SUBSISTENCE

Teosinte Becomes Maize

~9,000 years ago

Neolithic · Neolithic · Holocene · Greenlandian

Maize has a wild ancestor so unlike it that botanists argued for a century: teosinte, a Mexican grass whose hard little ears hold a dozen armoured kernels. Genotyping hundreds of plants came down on one origin rather than several: all maize appears to descend from a single domestication in southern Mexico about 9,000 years ago, and the oldest surviving types are those of the Mexican highlands, from which maize spread along two great paths across the Americas. Ancient cobs show the change still unfinished thousands of years on.

Why it matters

Few crops have been carried so far from their ancestor by ordinary selection: the stony fruitcases of teosinte gave way to the naked, swollen, human-dependent cob, a plant that can no longer sow itself. Maize fed the Olmec, Maya, Aztec and Inca worlds and, after 1492, much of the old one. It is the American half of the answer to what farming did to our species.

Dating & uncertainty

The ~9,000 year date is genetic: microsatellites across maize landraces point to a single domestication in southern Mexico around then. The oldest cobs actually preserved, from Guilá Naquitz, are younger, about 6,200 years, and already do not break apart on their own; cobs of about 5,300 years from Tehuacán were still only partial domesticates. The genetic estimate dates the start of the change, not the plant we know.

Sources

1. Matsuoka et al. (2002), PNAS · A single domestication for maize shown by multilocus microsatellite genotypingdoi:10.1073/pnas.052125199
2. Benz (2001), PNAS · Archaeological evidence of teosinte domestication from Guilá Naquitz, Oaxacadoi:10.1073/pnas.98.4.2104
3. Vallebueno-Estrada et al. (2016), PNAS · The earliest maize from San Marcos Tehuacán is a partial domesticate with genomic evidence of inbreedingdoi:10.1073/pnas.1609701113

Our species’ history as one day

23:18:5141 min 9 s before midnight

if the 315,000 years of Homo sapiens were compressed into a single day