Evolution Of Equine’s Single Toe Not For Speed, But Endurance

by | 04.25.2019 | 10:06pm

Though horses are known for their speed, it's thought that the horse's leg has adapted from three toes to one toe over time to be used more for endurance rather than speed. It was thought that as only single-toed horses survive today that the evolution was to allow horses the speed needed to outrun predators.

Historically, the ability of horses to carry riders at slower speeds over great distances was significantly more important than speed, researchers from the University of Bristol in Britain and Howard University in Washington, D.C. believe.

Using fossil records and studies on equine locomotion, Dr. Christine M. Janis and Dr. Raymond L. Bernor concluded that the adaptation of a single toe was for trotting during the search for food and water, not for galloping away from predators. The evolution of the horse's hoof was not the loss of toes, but the evolution of a “spring foot,” they report.

The development of the spring foot coincided with the spread of grasslands in North America 20 million years ago, but only the animals with the lineage that lead to the modern horse had a reduced number of toes; the others continued to have three toes.

The predecessors to the modern horse also had backs that became shorter and stiffer, indicating that the favorite gait was a trot, the scientists note. They propose that this was in relation to the changing foraging behavior, where they had to roam vaster areas in search of food; the single toe helped them save energy.

As the climate began to get cooler and drier, horses had to roam more to find food, promoting the selection for the energy-efficient single-toe. This necessary travel was the impetus behind the evolution, not the need to run from predators as was previously believed.

Read more at HorseTalk.

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