Scientists have traced the ancestry of the modern horse to a lineage that emerged 4,200 years ago and quickly became dominant across Eurasia. The research published Thursday suggests that’s when humans started to spread domesticated horses around the world. This horse lineage had a genetic mutation that changed the shape of its back, likely making it easier to ride. People had domesticated other animals several thousand years before horses — including dogs, pigs, cattle, goats and sheep. But the new research that analyzed 475 ancient horse genomes shows that the shrinking genetic diversity associated with domestication happened much faster in horses.
