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.
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.
> 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 convergent evolution, which it would be, over a very long time period?
No, because conditions have changed markedly. For metals to act as catalysts, and replace some metabolic enzymes, they need to be in highly reduced conditions. This was true in early Earth, but about 2.5 billion years ago, we had the great oxygenation event, and over the next billion years free oxygen has gone up enough that you won’t find the reduced conditions where metal can take over the job of metabolic enzymes in much of Earth anymore.
That is, what sustains today’s life prevents new proto-life for forming. You need to have the fancy gadgets life has today to continue to survive and replicate on Earth.
Note though, it was other life forms that contributed to the great oxygenation event, too. This is all a continuous web.
Just curious, are there lifeforms today that rely on these metals to live in anaerobic environments? Maybe the hydrothermal vents that are talked about?
Do you think complex life could develop (perhaps by moving backwards) in a way that they rely on an anaerobic metal-rich environment?
I guess the oxidation event maybe was necessary for life to develop enzymes (since there wasn't sufficient evolutionary advantage for it to develop in an anaerobic environment?) but maybe something could go backwards? I'm just curious if there might be advantages for live in that sort of environment.
> Just curious, are there lifeforms today that rely on these metals to live in anaerobic environments? Maybe the hydrothermal vents that are talked about?
Yes! There are a few interesting variants called, "dissimilatory metal-reducing microorganisms"[1] and "sulfate-reducing microorganisms." They're a class that's being studied as a model for non-Terran life.
There are actually quite a few environments on Earth that are time capsules / have little ship bottles of very different life inside of them. For example, the Movile cave, https://en.wikipedia.org/wiki/Movile_Cave
Life in the cave has been separated from the outside for the past 5.5 million years and it is based completely on chemosynthesis. Due to its extreme environment, access to Movile Cave is strictly controlled, and a limited number of researchers have permission to study its conditions.
It's my dream to find one of these sites. I think there are quite a few locations out there yet to be discovered.
There could be deep subsurface microbes that are exposed to both pure metal and anoxic conditions that are similar, but note, it’s not “metal or protein” for catalysis. Many protein catalysts have metals incorporated.
What proto life did, it seems, was completely depend on metal surfaces to speed up some reactions. But that’s messy. The same metal can’t distinguish different components, so there would be competition for these surfaces, even within the same “cell”. That’s not ideal.
Enzymes are much more specific. You can actually sequester different reactions. And once you have life that’s learned to do that, it will out compete any proto life like matter that may access such environments.
Anaerobic microbes have enzymes also. So don’t think that reducing conditions mean no enzymes. It’s merely that in reduced conditions, you have metal that’s not oxidized available for early life -like goo to make use of. Over time, once this life learns to make newer and newer enzymes, the need to be metal dependent went away.
Somewhat separately, you also had some of this lineage learn to photosynthesize, and that lead to bulk oxygen in the atmosphere, and that was initially catastrophic, then highly beneficial because oxygen based chemistry is way more energetic than anaerobic chemistry.
It would be wrong to think of either condition as “better” though. They’re different. They force different tradeoffs. And both demand fine balance and dependence on the environment, eventually.
Coacervates, liposomes, acetogenic precursors, etc are all commonplace and could be considered proto-life. Some scientists have even argued that viruses are proto life. Prions (misfolded proteins that can self-replicate) and plasmids (non-chromosomal DNA strands that play a major role in horizontal gene transfer) are also candidates for proto-life that blur the line between living and non-living
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 that process stop, just because some other life already exists? Maybe we just can't detect this, because whatever new life happens to appear —more or less— resembles life that's already there.
They're pretty sure the primordial environment was a hydrothermal vent in an anoxic high phosphorus soda lake with methane, ammonia, and UV exposure. Nowadays those lakes don't have the methane and ammonia, so that environment isn't there anymore. https://www.science.org/content/article/unusual-soda-lakes-m...
The surfaces of clay particles in these lakes have been dubbed "the primordial sandwich".
The early protocells were 'alive', they were self-replicating, but they required nutrients and metabolic processes that only existed near mineral surfaces and would starve if they drifted away. They had to evolve new enzymes to become 'free-living'.
So it looks like the LUCA was one of these early protocells with an incomplete metabolism.
But the enviroments that have the easy/free energy that would give rise to life is almost always contaminated with life competing for and consuming that chemical energy.
> Shouldn't entirely new life develop all the time on earth?
It's possible OoL requires some exponentially unlikely step. We wouldn't realize that because of observer selection: had the step not occurred, we wouldn't be here to be thinking about it. There's a huge complexity gap between the stuff produced in OoL experiments and the simplest known life.
