You may be familiar with my understanding (also suggested by others, I guess) that West Asia has (at least) two ancient populations whose spread now overlaps but is relatively easy to discern. A clear example is the duality between Y-DNA haplogroups J1 (south/SW or lowlands) and J2 (north/NE or highlands). To my knowledge this is however the first study that formally asserts that duality for autosomal DNA.
Marc Haber et al., Genome-Wide Diversity in the Levant Reveals Recent Structuring by Culture. PLoS Genetics 2013. Open access → LINK [doi:10.1371/journal.pgen.1003316]
The Levant is a region in the Near East with an impressive record of continuous human existence and major cultural developments since the Paleolithic period. Genetic and archeological studies present solid evidence placing the Middle East and the Arabian Peninsula as the first stepping-stone outside Africa. There is, however, little understanding of demographic changes in the Middle East, particularly the Levant, after the first Out-of-Africa expansion and how the Levantine peoples relate genetically to each other and to their neighbors. In this study we analyze more than 500,000 genome-wide SNPs in 1,341 new samples from the Levant and compare them to samples from 48 populations worldwide. Our results show recent genetic stratifications in the Levant are driven by the religious affiliations of the populations within the region. Cultural changes within the last two millennia appear to have facilitated/maintained admixture between culturally similar populations from the Levant, Arabian Peninsula, and Africa. The same cultural changes seem to have resulted in genetic isolation of other groups by limiting admixture with culturally different neighboring populations. Consequently, Levant populations today fall into two main groups: one sharing more genetic characteristics with modern-day Europeans and Central Asians, and the other with closer genetic affinities to other Middle Easterners and Africans. Finally, we identify a putative Levantine ancestral component that diverged from other Middle Easterners ~23,700–15,500 years ago during the last glacial period, and diverged from Europeans ~15,900–9,100 years ago between the last glacial warming and the start of the Neolithic.
Take the age estimates with all the caution, as always. My own estimates
suggest a quite older divergence, soon after
the time of the settling of West Eurasia, what could be 40-30 Ka ago.
As I have said before
also, modern Jews (in this case Ashkenazim but in general all Western or Hellenistic Jews from other studies academic and amateur) cluster quite strongly towards the Northern or Highlander cluster, close to Cypriots, Turks and Lebanese but far away from the Palestinians (way too diverse to be an issue of misunderstanding because of endogamy or a recent arrival from the, quite unrelated genetically, Peninsular Arabia (or any other place). Therefore the bulk of the ancestry of modern Jews does not come from ancient Palestine but some other areas further North, where we know that Judaism (and its offshoot Christianity) proselytized heavily in Antiquity.
Very interesting is also that the “lowlander” component is rather intensely scattered towards North and East Africa, with almost no influence in Europe and South Asia. Instead the “highlander” one has influenced especially Europe with minor influence into South Asia, as well as, to some extent, parts of North Africa (but not The Horn).
|Figure 4. Comparisons of the Levantine and Middle Eastern modal components.
ADMIXTURE analysis based on 10 constructed ancestral components, with
only the Levantine and Middle Eastern components highlighted. B)
Frequency of the Middle Eastern component in world populations. C)
Frequency of the Levantine component in world populations. Intensity of
the colors reflects the frequency of a component in the plotted
populations. Maps were produced using a weighted average interpolating
algorithm, and therefore should be used as a guide rather than a precise
representation of the frequency distribution.
I must say, as an aside, that the terms chosen to designate the components sound horrible and imprecise, because nobody really knows for sure what Levant and Middle East mean. West Asia is a more clear and neutral nomenclature and North and South (or, as I choose, highlands and lowlands) are very descriptive, even if they overlap, especially about their likely origins in or near Kurdistan and Palestine respectively (most likely, as they are two archaeologically very rich regions in the Paleolithic as well as in the Neolithic).