Omar Ali in Brown Pundits:
The debate about the origins of the “Aryans” and their arrival in India has flared up again, this time triggered by new genetic findings that appear to confirm beyond any reasonable doubt that large numbers of Indo-Europeans herders migrated into the Indian subcontinent about 4000 or so years ago. Razib Khan (one of the best informed and unbiased bloggers on this topic) has written in detail about this topic in several posts, the most recent of which is here. I am not going to go into the genetics or the details, I just wanted to recap the story in very simple layperson outline and focus mostly on some of the politics around this topic. My basic argument is that the Hindutvadi reaction to the political uses of “Aryan Invasion Theory” is relatively justified, but opting to take a stand against population genetics and common sense in the form of a relatively recently concocted (and very unlikely) “Out of India” (OIT) theory is an unfortunate and self-defeating mistake.
The Indo-Europeans who migrated into India were one of several migratory stream that, between 4000-2000 BCE, spread in all directions out of the Pontic Steppe (what is now Eastern Ukraine and Southern Russia, North and North-East of the Black Sea). They were cattle herding, horse breeding steppe dwellers who, like practically all other human populations, were themselves a product of the layers of human settlement and migration that have woven the intricate net of human racial groups since the first emergence of modern humans in Africa. They were also a very successful, capable and warlike people who had developed light, fast, spoke-wheeled chariots (and possibly, the composite bow) that were the wonder weapon of their time.
More here.