What ancestors did slavs and north indians have in common to explain the distribution of the r1a1 haplogroup?

to put in it a vulgar parlance.

>into Indo-Europeans and Indo-Iranians
no, Sintashta was Indo-European.
Indo-Iranians were Indo-European. Andronovo horizon (identified as proto-Indo-Iranian with Sintashta) was an expansion of Corded Ware, and they were Indo-European.

either way, why did they go east?

> was an expansion of Corded Ware, and they were Indo-European.

My homeland :- )

nope. Indo-Iranians descend from the urals and later Scythio-sarmatian migrations back westward is why some slavs have indo-iranian hapologroups

Nope what? What he said is true.

Original Indo-Iranians were Eastern Europeans.

>Indo-Iranians descend from the urals
what exactly do you think this means?

uh population expansion leading to migration maybe

...

It's missing Bell Beakers.

The indo-Iranians essentially broke off the main body of the Andronovo culture which was a larger off shoot of indo-europeans. Then their ancestors spread southwards through central asia to the iranian plateau and the indian subcontinent, leaving a trail of haplogroups to attest to their conquest.

they lived in eastern europe but certainly weren't the same as slavs: which is a group that probably emerged later, as it was implied.

They both shared the same forefathers and to this day they cluster closer to Slavs than they do to modern Iranians.

great map. if it is correct, i might have it backwards in that Sinhastra --> Andronovo might be correct

could be because of these guys who moved back westwards

>The early Indo-Iranians are commonly identified with the descendants of the Proto-Indo-Europeans known as the Sintashta culture and the subsequent Andronovo culture within the broader Andronovo horizon, and their homeland with an area of the Eurasian steppe that borders the Ural River on the west, the Tian Shan on the east. Historical linguists broadly estimate that a continuum of Indo-Iranian languages probably began to diverge by 2000 BC, if not earlier,[9]:38–39 preceding both the Vedic and Iranian cultures. The earliest recorded forms of these languages, Vedic Sanskrit and Gathic Avestan, are remarkably similar, descended from the common Proto–Indo-Iranian language.

the proto-indo-iranian speaking peoples were indo-european deal with it
afanasevo was relevant

way, way too late chronologically
R1a1a expanded out of the Ukraine

...

They certainly were indo european.

My argument is that the maternal ancestors of slavs and many North indians were raped by these Indo-european is why they share r1a

>the maternal ancestors of slavs and many North indians

of both*, otherwise you imply slavs and south asians share a specifically recent common maternal lineage
and it wasn't rape in most cases but more likely consensual in the historically relevant sense of the word, unless you'd like to suggest that demographic change happens very quickly

beyond that I'd suggest you look into ANI