by optically stimulated luminescence (OSL) technology, which can determine the last time a single buried grain of sand was exposed to light by measuring the amount of energy trapped inside of it. The technique revealed the tools to be 106,000 years old, exactly the same time the Nubian Complex flourished in Africa. This also means Rose's theory places the first exit from Africa much earlier than previously believed. "Geneticists have shown that the modern human family tree began to branch out 60,000 years ago. I'm not questioning when it happened, but where. I suggest the great modern human expansion to the rest of the world was launched from Arabia rather than Africa."
Rose's passion for the past extends beyond fieldwork to how science can be shared with the public. "A few years ago, I was going through an incredibly dramatic wadi (valley) in Oman, hours off the beaten track, and I thought, wouldn't it be great if we could share this place with other people, I bet they'd love to see this." He began shooting short videos every few days and chronicling his work via Twitter updates and website posts. "You can't put into words how unique the landscape here is. Arabia feels like this romantic lost world filled with mysterious ruins; it's a living museum of artifacts. Everyone on Earth had ancestors who passed through this place; why wouldn't you want to show it to people?"
"I'm like a kid in a candy store, there's so much to learn; and now we have so many ways to disseminate information—the Internet, blogs, myriad TV channels, documentaries—it's all making science more interesting, digestible, and relevant to the public," he says. "There's no reason for archaeology and history to be stuffy. How could you not want to know how you got here? It's been said that there's more diversity within a group of 55 chimpanzees than in the entire human population. I think if we help people conceptualize how tiny the genetic distance is between them, it might even help bridge some of the tensions in our world today."
Trying to explain what keeps him based in a desert truck stop, digging through sand, and lugging 100-pound loads of rocks in 100-degree heat, Rose says, "It's like an itch you absolutely have to scratch. An answer you have to find. Who lived here? What were they doing? Are these the people who went on to colonize the entire world? Now that we know it was the Nubians who spread from Africa, I want to know why them in particular? What was it about their technology and culture that enabled them to expand so successfully? And what happened next? That's one of the defining characteristics of our species—we've always looked to the beginning and wanted to understand how we got here. That's what it means to be human."
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