Also, one group of early proto-Indo-Europeans whom we call the Yamnaya were attributed to either their domestication or utilizing their full potential for animal husbandry, transportation, and warfare.

However, we know that this isn't the case. The Yamnya's horses were too small still to support the weight of a person, and also, the Yamnaya had disc-shaped wheels which had too much inertia to be able to go fast as a chariot or wagon.

So about 1,000 years after the Yamnaya started their journey, one of their offshoots became the Sintashta of East of the Urals just north of Kazakhstan. These Sintashta spoke a language that descended from the Yamnaya's language, but it skewed more like Proto-Indo-Iranian.

Anyways, these Sintashta people selectively bred horses until they were big, and also, they innovated the spoked wheel, which made them unstoppable in war. The Sintashta lived from 2100 BC - 1800 BC.