American Scientist

To the Editors:

It was with great pleasure I read the article "Ancient Lakes of the Sahara" (January-February) by Kevin White and David J. Mattingly.

In the mid-1980s, I produced a dissertation at the University of Kansas which, as part of its study, compared the intensity of world desert regions and encompassed a review of climate-change evidence over what I identified and termed the "Saharasian Desert Belt." The shift from relatively moist to arid conditions which was recorded in the Sahara was generally reflected in climate-change records over a much larger territory, ranging across North Africa, the Middle East and into Central Asia as well, thus the term "Saharasia."

Evidence is clear for previously moist conditions across nearly all of Saharasia prior to circa 3000 B.C.E., with large lakes and year-round rivers, as well as a vast semi-forested grassland thick with large and small animals, to include fish, crocodile, hippo, elephant, lion, giraffe, equines, bovines and so forth, upon which early humans hunted and thrived. The drying up of Saharasia, which appears earliest in the region encompassing the dry core of Arabia, continues across the Levant and into Central Asia, started around 4000-3500 B.C.E., possibly as early as 5000 B.C.E. in a few spots, but with North Africa and the more peripheral areas of the Western Sahara and Gobi drying out only later on—I haven't seen anything since my original 1986 publication that would significantly alter those conclusions.

What is most remarkable, however, is the change in human subsistence, settlement, migration and even behavior patterns (related to early childhood, status of women, family life and social violence) that attended the massive climate change. For those early peoples it could only be termed a giant climatic disaster that progressively destroyed their subsistence, sometimes in a dramatic manner, with the quick appearance of extreme multi-year droughts, and often leading to widespread famines, starvation, social collapse and forced migrations. The Garamantes were notable for their finding a way to survive this climate change—most other human societies were not so fortunate. It was the largest single climate-change episode to occur on the planet since the end of the Pleistocene glaciation, and it profoundly affected early Homo sapiens and human social existence.

James DeMeo
Ashland, OR