New research shows that the story of how horses became calm and steady enough to carry people is written deep in their genetic code.
Two recently published studies in Science show how ancient DNA reveals the moment horses tipped from being wild and flighty to being steady enough for the saddle.
Scientists sequenced the genomes of hundreds of ancient horse remains, some more than 5000 years old, and compared them with modern horses. They found strong evidence that early herders unconsciously selected animals that were less anxious and more tolerant of human handling.
One key gene region, linked to ZFPM1, appears to influence fear and anxiety responses. Around 5000 years ago, horses carrying the “calmer” version of this gene began to spread more widely. That genetic change likely made it easier to halter, handle and eventually ride horses without constant risk of being thrown.
But temperament wasn’t the only change. Another region of the genome, near the GSDMC gene, surged in frequency about 4,700 years ago. This variant is associated with stronger backs, better coordination and improved balance, all traits that make a horse physically suited to carrying a rider.
In lab tests, mice engineered with this gene variant showed flatter backs, stronger forelimbs and improved motor skills. For horses, those same changes would have meant steadier gaits and less risk of stumbling under weight — an evolutionary nudge toward becoming reliable saddle animals.
The researchers say this genetic “tipping point” helped one particular horse lineage, known as DOM2, spread rapidly across Eurasia about 4,200 years ago, eventually becoming the foundation stock for nearly all modern domesticated horses.
One factor highlighted by the research is that although horses have played a transformative role in the recent evolution of humans, altering communication, transportation, farming, and warfare, their domestication occurred unexpectedly late, only around 4500 years ago – more than 5000 years after the domestication of pigs, goats, cattle, and sheep.
Genes affecting height, body size, coat color and other “classical” traits show up later in the record (e.g. ~2,700 years ago) – meaning the early phases of domestication focused more on behavior and function than appearance.