James DeMeo's OBRL-News Blog

A Note from James DeMeo, PhD

New findings on the ancient history of the Sahara Desert both clarifies and confirms various aspects of my 1980s work on the origins of violence and human armoring, as summarized in the book Saharasia.

The new findings come from the field of oceanography, notably from Dr. Peter deMonocal of Columbia University, regarding sediment core samples from the deep Atlantic Ocean.   Sahara Desert dusts and aerosols typically blow to other world regions, including out over the open oceans, where they become incorporated into ocean sediments far out into the Atlantic Ocean.  This is not itself a new finding, but deMonocal identifies repeating and episodic changes in the abundance of these same Saharan dusts going back over millions of years. This indicates repeated oscillatory or pulsating climate changes from wet to dry and then wet again.  There were many "Sahara Deserts" in the past, punctuated by similar long episodes when the Sahara would vanish and be replaced by very wet conditions across North Africa.

Today we can directly observe large clouds of Saharan dust being blown westward out across the open Atlantic Ocean, and know very well how the desert dust materials could be deposited into the ocean, and then drift down to become a constituent of the ocean sediment layers.  The Sahara Desert dusts actually give the ocean sediments a slight yellow-orange color, setting them off from the normally grey-green ocean sediment layers characteristic of a wet North Africa.  The ocean sediment cores thereby reveal periods of a dry North Africa creating the Sahara Desert, oscillating between other periods of a wet North Africa, when the Sahara was replaced by a natural greening with trees, grasslands, and abundant wildlife.  The periodicity of these strata are further documented in rock art, lake levels, wildlife abundances and species, and so forth, as given in my Saharasia book.

This set of findings solves the larger question of "what made the Sahara Desert", and by extension the entire Saharasian Desert Belt which is identified in my writings, and which had its most recent origins in Arabia and Central Asia between 5000-4000 BCE.  After 4000 BCE, desert conditions more definitively expanded west from Arabia and the Nile River Valley, across North Africa, which thereafter dried out over most of its territory by around 3000 BCE.   The far Western part of North Africa were the last to succumb to the vast expansion of Saharasian desert conditions.

The document "Update on Saharasia: Ambiguities and Uncertainties about 'War Before Civilization'," published originally in the 2002 publication Heretic's Notebook and also contained in the 2006 revised 2nd edition of Saharasia, discusses these same repeating climate changes, as the solution to understanding how the Sahara Desert -- and all of Saharasia -- was formed.

Cyclical climate changes, or pulsations in climate, was the driving force, and this was affirmed in many lines of evidence beyond merely the new findings from ocean sediment core samples.  The very last change from wet to dry conditions, at c.4000-3500 BCE, occurred at the time of the first emerging human societies, which had grown in size within early villages and cities, in the earliest agricultural settlements with animal domestication, and being highly dependent upon good rains.  Earlier episodes of change from wet to dry conditions also had smaller influences upon human behavior, but never to such an extent as recorded within that most recent epoch of major climatic shifts.

Another aspect of these new findings is quite important for my larger Saharasian findings, notably the necessity for the c.4000-3500 BCE climate change to have occurred in a quick and rapid manner, over only a few generations at most, and not something drawn out over many thousands of years.   A rapid climate-change was necessary.  Otherwise, the early human societies could have migrated out towards wetter regions, and thereby avoided the repeated episodes of famine and starvation, as well as mass-migrations which were recorded in their archaeology.

As deMonocal noted, the ocean core sediments indicate a rapid climate change.  The last epoch of a wet North Africa ended rather sharply around 3500 BCE, converting into dry Sahara Desert conditions within a period of only a few hundred years at most.

Here's a graphic detailing the changes, identifying a major increase in dust-aerosol transport West from North Africa into the nearby Atlantic Ocean, which also indicates a severe reduction in rainfall, dated centrally at c.5500 BP years (before the present) or c.3500 BCE.  The very last graphic in the sequence reflects the actual measurements from the ocean sediment core samples.

