There is still debate about the origins of eukaryotes, and many of the theories focus on the idea that a bacterium first became an endosymbiont of an anaerobic archean and then fused with it to become one organism.
Aínda hai un debate sobre as orixes dos eucariotas, e moitas das teorías céntranse na idea de que unha bacteria se converteu primeiro nun endosimbionte dunha arquea anaerobia e despois fusionouse con ela nun só organismo con novas capacidades.