Legumes were domesticated in at least six places independently, by people who had no contact with each other, within a few thousand years. That is not coincidence. A seed that stores for a year, carries a fifth of its weight as protein, and improves the soil it grows in is a solution that any settled agriculture eventually finds.
The track is spaced by event, not by elapsed time — the first four points cover nine thousand years and the last four cover thirty.
Where each of the major food legumes was first brought under cultivation. Hover a marker for the species; the arcs are the three dispersals that rearranged what the world ate.
Two populations of the same wild species, four thousand kilometres apart, taken into cultivation by two unconnected peoples, producing two gene pools that are still distinguishable — and still partially incompatible.
Phylogeography published in 2012 places the wild ancestor's own origin here too, which means the Andean population is a much older migration that then went through its own bottleneck before anyone cultivated it.
Every large-seeded bean in European cooking descends from this pool. Italy's borlotti and cannellini, Spain's fabada beans and the French flageolet are all Andean stock, carried east after 1492.
Athenian juries dropped a bean into an urn — white to acquit, black to condemn — and magistrates were selected by drawing beans from a pot rather than by election, on the theory that election favours the well-connected. Rome kept the practice. Venice was still drawing its Doge by ballotta, "little ball", in the eighteenth century, which is where the English word ballot comes from. And a clerk who counted the beans was, inevitably, a bean counter.
The Pythagorean ban on fava beans is reported by Aristotle, Diogenes Laërtius and Pliny, with wildly different explanations: that beans contain the souls of the dead, that they resemble the gates of Hades, that they look like testicles, that they cause bad dreams. The medical reading is simpler. G6PD deficiency exceeds 20% of men in parts of the Mediterranean because it protects against malaria, and in those men fava beans cause acute haemolysis. A community that watched people fall ill after eating them and could not say why would arrive at a taboo.
Mendel crossed roughly 28,000 pea plants across seven characters and found that inheritance was particulate rather than blending. The paper was read in 1865, printed in 1866, cited three times in thirty-five years, and rediscovered independently by three people in 1900. The wrinkled-seed allele he used turned out, in 1990, to be a transposon insertion in the starch-branching enzyme gene SBEI: without it the pea makes less amylopectin, holds more sucrose and water, and shrivels as it dries.
James Sumner crystallised urease from the jack bean and showed it was a protein — against a field that largely believed enzymes were something else entirely, with protein merely carrying them. He had lost an arm in a childhood shooting accident and worked for nine years on a problem his colleagues told him was unsolvable. He shared the 1946 Nobel Prize in Chemistry. His other jack-bean protein, concanavalin A, became the standard laboratory mitogen.
In 1994 a man bought a bag of yellow beans in Mexico, grew them out in Colorado, selected for uniform colour for two seasons, and in 1999 was granted US Patent 5,894,079 on a yellow bean he named Enola. He then sued importers and demanded royalties on Mexican yellow beans entering the United States. Exports of Mexican Mayocoba — the same bean, grown by Mexican farmers for generations — fell sharply. CIAT filed a challenge; the USPTO rejected every claim; the applicant appealed twice; in July 2009 the Federal Circuit upheld the rejection and the patent was dead. It had run for ten of its twenty years, and the farmers it had cost were never compensated. It is the standard teaching case for what a patent system does when it cannot see prior art that was never written down.
Maize, bean and squash grown in the same mound. It is the most-cited intercrop in the world because it works on four axes at once, and it was engineered by people with no access to any of the chemistry that explains it.