 

(Graphic from:  W. Steffen, et al: "Abrupt Changes: The Achilles Heel of the Earth System", Environment, April 2004, p.16.)

My original 1980s research into the problems of world deserts indicated there was no mainstream consensus on what had created the Sahara Desert, or the related and connecting deserts of the Middle East and Central Asia which together formed the Saharasian Desert Belt.  It was only known, that the changes occurred.  Earlier climatic epochs were not so well documented as the last one recording the changes from wet to dry conditions at c.4000-3500 BCE.

By the 1990s, however, newer methods of analysis and dating allowed a more definitive picture to be assembled.  As noted above, and in addition to the wealth of documentation presented in the original Saharasia book, I addressed these new findings in the article "Update on Saharasia".  I cited and reproduced the climate maps of Jonathan Adams, reconstructing ancient climate conditions over the last 18,000 years, and depicting the most recent epochs of this dry-wet-dry pulsation of conditions across North Africa.  http://www.esd.ornl.gov/projects/qen/nerc.html

There were in fact many Sahara Deserts (plural) which came and went over a very long period of time.

The new data therefore suggests, the 4000-3500 BCE climate transition which swept across Saharasia was indeed rather abrupt and quick within any given region.  For North Africa, the transition into harsh aridity required no more than one or a few hundred years, and probably was characterized by great swings in weather during that period.  These swings would have included decades-long periods of intense high temperature and drought-dryness, punctuated by shorter periods of ever-diminishing rainfalls.  It had to "catch people by surprise", destroying their sustenance by subjecting them to recurring hard drought and devastating all vegetation and animal life.  They would have been reduced to starvation-death conditions, repeatedly, recovering when the scant rains returned, and slowly developing specialized methods (ie, nomadism) by which to survive under the increasingly desertified conditions.  The conditions suggest something similar to what was observed in the starving Sahel regions of Africa during the 1960s and 1970s, and which prompted action by international aid organizations.  But in those early times, there was no international aid forthcoming, and so people simply starved or migrated, and died in large numbers.  The emotional and physical devastation of starvation and famine, as I showed, was a severe emotional blow against the early peaceful human societies of the once-wet Saharasian regions, driving their emotional-behavioral structure, and character structure, towards a highly armored and violent condition.  The newer edition of the work Saharasia gives a full detail of the findings.

I argued for such abrupt climate changes back in the early 1980s.  The discussion by deMonocal, as given in the publications and documentary film cited above, validates my expectation, and indicates the transition from a wet to a dry North Africa occurred over a period of 100-200 years, being dated off the coast of West Africa at c.3500 BCE.  This provides a rather exact confirmation of the rapidity of the climate transition outlined in my Saharasia work.  It also falls within the generalized dates for the onset of aridity across different sub-regions of Saharasia as given in my writings.

Newer findings from archaeology and climatology continue to support the findings in my Saharasia work, which remains the most robust and firmly established proof for the origins of human armoring, as for the origins of human social violence and warfare.  From this, I can make additional predictions. We should expect that as new ocean core samples are made across the Mediterranean Sea, the Red Sea, the Indian Ocean, Persian Gulf and even in the China Sea just east of Beijing, similar desert dusts and aerosols will be found indicating a similar relatively abrupt and rapid transition from wet to dry conditions, and dated to periods as I have given them in Saharasia, as taken from the literature of archaeological and earlier paleoclimate studies.

For more information on the Saharasia book, with related "Update" articles, visit these webpages:

References:

P. B. DeMonocal et al., "Abrupt Onset and Termination of the African
Humid Period: Rapid Climate Response to Gradual Insolation Forcing,"

Quaternary Science Review 19 (2000): 347-61.

M. Claussen, et al., "Simulation of an abrupt change in Saharan vegetation

in the mid-Holocene", Geophysical Research Letters, V.26, No.14, pp.2037-2040, July 15, 1999