A very useful fresh paper on the origin as well as also spread of mitochondrial (mtDNA) haplogroup U7 has just appeared at Scientific Reports.
This kind of re-iterates some key points that will I’ve made about This kind of haplogroup; that will This kind of’s a South Caspian-specific lineage as well as also conspicuous by its absence by all Yamnaya samples sequenced to date. In fact, along with various other South Caspian-specific lineages, such as U1, U3a, HV2 as well as also HV0, This kind of’s missing by all Early Bronze Age steppe samples sequenced to date (see here).
This kind of can be surely a major problem for those positing that will ancient populations by the South Caspian, in various other words what can be today mostly Iran, made a significant contribution to the formation of Early Bronze Age steppe pastoralist groups, including Yamnaya.
However, I’d say the paper’s conclusion that will U7 probably spread into Europe before the Early Bronze Age can be a bit iffy. Based on the available ancient European mtDNA, This kind of looks to me as if This kind of mostly spread into Europe after the Early Bronze Age. So why are there European-specific U7 lineages, such as U7a19, seemingly with coalescent times dating to the Neolithic in Europe? Well, perhaps because after these lineages moved to Europe, they went extinct inside the Near East? by the paper, emphasis can be mine:
Abstract: Human mitochondrial DNA haplogroup U can be among the initial maternal founders in Southwest Asia as well as also Europe as well as also one that will best indicates matrilineal genetic continuity between late Pleistocene hunter-gatherer groups as well as also present-day populations of Europe. While most haplogroup U subclades are older than 30 thousand years, the comparatively recent coalescence time of the extant variation of haplogroup U7 (~16–19 thousand years ago) suggests that will its current distribution can be the consequence of more recent dispersal events, despite its wide geographical range across Europe, the Near East as well as also South Asia. Here we report 267 fresh U7 mitogenomes that will – analysed alongside 100 published ones – enable us to discern at least two distinct temporal phases of dispersal, both of which most likely emanated by the Near East. The earlier one began prior to the Holocene (~11.5 thousand years ago) towards South Asia, while the later dispersal took place more recently towards Mediterranean Europe during the Neolithic (~8 thousand years ago). These findings imply that will the carriers of haplogroup U7 spread to South Asia as well as also Europe before the suggested Bronze Age expansion of Indo-European languages by the Pontic-Caspian Steppe region.
Compared to various other subclades of hg U, both the phylogenetic structure as well as also the ancestral origin of hg U7 are rather obscure. This kind of haplogroup can be characterized by generally low population frequencies as well as also limited sequence diversity, despite a geographic distribution ranging by Europe to India [14,16,25,27,30,31,32,33]. Recently, This kind of has been detected in skeletal remains by Southwest Iran [my note: that will was U7a] dated ~six thousand years ago (kya)  as well as in remains by the Tarim Basin in Northwest China (3.5–4.0 kya) .
Another major episode of gene flow affecting the European gene pool appears to have occurred during the Late Neolithic as well as also Early Bronze Age, by a source inside the Pontic-Caspian Steppe region north of the Caucasus [3,54,66,72]. This kind of has been suggested that will This kind of migration resulted in a further substantial shift inside the genetic profile of Europeans as well as also was a major vehicle for the movement of Indo-European languages to Europe [3,72], as well as also likely also to South Asia54. Interestingly, the autosomal genetic component in Europeans considered to derive by the Steppe can be almost fixed in two pre-Neolithic ancient genomes by the South Caucasus. This kind of component can be distributed eastwards towards South Asia as well54, where This kind of mimics the distribution of U7 (Pearson’s r = 0.65, p = 0.01). Our time estimates for the expansion as well as also differentiation of hg U7 inside the Near East, Central Asia, South Asia, as well as also Europe, however, predate these putative late Neolithic-early Bronze Age migrations as well as also thereby rule them out as a major vehicle for the spread of U7 to Europe as well as also South Asia. In This kind of respect, This kind of can be also noteworthy that will Yamnaya herders of the Steppe so far analysed (n = 43) show no traces of U7 [3,55,72,73] – as well as also U7 can be rarely found in This kind of region today (Fig. 2).
The expansion time of hg U7 inside the Near East, Central Asia as well as also South Asia can be more consistent with autosomal multi-locus estimates for the genetic separation of these regions during the Terminal Pleistocene74, suggesting a common demographic process, whose origin was unclear previously. Here, we show that will the frequency as well as also distribution of U7b lineages indicate an origin of This kind of clade inside the Near East, whilst for U7a these statistics cannot differentiate between South Asia as well as also the Near East (including the Caucasus) as a possible homeland.
Sahakyan et al., Origin as well as also spread of human mitochondrial DNA haplogroup U7, Scientific Reports 7, Article number: 46044 (2017), doi:10.1038/srep46044
Mitogenomes reveal post-Neolithic gene flow by the Near East to Tuscany
Big deal of 2016: the territory of present-day Iran cannot be the Indo-European homeland
The story of mtDNA haplogroup U7