Wouldn't LUCA by definition be the last common ancestor of every organism of which we have evidence? If so then by definition we wouldn't have evidence of those other lineages. Or is it just the last common ancestor of everything currently alive?

[–] AbouBenAdhem 11 points 5 months ago* (last edited 5 months ago)

The definition I’ve seen is the last common ancestor of procaryotes, eucaryotes, and archaea—which doesn’t strictly rule out the possibility of extinct domains whose existence we might infer.

And actually, there’s evidence of non-LUCA-descended organisms mentioned right in the paper: the other organisms that constituted the ecosystem of which LUCA was a part, whose existence (and some of whose characteristics) could be inferred from LUCA’s metabolism and immune system.