The first colonial horses of the Americas: the Iberian founding stock and what a 16th-century tooth from Haiti shows
Horses re-entered the Americas on Columbus's second voyage, landing at La Isabela on Hispaniola on 28 November 1493. The Caribbean became the breeding reservoir from which horses reached Mexico, Peru and Florida, and from which feral herds spread to the Great Plains. A tooth from Puerto Real in Haiti, from a layer laid down when the town was abandoned in 1578, has yielded the first complete mitochondrial genome of a post-Columbian horse in the hemisphere, and it reads as Iberian.
Why this wins its question: The standard account says the Spanish brought the horse and then jumps straight to the Plains. What it skips is the mechanism and the evidence: a dated royal ordinance and a landing date in 1493, a Caribbean breeding reservoir that within a decade made further imports unnecessary, sixteen named animals at Veracruz in 1519, and an actual sequenced genome from a tooth in a 1578 abandonment layer at Puerto Real - the first post-Columbian horse genome from the hemisphere. This object binds each step to the peer-reviewed archaeogenomics, prices the Iberian reading honestly by naming the haplogroup's wide distribution and the single-lineage limit the authors themselves state, keeps the conquest and the ranching economy on the record beside the equestrian cultures, and marks the boundary of the claim with the Jamestown evidence that the eastern seaboard was stocked from elsewhere.
Claims
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A royal ordinance of the Castilian monarchs in 1493 directed Fernando de Zafra to hire Andalusian horsemen to accompany Columbus on his second voyage, and the horses landed at La Isabela on Hispaniola, in what is now the Dominican Republic, on 28 November 1493. The date is the beginning of the continuous presence of the domestic horse in the Americas.
Within a decade the herds on Hispaniola grew from a few dozen animals to large herds, helped by favourable conditions and by continued importation from the Iberian Peninsula, until the governor decreed that there was no further need to import because the island population was sufficient. The Caribbean, not Spain, became the reservoir the mainland was stocked from.
Cortes reached the Mexican Gulf coast in 1519 with sixteen horses, few enough that the chronicler Bernal Diaz del Castillo described each animal individually. Horses had reached the Mesoamerican mainland by the 1520s and the northern coast of the Gulf of Mexico, in what is now Florida, by 1538.
A horse tooth from Puerto Real, a town founded by Spain in northern Haiti in 1503, recovered from a stratigraphic level deposited during the town's initial abandonment in 1578, has yielded the first complete mitochondrial genome of a post-Columbian horse in the Western Hemisphere. It belongs to equine haplogroup A, and the authors read that as consistent with an Iberian origin, since the haplogroup is present in the Iberian Peninsula as early as the Bronze Age.
The Iberian reading is an inference and not an exclusion. Haplogroup A is distributed widely - in the modern specimens compared, about 46.7 per cent are from Central Asia, 37.3 per cent from Southern Europe and 10.0 per cent from the Middle East - so the haplogroup does not by itself demonstrate Spanish ancestry. The documentary record of where these animals came from is carrying part of the weight of the conclusion.
In the comparison the Puerto Real animal came out closest to a modern specimen of the Chincoteague pony, a feral North American population, at a distance of six mutations. This is suggestive of continuity between the earliest Caribbean colonial stock and later feral American horses, and it is not more than suggestive: the study reads one maternal lineage from one animal, and its authors say so.
As the herds grew, many horses became feral, and by the 1650s they were widespread from Mexico to the Great Plains of North America, where they were tamed and re-domesticated by Native American communities. In many regions horses reshaped Native cultures by making an equestrian way of life possible.
The same animals were instruments of the invasion. They were pivotal to European military expeditions in the Americas, and horse labour was afterwards vital to colonial economies such as ranching, which conditioned how colonists used American environments. The transfer that gave the Plains and the Pampas their horse cultures is the same transfer that mounted the conquest, and both belong in any account of it.
Not every equid in the Americas descends from Spanish stock. While the first horses reached western and southeastern North America through Spanish activity, many of the first domestic equids on the eastern seaboard arrived with English settlers, and genomic work on the Jamestown animals of 1607-1610 models their donkey as European with West African ancestry, best fitted from Mauritania, with no contribution from mainland Spain.