Earlier quoted context omitted.
Before any of that is possible, a "Cambrian Explosion" is required. It may be that prokaryotic life is common, but the mitochondria and plastids of eukaryotes took a very long time to emerge (absent for more than half of the total habitable life of the earth).
> but the mitochondria and plastids of eukaryotes took a very long time to emerge. Not an expert, but mitochondria didn't " e merge." Mitochondria co-evolved as bacteria, merged and became organelles through complex protein-import machinery and insertion into inner membranes of protein carriers for extracting energy for the host cell.
This was the ignition of complex, multicellular biology. What else could explain it?
I will admit that I thought they were closer to the Cambrian Explosion. This is much farther away than I thought.
"Eukaryotes emerged approximately 2.2 billion years ago, during the Proterozoic eon, likely as flagellated phagotrophs."