Genetically engineered crops have made their way into most of the food consumed in the United States, and transgenic animals may be next on the dinner plate. The scientific advances could usher in an era of more nutritious food, reduce pesticide use and perhaps even end world hunger, advocates say. But opponents view genetic engineering as one of the most reckless ventures of modern science, threatening to unleash new plant and animal species that could damage both human health and the environment. To guard against such potential calamities, the skeptics want labeling for genetically altered foods and more stringent government regulation and testing. Meanwhile, consumer protests, especially in Europe, are putting the future of genetically engineered food in doubt.