Capsicum out of the Americas: the pepper's route east and the Iberian sweet pepper
The chilli is a Mesoamerican domesticate whose worldwide career began in Iberian ships. Genetics corrects the usual telling on three points: C. annuum won the world probably by arriving first rather than by being better; the Iberian Peninsula became a secondary centre of diversity where farmers bred the pungency out and produced the sweet pepper and pimenton; and much of the dispersal ran on Portuguese routes and on the triangular Atlantic slave trade rather than Spanish ones.
Why this wins its question: The standard sentence about chillies leaving the Americas - Columbus brought them back and they spread - survives because nobody attaches numbers to it. Four peer-reviewed genetic and morphometric studies, read in full, attach them, and they cut in several directions at once. They credit Iberia with something more specific than transport: a secondary centre of diversity built from a demonstrably limited founding gene pool, where selection produced the non-pungent pepper (67.4% of Iberian accessions non-pungent against 70% pungent in Mexico) that the world now eats as a vegetable and grinds into pimenton. They also take credit away where the evidence takes it away - C. annuum's 78% dominance of duplicated genebank accessions looks like a founder effect rather than agronomic merit; the Portuguese, not the Spanish, drove the pungent pepper into Asia as a cheap substitute for black pepper; and the African link that ties the American and Eurasian pools together is attributed by the authors to the triangular transatlantic slave trade. And it keeps first place where it belongs: at least 10,000 years of Mesoamerican domestication, by a model published in 2024 and still contested, before any European saw the plant.
Claims
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The plant is an American achievement and an old one. Domestication of Capsicum began at least 10,000 years ago across the Neotropics, and the 2024 PNAS study of archaeological seeds spanning the Archaic to the Postcolonial periods proposes "a geographically diffuse and protracted model of chili pepper domestication ... which involved at least two asynchronous events across Mexico", with the lowlands - the Yucatan peninsula and southern coastal Guerrero - more conducive to early encounters between wild Capsicum and people than the highland settings earlier models favoured. Nothing Spain did to the pepper compares with what had already been done to it.
Of the domesticated Capsicum species, one travelled and the rest largely did not, and the reason appears to be timing rather than merit. C. annuum "was the most successful in this conquest, probably due to it being the first Capsicum that arrived to Europe, rather than to any superior agronomic trait". In the global genebank census it accounts for roughly 78% of duplicated accessions, while C. frutescens and C. chinense show much more limited geographic spread.
The Iberian Peninsula was not merely the door but a breeding ground. "The Iberian Peninsula emerged as a highly relevant secondary diversification center for pepper as for other crops that originated in America": material selected over five centuries by farmers to fit distinctive environments, producing hundreds of landraces, with trade routes carrying them on to the Mediterranean basin and thence to Africa, India and China.
The clearest thing Iberian farmers did to the pepper was take the heat out of it. Measured across accessions, "Mexico was the region with the highest percentage of plants with pungent fruits (70%), while the Iberian Peninsula mostly comprised non-pungent accessions (67.4%)". Within Spain the split is geographic: pungent, elongated fruits in the south and centre; large blocky and triangular sweet types carrying the non-pungent allele predominantly in the north. The sweet pepper eaten as a vegetable and the powder sold as pimenton are products of that selection, not of the plant as it left America.
That breeding was done on a narrow founding sample. Genotyping 102 accessions with 39 microsatellite markers, 51 of them C. annuum landraces mainly from Spain, the 2014 study concludes that "the diversification of C. annuum in Spain may occur from a rather limited gene pool" - the variety was generated in Iberia rather than imported with the seed.
Iberian landraces still carry a gradient back towards their origin. Iberian peppers "maintained close proximity to the American accessions in terms of fruit phenomics, with the highest similarities observed for those coming from the southeastern edge of the Peninsula, while northwestern accessions displayed more significant differences" - consistent with entry through the south and divergence as the crop moved north, though the evidence is morphological and the paper carries no archival documentation of routes or dates.
The dispersal that followed was not mainly a Spanish achievement and its principal vector is not a creditable one. Analysing 10,038 genebank accessions, the 2021 PNAS study finds that "Africa forms a natural link between the Americas and the Eurasian pepper complements, likely owing in part to the triangular transatlantic slave trade and to Portuguese maritime trade routes", and that "the Portuguese did not have any great interest in introducing pungent peppers to Europe", favouring them instead in the Far East as a cheaper surrogate for black pepper. The crop's global career was carried on the same shipping that carried enslaved people.
Asia's peppers trace to the American pool rather than to a European intermediate stock: the peppers grown in East Eurasian regions were "primarily sourced - directly or indirectly - from the South/Mesoamerican diversity pool". The same study identifies Mesoamerica, East, South and Southeast Asia, and Africa as regions holding substantial unique diversity, so Iberia is one secondary centre among several rather than the world's pepper nursery.