Intensive selective breeding in recent centuries, using limited numbers of stallions, has robbed many modern horse breeds of genetic diversity in their male lineages.
Scientists who recently examined the male-specific Y chromosome of Chinese Mongolian horses found ancient signatures of paternal genes that have not previously been described in other existing horse populations.
In other words, male-specific genes still exist in the Chinese-Mongolian horse population which appear to be lost to most modern horse breeds.
Dr Haige Han and her colleagues, writing in the journal Animal Genetics, note that the Mongolian horse represents one of the most ancient equine populations in existence today.
They inhabit the Central Asian steppe, mainly in parts of northeastern and northern China, the Mongolia People’s Republic and some areas of eastern Russia. This area is most likely one of the centres of early horse domestication.
Mongolian horses have not been subject to the same intense artificial selection that has shaped modern horse breeds found mainly in Europe and North America.
But the various Mongolian sub-types do have some distinct characteristics arising from the long-term selection by herdsmen for adaptation to local conditions
For their study, the researchers analysed DNA from hair samples collected from 60 Chinese Mongolian horses, representing five distinct sub-types.
The male genetic profile seen in the Sanhe, Baicha Iron Hoof and Abaga Black populations were found to be cosmopolitan. This international look to their male lines indicates efforts to improve the breed through outcrossing.
While the Wushen and Wuzhumuqin horses had this same genetic signature of outcrossing, they also had an ancient signature of males lines that have not previously been described in modern horse populations.
“These relatively undisturbed landrace populations represent windows into the past,” the study team said.
Further investigation of these variations will be important for the discovery of lost diversity in modern domestic horses, the authors said, as well as helping our understanding of the evolutionary history of equine paternal lines.
The researchers’ findings also pointed to the movement of genes between Chinese Mongolian and Arabian horses.
An appreciable number of Wuzhumuqin horses were found to carry male genetic profiles typically observed in Arabian horses.
“Rather than inferring that these [male genetic profiles] arose in Arabian horses and migrated east, we contend that this finding reflects millennial-old gene flow from Chinese Mongolian populations into horse populations on the Arabian Peninsula, possibly during historic human expansions led by Genghis Khan that were associated with a dynamic horse culture.”
The scientists said 38% of the Chinese Mongolian horses tested had male genetic profiles that had not previously been described, which might be a consequence of the majority of genetic markers being identified through analysing modern European horse breeds.
This new genetic evidence suggests that one-third of authentic Chinese Mongolian male lineages have roots going back more than 1400 years.
“These Y lineages may be found to pre-date domestication, as these results also strongly suggest that the authentic Chinese Mongolian horses contain ‘private’ [male genetic profiles] that have not yet been described within modern populations.”
The full study team comprised Haige Han, David MacHugh and Emmeline Hill, from University College Dublin; Barbara Wallner and Doris Rigler, from the University of Veterinary Medicine, Vienna; and Manglai Dugarjaviin, from Inner Mongolia Agricultural University.
Chinese Mongolian horses may retain early domestic male genetic lineages yet to be discovered.
Han H, Wallner B, Rigler D, MacHugh DE, Manglai D, Hill EW.
Anim Genet. 2019 Aug;50(4):399-402. doi: 10.1111/age.12780. Epub 2019 May 9.