In principle, science should set itself apart from the hue and cry of partisan bickering. After all, the scientific enterprise reaches its conclusions by testing theories about the workings of the natural world. Consider the porpoise. Based on its appearance and aquatic home, the animal was assumed to be a fish. But evidence gleaned from observing its bone structure, its lack of gills and the genes it holds in common with other warm-blooded land animals leads to its being classified as a mammal with a very high level of confidence.