A curious individual asked the above question, in the context of discussion of AIT/OIT in the context of genetics and linguistics arguments flying in the SMsphere.
Here was my brief reply. I thought it would be worth documenting for posterity.
If by AIT, it means these AIT folks also brought in Sansrkit and/or Rigveda sanskrit, and also horses, chariots, etc. to Indian subcontinent and word ‘Arya’ with them.. then it could have happened only before ~ 15000 BCE (note 15K BCE and not 1.5K BCE). As to OIT, there are literary allusions (and certainly enough to assert for outward migrations to Iran, west of Iran, Afganistan..etc…. I am being careful here…since outward may be a wrong word.. as Iran/Afganistan was very much the playground (at least Afganistan, modern Pakistan) of Ramayana or Mahabharata times. I have made a case for (purely on astronomy and subsequent chronological grounds) that OIT (s) could have occurred ~17000-15000 BCE, post 12000 BCE, pre 5600 BCE, post 5000 BCE and so on. And I am all for exposing these to corroboration/falsification by Genetics research. Now this is not to discount potential OIT(s) and also AIT(s), prior to say 20K BCE, but then ‘astronomy based’ evidence runs into its own limitations, in tracking things beyond ~25K BCE.