It's also possible OoL requires conditions that no longer exist on Earth, or that only existed in the early Earth (or wherever life got started in the Solar System). For example, if it depended on the existence of short lived radioactive isotopes or free ammonia.
I'd imagine the bar for becoming new life is much higher now, because it requires finding a niche that isn't already filled by an existing organism or requires being immediately competitive with existing life.
It has to survive though in the sense that it has to live long enough for us to see it. If we think of life as "spontaneously" (roughly speaking) emerging from the right conditions reasonably rarely, it has to outcompete other existing life for some time. And then there's the chance that we might not recognize it as "new" at all.
A step further "novel" life (hence still simpler) made from the same raw materials as existing life would look exactly like decomposing existing life and be routinely scavenged for material.
The ingredients and building blocks aren’t there in the same way. Because life formed, those early ingredients are now transformed, as is the environment. This blocks new life of the type that formed 4 billion years ago from forming again.
Indeed, all species branch out from that one universal common ancestor that was the first free living successful cell.
Put another way: forming life isn’t easy at all. And once it forms it changes conditions to suit its continuation, not to allow new life to form.
Life is vastly faster than random chance at producing more life. So living things go fill niches faster than random chance can use those niches to produce new life.
Probably this. How would we know what such 'proto-life' (perhaps even just some self-replicating soup of chemicals, no cell wall) would look like? Where to find it? How rare its occurence? Etc etc.
Scientists might not even recognise it if happened right in front of them.
I'd put my money on coming up with a more general definition of "life", and then looking for short(est) pathways from "soup of random chemicals" to "something in there that replicates (parts of) itself".
Doesn't need to look like life as we know it, as long as some elements of "self-organising structures, something being replicated" are there.
The building blocks will be immediately consumed by existing life. And that's just one way in which the world is radically different from the one in which life arose.
And life may have arisen from a very low probability set of circumstances ... there's no reason to expect it to be happening all the time.
>ike availability of water, temperatures, etc. We should see a constant emergence of new life all the time. Why would that process stop,
Anything that's so agreeable to abiogenesis that life might spontaneously manifest, is actually pretty tasty for things already alive. They swoop in and eat it before it gets started. So, I suspect that even what the article says isn't that they both arose in the same place, but in different places separated by distance, time, and/or environmental barriers.
It could be happening on my kitchen counter right this very second. But my kitchen counter, despite a recent cleaning, is absolutely lousy with microorganisms. So the new proto-life is immediately starved or more likely eaten by existing life. There's very few places on Earth that has not been colonized by some sort of life so there's very few places a new form of life could form and succeed long enough to itself grow and spread without being starved or eaten.
"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.
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.
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.
> “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.
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.
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.
Honestly just more “biology has enormous areas without enough data that need filling in” causing previous generalizations (e.g. the central dogma of information flow being replaced by protein regulation of gene expression, non-coding DNA, even neurons and egg cells being produced thru life) to be overthrown, more than anything, IMO.
I have absolutely no doubt that the next LLM/ML startup will be able to confidently, rapidly, productively and correctly fill in the missing data. Onward science!
I was already under the impression that life on Earth has had several "Game Over -Play Again?" periods.
I assume that the difference here, is that it went completely to zero, before restarting. The other times, there was a bit clinging on, that seeded the restart.
unfortunately the field of abiogenesis, just like extraterrestrial life, is a lost cause.
The reality we will never be able to replicate creation of life nor find life on other planets (except via contamination). it's why we've never gotten any closer. and i'm not even religious
Likely we don't need to replicate. We just need to get a sample of life with completely independent origin to our kind of life here on Earth, to study. This way we would be able to separate what are universal properties for any life from historical contingencies specific to us. To have samples of a single kind of life complicates things.
Were that to happen it could be the worst news humanity ever receives, since it would greatly increase the chance the "Great Filter" is in front of us, not behind us.
Not if it's just microbial life. Anyway it's just one case or another. We knowing what's the case doesn't change it. If the news never break it would be just as bad, perhaps even slightly worse, as we would not have early warning to prepare.
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
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.
If life could arise once, why would the conditions not be amenable to it arising more than once? Sure, life tends to pollute-terraform for itself, but it's a big planet, with more than enough distance between the first occurrence and pristine environment for it to happen several more times.
binaryturtle asked this question above and got about 10 responses. Conditions are very different, precursors to life get quickly consumed by existing life, origin of life is a rare event, etc.
Its an exciting time to be alive because as of recently we certainly can detect planetary atmosphere major components out to at least 700 or so light years.
