To me, evolution is the greatest theory ever. It does a remarkable job of explaining our existence and our relationship with every other living thing on the planet. The theory of evolution is implicit in many modern disciplines. The fields of biology and medicine would have no basis without it. It has been one of the most useful ideas in the history of humankind as it, in part, explains how diseases work and has helped us be better prepared against exploits to many of our weaknesses. We live longer than our ancestors did because of our knowledge of evolution.