Oldest DNA from a domesticated American horse lends credibility to drowned folklore

Oldest DNA from a domesticated American horse lends credibility to drowned folklore

The origin of the Assateague horses has remained a mystery for centuries, but new genetic data supports the theory that they descended from Spanish horses stranded on the barrier island. Credit: Florida Museum photo by Jeff Gage

An abandoned Caribbean colony has been discovered after centuries of being forgotten and a case of mistaken identity in the archaeological record plots to rewrite the history of a barrier island off the coasts of Virginia and Maryland.

These seemingly unrelated strands were woven together when Nicholas Delsol, a postdoctoral researcher at the Florida Museum of Natural History, set out to analyze ancient DNA recovered from cow bones found in historical location. Delsol wanted to understand how cattle were domesticated in the Americas, and genetic information preserved in centuries-old teeth held the answer. But they encountered a surprise, too.

“It was a serendipitous discovery,” he said. “I was sequencing mitochondrial DNA from fossil cow teeth for my Ph.D., and I realized something was completely different with one of the samples when I analyzed the sequence.”

That’s because the specimen in question, part of an adult molar, was not from a cow’s tooth at all, but rather from a horse. According to a study published Wednesday in the journal, PLUS ONE, DNA obtained from the tooth is also the oldest-ever sequence of a domesticated horse from the Americas. The tooth was excavated from one of the first colonial settlements in Spain. Located on the island of Hispaniola, Puerto Real was founded in 1507 and for decades was the last port of call for ships sailing from the Caribbean. But rampant piracy and the emergence of illegal trade in the 16th century forced the Spaniards to consolidate their power elsewhere on the island, and in 1578, the inhabitants were ordered to evacuate Puerto Real. The deserted city was destroyed the following year by Spanish officials.

The remains of a harbor that was inadvertently crowded were discovered by a medical missionary named William Hodges in 1975. Archaeological excavations of the site were led by the eminent research curator at the Florida Museum Kathleen Deegan between 1979 and 1990.

Oldest DNA from a domesticated American horse lends credibility to drowned folklore

Nicholas Delsol was originally sequencing ancient DNA from cow teeth preserved at archaeological sites when he realized that one of his samples actually belonged to a horse. Credit: Florida Museum photo by Jeff Gage

Horse fossils and associated artifacts are incredibly rare in Puerto Real and similar sites from the time period, but bovine remains are a common find. According to Delsol, this skewed ratio is primarily due to the way Spanish colonists valued their livestock.

“The horses were reserved for individuals of high status and owning them was a sign of prestige,” he said. There are full-page descriptions of the horses in the documents chronicling the horses’ arrival [HernĂ¡n] Cortes in Mexico, which shows how important it was to the Spaniards.”

By contrast, cows were used as a source of meat and hides, and their bones were regularly disposed of in the communal waste piles called Middens. But a community’s waste is a treasure for an archaeologist, as waste from mediums often gives the clearest glimpse of what people eat and how they live.

The specimen’s biggest surprise wasn’t revealed until Delsol compared its DNA with that of modern horses from around the world. Since the Spaniards brought their horses from the Iberian Peninsula in southern Europe, it was speculated that the horses still living in that region would be the closest living relatives of the 500-year-old specimen of Puerto Real.

Instead, Delsol found his closest relatives 1,000 miles north of Hispaniola, on Assateague Island off the coasts of Maryland and Virginia. Wild horses roamed freely across the long stretch of barrier island for hundreds of years, but exactly how they got there has remained a mystery.

Oldest DNA from a domesticated American horse lends credibility to drowned folklore

This tooth is all that remains of one of the first horses introduced to the Americas, and its DNA helps rewrite the history of one of the most famous horse breeds in the United States: the Chincoteague pony. Credit: Florida Museum photo by Jeff Gage

According to the National Park Service, which operates the northern half of Assateague, the most likely explanation is that English colonists in the 17th century brought horses from the mainland in an effort to evade cattle taxes and fencing laws. Others believe the feral herds are descended from horses that survived the wreck of a Spanish galleon and swam ashore, a theory perpetuated in the 1947 children’s novel “Chincoteague Fog.” The book was later adapted into the movie, helping to spread the legend of the shipwreck to a wider audience.

So far, there has been little evidence to support either theory. Supporters of the shipwreck theory claim that English colonists are unlikely to lose track of valuable livestock, while those who favor the English origin of the herds point out that there were no sunken ships nearby and an omission wild horses in the historical records of the region.

Ancient DNA illustrates the early history of American colonial horses

Picture of a horse specimen. Credit: Nicholas Delsol, CC-BY 4.0 (creativecommons.org/licenses/by/4.0/)

Delsol explained that the results of the DNA analysis unequivocally point to Spanish explorers as the most likely source of horses in the Assateague.

“It is not widely reported in the historical literature, but the Spaniards were exploring this region of the mid-Atlantic as early as the 16th century. Early colonial literature is often incomplete and not completely comprehensive. Just because they didn’t mention horses doesn’t mean They weren’t there.”

The Assateague’s feral herds weren’t the only horses that returned to their wild heritage after arriving in the Americas. Colonists from all over Europe brought with them horses of different breeds and lineage, some of which broke their ties and fled to the surrounding countryside.

Today, the United States Bureau of Land Management estimates that there are Approximately 86,000 wild horses Throughout the country, most are located in western states, such as Nevada and Utah. Delsol hopes that future ancient DNA studies will help decipher the complex history of equine introductions and migrations that have occurred over the past several centuries and provide a clearer understanding of the current diversity of wild and domesticated horses.

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more information:
The oldest complete mtDNA genome analysis of a colonial Caribbean horse (Equus caballus) from 16th century Haiti, PLUS ONE (2022). DOI: 10.1371 / journal.pone.0270600

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