Przewalski's horse Photo by Claudia Feh
CC BY-SA 4.0
The Botai Culture of Central Asia has been tied to domestication of horses some 5500 years ago. Ancient DNA was extracted from the bones of Botai horses and the genomes compared with those of other ancient and modern horses.
Cord at term of Przewalski's horse
From Benirschke Comparative Placentation
The first surprise was that Przewalski's horse clustered with the Botai horses. The inescapable conclusion is that Przewalski's is a feral population descended from those domesticated at Botai.
The second finding was that all other horses descend from a separate branch. This was foreshadowed in a previous study (previous post). The most parsimonious explanation is that there was a second centre of domestication yet to be identified.
Benirschke has several images of the placenta of Przewalski's horse (see also previous post).