Indeed, the author does recognize it: > The next major problem Carell wants to tackle is what reactions could have formed the sugar ribose, which needs to link

Indeed, the author does recognize it: > The next major problem Carell wants to tackle is what reactions could have formed the sugar ribose, which needs to link to nucleobases before RNA can form. Possibly something resembling the Calvin cycle could be the start you talk of. [1] [1] https://link.springer.com/article/10.1007/s00239-018-9840-1 https://link.springer.com/article/10.1007/s00239-018-9840-1