We established in recent posts that modern archaeology agrees the Persian Gulf was dry and its floor a refuge valley during the Last Glacial Maximum. Sea level was 120 meters lower than today, because 10 million cubic miles of water were frozen above sea level in northern glaciers. Eastbound migrants departing northeast Africa crossed the Sinai to follow the exposed Arabian coast along the Red Sea to the Straits of Djibouti. Another migrant stream from Ethiopia took advantage of low sea levels to cross over and join the route up the east coast of Arabia to Oman. At Oman, the seacoast turned east toward India and beyond. This was the eastbound route leading out of Africa to Asia and Australia, and ultimately to the Americas. We used the graph below to illustrate this and other points in the prior Post 80.
Archaeologist define such a “refuge” as a place where African migrants, fleeing weather conditions threatening their survival, found refuge before perishing. In Post 80 you saw that even during interglacial warming periods, weather was dangerously unpredictable. Small distances sometimes separated major differences in micro-climates, and these could vary widely over short periods of time. If the refuge was attractive, or the hazard nearly fatal, many would be tempted to settle there “temporarily.” Over time, such a refuge would attract a permanent, genetically diverse population, perhaps the smartest. Since this alluvial valley was about 1,000 kilometers long, it’s not surprising the Ubaid’s ancestors got a head start. The map below (from Post 70) shows there was plentiful fresh water during the Last Glacial Maximum (LGM) around which the refugees would find conditions favorable to begin the Neolithic Revolution.
18,000 BP. I am now going to again use Dr. Lambeck’s four maps from post 70, this time to illustrate how the valley residents most likely exited as the waters rose. My conclusions are supported by prior posts on the valley. In the map below, at the Last Glacial Maximum in 18,000 BP, the weather conditions were as bad as they were going to get. Regional Anatomically Modern Humans (AMH) would be in this valley refuge (at least the smart ones still present in today’s gene pool). The Neanderthals previously occupying the Zagros Mountains were already extinct. With high, cold, desiccating winds and low humidity (see graph beneath map below), leaving this well-watered, valley refuge would be foolhardy.
Contour map of Persian Gulf sea floor refuge exposed during LGM
The graph below (from Post 80) illustrates on a macro-scale two key features of climate change since the Last Glacial Maximum: The Holocene Pluvial Phase (abundant rainfall) in the grey band, and the enormous swings in aeolian activity (wind) in the plotted line.
12,000 BP. From the above graph, we know winds are approaching the Holocene peak at this time, while the Pluvial has not yet started. The northern fresh water lake remains. The southern fresh water lake is now a brackish estuary. Pastoralists along the estuary’s littoral no longer have the fresh water lake for flocks, and must seek water for flocks through wells, crowding with other flocks around a few streams from the Zagros or Arabia, or moving their flocks several hundred kilometers to the remaining fresh water lake or its feeder river. High winds continue to desiccate the terrain outside the refuge valley. Under these conditions, valley residents would follow the fresh water north, coming into conflict. I foresee some fighting over prime locations. Smart folks who exploited fresh water fishing before the flooding would be exploiting much richer fishing resources in the estuary, including oysters and clams.
10,000 BP. Wind speeds are plummeting and Pluvial rains have been generous for well over a thousand years (see graph above). The last fresh water lake is now absorbed into the brackish estuary; its water is unfit for human consumption or for watering flocks. But the estuary is now a very rich producer of fish and shellfish. Rivers and creeks along both the northern and southern littoral should now be flowing. Ground water has been rising, making wells easier to dig, certainly for village and for well-placed homes. Shepherds on the northern littoral are now competing for much smaller refuge pastures, and logically begin to exit the refuge to the north, creating (or joining) the FARS Mobile Pastoralist culture discussed in Post 78. Fishing should now be a major food source. Pastoralists will find water for flocks, but most will need to dig wells. Forests should again be growing around the littoral. Hunter-gathering would be as good as it ever will be. The emerging agriculturalists will be moving upstream, soon to enter what we now call Southern Mesopotamia; the Mesopotamia they are leaving exceeded that which they will enter. Savannah is spreading into the Arabian Peninsula, and the water table beneath the savanna is beginning to flow “downhill” toward the Gulf, creating springs along the Arabian littoral.
8000 BP. From the above weather graph, we see the winds have bottomed out and we are in the middle of the Holocene Pluvial Phase. The ground water table will be near its peak, making wells as easy to dig and springs as abundant as they ever will be. Streams and rivers will be peaking about now. The Neolithic Agricultural Revolution is in full bloom. Copper is entering the material culture. The Ubaid identity is peaking as they absorb the Halaf culture. Prosperity will last from here through the Uruk era, until the precipitous drought which ends the Holocene Pluvial Phase. The Persian Gulf refuge is now relegated to legends about creation, titanic floods, and Edenic Dilmun now forever hidden beneath the waves. Black on buff pottery spreads to become ubiquitous outside the Persian Gulf, between India and the Mediterranean Sea.
As Mesopotamian population grew geometrically with food production during the 4th millennium BC, well-fed humanity was living for the first time in the close quarters of cities. City living had new risks. Mankind soon encountered the Four Horsemen of Apocalyptic War, Famine, Pestilence, and Death. The graph below (from Post #4) illustrates the limits of earth’s bounty at that time. A cursory look at subsequent history shows the Four Horsemen are never done.
This is a good time for you to look at the Timeline of Environmental History and check what has happened and what lies beyond those events. While scanning this link, I found the newly discovered Burckle Crater and realized the horrific impact its tsunami would have delivered upon the Indus Valley Civilization and the entrance to the Persian Gulf in 3,000 BC–about the same time as the scientifically proven big flood(s) of Mesopotamia, previously thought to be products of the peaking sea level and Mesopotamian-specific geologic phenomena. This is another proof of Murphy’s Law, “If anything can go wrong, it will,” and also of the old adage, “When it rains, it pours.” It is willful obstinacy to ridicule old “legends” and “myths” such as the story of Genesis, including the Fall and the Big Flood.
I’m sure the horror of that stabilization of mankind’s growth rate, at the beginning of recorded history, led to the recognition of man’s hubris, and that “you reap what you sow, more than you sow, and later than you sow.” In the crucible of that melt-down, there undoubtedly was much cogitating about the nature of creation and from whence it sprang–as there was during subsequent historic moments of reckoning. But, from this ancient Mesopotamia came the discernment and genesis of Mono-theism, the concept that now serves as the foundation for the lives of 59% of the world’s present population.
That’s enough food for thought from this post.
Thanks for visiting.
R. E. J. Burke