As with the Norman invasions of England…?
It didn’t take me long to find this:
Wikipedia on Indo-Aryan migration
Kivisild et al. (2003) point out that, although northwest India was ruled for several centuries by dynasties
descended from the armies of Alexander the Great, neither the M170 nor M35 genetic markers associated with Greeks and Macedonians has been found anywhere in India, and cautions that the shared prehistoric genetic inheritance of Indian tribal and caste populations “does not refute the existence of genetic footprints laid down by known historical events. This would include invasions by the Huns, Greeks, Kushans, Moghuls, Muslims, English, and others.” However, Kennedy (in Erdosy 1995:60) states that discontinuities in the prehistoric skeletal record occur either too early or too late to fit the classic scenario of a mid-second millennium B.C. Aryan invasion, but that this does not preclude “a gradual infiltration of foreigners”. Witzel (in Erdosy 1995:113) states that ‘their genetic impact would have been negligible and, as was the case with the Normans in England, would have been “lost” in a few generations in the much larger gene pool of the Indus people.’ Vijendra Kashyap, one of the authors of Sahoo et al. (2006), states that the people of the Indian subcontinent are indigenous to South Asia, but that Indo-European languages are not, and that language change resulted from the migration of numerically small superstrate groups that are difficult to trace genetically. Cavalli-Sforza (2000) states that “Archeology can verify the occurrence of migration only in exceptional cases” and identifies the introduction of Indo-European languages to India as an instance of language replacement, when the language of a population changes accompanied by only modest genetic effects.