I've often used this "fact" as an argument against complex extraterrestrial life. Glad to see it might be wrong after all.
This is really where the mitochondria come into play, as they allowed their host to utilize oxygen for this purpose. This can be seen by looking at modern eukaryotes that have reverted back to an anaerobic lifestyle:
> "In lineages of eukaryotes adapted to low oxygen conditions, mitochondria have been drastically reduced, functionally altered and, in one case, completely lost."
"The Origin and Diversification of Mitochondria (2017)"
https://www.cell.com/current-biology/pdf/S0960-9822(17)31179...
Hence, looking for the signature of free oxygen in the atmosphere of exoplanets orbiting distant stars is considered to be a fairly good indicator of the possibility of complex multicellular life of some sort, and at least of an active photosynthetic microbial ecosystem.
(Incidentally, the historical divisions withing academic university departments led to evolutionary biology generally ignoring the importance of early Earth's geochemistry in the evolution of life, as they saw evolution as a kind of cellular/organismal process divorced from the physical surroundings - the latter being the province of the geology department. The renewed interest in exobiology and origin-of-life research has tended to bridge this gap.)
As usual, people always seem to foreget that in this universe, what happened once, happens all the time and we are not special.
I get the convergent evolution point, but so far the story is that 1) life arose very quickly 2) then proceeded to do very little for billions of years. If that's true, then it's bad news for the possibility of complex life being common.
This is understating the feats of unicelular life. Those tiny organisms essentially terraformed the whole planet in those billions of years, oxidizing nearly all the iron close to earth surface, burying most carbon and then pumping so much oxygen in the atmosphere that at a point it comprised 30% of Earth gaseous envelope by weight. I wouldn't call that very little. To come close we'll need at least to terraform Mars or Venus, to match the feats of our microbial forebears.
Well, it's quite possible that once it happens, it voids any chance of it happening again just because life filling that niche already exists. If so, it only happens once, and this says absolutely nothing about the odds of that first occurrence.
> what happened once, happens all the time
That's a fallacy people do all the time here when talking about exobiology. It's basically states that all small numbers and all big numbers are alike, and that all small numbers are like the inverse of all big numbers.
We know very little about modes of sentience with N=1. Perhaps life is generally mutualistic.