Greenpeace stages a protest against a new Mexican bio-security law that, it claims, does not include safeguards to prevent transgenic contamination of corn seeds (Image: Marco Ugarte/AP/PA)

NOW it’s official: genes from genetically modified corn have escaped into wild varieties in rural Mexico. A new study resolves a long-running controversy over the spread of GM genes and suggests that detecting such escapes may be tougher than previously thought.

In 2001, when biologists David Quist and Ignacio Chapela reported finding transgenes from GM corn in traditional varieties in Oaxaca, Mexico, they faced a barrage of criticism over their techniques. Nature, …