> blossom into the complexity of the eukaryotic cell, via a very specific endosymbiotic event.
Citation needed. There is a hell of a lot more to being a eukaryote than having mitochondria. They're defined by having a nucleus, not mitochondria, and I think that's a good definition.
If mitochondria were a necessary step to modern eukaryotic complexity, it could only be by providing a bigger power budget, which could have happened lots of ways. Again, cellular endosymbiosis is common, other notable examples being chloroplasts and red algae serving as chloroplasts for brown algae.
So, I'm not saying mitochondria are not important, but I don't think they were the blocker to eukaryote evolution.
Eukaryote does mean "true nucleus", but all* eukaryotes have mitochondria. They only became eukaryotes via the merger. Again-- archea (and bacteria) have existed for billions of years, and never became "complex", even by unicellular eukaryotic standards, let alone multicellular creatures, except when the two got together (once, as far as we know) to form eukaryotic cells with mitochondria.
(Among other things, it suggests that the nucleus itself developed because of the inflow of bacterial DNA and the need to parse out meaningless intron segments of genetic code.)
Note also that the subsequent endosymbiotic absorption of chloroplasts is not a "common" event, although of course it is very important-- at least to us, as we wouldn't be here without it.
* Some have lost them, when they are involved in symbiotic relationships that supply the required energy, or, as part of multicellular organisms-- for example, our red blood cells. Note that our red blood cells also lack nuclei.
You're not even attempting to make an argument about why the origin of mitochondria deserves all the press it gets, just restating the intro biology story. I already know they're "the powerhouse of the cell". Biology has lots of powerhouses but only one nucleus.
Citation needed. There is a hell of a lot more to being a eukaryote than having mitochondria. They're defined by having a nucleus, not mitochondria, and I think that's a good definition.
If mitochondria were a necessary step to modern eukaryotic complexity, it could only be by providing a bigger power budget, which could have happened lots of ways. Again, cellular endosymbiosis is common, other notable examples being chloroplasts and red algae serving as chloroplasts for brown algae.
So, I'm not saying mitochondria are not important, but I don't think they were the blocker to eukaryote evolution.