The next time you pause to take in the calming sight of a horse resting under a tree, consider that you are sharing an esthetic experience with people around the globe.
There are some 300 horse breeds in the world today; each has its distinguishing features, but the breeds evidently also have much in common. A new study published in the Canadian Journal of Animal Science has revealed that these modern horses all have an intriguing combination of genetic diversity and connectedness that has existed since antiquity.
Researchers at Shaanxi University of Technology in China drew on a unique assembly of mitochondrial DNA (mtDNA) data from 3,965 horses—the largest ever data set of its kind.
They collected 348 horse blood samples and accessed previously published data for horses in Africa, the Americas, the Middle East, India, Europe, and Asia. The researchers also studied 194 archaeological samples.
The Shaanxi University scientists, motivated by a specific interest in China’s indigenous breeds, wanted to illuminate the genetic nature of the modern horse. By analyzing mtDNA, DNA drawn from a cell’s mitochondrion rather than its nucleus, the team was able to infer not only the current level of genetic diversity but also the evolutionary history of the horses in the study. Though thoroughbred horse breeding emphasizes paternal lineage, much can be learned from studying maternal lines, which is the unique feature of the D-Loop segment of mtDNA.
Through D-Loop analysis of the data set, the researchers found that not only do Chinese breeds of horses express high genetic diversity and reflect multiple maternal origins, but these same qualities can also be found in horse breeds in other regions.
Interestingly, this diversity is coupled with strong linkages among all modern horses. The researchers suggest these linkages show that “extensive gene flow had occurred (long ago) between different horse breeds in Asian and European regions.”
The scientists reached this conclusion because the varied horse genes form patterns that align with a limited number of haplogroups, groupings associated within single lines of the phylogenetic tree. All 18 of the known horse haplogroups were evident in the Chinese horse breeds tested, and with some qualifications, most of the haplogroups are found in other parts of the world. Many groups were also found in the samples from ancient times.
So, the next time you see a horse standing in the shade of a tree, you might pause and think of our connection with it as well as the connections within the horse’s evolutionary tree.
Read the paper: Abundant genetic diversity and maternal origins of modern horses in the Canadian Journal of Animal Science.