There are astronomers actively working on minor component, more biologically interesting spectrographs like chlorophyll rather than spectrograms of carbon dioxide. That'll be harder to detect and limited to shorter ranges.
At some point, probably very soon, like less than a decade, we'll be able to definitively state that we have atmospheric data in an onion layer shaped shell where we have unequivocable proof that out to X lightyears from Earth there's no planetary scale chlorophyll higher than a minimal level aka there's no earth-like plants on that planet. That shell will likely expand over time. Or, perhaps we will find a forested, or at least algae covered, planet, some light years away, which would be very interesting indeed.
The question is rapidly changing from a purely philosophical belief to scientific observation, like right now, in real time, in the 2020s. What a cool time to be alive!
This follows old, old stuff from radio astronomy along the lines of how far away could a 1960s radio telescope realistically detect life on earth. The answer IIRC was not very far LOL. But there's been a lot of progress in radio astronomy, etc.
With respect to fermi filters etc people need to pay attention to how far away the Earth can be detected using radio telescopes. That distance has imploded since the end of analog UHF TV broadcasts. We still broadcast absolute swill, in fact more than ever, but digital detection range is much lower than analog AM carrier detection range from analog TV. The Earth has, to some extent, recently gone radio-quiet, which is interesting because we are still here, in fact more of us than ever. So WRT fermi filters of not being able to detect civilizations, disappearance of 1950s/1960s signals does not necessarily imply disappearance of civilization. Another example, if any aliens are watching the high altitude freon contamination of our atmosphere they're likely really confused right about now.
I agree. The Fermi Argument, and the apparent rarity of K3 civilizations in other galaxies, is to me powerful evidence of the scarcity of life. At the least, this suggests SETI should focus on distant galaxies where the Fermi argument doesn't bite as much.
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
but complex life far more difficult and unlikely, very rare, as explained in the PBS Space Time I linked above, the "Cambrian Explosion"
"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 links you provided.
Sorry, when you make an assertion, you don't get to demand I justify questioning it. You need to explain why I should believe you.
Your reversal of burden of proof is a red flag that you don't have a good argument.
IMO, it is quite plausible that OoL is extremely unlikely and that our solar system is the only place where life occurs in the visible universe. Not proved, of course, but the possibility is by no means unreasonable.
wasn't demanding, just wanted to hear what your own logic was instead
but it's pointless to go any further I guess as it's getting outside science
the weak anthropic principle can't be falsified so it cannot be argued
I don't think we'll ever hear from "ET" but I do think it's perfectly plausible to find single-celled or simple bacteria elsewhere someday (ie. Europa, comet or asteroid)
The idea that life came about by luck is completely absurd, even more so than thinking that a computer chip was created by chance erosion of a silicone wafer in exactly the right pattern.
It’s a big universe and there are a lot of years, so chemical evolution seems like a decent tool for God to use. Much like General Relativity is a more efficient way to rule the world than assigning angels to push the planets thru the sky. And a passing familiarity with birth defects will prove to most hard hearted people that each specific fact of biology is not designed by a loving creator. Unless you believe this messy but gloriously complex universe to be the best of all possible worlds, right up till you lie to your friend, it is difficult to believe whole heartedly in a loving creator.
I'm not a biblical scholar, but I think the "loving creator" thing was invented by people and not necessarily in the Bible. I'm pretty sure Old Testament God is pretty vengeful.
Theistic Evolution is wide-enough belief, especially with Protestants.
It is definitely in the Bible. Cynically, God seems to swing wildly between mercy and vengeance, but it's clear he would feel justified in a lot more vengeance than he takes but doesn't because he loves people. Less cynically, he's planning for Jesus and salvation the whole time, and sorta trying to keep the evil from getting out of hand with the occasional smiting. You can make the logic work if you want to.
And where did that god come from? Primordial soup full of magic and stardust? The idea of life starting by chance is completely absurd to you but somehow a god that just came out of nowhere is perfectly reasonable.
I don’t think what you are pointing at is a real issue.
Something exists. Therefore, on of the following 3 must hold: “one or more things exists or have existed which were not a consequence of another thing existing”, “an infinite regress of things existing as a consequence of other things”, “a cycles of consequences”.
The purported absurdity of life arising by chance is not about life existing, but about it arising by chance as a consequence of other non-living things.
The idea that god coming from nothing is absurd, well, that absurdity seemingly has to apply somewhere, as all 3 cases of the trichotomy above seem around as absurd? Eventually something has to be without explanation, whether it be a thing or a chain or cycle of things.
Or, were you not aware that most people who believe that God exists believe that God is the first cause?
