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All Life on Earth Comes From One Single Ancestor. And It's So Much Older Than We Thought.
(www.popularmechanics.com)
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this post was submitted on 15 Jul 2024
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Any way of estimating when the last lineages of organisms not descended from the LUCA died out?
No, since everything we know about the LUCA is from its descendants. Microorganisms without descendants wouldn’t leave behind any evidence of their existence.
Using genetics alone, sure. But maybe there’s fossil or geochemical evidence of early organisms not belonging to any of the three surviving domains—or maybe we could estimate it just from statistics.
Maybe but I don’t think fossil evidence has enough information to confirm something isn’t from the main branch of the tree of life.
especially when some of that stuff took a while for us to realize it's even part of the same organism, or an organism at all.
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?
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.