Distribution of J2a
Sengupta, S.et al., 2006
Dienekes covered the Sengupta paper, which discusses the distribution of J2 and other West Asian y-haplogroups, back in 2005. In light of ADMIXTURE results, it is helpful to revisit this paper (Sengupta et al 2006). From this paper, two major branches of J2, J2a and J2b, are described on the phylogenic tree:
Based on the distribution and diversity of the J2b branch of the tree, it is likely of a Central or South Asian provenance, as discussed in Senguta et al.
Sengupta notes that many y-haplogroups in India appear to be of a pre-Neolithic origin. Regarding the eastward expansion of J2, he has this to say:
"One interpretation of the presence of J2a-M410 chromosomes in North Africa and Eurasia is that it reflects the demographic spread of Neolithic farmers. This is consistent with previous interpretations of M172-associated HGs (Semino et al. 2000; King and Underhill 2002). Figure 3 [above] demonstrates the eastward expansion of J2a-M410 to Iraq, Iran, and Central Asia coincident with painted pottery and ceramic figurines, well documented in the Neolithic archeological record (Cauvin 2000). Near the Indus Valley, the Neolithic site of Mehrgarh, estimated to have been founded 7 KYA (Kenoyer 1998), displays the presence of these types of material culture correlated with the spread J2a-M410 in Pakistan. Although the association of agriculture with J2a-M410 is recognized, the spread of agriculture may not be the only explanation for the spread of this HG. Despite an apparent exogenous frequency spread pattern of HG J2a toward North and Central India from the west (fig. 3), it is premature to attribute the spread to a simplistic demic expansion of early agriculturalists and pastoralists from the Middle East. It reflects the overall net process of spread that may contain numerous as-yet-unrevealed movements embedded within the general pattern. It may also reflect a combination of elements of earlier prehistoric Holocene epi-Paleolithic peoples from the Middle East, subsequent Bronze Age Harappans of uncertain provenance, and succeeding Iron Age Indo-Aryans from Central Asia (Kennedy 2000). Although the overall age of J2a Y-microsatellite variation (table 11) exceeds the appearance of agriculture in the Indus Valley (6 KYA), the current lack of informative subdivision within HG J2a in southwestern Asia prevents analysis of such potential layers, which are currently more evident in Anatolia, southeastern Europe, and the Mediterranean. In these regions, HGs J2a1b-M67(xM92) and J2a1b1-M92 have spatial and temporal characteristics consistent with the spread of early farmers and Bronze Age cultures (Di Giacomo et al. 2004). Besides the notable absence of J2a1b-M67(xM92) and J2a1b1-M92 in southwestern Asia, HGs J1-M267 and G-M201 that, respectively, occur at 9% and 10.9% in Turkey (Cinnioglu et al. 2004), 33.1% and 2.2% in Iraq (Al-Zahery et al. 2003), and 3.4% and 6% in Pakistan are also virtually absent in India, indicating differential influences from the Middle East in southeastern Europe and southwestern Asia. Similarly, the presence of HG E lineages, thought to possibly be associated with the spread of agriculturalists in southeastern Europe (Hammer et al. 1998; Semino et al. 2004), are absent in India except in specific populations known to have recent African heritage (Thangaraj et al. 1999). Until the paraphyletic J2a-M410* with DYS413 short-alleles chromosomes are better resolved molecularly in southeastern European, western Asian, and southwestern Asian regions, the magnitude of the contribution of agriculturalists within this HG remains uncertain. The mean variance for J2b2-M241 chromosomes is highest in southwestern Asia(0.33), in contrast with Turkey (0.24) (Cinnioglu et al. 2004) and the Balkans (Pericic et al. 2005). Further, the mean expansion time of J2b2 in India is 13.8KYA, clearly earlier than the appearance of agriculture."
A pre-Holocene expansion of J in the Fertile Crescent is consistent with both the Sengupta findings and the recent suggested early Holocene southward expansion of J1 from the Taurus-Zagros region (Charioni et al).
From ISOGG: "Y-DNA haplogroup J evolved in the ancient Near East and was carried into North Africa, Europe, Central Asia, Pakistan and India. J2 lineages originated in the area known as the Fertile Crescent. The main spread of J2 into the Mediterranean area is thought to have coincided with the expansion of agricultural peoples during the Neolithic period. The timing of the demographic events that brought J2 to Central Asia, Pakistan, and India is not yet known."
(1) Cinnioglu, C (2004); Excavating y-chromosome haplotype strata in Anatolia. (Link)
(2) Regueiro, M (2006); Iran: Tricontinental Nexus for Y-Chromosome Driven Migration. (Link)
(3) Sengupta, S (2006); Polarity and Temporality of High-Resolution Y-Chromosome Distributions in India Identify Both Indigenous and Exogenous Expansions and Reveal Minor Genetic Influence of Central Asian Pastoralists. (Link)
(4) ISOGG Y-DNA Haplogroup J and its Subclades - 2010 (Link)