History of horse domestication theories

One set hypothesized multiple ancestral body types of the single species Equus ferus or the original wild horse, each adapted to a given environment.

[3] Another hypothesis held that prototypes originated from a single wild species and that all different body types were entirely a result of selective breeding after domestication.

A theory associated with James Cossar Ewart in Scotland and Johann Ulrich Duerst in Germany postulated three primitive horse types, considered subspecies of Equus caballus, as ancestors of modern breeds.

They were:[6] To these Elwyn Hartley Edwards adds a fourth, the "Tundra Horse", supposedly ancestor of the Yakut pony, and "largely unconsidered by hippologists".

[6] A later theory associated with European scholars such as Jimmy Speed, Ruy d'Andrade, Hermann Ebhardt and Edward Skorkowski, postulated four basic body types, which were not considered to be named species.

[6] They were: Bennett (1998) postulated seven subspecies of E. caballus,[7] of which four supposedly contributed most to the ancestry of the domesticated horse, both directly and via assorted crossbred lineages between them.

It also shows that certain adaptations were strongly selected for by horse riding, and that equestrian material culture – including Sintashta spoke-wheeled chariots (but not Indo-European languages) spread alongside.