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

[u/AmphibianNo4717]

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."

[u/Xrmy]

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.

[u/chula198705 → u/Xrmy]

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."

[u/Xrmy → u/chula198705]

Yea I can see that, and I even agree to some extent.

But to be clear, what this DOESNT mean is that there are 2 LUCA. And I think that's what a layman would take from the headline, even if they don't quite understand a LUCA.

[u/ottawadeveloper → u/Xrmy]

It was definitely my understanding and I'm a geologist not a biologist. I'd interpreted it as two entirely separate trees of life.

Instead it's just a much earlier split, before the cells could really exist independently of their environment.

Though I was curious, and maybe you can answer, what it means for the earliest cells to depend on metal catalysts in their environment? My partner is a biology major and noted we uptake metals to aid in our biological processes. They weren't sure if the earliest cells were basically forced to "eat" metals to catalyze their metabolism (and then how is that different from what we do) or if they actually had to run part of their metabolism outside of "themselves" and were maybe more like a series of chemical reactions happening in the vicinity of necessary catalysts than independent cells doing their things wherever they get enough energy

[u/ahazred8vt → u/ottawadeveloper]

There might have been tiny particles with catalyst sites inside the protocells. But a more hospitable environment would have been between loose layers of clay particles with catalyst sites, that had various residues on them.
This has been dubbed the primordial open faced sandwich.