for National Geographic News
The pharaohs of ancient Egypt owed their existence to prehistoric climate change in the eastern Sahara, according to an exhaustive study of archaeological data that bolsters this theory.
Starting at about 8500 B.C., researchers say, broad swaths of what are now Egypt, Chad, Libya, and Sudan experienced a "sudden onset of humid conditions." (See a map of Africa.)
For centuries the region supported savannahs full of wildlife, lush acacia forests, and areas so swampy they were uninhabitable.
During this time the prehistoric peoples of the eastern Sahara followed the rains to keep pace with the most hospitable ecosystems.
But around 5300 B.C. this climate-driven environmental abundance started to decline, and most humans began leaving the increasingly arid region.
"Around 5,500 to 6,000 years ago the Egyptian Sahara became so dry that nobody could survive there," said Stefan Kröpelin, a geoarchaeologist at the University of Cologne in Germany and study co-author.
Without rain, rivers, or the ephemeral desert streams known as waddis, vegetation became sparse, and people had to leave the desert or die, Kröpelin says.
Members of this skilled human population settled near the Nile River, giving rise to the first pharaonic cultures in Egypt (related feature: sample and download Egyptian music).
Gift of Pottery
The new study, which appears online today on the Science Express Web site, is based on painstaking research that combines new radiocarbon dating of about 500 artifacts from the region with data from past studies.
Kröpelin and study co-author Rudolph Kuper also collected geological climate data from countless ancient lakebeds, rain pools, and rivers.
Over the course of 30 years the researchers labored for months at a time in deserts where daytime temperatures sometimes topped 120° to 140°F (50° to 60°C).
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