The Cambrian period began a little over 500 million years ago. Before the Cambrian period, life on earth consisted of mostly single-celled organisms and bacteria. Afterwards the evolutionary ancestors of all the major groups of living things today were hanging around the planet. So what caused this evolutionary leap? According to one scientist, poop.
Biogeochemist Graham Logan published his opinion on the matter a few years ago. He points out that feces producing creatures, ones that ate food then excreted it like humans today, first arrived around 40 million years before the Cambrian period. He argued that their poo was what allowed oxygen levels to rise, and evolution to explode.