Fifty-six-million years later, in the same place we now call Wyoming, their descendants are working together in perfect harmony, human and horse, to move a herd of cattle off a northern slope into a grassy valley. As the horse gallops up a ridgeline, suddenly the topography changes, and the herd of cattle makes an abrupt shift. In response, the horse effortlessly executes what is known as a flying lead change—a gravity-defying maneuver that allows them to change balance and respond to the changing scenario without losing momentum or unseating their rider. Like this, horses have been our partner in successfully navigating change for thousands of years—the perfect power couple.