Tuesday, November 16, 2010

Syria to Assyria: 3500 years of Demic Diffusion

Working from the simple demic diffusion model for Syria, I've adjusted the diffusion rates, based on the assumption that the Modern Assyrian population  is a snapshot of the central Fertile Crescent in the Middle Assyrian Period 3500 years ago.  Again, that date is chosen because it is before the Egyptian occupation of Syria and after the conquest Assyria by the Amorites (1840BC).  The assumptions behind that dating are further discussed in the Assyrian post.

The first bar in the above graph represents the modern population of Syria. The next four "five bar sets" account for four sources of demic diffusion into the Syrian population:  Egypt, Babylonia, Saudi Arabia and Cyprus.   Working backward through time, each bar represents 700 years of history.  The bar second from the right is the "snapshot" Assyrian population which we've assumed has been isolated for the last 3500 years.  The far right bar is the remaining population not accounted for by diffusion from Egypt, Babylonia, Saudi Arabia and Cyprus.  This combined remaining population accounts for less than 4% of Syrian population components.

From this, I calculate a diffusion rate for Syrians:

Egypt:             10%/3500 years = 0.002857% per year
Iraq(Burusho):   4%/3500 years = 0.001143% per year
Saudi Arabia:  18%/3500 years = 0.005143% per year
Cyprus:           13%/3500 years = 0.003714% per year


0.5% East African
0.5% West African
0.25% Northern European
0.25% Northeast Asian
1.5% Southern European
0.25% Northwest African

These diffusion rates can be used to interpolate further backward in time through the Bronze and Neolithic ages.  It is important to note that these diffusion rates represent the average rate of diffusion.  They are first order approximations of the more accurate decaying exponential predicted by the diffusion equation.  These rates are directionless and represent a "point" diffusion rate for the geographic region of Syria. 
Using these rates, it is possible to estimate a last possible date for the postulated departure from the Fertile Crescent to Europe.  That will be the topic of tomorrow's post.

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