AS early as 4300 years ago the farmers of Mexico bred maize with many modern characteristics. This was just 2000 years after the first evidence of maize being grown for domestic use.
Teosinte, the grassy ancestor of maize still found in Mexico, looks very different to the food crop. For instance, the wild plant has a more branching shape. Previous comparisons with modern maize have revealed some of the genetic differences responsible. Modern maize has a version of a gene called tb1 that makes the plant less branched, a version of pbf that makes the proteins in the kernels more nutritious, and a version of su1 that changes the chemistry of starch, making maize flour better for tortillas. These gene versions are all found in teosinte, but are rare.
To see how soon farmers selected for these rare versions, Viviane Jaenicke-Despr茅s at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, compared the versions of the three genes found in modern maize and teosinte with those in ancient cobs 4300 to 650 years old. Even the earliest plants had the modern versions of tb1 and pdf. Only one 2000-year-old cob had a version of su1 more common in teosinte (Science, vol 302, p 1206). 鈥淭he early farmers really knew what they wanted,鈥� Jaenicke-Despr茅s says. Genetic studies will allow us to trace exactly how plants were domesticated, she says.
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