Comment by jyounker | Hacker News Reader

Comment by jyounker | Hacker News Reader

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> Common descent is a core tenet...

It's taken that (known) modern organisms descend from a common set of ancestors, but the tree of life isn't a tree. Organisms diverged and merged multiple times along the way to the modern world.

It says nothing about how that/those points of common descent came to be.

What originally constituted living things probably weren't very good at living by modern standards. They probably leaked like sieves, and they probably traded RNA, polypeptides, and other small molecules back and forth.

When was this soup alive, and when wasn't it? I suspect it's just a continuum, and that complicated soup probably went back and forth across that grey zone of living-nonliving many times.

> but the tree of life isn't a tree

That’s correct but I don’t see what this has to do with my comment. It’s still a fact that all modern life, at some point, came through the same individual organism (EDIT: this should be population) which, furthermore, already possessed the fundamental machinery of DNA replication, RNA transcription and protein synthesis (amongst other things).

EDIT: I misunderstood. Yes, you’re right: due to lateral gene/molecule transfer, it’s not certain that the last universal common ancestor was an individual cell, and at that time the label “individual” probably didn’t make much sense (although the paper I linked argues strongly that it was in fact one single cell).

> That’s correct but I don’t see what this has to do with my comment. It’s still a fact that all modern life, at some point, came through the same individual organism which, furthermore, already possessed the fundamental machinery of DNA replication, RNA transcription and protein synthesis (amongst other things)

This is a contentious statement that I don't think is established - a fact that the grandparent comment is trying to raise.

I misunderstood both your and the grandparent comment. You’re right. I’ve amended my other comment.

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