South Asia — comprising India, Pakistan, countries in the sub-Himalayan region and Myanmar — was one of the first geographical regions to have been peopled by modern humans. This region has served as a major route of dispersal to other geographical regions, including southeast Asia. The Indian society comprises tribal, ranked caste, and other populations that are largely endogamous. As a result of evolutionary antiquity and endogamy, populations of India show high genetic differentiation and extensive structuring. Linguistic differences of populations provide the best explanation of genetic differences observed in this region of the world. Within India, consistent with social history, extant populations inhabiting northern regions show closer affinities with Indo-European speaking populations of central Asia that those inhabiting southern regions. Extant southern Indian populations may have been derived from early colonizers arriving from Africa along the southern exit route. The higher-ranked caste populations, who were the torch-bearers of Hindu rituals, show closer affinities with central Asian, Indo-European speaking, populations.
Nothing radically new, but its good to have a review article that compiles genetic studies done on extant Indian populations along with references to primary literature.
Missing though from this emerging data bank is ancient - but within a historical time frame- skeletal material and DNA from the subcontinent for comparison, which could potentially answer many vexing and controversial questions about historical migrations into India.
In this regard the recent find of Harappan age skeletons along with pottery and artifacts from Farmana, Haryana about 60 km from Delhi gains significance as recovered DNA from these skeletons could give data about the relatedness of these ancient northwestern Indian populations with Eurasians and central Asians and clarifying to some extent when admixtures of central Asian and Eurasian genes with Indian populations occurred.
There are other excellent articles in this issue. Particularly the one by Pritchard et.al. on The Genetics of Human Adaptation: Hard Sweeps, Soft Sweeps, and Polygenic Adaptation.