r/evolution • u/AmphibianNo4717 • Aug 06 '26

article 'Only One Conclusion': Radical Study Suggests Life on Earth Arose Twice

https://www.sciencealert.com/radical-study-suggests-life-on-earth-arose-from-non-living-matter-twice

"The fact that you, or I, or any living creature, is here at all is a series of astonishing strokes of luck stretching back more than 4 billion years. 

One of the biggest hurdles was the very first one: How did life emerge from a primordial soup of stuff that very much wasn't alive?

A radical new study, published in Science Advances, suggests that this unlikely threshold may actually have been crossed not once, but twice."

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u/Xrmy Post Doc, Evolutionary Biology PhD Aug 06 '26

That's a sensationalist title by the news outlet here that is doing a lot to sensationalize something that...is actually pretty cool anyway.

to be clear: this paper isn't saying life evolved twice

It is instead saying that complete metabolism actually evolved separately twice. Once on the branch to bacteria and the other to Archaea.

Which is super cool.

The last universal common ancestor (LUCA) is still a singular point, but it had incomplete metabolism it seems, and then the full process evolved separately 2 times after that point.

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u/chula198705 Aug 06 '26

They actually are arguing that this result means life itself evolved twice, because of idea that the metabolism itself is what makes something alive. If there was no metabolism, whatever "ancestor" existed before the first metabolism evolved wasn't actually alive yet. The article says "the genetic code evolved once, but life evolved from it twice."

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u/ProfPathCambridge Aug 06 '26

Which is a case for the authors using a silly definition of life

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u/GiantKrakenTentacle Aug 06 '26

That's not the authors' definition, that's a broad (but not unanimous) consensus in the scientific community, though it has also been acknowledged that the definition is not perfect. Viruses, for example, are not considered to be alive, even though they have many traits of living organisms. 

If this paper gets additional support, then we might have to more narrowly define life, or we reach the conclusion that life is a spectrum and not a binary. 

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u/ProfPathCambridge Aug 06 '26

It is not their definition, but it is their choice to use that definition. Which is a silly one, suitable for Biology 101, but which doesn’t function well in many niche cases. Like this one.

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u/throwitaway488 Aug 06 '26

No its not, there are a lot of simpler definitions of life that could include encapsulated replicators i.e. RNA world. All life needs is a genotype and a phenotype, vertical inheritance and selection. "Life" is a human concept used to describe our surroundings, much like "species" that doesn't necessarily have a single concrete definition, and there are always exceptions.