Scientists, consumer groups, and activists yesterday presented Congress and the Food and Drug Administration with a 500,000-signature petition calling for genetically modified foods to be labeled. The demonstration suggested that distrust of genetically altered foods is growing in the U.S.; it is already rampant in Europe. Scientists and protestors pointed out that little research has been done on the long-term effects of genetically modified foods on humans and the environment. Greenpeace released a survey yesterday showing that three top baby foods and nutritional products in the U.S. contain DNA from genetically engineered corn and soybeans. Another study released yesterday, funded by the U.K. government, found that genetically modified crops will “inevitably” contaminate organic crops.