Apparently you weren’t aware of that, because you said something about magic and stardust??
Could you go into why you consider the existence of an invisible (all powerful? Depends which god you mean, you didn't say) being that happens to concern itself with life on Sol's third planet, to be less absurd than what you describe?
We know that intricate machines are designed by smart people; they don't just happen by luck. The idea that living things, which are far more intricately organized at every level than any machine we have made, could have arisen by some unknown series of chance steps is a fairy tale. It has never been observed, and even in the most controlled of environments it cannot be replicated. To me it's far more reasonable to conclude that life was designed by a super intelligent Creator. Just as a piano implies a piano maker (even if we haven't seen them), life implies an original Life-giver.
The dogma in many religions is that nothing created God or at least, there's no way to know. He exists outside our time and space. So from our perspective, God has always existed. If you believe that free will is true, then he can see all outcomes of the universe at once. If you don't believe in true free will, he sees the single timeline at once, from the big bang to the heat death of the universe.
Personally, I don't believe in any religions. They were all developed before we had a much clearer idea of how our world works and there's just too much folklore mixed in with actual, yet primitive, philosophical discussions to abide by any of it. But like with the simulation theory, we have no way to know what exists outside our time and space so you shouldn't worry. If there is some bored extra dimensional teenager simulating our universe on their GPU, it ultimately doesn't matter because we'll never know.
I believe that according to Catholic and Orthodox thought, God is Being itself. If you're familiar with Plato and Aristotle, God is the Form of Being. If not, I guess you could say God is Being as a noun, or God is where the idea of Being comes from. God exists because he is existence itself. (He is also Life and Love, in the same way)
Interesting comment. FWIW the idea of God as Being accords with Spinoza's philosophy, which in turn accords with Greek philosophy and ultimately accords with biblical philosophy. These are roots among the many roots of our modern world.
What we learn from these philosophies is that God is necessarily the author of life and love, but as well hatred and destruction. Worth noting that the latter are most (but not exclusively) expressed in human conduct. Among all animals humans have the most developed ability to decide how to act. That ability is not absolute, often enough logic or reasoning is bypassed and emotion rules.
Naturally cognition is not unbounded, we are limited by constraints of our construction. It means aspects of the universe are unknowable, we can't know what we're missing.
But knowing what we can know is an obligation of our privileged existence. As knowledge expands it exposes the utter complexity of all things emerging from common fundamental processes.
Seeing what is seen, a human may for a moment get a glimpse of the hand that binds everything together. That's a gift if there ever was one.
> The idea that life came about by luck is completely absurd
Argument by ridicule is a fallacy.
> even more so than thinking that a computer chip was created by chance erosion of a silicone wafer in exactly the right pattern.
But, as I'm sure you have been told many times, that's an absurd strawman, and suggests that you didn't read TFA or anything else that discusses how life may have arisen, including any of the other comments here. Life didn't spring up fully formed, it developed in stages.
> As I see it
I can't think of anything less compelling.
> life was clearly designed by God.
That is semantically incoherent, as well as being a violation of HN guidelines ("Please don't use Hacker News for political or ideological battle.")
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.
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.
> …one of them at the other,
The origin of life is as romantic as I’d hoped.
> 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 convergent evolution, which it would be, over a very long time period?
You would think there would be some isolated places where proto-life still exists for this to be true.
No, because conditions have changed markedly. For metals to act as catalysts, and replace some metabolic enzymes, they need to be in highly reduced conditions. This was true in early Earth, but about 2.5 billion years ago, we had the great oxygenation event, and over the next billion years free oxygen has gone up enough that you won’t find the reduced conditions where metal can take over the job of metabolic enzymes in much of Earth anymore.
That is, what sustains today’s life prevents new proto-life for forming. You need to have the fancy gadgets life has today to continue to survive and replicate on Earth.
Note though, it was other life forms that contributed to the great oxygenation event, too. This is all a continuous web.
Just curious, are there lifeforms today that rely on these metals to live in anaerobic environments? Maybe the hydrothermal vents that are talked about?
Do you think complex life could develop (perhaps by moving backwards) in a way that they rely on an anaerobic metal-rich environment?
I guess the oxidation event maybe was necessary for life to develop enzymes (since there wasn't sufficient evolutionary advantage for it to develop in an anaerobic environment?) but maybe something could go backwards? I'm just curious if there might be advantages for live in that sort of environment.
There are actually quite a few environments on Earth that are time capsules / have little ship bottles of very different life inside of them. For example, the Movile cave, https://en.wikipedia.org/wiki/Movile_Cave
It's my dream to find one of these sites. I think there are quite a few locations out there yet to be discovered.[1] https://en.wikipedia.org/wiki/Dissimilatory_metal-reducing_m...
