An eastward migration from the Poltavka culture (an outgrowth of the Yamnaya culture) gave rise to the Sintashta-Arkaim culture during the Middle Bronze Age (2100 BC to 1800 BC). This culture was located east of the Ural Mountains in the northern steppes.
The archeological evidence seems to indicate that the Sintashta were highly militaristic—they created extensively fortified settlements, 23 of which have been found. The weapons found on their sites include spearheads, trilobed arrowheads, chisels, and large shaft-hole axes, It is not known why the Sintashta created such fortified settlements which are unusual in the nomadic steppe culture. Against what enemy were they defending their settlements?
The funerary complexes located outside the Sintashta sites contain the remains of extravagant sacrifices, including whole horses. They also contain the remains of some of the earliest chariots. Some scholars have theorized that there are parallels between the funeral services in the Sintashta sites, and the funeral rituals described in the Rig Veda. They suggest that the Sintashta might be the inventors of the chariots with spoked wheels.
The word “asva” (horse) occurs in the Rig Veda 792 times, and the word for chariot, “ratha,” is equally numerous. In the verse 1.162.22 of the Rig Veda a prayer that accompanies a horse sacrifice is described—in it, it is said: “May this Steed bring us all-sustaining riches, wealth in good kine, good horses, manly offspring.”
Did the people who built these strongholds [Sintashta fortifications] invent chariots? And were they the original Aryans, the ancestors of the people who later composed the Rig Veda and the Avesta? These two questions are asked by David W. Anthony in his book The Horse, the Wheel, and Language.
There is a problem with the thesis that seeks to connect the Sintashta with the creators of the Rig Veda: There is not a shred of evidence that the Sintashta spoke an ancient version of Proto-Indo-European which is supposed to have led to the development of Sanskrit and several other languages. We don’t know what the language of the Sintashta was.