Oh man, I just listened to that podcast with Jorn Dyerberg to hear his design inference. It’s standard irreducible complexity stuff. The idea is that the full Krebs cycle couldn’t evolve by standard “neo-Darwinian” means because what good would one or a few enzymes of the pathway be, you’d need the complete cycle, otherwise you have one or a handful of useless enzymes waiting millions of years before the next enzymes in the cycle evolves. And so on and so forth until finally the complete cycle.
But this is exactly where this putative “lack of progress in origin of life research” we’ve been told about before isn’t actually lacking. Turns out you don’t actually need hosts of enzymes to catalyze basic reactions in ancient metabolic networks. Metals and minerals can catalyze the reactions. And there’s even a good historical explanation for why this wasn’t discovered until about 2016-2017(it has to do with whether the instruments are capable of detecting the reactions), which you can read about in the first reference below:
Ralser M. An appeal to magic? The discovery of a non-enzymatic metabolism and its role in the origins of life. Biochem J . 2018;475(16):2577-2592. Published 2018 Aug 30. doi:10.1042/BCJ20160866
Keller MA, Kampjut D, Harrison SA, Ralser M. Sulfate radicals enable a non-enzymatic Krebs cycle precursor. Nat Ecol Evol . 2017;1(4):83. doi:10.1038/s41559-017-0083
Muchowska KB, Varma SJ, Chevallot-Beroux E, Lethuillier-Karl L, Li G, Moran J. Metals promote sequences of the reverse Krebs cycle. Nat Ecol Evol . 2017;1(11):1716-1721. doi:10.1038/s41559-017-0311-7
Springsteen G, Yerabolu JR, Nelson J, Rhea CJ, Krishnamurthy R. Linked cycles of oxidative decarboxylation of glyoxylate as protometabolic analogs of the citric acid cycle. Nat Commun . 2018;9(1):91. Published 2018 Jan 8. doi:10.1038/s41467-017-02591-0
Varma SJ, Muchowska KB, Chatelain P, Moran J. Native iron reduces CO2 to intermediates and end-products of the acetyl-CoA pathway. Nat Ecol Evol . 2018;2(6):1019-1024. doi:10.1038/s41559-018-0542-2
Muchowska KB, Varma SJ, Moran J. Synthesis and breakdown of universal metabolic precursors promoted by iron. Nature . 2019;569(7754):104-107. doi:10.1038/s41586-019-1151-1
There seems to have been a veritable explosion of research into these kinds of metal/mineral catalyzed versions of primitive metabolism recently.