A single mutation gave horses a temperament amenable to human riders

Tibi Puiu, A Single Mutation Made Horses Rideable and Changed Human History, ZME Science, Aug. 28, 2025.

Horses didn’t just change how people traveled. They rewired the course of civilization. Yet scientists have always puzzled over how, exactly, wild steppe animals transformed into the rideable companions that pulled chariots, carried warriors, and eventually powered empires.

Now, a sweeping new study of ancient horse DNA offers a precise answer: a genetic quirk in a single gene, called GSDMC, helped turn skittish animals into the creatures humans could saddle and ride. Once that gene variant spread, humanity’s history took off at a gallop.

Researchers led by Xuexue Liu and Ludovic Orlando analyzed horse genomes spanning thousands of years, tracking 266 genetic markers tied to traits like behavior, body size, and coat color. Their results, published in Science, suggest that early domestication didn’t begin with flashy coats or taller frames. Instead, the first breeders unsurprisingly selected for temperament.

One of the earliest signals of selection appeared at the ZFPM1 gene, linked in mice to anxiety and stress tolerance. That genetic shift, around 5,000 years ago, may have made horses just a little calmer — tame enough for people to keep close.

But the real game-changer came a few centuries later. Around 4,200 years ago, horses carrying a particular version of the GSDMC gene began to dominate. In humans, variants near this gene are associated with chronic back pain and spinal structure. But for horses and lab mice, the mutation reshapes vertebrae, improves motor coordination, and boosts limb strength. In short, it made horses rideable.

There's more at the link. H/t Tyler Cowen.