When I was a kid in Utah, I remember hearing something about some fellow who had a theory that horses hadn't been wiped out but were part of the ecology of the pre-Colombian world. The piece of evidence I can recall supporting his position was that it took the Kurgan(?) people of the Asiatic steppes 2,000 years to develop horse culture and the Blackfoot/Crow/Cheyenne et al, were able to get horses, breed them, and develop a sophisticated culture in less than 300 years after horses were re-introduced to North America by the Spanish colonies in New Mexico.
How accurate and solid is the timeline for the development of horse culture in the Great Plains? How certain are we that horses became extinct in the pre-Colombian era? What are the metrics for establishing this? Thanks horse-storians!
There is no doubt at all that horse became extinct in North America very long before their reintroduction by the Spanish. That said, there is a debate about whether or not horses went extinct prior to the arrival of humans in the Americas at the end of the Pleistocene about 15,000 years ago or if there was a short period (a couple thousand years at best) where humans and horses coexisted in the Americas. Quite likely there were remnant populations of horses somewhere in the Americas that humans could have interacted with, but the order of horse extinction and human arrival is still unresolved. Regardless, there are more than ten thousand years between the extinction of horses in the Americas and their reintroduction, so I doubt this had any impact on the ability of native groups to develop a horse culture.
One thing to consider is that horses were not introduced entirely in a vacuum. While certainly horses were often obtained without direct interaction with the Spanish, this doesn't preclude the adoption of such technologies as the saddle and stirrup which took a considerable amount of time to develop in the Old World, not to mention any transmitted cultural information about horse husbandry and riding.
Sources: Just one recent article about timing horse extinction (alongside mammoth extinction) in Alaska, but representative of considerable other literature.
Edit: Consider that at least by the 1620s, Utes, Navajos, and Apache all were directly trading with the Spanish and some of these groups had developed robust horse cultures within another century or two. There were certainly some opportunities for direct transmission of the trappings of horse culture, as then applied by these groups to their preexisting mobile lifestyles and raiding tactics.
Buck, E. Caitlin, and Edouard Bard. 2007 A calendar chronology for Pleistocene mammoth and horse extinction in North America based on Bayesian radiocarbon calibration. Quaternary Science Reviews, 26(17-18): 2031-2035.