Science - Ancient Cultures

The remains of what might have been a corral for horses has been found in Khazakhistan, where the Boltoi culture existed from 4 to almost 6 thousand years ago.

"From 3600 to 2300 B.C., the Botai culture lived in the steppe environment of Kazakhstan, where temperatures can reach subzero during winters. Domesticated horses could have weathered the deep chill, allowing the Botai people to stay put all-year round."

While it was known that the Boltoi hunted horses, it was not clear that they had domesticated horses, although it is not thought they were not the first to do so - that privelige appears to belong the Samarra culture (related to the Kurgan/Proto Indo-European hypthosis) of the current day Ukraine, but the timelines appear to be pretty close and the info here at Wiki isn't very clear, although they do lede some credence to either the Botai or the Sredny Stog culture. Interesting archaeological conundrum here.