Two herds of wild ponies have lived for hundreds of years on Assateague Island, a 37-mile-long Atlantic barrier island that crosses the border between the states of Virginia and Maryland. The Virginia side of the island is just east of Chincoteague Island.

This week was the 97th Annual Chincoteague Island Pony Swim, where local wranglers, dubbed “Salt Water Cowboys,” swim the herd across to Chincoteague Island. Following a parade of the horses through the village, foals are auctioned off to help maintain the size of the herd at around 150, roughly the number of horses that the island can support. The remaining horses are then led back to Assateague Island.

Where did the ponies come from? Until recently, most historians and scientists have thought that the herd grew from horses left to graze by English settlers. Local folklore, however, told a different tale — that the ponies escaped from the wreck of a Spanish galleon. While the coast has seen many shipwrecks, there is no record of any such Spanish wreck carrying horses.

Now, there is evidence that the legend of the Spanish galleon may be plausible. National Geographic reports that DNA preserved in a fossilized horse tooth found 1,200 miles away in the Caribbean may lend credence to this supposedly mythical shipwreck. In a study published in the journal PLOS One, researchers posit that the tooth belonged to a cousin of the ponies roving Virginia and Maryland’s barrier islands.

Importantly, both the Caribbean horse and Chincoteague ponies share an evolutionary lineage that originated in Bronze Age Spain, says study co-author Nicolas Delsol, a zooarchaeologist at the University of Florida.

While researching century-old fossils, Delsol came across a 450-year-old shard of horse tooth molar that archaeologists had collected in the 1980s in northern Haiti, at the site of an early Spanish colony called Puerto Real. The tooth, thought to belong to a cow, had sat forgotten in the university’s museum collections for decades.

Founded in 1503, just 10 years after Christopher Columbus reached the Caribbean, Puerto Real was a prominent Spanish ranching hub surrounded by fertile pasturelands. Colonists imported Spanish horses from southern Europe to help herd cattle, which were raised both for their hides and as food.

Mitochondrial DNA revealed the Puerto Real horse’s closest relative were the ponies from Assateague Island.

Beyond identifying the origins of the ponies, Delsol believes this tooth fragment has an even greater story to tell: It hints that Spanish settlers were sailing further north into the mid-Atlantic region when their ship sank.

While historical records of these explorations are scant, the information preserved in the colonial tooth may help connect the dots. 

“It’s more than just a horse story,” Delsol says.