An estimated 2,500 protestors marched peaceably through Boston streets yesterday in what organizers called the biggest demonstration in the U.S. against genetically modified (GM) foods. Protestors — many dressed as mutant creatures, macabre vegetables, and mad scientists — were making their voices heard during the largest biotechnology conference ever held in the U.S., which has gathered nearly 8,000 scientists and biotech executives in Boston. The protestors argue that GM foods are being pushed into markets though scientists don’t understand their effects on humans or ecosystems. Nearly two-thirds of the food products on American supermarket shelves are estimated to contain GM crops. While many European citizens vehemently oppose GM foods, Americans have been more apathetic. Yesterday’s protest may be a sign that Americans are becoming more alarmed about the issue.