Changes

Most studies suggest that domestication of the horse took place along the Eurasian steppe. However, it is not clear where exactly and most likely there were several independent domestication attempts. Interestingly, wild horses before domestication show a wide range of interspecies variation; however, it is believe that only one type of species became domesticated.<ref> For more information regarding the debate of horse domestication, see: Olsen, Sandra. 2006. “Early domestication on the Eurasian Steppe,” In: ''Documenting Domestication: New Genetic and Archaeological Paradigms'', Melinda Zeder (Ed.). Berkeley, Calif: University of California Press, pg. 245-269.</ref> Most likely, the horse was domesticated by 4000-3500 BC. All domesticate horses are classified as Equus ferus caballus, with Equius ferus as being the species that domesticated horses derive from.<ref>For more information on the species of horses, including how a single species became domesticated, and their genetics, see: Weinstock, Jaco, Eske Willerslev, Andrei Sher, Wenfei Tong, Simon Y.W Ho, Dan Rubenstein, John Storer, et al. 2005. “Evolution, Systematics, and Phylogeography of Pleistocene Horses in the New World: A Molecular Perspective.” Edited by David Hillis. ''PLoS Biology 3'' (8): e241. dos:10.1371/journal.pbio.0030241.</ref>  Initial domestication may have been done as a means to develop horses as traction animals, or use in agriculture and plowing, and also for riding.<ref>For more information for the early domestication of the horse, see: Mills, D. S., and Sue M. McDonnell, eds. 2005. ''The Domestic Horse: The Origins, Developments, and Management of Its Behavior''. Cambridge, UK ; New York: Cambridge University Press, pg. 7.</ref> Probably at around the 3rd millennium BC, the horse began to spread across Eurasia and into China, Europe, and India. This could have been associated with the migration of Indo-European and Eurasian groups that were likely migrating across Asia during this time. These populations may have introduced horses, therefore, to new regions such as the Near East, India, and China.