The tomato's first fifty years in Europe: ten herbarium sheets, thirteen pictures and one sequenced leaf
The tomato crossed the Atlantic in Spanish hands and nobody wrote it down. Seville was the port of entry for American plants, and there is no record of the tomato arriving there. What survives instead is on the far side: a description of 1544, ten sixteenth-century herbarium specimens, thirteen drawings, and a leaf from about 1558 whose DNA has been read. It is a domesticated Mesoamerican tomato, and its European names still argue about whether it came from Mexico or Peru.
Why this wins its question: The tomato's arrival in Europe is normally told as an anecdote with a confident date and a confident port. The peer-reviewed reconstruction has neither, and is far more interesting: an undocumented passage through Seville that the authors state cannot be evidenced, ten surviving specimens and thirteen pictures that are the whole physical record, a first description in 1544 and a first printed image in 1553, and a sequenced leaf of about 1558 that comes out Mesoamerican against contemporaries who were calling the fruit Peruvian. This object binds each of those to the study that established it, adds the genomic evidence that the American domestication itself ran forward, backward and forward again, and keeps on the record what the European botanists left out - the origin of the plants they were drawing.
Claims
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The plant was a cultivated Aztec crop when Europeans met it. After the conquest of Tenochtitlan in 1521 by Cortes, the Franciscan chronicler Sahagun reported that the Aztecs cultivated a great variety of tomatoes, and the Spanish adopted their Nahuatl term tomatl as tomate - the word most European languages still use.
The Spanish leg of the journey is undocumented, and the study says so plainly. The port of Seville was the principal point of entry for products from the New World, but there is no record of the introduction of the tomato in that port or of its cultivation in the royal Iberian gardens, because plant transfers were rarely considered important enough to document. Spain's role here is an inference from the shipping, not a recorded fact.
From Spanish territory the plant moved into Italian gardens quickly. The authors attribute this to the many Italian merchants sailing under Portuguese and Spanish flags and to the Kingdom of Naples being under Spanish rule; seeds of maize, marigold and chili peppers were planted in noblemen's gardens as exquisite novelties, and the first tomato seeds sprouted in the gardens of Italian aristocrats in the 1540s.
The documentary firsts are datable. Pietro Andrea Matthioli gave the first description of a tomato in 1544 in his commentary on Dioscorides, calling the fruits segmented, green at first and golden when ripe; Rembert Dodoens published the first image in his Latin herbal of 1553, with a coloured version in 1554; an earlier drawing in Leonhard Fuchs's Vienna Codex (1549-1561) was never published.
The physical evidence is small and countable: ten surviving sixteenth-century tomato specimens and thirteen illustrations, studied together. The oldest were collected by Ulisse Aldrovandi and Francesco Petrollini in about 1551, probably from plants in the Pisa botanical garden; the En Tibi specimen of about 1558 is the first that shows a mature fruit. The sheets are held at Bologna, the Biblioteca Angelica in Rome, Naturalis in Leiden, Basel, Munich, Modena and Kassel.
Sixteenth-century names record an argument about origin that was never settled at the time. Some called it poma del Peru or mala Peruviana, Peruvian apples; Guilandinus used the Nahuatl-derived Tumatle Americanorum and referred it to Themistithan, a corruption of Tenochtitlan. Other contemporary names were mala aurea or pomi d'oro, golden apples, and pomum amoris, love apple - a name the Spanish had first given to the Mexican tomatillo and then transferred to the tomato.
The molecular reading of the En Tibi leaf settles part of it. The specimen is a fully domesticated tomato, genetically close to three Mexican landraces and two Peruvian specimens that probably also had a Mesoamerican origin, and its chloroplast DNA falls in the same node as all Mesoamerican individuals - so its predecessor likely came from Mesoamerica rather than from the Andes.
The deeper history the plant carried with it is not simple. A genomic study of 295 accessions - 49 wild S. pimpinellifolium from South America, 153 semi-domesticated S. lycopersicum var. cerasiforme from South and Mesoamerica and 92 fully domesticated accessions - with some 23.8 million single-nucleotide polymorphisms, dates the split of the intermediate form from the wild species to roughly 78,000 years ago in Ecuador, long before any human involvement, and places the fully domesticated tomato at about 7,000 years ago, most likely in Mexico.
That study also finds the domestication run backwards in the middle. Fruit traits show what the authors describe as an N-shaped pattern: South American intermediate populations already carried domestication-like characters, the northernmost intermediate populations in Mexico and Central America show wild-like fruit phenotypes, and larger fruit was then reselected in a convergent fashion in the common cultivated tomato. What reached Spain was the product of a long American process with a reversal in it, not of a single event.
Both studies mark their limits. The exact time and place of domestication are still not known with certainty for either Mexico, Ecuador or Peru; degraded ancient DNA cannot reconstruct taste or pest resistance from the old specimens; and the genomic authors note there is insufficient archaeological evidence of ancestral tomato phenotypes to close the question.
The omission is part of the record. Despite their scientific interest in a recently introduced crop, most sixteenth-century botanists did not specify where their tomatoes came from - so the American growers who had made the plant, and whose word for it Europe adopted, appear in the European archive mainly through a chronicler in Mexico and through a name.