[2] https://en.wikipedia.org/wiki/Sulfate-reducing_microorganism
There could be deep subsurface microbes that are exposed to both pure metal and anoxic conditions that are similar, but note, it’s not “metal or protein” for catalysis. Many protein catalysts have metals incorporated.
What proto life did, it seems, was completely depend on metal surfaces to speed up some reactions. But that’s messy. The same metal can’t distinguish different components, so there would be competition for these surfaces, even within the same “cell”. That’s not ideal.
Enzymes are much more specific. You can actually sequester different reactions. And once you have life that’s learned to do that, it will out compete any proto life like matter that may access such environments.
Anaerobic microbes have enzymes also. So don’t think that reducing conditions mean no enzymes. It’s merely that in reduced conditions, you have metal that’s not oxidized available for early life -like goo to make use of. Over time, once this life learns to make newer and newer enzymes, the need to be metal dependent went away.
Somewhat separately, you also had some of this lineage learn to photosynthesize, and that lead to bulk oxygen in the atmosphere, and that was initially catastrophic, then highly beneficial because oxygen based chemistry is way more energetic than anaerobic chemistry.
It would be wrong to think of either condition as “better” though. They’re different. They force different tradeoffs. And both demand fine balance and dependence on the environment, eventually.
Coacervates, liposomes, acetogenic precursors, etc are all commonplace and could be considered proto-life. Some scientists have even argued that viruses are proto life. Prions (misfolded proteins that can self-replicate) and plasmids (non-chromosomal DNA strands that play a major role in horizontal gene transfer) are also candidates for proto-life that blur the line between living and non-living
For what it's worth, metals are still critical catalysts all over biology, they just tend to be encapsulated in biomolecules.
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 that process stop, just because some other life already exists? Maybe we just can't detect this, because whatever new life happens to appear —more or less— resembles life that's already there.
They're pretty sure the primordial environment was a hydrothermal vent in an anoxic high phosphorus soda lake with methane, ammonia, and UV exposure. Nowadays those lakes don't have the methane and ammonia, so that environment isn't there anymore. https://www.science.org/content/article/unusual-soda-lakes-m...
The surfaces of clay particles in these lakes have been dubbed "the primordial sandwich".
The early protocells were 'alive', they were self-replicating, but they required nutrients and metabolic processes that only existed near mineral surfaces and would starve if they drifted away. They had to evolve new enzymes to become 'free-living'.
So it looks like the LUCA was one of these early protocells with an incomplete metabolism.
But the enviroments that have the easy/free energy that would give rise to life is almost always contaminated with life competing for and consuming that chemical energy.
> Shouldn't entirely new life develop all the time on earth?
It's possible OoL requires some exponentially unlikely step. We wouldn't realize that because of observer selection: had the step not occurred, we wouldn't be here to be thinking about it. There's a huge complexity gap between the stuff produced in OoL experiments and the simplest known life.
It's also possible OoL requires conditions that no longer exist on Earth, or that only existed in the early Earth (or wherever life got started in the Solar System). For example, if it depended on the existence of short lived radioactive isotopes or free ammonia.
I'd imagine the bar for becoming new life is much higher now, because it requires finding a niche that isn't already filled by an existing organism or requires being immediately competitive with existing life.
It has to survive though in the sense that it has to live long enough for us to see it. If we think of life as "spontaneously" (roughly speaking) emerging from the right conditions reasonably rarely, it has to outcompete other existing life for some time. And then there's the chance that we might not recognize it as "new" at all.
A step further "novel" life (hence still simpler) made from the same raw materials as existing life would look exactly like decomposing existing life and be routinely scavenged for material.
The ingredients and building blocks aren’t there in the same way. Because life formed, those early ingredients are now transformed, as is the environment. This blocks new life of the type that formed 4 billion years ago from forming again.
Indeed, all species branch out from that one universal common ancestor that was the first free living successful cell.
Put another way: forming life isn’t easy at all. And once it forms it changes conditions to suit its continuation, not to allow new life to form.
Life is vastly faster than random chance at producing more life. So living things go fill niches faster than random chance can use those niches to produce new life.
> Maybe we just can't detect this
Probably this. How would we know what such 'proto-life' (perhaps even just some self-replicating soup of chemicals, no cell wall) would look like? Where to find it? How rare its occurence? Etc etc.
Scientists might not even recognise it if happened right in front of them.
