I’m asking if you can plausibly explain how it could have come about ‘naturally'.
Im not an authority on the biochem of ATP and oxygen transfer by eukaryotes, everything I learnt is from reading and discussion with colleagues
Ive asked you to read stuff by Lynn Margulis because she was the one who first noted that the Mitochondria in all animal and plant life appeared to be free living at some time before the somatic cells did assimilation of the free living MtDNA and annexed and extended the mtDNA in their own cells. If you woulda payed attention to me back then when you were asking other questions similarly scripted by AIG and DI.
Lynn MArgulis, who died in 2012 had first been poo poo'd by science .She's been "resurrected" by science (especially recent work at Cold Spring Harbor
where Margulis work on
endosymbiosis was tested and found acccurate by Koonin (2010) and by Lane and Martin (2010) who argued the ionic transfer systematics in mtDNA in eukaryotic symbionts.
I was a fan of her work because it actually made sense from an ecology and worldwide species distribution through geologic history.The veracity of her "circumstantial evidence" was borne out by other evidence that showed throughout geologic history species were NEVER a mish mash of all "kinds" from early to recent ages. Everything lived in its environment and in its time and mtDNA of many species show that they have not fully assimilated their own mitochondria because the species had changed its life style or environment.
Cheetahs' are such an example .
I predict that polar bears WILL evolve (eg the subspecies in the Hudson Bay estuary is already changing its diet based on an open sea environment and the irATP needs will be entirely different from those bears that were basing their diets on stealth attack).
I asked you to at least scan Margulis"evolution of the eukaryotic cell" a few years ago. You insulted me that all I could do is post some paper and be done. Since you believe you are as smart as Dr margulis but dont want to be bothered with the actual work involved, Im gonna leave you with that recc .