CREDIT: Oak Ridge National Laboratory
This week’s post is focused upon the Sahara Desert because DNA theory traces anatomically modern humans back to Africa, and the cyclic climatic behavior of the Sahara leads to the Sahara Pump Theory. This theory applies to human and animal movements out of Africa and into Asia and Europe, and from there throughout the world. I strongly suggest you invest the time to read the preceding Sahara and DNA articles. I can add nothing to them in making that point.
Now, let’s note that the paleoclimate of the Sahara at the Last Glacial Maximum (26,500 BP) as shown in the map and its legend below as “Tropical Extreme Desert.”
The most recent cycle of the Saharan pump is best illustrated in the following four maps of the Sahara from 8500 BC (10500 BP) to 3500 BCE (5500 BP). Note the color-coded rainfall legend in Map A applies to all four maps. Also note that before 8500 BC (Map A) rainfall was equal to or less than 50 mm/year. In Map B from 8500 BC (10500 BP) until 7000 BC (9000 BP) rainfall in the different regions ranges from 50 mm to 450 mm. In Map C from 7000 BC to 5300 BC, the rainfall still ranges from 50 mm to 450 mm but is starting to decrease as indicated by the shift to the south of the borders of the heavier rains. In the last Map D, we see that the drying has accelerated and desert has reappeared along the lower Nile River and to its west.
Also note that the small colored circles in the four maps above represent archaeological settlement sites dating to each specific period. Confirming the Saharan Pump Theory, you’ll notice that the settlements from the wet phases in the regions that dried back to desert in Map D have all moved to the banks of the Nile. Once they congregate along the Nile in Map D, their next step as it gets drier is out of Africa and into West Asia and from there east along the coasts to South, Central, and East Asia as-well-as north through the Levant into Mesopotamia, Anatolia, the Steppes and east into Europe. The cyclical pump theory is best understood if you imagine the rainfall drying (as it has) to the present state of the uninhabitable Sahara today, then restarting the sequence of the maps A to B to C to D, which “pumps” more people eastward. You can see some of the previous pulses when you read this.
To wrap this up, you can now place the map at the top of this post as lying between maps B and C above.
It has taken me a while to truly comprehend the Saharan Pump Theory (also known as the African Pump Theory) and be able to present it to you. This should prove a shortcut for you.
Thanks for visiting,
R. E. J. Burke