If you listen to Introduction to Asian Civilizations: History of India, a course taught at UCLA and which has Jawaharlal Nehru’s Discovery of India as mandatory reading, you will get a good introduction to the Aryan Invasion/Migration Theory. Unlike Matthew Herbst or Tara Carter of the MMW courses at UCSD, the UCLA instructor teaches in a very confusing manner and hence it is hard to figure out if he is touting the Aryan Invasion Theory or the Aryan Migration Theory or if he knows the difference between the two. In one part he mentions Aryans arriving on their horses in 2000 B.C.E and subduing the snub-nosed Dasas and later mentions the migration of Aryans.
This is at a time when even Marxist historians have written off the AIT. According to Romila Thapar:
There is virtually no evidence of the invasion and the conquest of northwestern India by a dominant culture coming from across the border. Most sites register a gradual change of archaeological cultures. Where there is evidence of destruction and burning it could as easily have been a local activity and is not indicative of a large-scale invasion. The borderlands of the northwest were in communication with Iran and Central Asia even before the Harappa culture with evidence of the passage of goods and ideas across the region. This situation continued into later times and if seen in this light when the intermittent arrival of groups of Indo-European speakers in the northwest, perhaps as pastoralists or farmers or itinerant traders, would pose little problem. It is equally possible that in some cases local languages became Indo-Europeanized through contact. [From Aryan Invasions to Aryan Migrations]