While I agree with most of what you say, i would put it that the iranic invasion from the north destroyed the uruks, with this invasion from the north came, R, G, J1, J2 and T ..........there was no T in mesopotamia, there was originally only K, T formed in the pamir regions according to nat geno and Ftdna project people.The Sumerian civilization in southern Mesopotamia arose circa 4500 BCE with the foundation of Eridu, the world's first city. Enigmatic speakers of a language isolate, the Sumerians played a leading role in the development of Near Eastern civilizations. They invented writing (cuneiform script), hierarchical administration, and the division of labour in specialised arts and crafts, among others.
During the Uruk period (ca. 4000 to 3100 BCE), stratified, temple-centred cities started developing in what may have been the world's earliest theocratic state. Rough, unpainted, mass-produced pottery replaced painted pottery. As the Sumerian population expanded, slave were captured from the hill country, and colonies were founded beyond Babylonia, in northern Mesopotamia, Syria, eastern Anatolia, the southern Caucasus and western Iran, to acquire natural resources lacking in Sumer (notably copper). This Uruk expansion is characterised by the sudden appearance of Uruk pottery, cylinder seals, cuneiform script and other typically Sumerian artefacts in much less developed regions. All evidence point at the establishment of population colonies by Sumerian settlers, rather than a propagation of artefacts and technologies through mere contact or trade.
Around 3100 BCE, all Sumerian colonies were suddenly destroyed, and contact ceased for several centuries between Sumer and surrounding regions. What happened ?
The events happen to coincide with the expansion of the Maykop culture (3700-2500 BCE) from the Northwest Caucasus to the Northeast and Central Caucasus, and the consequent displacement and expansion of the Kura-Araxes culture (3400-2600 BCE) from the Caucasus (Daghestan, Georgia, Armenia) toward eastern Anatolia, northern Syria, northern Mesopotamia and north-western Iran. Both Maykop and Kura-Araxes were Bronze Age cultures - the world's two oldest. Both produced an amazing number of metal objects (esp. Kura-Araxes) and metal weapons (esp. Maykop), although the two cultures were radically different in many other respects (burial style, settlement types, stratification of society, artistic style, etc.).
It is very likely that the southward expansion of the Kura-Araxes culture played a major role in the demise of the Uruk settlement in the region. Since Sumerians captured slaves and apparently exploited the conquered populations, it is easy to imagine that the indigenous populations revolted against Sumerian rule, perhaps with the help of Kura-Araxes people, or by purchasing metal weapons from them.
During that period farming was only practised in regions with enough annual precipitations, or in areas where irrigation could be practised like in southern Mesopotamia. The steppe and highlands beyond the rain curve were inhabited mostly by semi-nomadic herders. It can also be envisaged that these herders decided to attack Sumerian colonies, just as bronze weapons began to appear in the region.
A fourth possibility is that of an early Indo-European incursion in the Fertile Crescent from the Maykop/Yamna culture. The best evidence to support this is the presence of mtDNA U4 in the Sumerian city of Mari in Syria dating from 2900-2700 BCE, i.e. after the Uruk collapse. U4 is strongly associated with haplogroup R1a, and to a lesser extent R1b. U4 is also very common in the Caucasus region, so this could also be the sign of a Kura-Araxes invasion.
Which culture can be associated with which Y-DNA haplogroup ?
The genetic landscape of the Near East is very complex and without any ancient Y-DNA result it is extremely difficult to guess the composition of each culture at such an early stage of development. However what ancient DNA studies have taught us so far is that the earliest one goes back in time, the more likely it is that separate populations will belong primarily to a single, or at least a very small number of paternal haplogroup. Successive invasions, migrations, intermarriages and linguistic fusions in history have entangled all haplogroups in a big, indiscernible mass. It is an interesting exercise to try to disentangle everything and try to figure out which haplogroup used to belong to whom.
In my opinion, based on the current data, I would make the following predictions:
- Maykop culture: R1b and G2a3b1
- Kura-Araxes culture: G2a, J1 and J2
- Sumerian civilization: T (Sumerian speakers) and E1b1b + J1 (Semitic Proto-Akkadian speakers)
- Highland herders from the Taurus and Zagros mountains: E1b1b, J1 and J2 (Proto-Semitic speakers)