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- Hacker News
- Major Seveneves vibes from thisby gyre007
- Because I had to look it up, a 2015 Neal Stephenson novel.by mttpgn
- what's really going to blow your mind is our solar system looked completely different several times with different proto-planets and Earth/Moon is likely made from remnants of those other planets
* https://en.wikipedia.org/wiki/Formation_and_evolution_of_the...
by ck2 - The Youtube channel Kyplanet recently had an episode on recent arguments that the Earth/Moon system was formed from at least three giant impact events, not just a single one between proto-Earth and Thea that formed the current Earth and the Moon.by pfdietz
- Many essential metabolic enzymes require metal ions for catalysis, structure, or substrate binding. So in some sense the dependence is still there, we just learned to take bits of substrate with us while travelling.by hamilyon2
- If true, fl in the Drake equation just got much bigger.by pingou
- Yep, now the probability of alien civilisations is completely unknown, but half the completely unknown it was before.by mellosouls
- They aren’t saying two totally different independent life creating event, they are saying that the earliest life depending on some external chemicals for parts of what is now covered by metabolism, and the tree of life diverged before those metabolic paths evolved inside the organism, so not totally the same emergence of life twice, but more stuff that reproduces and evolves but doesn’t meet modern standard for life.by lanstin
- Life may have arisen loads of times but life as we know it out competed the other forms. It's still a bit unknown how rare or common abiogenesis is. It'd be interesting to check out Mars more to see if there's any underground there.by tim333
- the article is about a study claiming that prokaryotes and eukaryotes emerged independently of each other. they're both still around, so "out competed" is a strange description.by pasquinelli
- I find this fascinating. LUCA clearly predates some pretty core, basic metabolic capabilities, and yet nucleotide metabolism is complete. This seems to indicate that LUCA and its progenitors were confined to their hydrothermal vents and that the cells could not survive beyond due to the missing metabolic networks.
I wonder if LUCA was not a single cell, but many different populations in different hydrothermal vents, exchanging genetic material wrapped by accident in the remains of the cell membranes as the host cells die and are ejected from their vents.
Perhaps the missing post-LUCA metabolic enzymes evolved by accident from proteins recruited simply to concentrate the required metal ions that are scarcer and ever more diluted the farther from the black smokers you get. Free living was merely a happy bonus effect.
by Rigdanir - The "life arose twice" makes for a sensational headline.
Free-living cells arose twice would be more accurate.
I heard a good way to describe LUCA is "half-alive", with about 40% of its metabolic reactions driven by the mineral substrates in the pores it lived in, and lacking a complete cell membrane.
I can't help but speculate LUCA would have some simple membranes to cover the "windows" of the mineral pores and keep vital molecules inside - a tiny pore-dwelling metabolic network.
The question of "how much independent metabolism counts as life" is looking a lot more like the question of "how many facial hairs make a beard"
by merogran - The headline is a little confusing. They're still talking about a "split" between bacteria and archaea, so even under this theory, the very roots of metabolism and (I'm guessing) genetic code etc still have a single origin.
Anyway, it does provide a nice reason that bacterial and archaeal cell membranes are different.
by andrewflnr - The link the site points to seems like a better source (no ads, cites DOI etc, affiliated with AAAS rather than random aggregator website):by gyomu
- Nice. This part was especially interesting:
> “When we react phosphite, a form of phosphorus that naturally occurs in hydrothermal vents, with organic compounds, we get metabolic phosphorylation reactions overnight in water. Phosphite and palladium replace ATP and enzymes; it’s amazing, and it makes early evolution a lot easier to grasp” says Schlikker.
As far as I know, there are no palladium enzymes ... checks ... ok, no _natural_ ones (that we know of). Which is interesting, as other enzymes in metabolism that use metals seem to have 'adopted' the metal(s) as a cofactor - like nickel, iron, molybdenum, even vanadium in at least one case.
by gilleain - Clickbait headline.
Should be "Life left mineral substrate at least twice" or some such. The research is interesting, but they're playing word games in the telling of it by saying the most recent common ancestor of all life wasn't alive (because it was dependent on a mineral surface), but two of it's children gave rise to lineages that were.
by MarkusQ - The metabolic science is really cool. The conclusion that life arose twice requires you to buy that proto-cells that grew on these vents and needed those metallic surfaces to survive didn’t count as “life”. Then, free living cells, bacteria and archea, could maybe be argued as having independent paths as they plugged the gaps in their metabolism independently. Same DNA/RNA, same proteins. Same broad rules of metabolism. Just some alternate paths through chemical space to plug in the metabolic gaps and get free from metal surfaces.
To me, these are clearly not independent paths, but rather the branching of proto-life into two of the great kingdoms of life. It’s a stretch to call this two origins rather than a branching.
Then a couple billion years later, one of em ate the other, and rather than destroy it, they both started a symbiotic relationship, and we were off to the eukaryotic race. This is all the same web of life. Not two independent streams.
- > …one of them at the other,
The origin of life is as romantic as I’d hoped.
by nativeit - You would think there would be some isolated places where proto-life still exists for this to be true.by mycall
- the Great Oxidation Event caused all kinds of crazy stress = crazy mutations/adaptations where one eventually started our path
* https://en.wikipedia.org/wiki/Great_Oxidation_Event
one of my absolute favorite PBS Space Time on the subject
by ck2 - > The conclusion that life arose twice requires you to buy that proto-cells that grew on these vents and needed those metallic surfaces to survive didn’t count as “life”.
Well, sure. For it to ever be possible to say "life arose more than once," one must decide where the boundary between life and non-life is. After all, every precursor of life arose all at once, in the Big Bang!
by tshaddox - "proto-cells that grew on these vents and needed those metallic surfaces to survive didn’t count as “life”"
What makes that argument extremely weak is analogies with contemporary obviously living animals.
For example, humans are not alive, because we get 100% of our vitamin D ascorbic acid by scavenging from the environment, along with a handful of other animals that presumably evolved in an extremely vitamin C rich environment. If any animal, including humans, ever evolve a new ability to internally synthesize vitamin C from glucose like every other animal, then given that there were non-synthesizer animals in their ancestry who we arbitrarily define as not-alive aka dead, then we could say that life evolved twice.
Note that humans could be defined as dead because we can't synthesize our own oxygen and have to scavenge 100% of it from the environment using lungs and so forth.
If you pencil whip the English language hard enough, anything with lungs or stomachs is not alive. A similar line of argument would lead to all saprophytes not being alive, which is pretty ridiculous. Wood eating mushrooms are not alive because they rely on the environment to provide all their wood dietary needs. Yeah OK whatever.
by VLM - The paper claims LUCA doesn't count as life because it still depended on its environment to metabolize.
It's kind of interesting that there's parasites that arguably don't meet this definition either. Looking it up: Chlamydia can't reproduce independently; relies on its host's metabolism. Microsporidia can't make ATP on its own. Are these "life"?
by neuralkoi