A bit difficult as many of the Scythians live in the Central Asian Steppe. In addition, as the onager pulled chariots charge north they are met by the archers mounted on cattle. Well if the Khoi could ride cattle, why not the Scythians?
In OTL Darius lead an expedition to that part of the unknown making contact with the Scythians. He was continuely fustrated by their fleeing, and ulitamately gave up. Without horses they would have a completely different tactics and lifestyle, one that was probably more setitary or if nomadic was pastoral. I think He or someone like him would have conquered that portion of Central Asia under these Nomads and Semi-nomads if they didn't have that same type of life-style.
