Origin of the Eukaryotic cell. A truly unlikely event.

According to Nick Lane in his books Life Ascending and Power, Sex, Suicide, the origin of the eukaryotic cell was truly an unlikely event.  If we could rewind the tape and try it again, chances are life would appear every time, but the appearance of eukaryotes was contingent on an unlikely chain of events.  Because of this, Lane doubts that life more complex than bacteria exists beyond earth. After all, after billions of years it only appeared once on earth.
We now know that the first eukaryote was formed by the merger of 2 prokaryotes.  The traditional idea of origins was that a primitive eukaryote engulfed the ancestor of our mitochondria since eukaryotes are known for phagocytosis, the abilty to engulf other cells.  However, this is probably not how it happened because the ability to engulf other cells requires energy.  It is now known that all eukaryotes either have mitochondria or have lost them at some point.  Lane believes that this links the origin of eukaryotes with the acquisition of mitochondria.  So, before the host cell acquired mitochondria, it wasn't going around engulfing other cells.  Lane suggests that perhaps the 2 prokaryotes started out their symbiotic relationship by living in close proximity and progressed over time to a one cell living inside the other.
Genetic studies suggest that host cell was a methanogen archea.  These cells are anaerobic meaning they survive on sulpher and stay away from oxygen.  This seems unlikely because if this were true, why did eukaryotes appear just as oxygen levels were rising?  As Lane points out, more oxygen means more sulphates because oxygen reacts with sulpher from volcanoes to produce sulphates.  But, as we all know, most eukaryotes thrive in the presence of oxygen.  Besides, what would use would a methenogen have for mitochondria which are useless without oxygen?  Lane believes that the most likely answer is that the ancestor of mitochondria had a diverse genetic toolkit.  Perhaps, it had the genes for utilizing hydrogen and oxygen.  Once it started supplying the hydrogen for the methanogen, it would no longer be dependent on deep sea vents and could venture off into oxygenated environments.  This primitive eukaryote would have had to adapt to the oxygenated environment before the mitochondria ancestor living inside it lost its oxygen utilizing genes through disuse.
This chain of events is just one way eukaryotes could have evolved.  The lesson here is that there were enough contingencies that the ascent beyond bacteria only happened once on earth in the billions of years that bacteria have populated the earth.  We are truly lucky to have made it through this bottleneck.  The biggest gulf in all of life is the divide between prokaryotes and eukaryotes.  We have more in common with a humble yeast cell than it does with a bacterium.