By Michael Price
Horse breeding records are some of the most impressive efforts to chronicle animal lineages in human history, with some stretching back thousands of years. Yet decoding the genetic origins of today’s horses has proved remarkably difficult. Now, a new study finds that nearly all modern horse breeds can be traced to two distinct, ancient Middle Eastern lines that were brought to Europe about 700 years ago. Understanding how these horses were traded, gifted, or stolen could shed light on human history as Eastern and Western civilization commingled and collided.
People first domesticated horses some 6000 years ago in the Eurasian Steppe, near modern-day Ukraine and western Kazakhstan. As we put these animals to work over the next several thousand years, we selectively bred them to have desirable traits like speed, stamina, strength, intelligence, and trainability. People have tracked horse pedigrees for almost as long as we have kept them, but it wasn’t until the 1700s that detailed “studbooks” emerged in Europe to keep tabs on which horses fathered which foals and what characteristics the foals inherited.
The new study’s lead author, Barbara Wallner, an evolutionary biologist at the University of Veterinary Medicine in Vienna, paired these old, yet meticulously kept data with modern DNA sequencing techniques to investigate the origins of today’s horse breeds.
Wallner and colleagues first located dozens of variations in a segment of DNA along the Y chromosomes of 52 living male horses representing 21 modern breeds. As tiny mutations pop up in a stallion’s Y chromosome, they are inherited by all of its future male progeny, allowing geneticists to trace which males came from which paternal line.
That may seem simple, says Ernest Bailey, a geneticist at the University of Kentucky’s Gluck Equine Research Center in Lexington, who wasn’t involved with the study, but it’s actually quite a challenge: Locating functional genes within the Y chromosome is notoriously tricky because of its long, repetitive sequences of nonfunctional DNA. Horses in particular have extremely low genetic diversity along the Y chromosome, making it even more difficult to locate meaningful variations between individuals.
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