New DNA Evidence Rewrites Ancient American History

A barrier island off the coasts of Virginia and Maryland has had its history rewritten by an abandoned Caribbean colony unearthed centuries later and a case of identity confusion in the archaeological record.

These ostensibly unrelated strands were knitted together when Nicolas Delsol, a postdoctoral researcher at the Florida Museum of Natural History, set out to investigate ancient DNA extracted from cow bones found in archaeological sites. Delsol sought to understand the origins of cattle domestication in the Americas, and he found the answer in the genetic data contained in thousands of year-old teeth. They did, however, also have a surprise.

It was a happy accident, he claimed. "For my Ph.D., I sequenced mitochondrial DNA from fossil cow teeth, and when I evaluated the sequences, I noticed something was really wrong with one of the specimens."

The DNA of one of the earliest horses brought to the Americas, represented by this tooth, is helping to rewrite the history of the Chincoteague pony, one of the most well-known horse breeds in the country. Credit: Jeff Gage's shot from the Florida Museum

This is due to the specimen in question being a horse tooth as opposed to a cow tooth. It was a piece of an adult molar. The DNA taken from the tooth is also the earliest domestic horse from the Americas whose DNA has ever been sequenced, according to recent research that was published in PLOS ONE.

The teeth was found as one of Spain's earliest colonial colonies was being excavated. Since its establishment in 1507, Puerto Real on the island of Hispaniola has been the last port of call for ships leaving the Caribbean. Puerto Real was forced to be abandoned in 1578 as a result of extensive piracy and the growth of illegal trade, which led the Spanish to focus their authority elsewhere on the island in the 16th century. The following year, Spanish authorities demolished the abandoned village.

A medical missionary by the name of William Hodges unexpectedly discovered the harbor's ruins in 1975. Archaeologists investigated the site between 1979 and 1990, under the direction of Kathleen Deagan, outstanding research curator for the Florida Museum.

When Nicolas Delsol discovered that one of his samples actually belonged to a horse, he had originally been analyzing ancient DNA from cow molars preserved in archaeological locations. Credit: Jeff Gage's shot from the Florida Museum

At Puerto Real and sites from a similar historical period, horse fossils and related artifacts are extremely rare, although cow remains are ubiquitous. Delsol claims that the Spanish colonialists' valuation of their livestock is mostly to blame for this unfavorable ratio.

Owning a horse was considered to be a display of status and was only reserved for people with high social standing, he explained. The importance of horses to the Spanish is shown by the full-page descriptions of horses in the papers that detail Hernán Cortés' arrival in Mexico.

Contrarily, cows were employed as a source of meat and leather, and their bones were frequently dumped in what are known as middens—collective trash mounds. However, a community's trash may be an archaeologist's treasure because midden waste frequently offers the best view of what people ate and lived like.

Delsol didn't discover the specimen's biggest surprise until after comparing its DNA to that of contemporary horses from various parts of the world. He anticipated that horses still existing in that region would be the 500-year-old Puerto Real specimen's closest living relatives given that the Spanish transported their horses from the Iberian Peninsula in southern Europe.

Instead, Delsol discovered its relatives on the island of Assateague off the coasts of Maryland and Virginia, more than 1,000 miles north of Hispaniola. For hundreds of years, wild horses have grazed freely over the extensive barrier island, but it is still unclear how they arrived there.

The National Park Service, which is in charge of the northern half of Assateague, says the most likely explanation is that the horses were carried over by English colonists from the mainland in the 1600s in an effort to avoid paying animal taxes and breaking the law about fencing. According to a hypothesis made popular by the 1947 children's book "Misty of Chincoteague," which was later made into a movie, the wild herds were descended from horses that managed to survive the Spanish galleon shipwreck and swim to land.

There hasn't been much proof for either idea up until now. While supporters of the shipwreck explanation contend that it is improbable that English colonists would misplace important animals, proponents of an English origin for the herds emphasize the absence of nearby wrecked ships and the absence of wild horses from historical accounts of the area.

But according to the DNA study, Spanish explorers are without a doubt the most likely source of the horses on Assateague, Delsol said.

There aren't many accounts of the Spanish exploring this part of the mid-Atlantic in the historical record, but it happened relatively early on in the 16th century. Early colonial writing is frequently sporadic and incomplete. They may not have mentioned the horses, but that doesn't mean they weren't there.

After coming in the Americas, horses didn't just return to their natural heritage in the feral herds on Assateague. Horses of various kinds and pedigrees were transported to North America by colonists from all over Europe, some of which managed to break free and go off into the surrounding countryside.

The U.S. today According to the Bureau of Land Management, there are around 86,000 wild horses in the nation, the most of which are found in western states like Nevada and Utah. Delsol thinks that more research on ancient DNA will shed light on the convoluted history of equine introductions and migrations that took place over the course of several centuries and help explain the diversity of wild and tamed horses that exist today.

The National Science Foundation provided funding for the study.

By FLORIDA MUSEUM OF NATURAL HISTORY