Thoroughbred Race Horses All Traced to One 17th-Century Mare

The Bazzani Scully Brand Lawyers Handicap race, Melbourne, Australia, Jan. 26, 2012. Scott Barbour/Getty Images

All the great names in thoroughbred horse racing - from Secretariat to Man O'War, from Seabiscuit to Seattle Slew - they're all related, and a team of geneticists has now traced their talent for speed back to a single ancestor. The "speed gene" that made them all so fast was apparently a genetic aberration, and it probably started with one British mare who lived in the mid-17th century.

Emmeline Hill of University College Dublin led a team that analyzed DNA in 593 horses from 22 modern breeds, as well as museum specimens from 12 historically famous stallions. Modern genetics have become sophisticated enough that they could tell, with considerable precision, what the horses had in common.

"The results show that the 'speed gene' entered the thoroughbred from a single founder, which was most likely a British mare about 300 years ago when local British horse types were the pre-eminent racing horses, prior to the formal foundation of the thoroughbred racehorse," said Hill in a prepared statement.

She and her colleagues published their findings in the journal Nature Communications.

Lest this seem like some arcane animal study, it does involve a big-money sport and, more important, questions about how genetic characteristics can be inherited and traced. If you can decipher the genes that make thoroughbreds so fast, say the researchers, you can also find clues to genetic diseases in people. Thoroughbred horses are useful for study because the records of their ancestry are - forgive the pun - really, really thorough, going back centuries.

The great speed horses all shared two genes associated with muscle development. The combination did not show up in regular farm horses, or donkeys, or zebras.

Horses with the two genes were consistently top sprinters. It's no accident that the Kentucky Derby is a mile and a quarter, usually won in just more than two minutes. Other genetic combinations were found in horses that were slower but able to run longer.

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