Telltale Stone Tools Yield Clues

Other studies have yielded similar conclusions and demonstrated how important the much-wetter Sahara was to human beings as they developed the culture and technology that would eventually enable them to dominate ecosystems on every continent. For instance, mysterious nomads wandered across the Sahara Desert between 8,000 and 5,500 years ago, according to a National Science Foundation study conducted by Angela Close, a University of Washington anthropologist.

These Stone Age people apparently used cattle to move sandstone boulders from which they manufactured the stone tools they used to harvest the wild grasses that then grew in certain areas of the Sahara. Already, the stable, moist conditions that had sustained the freshwater snails had waned, but summer monsoons still brought the rainfall totals to about 8 inches (203 mm) a year—about the same as the present-day Sonoran Desert in North America, perhaps the lushest of all modern deserts (shown in the color insert on page C-7). Because the Sahara dried out during this time, the stone tools of these vanished hunters and gatherers remain scattered near the surface rather than buried or carried off by rain as they would have been anyplace else. Moreover, few people have ventured into the forbidding wasteland of the Sahara in the past 5,000 years, which means these clues to the past remain undiscovered on the surface.

Close found that the area around the Bir Safsaf oasis some 570 miles (900 km) southwest of Cairo was dominated by a series of great, sandcovered ripples extending for 100 to 500 yards and rising three to six feet (1–3 m) above the sandy plain. Between the ripples, the monsoon rains of that wetter desert collected. This nourished a summer crop of grasses in the depressions between these natural features. That combination of water and grass drew the nomads between 5,000 and 8,000 years ago as they struggled to make a living in the gradually drying desert.

Close realized that the scattering of stone tools might tell her a lot about the people who once lived there. She could tell that some were made of sandstone hardened by a dash of quartz, which had to come from outcroppings some 10 to 13 miles (16–21 km) away. Clearly, they had gone to great effort in hauling boulders of tool-making sandstone great distances to these ripples and depressions so they could chip off stone tools to harvest the grasses. She also found some tools made of flint, which had to have come from outcroppings 90 miles (145 km) away.

Close gathered up every single fragment of a stone tool plus every chip flaked off the larger boulders when making such tools within five square miles. She then fit those pieces of stone together like a giant jigsaw puzzle. She eventually collected 5,000 artifacts, which she spent years matching up with one another and with the boulders from which they had been chipped.

She concluded first that they had used cattle to haul their precious boulders. Moreover, the pattern of the tool scatter demonstrated that they spent their lives moving from one ripple to another, setting up camp alongside the low, water-catching spaces between the ripples and using their stone tools to harvest the grass. In effect, they were early wheat farmers. So the research shows a slow drying of the Sahara between 130,000 years ago and 6,000 years ago. However, some time between 4,000 and 6,000 years ago, the transition to today's harsh desert escalated dramatically.