The question of whether mustangs in the West are feral versus wild is a controversial one; it’s got a knack for appearing in the comment section of many a mustang story. Mustang advocates are adamant the wild horse is a bona fide North American wildlife species – on par with deer, elk, bison and pronghorn. Scientists, ever the party poopers, beg to differ.
Horse evolution is well documented in North America’s fossil record – first as a small dog-sized animal that walked on five toes over 50 million years ago, on to larger equines that bore their weight on single hooves. Horses went extinct on North America some 12,000 years ago – likely due to some cocktail of climate change and overhunting by man – but not before they migrated over the land bridge into Asia (where they further diversified into asses and zebras).