ONE OF the earliest experiments in genetic engineering took place about 7,500 years ago and resulted in the first corn on the cob. Scientists have retraced steps taken by Stone Age farmers who created the first maize crop from a Mexican wild grass using a sophisticated process of genetic selection.
A study into the genetic ancestry of the maize plant found it is derived from a nondescript species of wild grass which grows in Mexico. The researchers have found how Neolithic farmers in North America selected specific strains of the wild grass which eventually resulted in a plant that produced a tightly knotted clump of nutritious seeds on a cob. The study found the farmers were unwittingly modifying a genetic-control region in the grass which caused long tassels of its seeds to shorten into edible ears that could be harvested more easily.
John Doebley, who led the research team at the University of Minnesota, said the study confirmed how the maize plant, which does not exist naturally, was derived artificially by a process of genetic selection from a wild Mexican grass called Balsas teosinte. The artificial selection carried out by the early farmers increased the total amount of variation seen in modern maize crops, which are far more diverse than the ancestral grass from which the were derived, the researchers report in Nature.
"Our results help to explain why maize is such a variable crop. They also suggest that maize domestication required hundreds of years, and confirm previous evidence that maize was domesticated from Balsas teosinte of south-western Mexico," they report.
Svante Paabo, an expert on archaeological genetics at the Max Planck Institute in Leipzig, said the research is important because it demonstrates how quickly domestic crops were produced from wild plants. "This is a significant result because archaeologists are still debating how many centuries or millennia were necessary for early farmers to achieve the changes that made maize a mainstay of farming," Dr Paabo said.
"Of all human inventions, none has had a more profound effect on our history - and on our biosphere as a whole - than agriculture ... This momentous development relied on the genetic manipulation of only a handful of plants by early farmers."
Wild Mexican grass looks so different from domesticated maize that their close relationship could only be confirmed by the genetic analysis that showed how the long tassels became short ears.
"This study is fascinating to me because it provides the first glimpse of what went on during one of the earliest genetic-engineering experiments," Dr Paabo said.
The genetic techniques used in the study could also be used to dissect the modification that took place to create other domestic plants and animals, including cats and dogs, he added.
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