One of the most often cited examples of evidence both for and against the Aryan Invasion Theory (AIT) is the presence of horses. Supporters of the AIT postulate that horses were domesticated by Aryans and brought to India during the invasion (or migration). Along with the horse, the chariot and spoked wheel (and thus a means to conquer) were also introduced to India around the fall of the Harappan Civilization.
Author R.S. Sharma (1995), an eminent historian and academic of Ancient and early Medieval India, whose 1977 Ancient India was banned by the Janata Party government in 1978, among other things for its criticism of the historicity of Krishna and the events of the Mahabharata epic, maintains that the Aryan and Harappan cultures were in fact separate and not co-mingled “it is significant that the Rig Vedic culture was pastoral and horse-centered while the Harappan culture was neither horse-centered nor pastoral” (source). Since the time of Sir John Marshall, British Archaeologist, the absence of the horse has been the mainstay of the belief that the speakers of the Vedic language must have succeeded the Harappan civilization: “in the lives of the Vedic-Aryans the horse plays an important part… to the people of Mohenjo-Daro and Harappa the horse seems to have been unknown” (Marshall 1931, 111 source).
Hans Hock, Ph.D. in linguistics from Yale University, currently teaches general historical linguistics, Indo-European linguistics, Sanskrit, diachronic sociolinguistics, and the history of linguistics. About the horse, he summarizes the problem very well: "no archaeological evidence from Harappan India has been presented that would indicate anything comparable to the cultural and religious significance of the horse (...) which can be observed in the traditions of the early IE peoples, including the Vedic Aryas. On balance, then, the 'equine' evidence at this point is more compatible with migration into India than with outward migration." (1999:13 source)