Horse version of ‘Who’s your daddy?’ answered

A few stallions from the Orient were the sires of all modern horses, a new genetics study suggests.

Using genetic analyses of more than 50 horse breeds, along with the pedigrees of three stallions that founded English Thoroughbreds, researchers traced the Y chromosomes of modern horses back hundreds of years. Arabian and Turkoman stallions were the source of Y chromosomes shared by all domestic stallions today, the team reports online June 29 in Current Biology. In particular, the three founding English Thoroughbred stallions were descendants of the now-extinct Turkoman horses and spread their Y chromosomes to many other breeds. This world domination started 647 years ago, give or take 229 years, Barbara Wallner of the University of Veterinary Medicine, Vienna and colleagues calculate.

Earlier studies had proposed that Y chromosome diversity is limited because only a few stallions were tamed and bred into domestic horses about 5,500 years ago. But a recent study of ancient Scythian horses showed that the winnowing of Y chromosome types happened within the last 2,000 years, long after horses were originally domesticated (SN: 5/27/17, p. 10). Wallner and colleagues’ estimate helps pinpoint when that shift happened.