Anyone who has seen teosinte, the wild grass from which maize
(corn) evolved, might be forgiven for assuming many genetic
changes underlie the transformation of one plant to the other.
However, a method for exploring the genetics of domestication
called Quantitative Trait Locus (QTL) mapping has revealed that
only modest modifications are needed to convert a wild plant to
a crop plant. Some major transitions in phenotype can even be
achieved by a single genetic change. The few artificial
experiments in domestication that have been conducted have also
shown that it is possible to achieve domesticate-like plants in
fewer than 20 generations. None of this pleases
archaeobotanists, who try to piece together the history of plant
domestication from scraps of ancient plant remains. Their data
are sparse and unimpressive — a 10,000-year-old squash seed
found in a cave in Oaxaca, Mexico, or four 12,000-year-old
grains of rice recovered from a rock shelter in Hunan Province
in China — but they have their own irrefutabl