When I started this work, I still thought of the mitochondrion as an independent unit, and pondered the possibility that the proto-mitochondrion was a reduced nucleus due to a mitosis gone wrong. In this way, two interdependent cells were obtained. The first would be the nucleus but without essential metabolic proteins, the second a remnant cell that had the metabolic proteins, but missed all the housekeeping genes. This would create an immediate dependency, where both could not function without each other. Although this would be attractive from a system point of view, it would mean that the intermembrane spaces of the nucleus and the mitochondrion where homologous. I did not find evidence for this and the more I read about mitochondria the more I think they are a normal part of the endomembrane structure. Also, the protein import problems into the mitochondrion were not resolved.