Shape-shifters

FROM humanity's point of view, one of the most important events in history was the evolution of the eukaryotic cell--the sort from which people's bodies are made. Without this innovation, which happened about 2 billion years ago, life on Earth would consist only of bacteria and a group of similarly simple creatures called archaea. Plants and animals, not to mention algae, fungi and myriad single-celled organisms like amoebae, would never have come into existence. Even today, bacteria and archaea...