The first of several posts on the evolution of life, mostly in the Archean and Proterozoic eons. This thread is about the origin of eukaryotes. I understand there are several different eukaryote phylogentic trees, but that (by definition?) all eukaryotes belong to a monophyletic domain - or is that just one hypothesis among many? Is the last common ancestor of eukaryotes - if there was one - a eukaryote? I expect there is no firm answer to this question, but I'd like to know what the main, current, hypotheses are. Related to this is the question of the origin of the eukaryote organelles, specifically the ones which have their own DNA. First, are the only eukaryote organelles with DNA mitochondria and plastids? If not, what others, even rare, eukaryote organelles have DNA? Second, as far as is known, do all eukaryote mitochondria have a common ancestor? Or do there appear to have been several separate instances of endosymbiosis? Third, same question for the plastids, perhaps separate questions for the various kinds (e.g. chloroplasts).