I'd put my money on coming up with a more general definition of "life", and then looking for short(est) pathways from "soup of random chemicals" to "something in there that replicates (parts of) itself".
Doesn't need to look like life as we know it, as long as some elements of "self-organising structures, something being replicated" are there.
> Shouldn't entirely new life develop all the time on earth?
The fact that it doesn't is a pretty simple solution to the Fermi Paradox.
The building blocks will be immediately consumed by existing life. And that's just one way in which the world is radically different from the one in which life arose.
And life may have arisen from a very low probability set of circumstances ... there's no reason to expect it to be happening all the time.
>ike availability of water, temperatures, etc. We should see a constant emergence of new life all the time. Why would that process stop,
Anything that's so agreeable to abiogenesis that life might spontaneously manifest, is actually pretty tasty for things already alive. They swoop in and eat it before it gets started. So, I suspect that even what the article says isn't that they both arose in the same place, but in different places separated by distance, time, and/or environmental barriers.
Hash competition from life might cause them to go extinct, and even if it happens again it just gets out-competed to extinction fast.
It could be happening on my kitchen counter right this very second. But my kitchen counter, despite a recent cleaning, is absolutely lousy with microorganisms. So the new proto-life is immediately starved or more likely eaten by existing life. There's very few places on Earth that has not been colonized by some sort of life so there's very few places a new form of life could form and succeed long enough to itself grow and spread without being starved or eaten.
Maybe, or maybe it was eaten into extinction.
Geology over large time-scales is profoundly unforgiving.
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
* https://www.youtube.com/watch?v=abvzkSJEhKk
"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.
No it’s not that simple. We don’t fall dead the moment we don’t get vitamin D. We can stay alive long enough to get more.
That wouldn’t have been the case in these early beings, that were simply not capable of doing anything without these metals.
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.
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.
The link the site points to seems like a better source (no ads, cites DOI etc, affiliated with AAAS rather than random aggregator website):
https://www.eurekalert.org/news-releases/1138775
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.
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.
If true, fl in the Drake equation just got much bigger.
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.
The science alert article should make this more clear, as its easy to get that impression.
The article does make it clear, though the headline misleads.
Well, it's Science Alert - not exactly a bastion of level-headed reporting.
Yes I saw that, but the concept of "life" being quite blurry, I feel it still has an impact on the equation.
Honestly just more “biology has enormous areas without enough data that need filling in” causing previous generalizations (e.g. the central dogma of information flow being replaced by protein regulation of gene expression, non-coding DNA, even neurons and egg cells being produced thru life) to be overthrown, more than anything, IMO.
I have absolutely no doubt that the next LLM/ML startup will be able to confidently, rapidly, productively and correctly fill in the missing data. Onward science!
Yep, now the probability of alien civilisations is completely unknown, but half the completely unknown it was before.
Major Seveneves vibes from this
Because I had to look it up, a 2015 Neal Stephenson novel.
I was already under the impression that life on Earth has had several "Game Over -Play Again?" periods.
I assume that the difference here, is that it went completely to zero, before restarting. The other times, there was a bit clinging on, that seeded the restart.
Sounds cool. Anyone with more knowledge that can say if this is really as proven as they suggest and if it is a big thing or not?
unfortunately the field of abiogenesis, just like extraterrestrial life, is a lost cause.
The reality we will never be able to replicate creation of life nor find life on other planets (except via contamination). it's why we've never gotten any closer. and i'm not even religious
Likely we don't need to replicate. We just need to get a sample of life with completely independent origin to our kind of life here on Earth, to study. This way we would be able to separate what are universal properties for any life from historical contingencies specific to us. To have samples of a single kind of life complicates things.
Were that to happen it could be the worst news humanity ever receives, since it would greatly increase the chance the "Great Filter" is in front of us, not behind us.
The Great Filter is only one possible answer to the Fermi Paradox.
Not if it's just microbial life. Anyway it's just one case or another. We knowing what's the case doesn't change it. If the news never break it would be just as bad, perhaps even slightly worse, as we would not have early warning to prepare.
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...
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.
If life could arise once, why would the conditions not be amenable to it arising more than once? Sure, life tends to pollute-terraform for itself, but it's a big planet, with more than enough distance between the first occurrence and pristine environment for it to happen several more times.
binaryturtle asked this question above and got about 10 responses. Conditions are very different, precursors to life get quickly consumed by existing life, origin of life is a rare event, etc.
Origin of life on earth is not very interesting to me. Origin of life in the universe is where it is at...
Until we get any tangible proof of life outside Earth, there is no difference
Actually I don't think there is life outside of Earth. I think we are truly alone in this universe.
