the ground at a time. Such a gait can be maintained for long distances, and sometimes at considerable speed. Modern genetic studies have verified that ambling ability is linked to a specific genetic mechanism. Ambling horses are now uncommon in Europe. They were effectively replaced by trotting horses for several reasons: The first was that as roads improved, travel by carriage became more common, and trotting horse breeds were generally larger and stronger, more suited to the job at hand. Another reason was the rise of the Thoroughbred and other breeds developed for horse racing and for light cavalry, both of which required horses able to gallop for substantial periods of time. Breeds swift at the gallop also tend to trot rather than pace or amble. In the Americas, ambling horses continued to be bred, both in the southern United States and in Latin America. The smooth ambling gaits today have many names, including the single-foot, the stepping pace, the tolt, the rack, the paso corto, and the fox trot (see ambling). There are still many ambling breeds, particularly in North America where today they are referred to as gaited horses. Some of these breeds include the Missouri Fox Trotter, Tennessee Walking Horse, Icelandic horse and a sub-group within the American Saddlebred. The Paso Fino and the Peruvian Paso, breeds developed in Latin America, perform two or three different ambling gaits of varying speed, and are probably the closest modern descendants of the medieval palfrey. See also Jennet References Types of horse Medieval society