It’s native to Mexico, where some 59 indigenous strains of corn exist. Which is why an emerging debate over whether to allow growers to cultivate genetically modified corn has heated up. Opponents of GMO corn have urged the Mexican government to ban GMO. To draw attention to their cause, on Thursday four local Greenpeace activists climbed a 335-foot monument on Mexico City’s busy Reforma Avenue and dropped a banner reading “No GMO” on the iconic Estela de Luz tower in protest, according to a Greenpeace spokeswoman. Mexico has already allowed limited cultivation of GMO corn in a handful of northern states as part of an experimental program. In March, according to local news reports, agribusinesses Monsanto and Syngenta solicited permits to expand GMO plantings. If granted, planting will begin in the fall.