Its an exciting time to be alive because as of recently we certainly can detect planetary atmosphere major components out to at least 700 or so light years.
https://en.wikipedia.org/wiki/WASP-39b
There are astronomers actively working on minor component, more biologically interesting spectrographs like chlorophyll rather than spectrograms of carbon dioxide. That'll be harder to detect and limited to shorter ranges.
At some point, probably very soon, like less than a decade, we'll be able to definitively state that we have atmospheric data in an onion layer shaped shell where we have unequivocable proof that out to X lightyears from Earth there's no planetary scale chlorophyll higher than a minimal level aka there's no earth-like plants on that planet. That shell will likely expand over time. Or, perhaps we will find a forested, or at least algae covered, planet, some light years away, which would be very interesting indeed.
The question is rapidly changing from a purely philosophical belief to scientific observation, like right now, in real time, in the 2020s. What a cool time to be alive!
This follows old, old stuff from radio astronomy along the lines of how far away could a 1960s radio telescope realistically detect life on earth. The answer IIRC was not very far LOL. But there's been a lot of progress in radio astronomy, etc.
With respect to fermi filters etc people need to pay attention to how far away the Earth can be detected using radio telescopes. That distance has imploded since the end of analog UHF TV broadcasts. We still broadcast absolute swill, in fact more than ever, but digital detection range is much lower than analog AM carrier detection range from analog TV. The Earth has, to some extent, recently gone radio-quiet, which is interesting because we are still here, in fact more of us than ever. So WRT fermi filters of not being able to detect civilizations, disappearance of 1950s/1960s signals does not necessarily imply disappearance of civilization. Another example, if any aliens are watching the high altitude freon contamination of our atmosphere they're likely really confused right about now.
I agree. The Fermi Argument, and the apparent rarity of K3 civilizations in other galaxies, is to me powerful evidence of the scarcity of life. At the least, this suggests SETI should focus on distant galaxies where the Fermi argument doesn't bite as much.
There is likely simple basic life as advanced as bacteria around the universe
But high level life was likely a series of complex accidents that is not reproducible or would be radically different than us
One of my absolute favorite PBS Space Time on the subject
* https://www.youtube.com/watch?v=abvzkSJEhKk
> There is likely simple basic life as advanced as bacteria around the universe
What is the basis for this assertion?
single-cell "life" can be so simple that scientists can create it in a lab "SpudCell"
* https://www.science.org/content/article/lab-created-spudcell...
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
but complex life far more difficult and unlikely, very rare, as explained in the PBS Space Time I linked above, the "Cambrian Explosion"
* https://en.wikipedia.org/wiki/Cambrian_explosion
if there are viruses and fungi out there however, they could mutate eventually with enough permutations and outside stressors
that video explains the huge leap forward with DNA vs simple protein patterns
"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 links you provided.
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)
Sorry, when you make an assertion, you don't get to demand I justify questioning it. You need to explain why I should believe you.
Your reversal of burden of proof is a red flag that you don't have a good argument.
IMO, it is quite plausible that OoL is extremely unlikely and that our solar system is the only place where life occurs in the visible universe. Not proved, of course, but the possibility is by no means unreasonable.
wasn't demanding, just wanted to hear what your own logic was instead
but it's pointless to go any further I guess as it's getting outside science
the weak anthropic principle can't be falsified so it cannot be argued
I don't think we'll ever hear from "ET" but I do think it's perfectly plausible to find single-celled or simple bacteria elsewhere someday (ie. Europa, comet or asteroid)
The idea that life came about by luck is completely absurd, even more so than thinking that a computer chip was created by chance erosion of a silicone wafer in exactly the right pattern.
As I see it life was clearly designed by God.
It’s a big universe and there are a lot of years, so chemical evolution seems like a decent tool for God to use. Much like General Relativity is a more efficient way to rule the world than assigning angels to push the planets thru the sky. And a passing familiarity with birth defects will prove to most hard hearted people that each specific fact of biology is not designed by a loving creator. Unless you believe this messy but gloriously complex universe to be the best of all possible worlds, right up till you lie to your friend, it is difficult to believe whole heartedly in a loving creator.
I'm not a biblical scholar, but I think the "loving creator" thing was invented by people and not necessarily in the Bible. I'm pretty sure Old Testament God is pretty vengeful.
Theistic Evolution is wide-enough belief, especially with Protestants.
It is definitely in the Bible. Cynically, God seems to swing wildly between mercy and vengeance, but it's clear he would feel justified in a lot more vengeance than he takes but doesn't because he loves people. Less cynically, he's planning for Jesus and salvation the whole time, and sorta trying to keep the evil from getting out of hand with the occasional smiting. You can make the logic work if you want to.
