My name is LUCA
I'm your distant ancestooor
I have some news for you
Yes, they think life came once before
Radical Study Suggests Life on Earth Arose Twice
101–110 of 116 posts
Re: Radical Study Suggests Life on Earth Arose Twice
#102Earlier quoted context omitted.
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"?
The difference is more on survival. A closed loop metabolism is indeed a good boundary marker. Viruses would fail this. But many have “closed but for a few critical dependencies”, and the argument here is that when life depended on metals like this, it’s more critical dependencies than closed loop. Somewhere in there is a transition. But it’s poorly defined, and so the argument can be there was a bifurcation of sorts…
> A closed loop metabolism is indeed a good boundary marker.
Presence of metallic catalysts is just an environmental factor. Not counting the organisms that can't live without them as life would be as not counting as life something that can't do metabolism without liquid water.
Life at time of LUCA just had a bit stricter environment requirements, but it should still be counted as life.
So I wouldn't read this as discovering that life evolved twice. Life just evolved a hack for dealing with environments without metallic catalysts twice.
Re: Radical Study Suggests Life on Earth Arose Twice
#103Earlier quoted context omitted.
This is edging into religious debate, which the guidelines ask people to keep off HN
The guidelines do not mention religion a single time. What are you talking about?
"Please don't use Hacker News for political or ideological battle. It tramples curiosity."
Re: Radical Study Suggests Life on Earth Arose Twice
#104Earlier quoted context omitted.
The difference is more on survival. A closed loop metabolism is indeed a good boundary marker. Viruses would fail this. But many have “closed but for a few critical dependencies”, and the argument here is that when life depended on metals like this, it’s more critical dependencies than closed loop. Somewhere in there is a transition. But it’s poorly defined, and so the argument can be there was a bifurcation of sorts…
People love to put things into neat boxes so that we can somehow reduce them to a single concept. Unfortunately the real world is usually a bit more messy than that. This is one example that makes it pretty obvious that our model is a little bit overly reductive, and at least to me the "Is this life?" question seems to have an answer that is on a spectrum rather than binary.
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Re: Radical Study Suggests Life on Earth Arose Twice
#105The 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 metaboli…
> …one of them at the other, The origin of life is as romantic as I’d hoped.
Procedural Mating to a Sexy Soundtrack
Re: Radical Study Suggests Life on Earth Arose Twice
#106Earlier quoted context omitted.
> 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!
Hardly. There are nucleic and amino acids pretty much in every star system, we now know. But not during the big bang. Theres a lot of intermediate stages before stars are young enough to have the mix of chemicals to give rise to these precursor chemicals to life. Its stages, but it’s a bit hard to say “early stage was a single origin, then we count each bifurcated radiation as a separate start point”. Why not call it…
The Big Bang is the precursor to everything, including to nucleic and amino acids.
Re: Radical Study Suggests Life on Earth Arose Twice
#107Earlier quoted context omitted.
You would think there would be some isolated places where proto-life still exists for this to be true.
I always found it odd that there's only one single origin of life point or even just a single common ancestor considered in history. Shouldn't entirely new life develop all the time on earth? I mean the ingredients and building blocks are still there, the environmental situation still should work out, like availability of water, temperatures, etc. We should see a constant emergence of new life all the time. Why would…
Because the moment life first appears, it multiplies and fills all easily available niches, and any new life is outcompeted by the more evolved pre-existing organisms.
Re: Radical Study Suggests Life on Earth Arose Twice
#108Earlier quoted context omitted.
I always found it odd that there's only one single origin of life point or even just a single common ancestor considered in history. Shouldn't entirely new life develop all the time on earth? I mean the ingredients and building blocks are still there, the environmental situation still should work out, like availability of water, temperatures, etc. We should see a constant emergence of new life all the time. Why would…
Because the moment life first appears, it multiplies and fills all easily available niches, and any new life is outcompeted by the more evolved pre-existing organisms.
I may be a dumb layman, but that argument seems too tidy and absolute to me - wouldn’t it suggest, for example, that viruses could never appear because they’d be outcompeted by more advanced bacteria? Earth seems to have room for an incredible diversity of types of life.
Re: Radical Study Suggests Life on Earth Arose Twice
#109The "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"
Re: Radical Study Suggests Life on Earth Arose Twice
#110Earlier quoted context omitted.
"SpudCell" already has 36 genes; the information encoded there basically cannot occur by random processes. There is still an enormous complexity gap between it and abiotic systems. > somewhere among 2 TRILLION planets in our galaxy there is a planet with enough atmosphere and magnetosphere to protect it from space radiation so there is likely bacteria I reject this conclusion; it certainly isn't justified by the link…
you don't think there is even single-cell life anywhere else but Earth? why would Earth be that incredibly unique? it's even plausible Earth was accidentally seeded by panspermia (bacteria on comets)
>why would Earth be that incredibly unique?
I think the answer to the question is easy if we consider quantum mechanics. It says every possible random event manifests in some universe. This means that an event or combination of events, no matter how incredibly unique, manifests in some universe.
Imagine the very first cell. Imagine that all the particles of that cell coming into the exact spatial location by pure random chance. It is a chain of incredibly random events. But it does not matter. QM says that it manifests in some universe.
So, We are just in one such universe. Of course, there might be universes where this incredibly random event have manifested more than once. But since then number of such universes are minuscule when compared to the number of universes where it happened only once, there is an overwhelming chance that we, as one conscious species, finds ourselves in a universe where life originated only once.
In the same manner, there could be universes where an entire brain assembled itself purely randomly. But the number of such worlds are a small fraction of the worlds where a single cell formed, and followed the relatively simple procedure of natural selection and end up as beings who can ask such kinds of questions.