In the past month, Monsanto and Dow Agri-Sciences have received government permission to plant transgenic maize across 24 plots, covering a total of nearly 13 hectares, in the northern states of Sonora, Sinaloa, Chihuahua, Coahuila and Tamaulipas. [...] nearly 2,000 scientists have signed a petition to block the experiments. ”There is no way to stop gene flow to the native crops,” says signatory Montgomery Slatkin, a geneticist at the University of California, Berkeley.