This is edging into religious debate, which the guidelines ask people to keep off HN
And where did that god come from? Primordial soup full of magic and stardust? The idea of life starting by chance is completely absurd to you but somehow a god that just came out of nowhere is perfectly reasonable.
I don’t think what you are pointing at is a real issue.
Something exists. Therefore, on of the following 3 must hold: “one or more things exists or have existed which were not a consequence of another thing existing”, “an infinite regress of things existing as a consequence of other things”, “a cycles of consequences”.
The purported absurdity of life arising by chance is not about life existing, but about it arising by chance as a consequence of other non-living things.
The idea that god coming from nothing is absurd, well, that absurdity seemingly has to apply somewhere, as all 3 cases of the trichotomy above seem around as absurd? Eventually something has to be without explanation, whether it be a thing or a chain or cycle of things.
Or, were you not aware that most people who believe that God exists believe that God is the first cause?
Apparently you weren’t aware of that, because you said something about magic and stardust??
> As I see it life was clearly designed by God
Yes, wide-bosomed Gaia, foundation of us all, this research is about the manner in which She did it, if it was one birth or two.
Could you go into why you consider the existence of an invisible (all powerful? Depends which god you mean, you didn't say) being that happens to concern itself with life on Sol's third planet, to be less absurd than what you describe?
Or is that the joke and I'm missing it?
We know that intricate machines are designed by smart people; they don't just happen by luck. The idea that living things, which are far more intricately organized at every level than any machine we have made, could have arisen by some unknown series of chance steps is a fairy tale. It has never been observed, and even in the most controlled of environments it cannot be replicated. To me it's far more reasonable to conclude that life was designed by a super intelligent Creator. Just as a piano implies a piano maker (even if we haven't seen them), life implies an original Life-giver.
I wish I were so vain as to think I'm so special, surely I could never have happened by chance.
> As I see it life was clearly designed by God.
Which one? There are so many to choose from...
And what created that God? I know it's turtles all the way down but still want to know.
The dogma in many religions is that nothing created God or at least, there's no way to know. He exists outside our time and space. So from our perspective, God has always existed. If you believe that free will is true, then he can see all outcomes of the universe at once. If you don't believe in true free will, he sees the single timeline at once, from the big bang to the heat death of the universe.
Personally, I don't believe in any religions. They were all developed before we had a much clearer idea of how our world works and there's just too much folklore mixed in with actual, yet primitive, philosophical discussions to abide by any of it. But like with the simulation theory, we have no way to know what exists outside our time and space so you shouldn't worry. If there is some bored extra dimensional teenager simulating our universe on their GPU, it ultimately doesn't matter because we'll never know.
I believe that according to Catholic and Orthodox thought, God is Being itself. If you're familiar with Plato and Aristotle, God is the Form of Being. If not, I guess you could say God is Being as a noun, or God is where the idea of Being comes from. God exists because he is existence itself. (He is also Life and Love, in the same way)
Interesting comment. FWIW the idea of God as Being accords with Spinoza's philosophy, which in turn accords with Greek philosophy and ultimately accords with biblical philosophy. These are roots among the many roots of our modern world.
What we learn from these philosophies is that God is necessarily the author of life and love, but as well hatred and destruction. Worth noting that the latter are most (but not exclusively) expressed in human conduct. Among all animals humans have the most developed ability to decide how to act. That ability is not absolute, often enough logic or reasoning is bypassed and emotion rules.
Naturally cognition is not unbounded, we are limited by constraints of our construction. It means aspects of the universe are unknowable, we can't know what we're missing.
But knowing what we can know is an obligation of our privileged existence. As knowledge expands it exposes the utter complexity of all things emerging from common fundamental processes.
Seeing what is seen, a human may for a moment get a glimpse of the hand that binds everything together. That's a gift if there ever was one.
Do you reject evolution or do you believe God only created bacteria etc?
Which god?
the Sun
> The idea that life came about by luck is completely absurd
Argument by ridicule is a fallacy.
> even more so than thinking that a computer chip was created by chance erosion of a silicone wafer in exactly the right pattern.
But, as I'm sure you have been told many times, that's an absurd strawman, and suggests that you didn't read TFA or anything else that discusses how life may have arisen, including any of the other comments here. Life didn't spring up fully formed, it developed in stages.
> As I see it
I can't think of anything less compelling.
> life was clearly designed by God.
That is semantically incoherent, as well as being a violation of HN guidelines ("Please don't use Hacker News for political or ideological battle.")