May 18, 2014

South Asian first Neolithic and its relation with West Asia

Informative compilation of dates for West and South Asian Neolithic sites.

Kavita Kangal et al., The Near-Eastern Roots of the Neolithic in South Asia. PLoS ONE 2014. Open access → LINK [doi:10.1371/journal.pone.0095714]

Abstract

The Fertile Crescent in the Near East is one of the independent origins of the Neolithic, the source from which farming and pottery-making spread across Europe from 9,000 to 6,000 years ago at an average rate of about 1 km/yr. There is also strong evidence for causal connections between the Near-Eastern Neolithic and that further east, up to the Indus Valley. The Neolithic in South Asia has been far less explored than its European counterpart, especially in terms of absolute (¹⁴C) dating; hence, there were no previous attempts to assess quantitatively its spread in Asia. We combine the available ¹⁴C data with the archaeological evidence for early Neolithic sites in South Asia to analyze the spatio-temporal continuity of the Neolithic dispersal from the Near East through the Middle East and to the Indian subcontinent. We reveal an approximately linear dependence between the age and the geodesic distance from the Near East, suggesting a systematic (but not necessarily uniform) spread at an average speed of about 0.65 km/yr.

We must be warned that the study dwells on statistical data, mostly ¹⁴C and other archaeological dates and not in pottery typology and such. So there are probably a lot of nuances to be added to what the authors conclude. However the study is a major effort to systematize West and South Asian Neolithic dates (details in the extensive supplementary materials) and that must be acknowledged as very useful on its own.

Fig. 2 synthesizes the findings of this study:

Figure 2. A linear envelope fit to the data using the weighted dates yields the average Neolithic dispersal speed km/yr.
The filled circles (red) and triangles (magenta) show the archaeologically dated sites from Iran and the Indus valley Civilization, respectively; filled circles (black) and open triangles represent sites with multiple and single 14C dates, respectively.
[Note: Gesher is one of the earliest PPNA sites, located in Northern Palestine].

The graph is a bit misleading because there are places in South Asia with ¹⁴C dates older than the apparent 7000 BP baseline (see Appendix in the study). Ayakagytma has several dates nearing 6000 BCE (i.e. ~8000 BP), while Merhgar is dated to as early as 8520 BCE (~10,500 BP), which overlaps the oldest sites of West Asia. These oldest Neolithic sites of South Asia are hardly recognizable in the graph, as they are shown as mere dots, whose only distinction is that they are ~3000 km away from Gesher. I had to investigate the Appendix to spot them.

The Merhgar ¹⁴C date is just one but it does not seem the authors felt compelled to discard it for any reason, so it should stand in principle.

Actually, rather than explain South Asian Neolithic as West Asian derived, the data in this study only offers an interesting overview of the dates but as such demonstrates nothing. Actually, if, as they argue, we are to consider always the oldest regional date (unless unreliable), then the expansion of Neolithic to South Asia was very fast. What was rather slow was its expansion within West Asia apparently.

Said that, there are many reasons to think that there was at least an important West Asian contribution to South Asian Neolithic, if nothing else because of the important presence of several important Western Y-DNA lineages (R1a, J), which seem somehow related to Neolithic spread, as well as the so-called "ANI" component, of clear West Asian affinity. Also many crops and animals were obviously imported from West Asia.

In this regard, a reader pointed to me weeks ago to a study that claims that sheep were independently domesticated in South Asia. However I found their conclusions far fetched so I never discussed it... until now.

Sachin Singh et al., Extensive Variation and Sub-Structuring in Lineage A mtDNA in Indian Sheep: Genetic Evidence for Domestication of Sheep in India. PLoS ONE 2013. Open accessLINK [doi: 10.1371/journal.pone.0077858]

What this study did find is a very specific founder effect of sheep lineages in India. However this cannot be accepted to be caused by an independent domestication but rather looks like a founder effect after domestication, which almost certainly owes to West Asia, where the ancestors of domestic sheep lives.

Figure 3. Neighbor-joining tree of domestic sheep based on 432 bp of control region mtDNA.
(A) Neighbor-joining tree of mtDNA sequences of Indian sheep (330) along with representative samples of five lineages (▲), namely; A, B, C, D & E. Indian sheep show three lineages, namely; A, B and C. (B) Neighbor-joining tree of mtDNA sequences of the Indian (330), Chinese (129), Central Asian, Caucasian and European (406), Portuguese (161), and West Balkan (60), sheep along with representative samples of five lineages (▲), namely; A, B, C, D & E . The sequences of wild Ovis species have been used as outgroups. MEGA 5 version 5.0.1.102 was used to construct the trees using Tamura-Nei model with 10,000 bootstrap. Numbers above a given branch represent bootstrap support for the branch as a percentage out of 10,000 re samplings.

Notice please how the root of the tree is at the bottom, where the various wild species of sheep are listed by their names. So the dominance of lineage A in South Asia surely owes to a founder effect and not local domestication.

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