By using genomic analysis, scientists have identified DNA changes that helped turn horses like those seen in prehistoric cave art into today's Secretariats and Black Beautys.
Being able to understand the genetic changes involved in equine domestication, which previous studies traced to the wind-swept steppes of Eurasia 5,500 years ago, has been high on the wish list of evolutionary geneticists due to the important role that taming wild horses played in early development of civilization.
When soldiers, explorers and merchants could all gallop instead of just walking, it revolutionized trade, warfare, transmission of ideas and movement of people. It also allowed the development of continent-sized empires like the Scythians 2,500 years ago in what is now Iran.
It was all made possible thanks to 125 genes, according to the study, published this week in the journal Proceedings of the National Academy of Sciences.
"Related to skeletal muscles, balance, coordination, and cardiac strength, they produced traits so desirable that ancient breeders selected horses for them," said geneticist Ludovic Orlando of the Natural History Museum of Denmark, who led the study, according to Reuters.
Genes active in the brain also went through selection. Variants linked to social behavior, fear response, agreeableness and learning are all more abundant in domesticated horses, according to Orlando.
Getting the chance to compare domesticated species to their wild relatives allowed scientists to figure out how organisms became domesticated.
With no wild horses to study, the team analyzed DNA from 29 horse bones found in the Siberian permafrost and dating from 16,000 and 43,000 years ago. Orlando's team then compared it to DNA from five modern domesticated horses.
Some genes in today's horses weren't there from the ancient ones, proving they showed up due to recent mutations. Among them: a short-distance "speed gene" that helps every Kentucky Derby winner each year.
Geneticists not involved in the study said that analyzing equine DNA from the time of domestication, instead of the millennia before, could show more clearly what genetic changes took place as horses were tamed.
"Comparing ancient genomes to modern genomes is tricky," said Arne Ludwig of the Leibniz Institute for Zoo and Wildlife Research in Berlin, according to Reuters.