Watch a fly land on the kitchen table, and the first thing it does is clean itself, very, very carefully. Although we can’t see it, the animal’s surface is covered with dust, pollen and even insidious mites that could burrow into its body if not removed.
Staying clean can be a matter of life and death. All animals, including us human beings, take cleaning just as seriously. Each year, we spend an entire day bathing, and another two weeks cleaning our houses. Cleaning may be as fundamental