Saturday, November 27, 2010

Rivers, Lakes and Mountains

Khor Virap Monastery with Mount Ararat
and the Fertile Valley of the Aras River in the Background

Update (November 2012):  This post of mine is extremely popular.  I wrote it over two years ago before I was able to aggregate a more complex picture of European ice age refuges.  I still do think that Anatolia has been a refuge for European populations.  I also continue to think that Europe was partially repopulated from Anatolia at the end of the last Ice Age.  However, the picture is much more complex than one would be led to believe from thinking that the population of Europe is comprised mostly of "farmers from the Fertile crescent."  There are a number of other ice age refuges in Europe that contribute to the modern population diversity of Europe.  It is a quite complex picture over time and space.  Suffice it to say that this post is a good description of the dynamic with the Anatolian ice age refuge.  However, then are many other European refuges and even an interaction with North Africa.

Update (April 2012):  The recent paper "Neolithic patrilineal signals indicate that the Armenian plateau was repopulated by agriculturalists" [Herrera, et al, (link)] reveals that the origin of agriculturalists is likely the Tigris and Euphrates River System.  Therefore, the movement of peoples along the river systems described below is from the Tigris and Euphrates into the Aras and Kara River systems in one branch, and in another westward branch, into the Kizilirmak River system.

Original Post (November 2010):

Revisiting the Haak et al paper, I'm going to review a little geography in this post.  During the water scarce Younger Dryas, access to a steady water supply for humans, and for the animals they hunted, would have been of paramount importance.

With that in mind, the genetic distance maps of Figure 3 in the Haak et al paper take on new meaning:

Figure 3A and 3B
"Mapped genetic distances are illustrated between 55 modern Western Eurasian populations and the total of 42 Neolithic LBK samples (A) or the single graveyard of Derenburg (B). Black dots denote the location of modern-day populations used in the analysis. The coloring indicates the degree of similarity of the modern local population(s) with the Neolithic sample set: short distances (greatest similarity) are marked by dark green and long distances (greatest dissimilarity) by orange, with fainter colors in between the extremes. Note that green intervals are scaled by genetic distance values of 0.02, with increasingly larger intervals towards the “orange” end of the scale."

The two maps, A and B, can be viewed as maps of a survival strategy in a water scarce world.

With Map 3A, what accounts for the peculiar Southern Caucasus-Central Anatolia pattern?  After looking at a map of rivers in the region, it isn't difficult to posit that this particular population was following systems of rivers and lakes.  Perhaps they weren't intensionly following rivers, but the animals they were hunting certainly were.

It isn't clear if the direction of migration was from Anatolia to the Caucasus or the Caucasus to Anatolia.  Let's assume the direction is westward.  The Aras and Kura rivers flow along the Southern Caucasus Mountains and connect Georgia to Azerbaijan:

Kura and Aras Rivers

Note that the dark green island in Figure 3A hugs the Kara and Aras Rivers.  But what connects this area to the dark green island in Central Anatolia?  Other river systems, of course!

Map of Rivers and Lakes in Turkey

Heading west again, the jumping off point from the Aras River was none other than the Tigris and Euphrates River system. Testing this idea, it's not surprising that the archaeological site Hallan Cemi Tepesi is located on the Batman River, a tributary of the Upper Euphrates River. Çayönü lies near the Bogazcay, a tributary of the upper Tigris River. Göbekli Tepe is located near the Upper Euphrates River. 

Jumping off from the westernmost source of the Euphrates is the Kizilirmak River. On a tributary of this river, the Melendiz River, Aşıklı Höyük is located. 

The earliest settlement dates for these locations have been dated to the late the Younger Dryas, 10,000 years ago. That puts our proto-LBK Figure 3A population on the Kizilirmak River 10,000 years ago. 

The Sakarya River (Sangarius River), a valley away from the Kizilirmak, would have taken a westward bound Figure 3A hunter-gatherer-farmer to the Bosphorus, just in time for the Holocene.

Looking at Figure 3B from the Haak et al paper, it is clear that this population created a refuge for themselves in the Northern Zagros mountains. They also followed rivers and established themselves on the Upper Tigris River as is evident by the settlements at Nemrik and Qermez Dere, for example. By way of the Aras and Kizilirmak Rivers, this population also reached the Southern Caucasus Mountains and Europe during the Holocene expansion.

Employing this river strategy, both populations were poised to push onward into the upper Danube and Dnieper, as is attested to by the near genetic distances of modern populations in these areas to LBK populations.