Almost All Modern Horses Descended From A Few Oriental Stallions

Garant 20, a purebred black Akhal-teke stallion.
(Credit: Artur Baboev / CC BY-SA 3.0)
La Mirage, a purebred gray Arabian stallion.
(Credit: Trescastillos /

Strong sex-biased selection severely limited Y chromosome lineages

Polymorphic DNA markers made it possible to identify individual stallion lineages

Figure 2. Maximum-Parsimony Tree of the Horse MSY from 52 Individuals
HT-defining mutations are indicated on branches, and the four mutations already described are marked with an asterisk. Bootstrap confidence values (500 replicates) are given on branches, and haplogroups are distinguished by colors. Source breeds are listed for each haplogroup, with number of samples per breed in parentheses. (doi

Almost all modern horse breeds clustered into one 700 year old haplogroup

Figure 4. MSY HTs Detected in 363 Purebred Horses of 57 Breeds
(A) Median-joining network. The size of each circle reflects the sample size of each HT. Haplogroups with confirmed Original Arabian ancestry are indicated by a dotted green line, and those with English Thoroughbred ancestry are indicated in red. Mutations are given on the branches. (Images: Przewalski’s Horse, domestic horse, and Bairactar: Archiv Otto Antonius, Tiergarten Schönbrunn; Darley Arabian by John Wotton, Wikimedia Commons.)
(B) Relative frequency of MSY HTs in different breeds and groups of breeds. The number of samples for each group of breeds is given in parentheses.

English Thoroughbred founder stallions can be traced back to a Turkoman stallion

2014 Triple Crown winner, American Pharoah, is a descendant of Eclipse.
American Pharoah and jockey Victor Espinoza win the 2014 Belmont Stakes to become only the 12th Triple Crown winner in history — and the first since Affirmed won in 1978. (Credit: Mike Lizzi / CC BY-SA 2.0)
Free jumping a purebred Akhal-Teke stallion, Dirkhan.
(Credit: Artur Baboev / CC BY-SA 3.0.)

Stallions experienced the most intense selection of any domestic animal



Written by

Evolutionary ecologist & ornithologist, science journalist. Freelance, job hunting. Writes about science for Forbes. Formerly: The Guardian. Always: Ravenclaw.

Welcome to a place where words matter. On Medium, smart voices and original ideas take center stage - with no ads in sight. Watch
Follow all the topics you care about, and we’ll deliver the best stories for you to your homepage and inbox. Explore
Get unlimited access to the best stories on Medium — and support writers while you’re at it. Just $5/month. Upgrade