The origin and domestication history of domestic horses and the domestication characteristics of breeds.

The horse (Equus caballus) was domesticated thousands of years after dog, cattle, pig, sheep, and goat. Importantly, it represents the domestic animal that mostly impacted the development of human civilization. Its excellent loading and moving ability prompted the changes from fixed farming mode into mobile sharing mode. Accordingly, its domestication history deserves considerable attention. So far, many issues have long been controversial, due to the extinction of the closest wild relatives and the dramatic reduction of genetic diversity. With the continuous development of sequencing technology and the utilization of ancient samples, we got more clues to the origin and domestication process. In this review, we summarize 1) current progresses on the domestication history revealed by nuclear genes, mtDNA, Y chromosome, and ancient DNA, 2) the characteristics of population structure and diversification among modern breeds, 3) the genetic basis of important phenotypes, such as coat color, speed, and body size. The overall aim of the review is to provide in-depth insights into the studies of horse domestication, the preservation and utilization of genetic resources, the direction of breeding improvement, and the development of modern horse industry in future.