Anthropology.net

Hat tip to Christine Kenneally who pointed out this research on climate change, “East African megadroughts between 135 and 75 thousand years ago and bearing on early-modern human origins,” published in PNAS. This is excellent research that comes right on the coat tails of this recent post.

Christopher Scholz and colleagues studied deep sediment cores from Lake Malawi in Africa and found evidence to suggest that the transition from a long dry period susceptible to extreme drought to a stable, wetter climate may have stimulated the expansion and migration of early human populations.

The authors say that a series of megadroughts occurred in the region around 135,000 to 75,000 years ago and they caused extreme drying of Rift Valley Lakes. During the most severe drought periods, Lake Malawi’s water volume was reduced by at least 95 percent while water levels fell to below 15 percent current levels. Other African lakes dried out completely and populations of African plant and animal populations fluctuated dramatically. The cores show that around 70,000 years ago, the climate stabilized and became much wetter, evidently creating conditions favorable for human populations, which expanded and eventually spread out across the globe. The authors write,

“Such climate change may have stimulated the expansion and migrations of early modern human populations.”

The results appear to support the “Out Of Africa” theory the humans arose in Africa and subsequently colonized the world during one or more migrations rather than the multiregional hypothesis for human evolution.

Jason Ur, Philip Karsgaard and Joan Oates write in the August 31st issue of Science, that ancient cities did not form because of a centralized political power, as commonly believed, but as the outgrowth of decisions made by smaller groups or individuals. Their paper is titled, “Early Urban Development in the Near East.”

Jason Ur comments,

“The results of our work show that the existing models for the origins of ancient cities may in fact be flawed. Urbanism does not appear to have originated with a single, powerful ruler or political entity. Instead, it was the organic outgrowth of many groups coming together.”

What they did to understand patterns of population growth in the early urban areas, was to survey the spatial distribution of artifacts at Tell Brak, an ancient pre-Akkadian and Akkadian city on the Khabur River in northeastern Syria. The site is now distinguished by a 40 meter high and 1 kilometer long mound and is one of the tallest archaeological mounds in the Middle East. It forms the remains of one of the largest urban sites in northern Mesopotamia. The work was based on observation of surface objects at the site, along with satellite imagery and GIS spatial analysis. To your right is an aerial photo of Tell Brak showing how ancient roads radiate from Tell Brak suggesting that the settlement was an important city. The surface artifacts included bits of broken pottery and other ancient garbage, which indicate where the inhabitants of the city lived. In this survey, the patterns of distribution of these objects were examined over an 800-year period.

According to the survey of distribution of artifacts, around 4,200 BCE the “central mound” was suddenly surrounded by these clusters, suggesting immigration to the city. These clusters were separated from one another, indicating social distance among the groups, possibly because the social mechanisms that allow strangers to live together in an urban environment had not yet evolved. The patterns of settlement and distance from the “central mound” also signified autonomy from the political center of the city.

The theory of a singular leader as the catalyst for urbanization has been widely supported in part because it is reinforced by the story of Gilgamesh, who “built” the city of Uruk. Uruk, located in what is today southern Iraq, had been considered the world’s oldest city. The field survey, along with recent related excavation by the University of Cambridge, has shown that the urban development of Tell Brak was concurrent with, or may have been earlier than, the development of Uruk.

Ur comments,

“Ours is a largely urban society, and the nascent urbanization of Tell Brak tells us about the formation of the very first cities in the world.”

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