a whole series of traits, from sex and ageing to speciation, none of which have ever been seen in bacteria or archaea. The earliest eukaryotes accumulated all these singular traits in a common ancestor without peer. There are no known evolutionary intermediates between the morphological simplicity of bacteria and that enormously complex eukaryotic common ancestor to tell the tale. All of this adds up to a thrilling prospect – the biggest questions in biology remain to be solved! Is there some pattern to these traits that might give an indication of how they evolved? I think so.
