Criollo pigs of the Americas: a Canary Islands cargo of 1493 and its Iberian signature
The first pigs in the Americas were loaded in the Canary Islands on Columbus's second voyage of 1493. The largest survey of their descendants - 1,715 animals across 46 populations - finds Criollo pigs still closest to Iberian breeds, the Iberian contribution coming mainly from the northern Celtic-type breeds rather than the famous Mediterranean ones, and no trace of the supposed colonial-era Chinese introduction. Several of these breeds now have double-digit censuses.
Why this wins its question: Pigs are the forgotten half of the Columbian livestock transfer - they get a clause in the Columbian Exchange summary and nothing else, even though they arrived on the same 1493 voyage as the cattle and mattered more to colonial subsistence. This object gives them the dated cargo, the port of loading in the Canaries, and then a result no general account carries: the largest survey of the descendants, 1,715 pigs across 46 populations, showing the Iberian relationship still closest at O = 0.021 against 0.04 for commercial breeds, and locating the ancestry in the Celtic-type breeds of the northern Iberian Peninsula rather than the Mediterranean Iberico that popular accounts assume. It records a clean negative - no Chinese genetic contribution, contrary to a long-repeated claim - and states the endangerment in census numbers rather than adjectives, down to 99 purebred San Pedreno. The ecological cost of free-ranging colonial swine is bound to a palaeoecological synthesis and given its own claim, so the entry is a transfer history and not an advertisement.
Claims
Every assertion below is bound to registered sources and carries its own confidence. Weight them; do not treat the page as uniformly authoritative.
The arrival is dated and the port named: "The first domestic swine arriving in the American continent came from the Canary Islands, in the second voyage of Columbus in 1493" - the same voyage and the same archipelago that supplied the founding cattle. The Canaries functioned as the breeding and provisioning stage between Europe and the Atlantic crossing.
The test of that history was done at unusual scale for a livestock survey: 24 microsatellite markers scored across 46 populations or breeds and 1,715 pigs, including 17 American Criollo breeds - among them Mulefoot, Red Wattle Hog and Guinea Hog in North America and Pelon Mexicano, Criollo Cubano, Criollo Salvadoreno, Criollo Venezolano and Criollo Ecuatoriano further south - set against 15 Iberian breeds, 5 commercial breeds, 4 wild boar populations, three British breeds, the Hungarian Mangalica and the Chinese Meishan.
Five hundred years on, the Iberian signature is still the closest relationship in the data. "The smallest distance was found between the CRI and IBE groups (O = 0.021)... The CRI then had distances of about 0.04 with the COM group and about 0.06 with the LBR and WBO" - that is, American Criollo pigs sit roughly twice as close to Iberian breeds as to commercial ones and three times as close as to wild boar.
Which Iberian pigs is the finding that overturns the expectation. The Iberian contribution runs not through the celebrated black Mediterranean pig of the south but through the north: "the Iberian influence on Criollos has been mostly through the Celtic group of breeds, which includes BIS and CEL (from the northern Iberian Peninsula), rather than from breeds of the Mediterranean group (from the south)". The Bisaro and Celta of the Atlantic north-west, not the Andalusian Iberico, are the closer relatives of the American herds.
A long-standing claim about Asian introductions fails the test. On the hypothesis that Chinese pigs reached the Americas through colonial trade and contributed to Criollo stock, the authors are direct: "no evidence of this event was revealed in our study". A negative result, and worth recording as one.
What survived is unusually diverse rather than degenerate. The Criollo group showed the highest diversity of any group measured - expected heterozygosity 0.702 against observed 0.566 - which is what an old, structured set of populations with limited commercial introgression looks like. Commercial contamination was in fact rare across the Criollo breeds, with the Red Wattle Hog the clear exception in sharing ancestry with Duroc.
At national scale the numbers are alarming. A 2024 genome-wide study of the four recognised Colombian Creole breeds - San Pedreno, Zungo, Casco de Mula and Criollo Chocoano - found effective population sizes of 16, 19, 16 and 10 respectively, and censuses of fewer than 138 purebred animals for each official breed, with San Pedreno reported at 99. It also detected Landrace introgression into San Pedreno, and confirmed the significant relationship with the Iberian pig. The per-breed samples were small (7 to 11 animals), which is why these figures are given with the sample size attached.
The conservation argument follows from the genetics rather than from sentiment: the Criollo populations hold their own identity and, given the endangered status of many of them, warrant recognition and protection to prevent their extinction - a genetic pool that no commercial breeding programme can reconstruct once it is gone.
The counterweight is ecological and it is specific. Pigs travelled as a colonising provision, went feral readily, and the palaeoecological record picks up the consequence at the far end of the Spanish world: on Pohnpei "the simultaneous introduction of pigs to the island by the Spanish" is offered as the likely reason the expected forest recovery did not follow the island's population decline. Free-ranging introduced swine were, in places, the thing that stopped a landscape healing.