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.
Radical Study Suggests Life on Earth Arose Twice
111–120 of 127 posts
Re: Radical Study Suggests Life on Earth Arose Twice
#112Earlier quoted context omitted.
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.
Viruses are not newly appearing forms of life, they are co-depending on the already present forms of life and they reuse some of their machinery.
Viruses are the opposite of starting from zero, they start from a functional organism and stop existing if the base organism gets extinct.
However, reading other answers, it seems the great oxygenation event is an even stronger argument against basic life appearing again. They would get oxidised and die.
Re: Radical Study Suggests Life on Earth Arose Twice
#113unfortunately 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
Any reasons? I mean we are proof that it happens.
We seem to make gradual progress in investigating like this article and recently there was stuff on how RNA could self replicate https://youtu.be/EhPgu0I8yaY
Re: Radical Study Suggests Life on Earth Arose Twice
#114Life 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.
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.
Re: Radical Study Suggests Life on Earth Arose Twice
#115Earlier quoted context omitted.
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.
Nope. It would suggest that new viruses could not spontaneously appear from abiotic matter, because they'd be outcompeted by existing viruses. Which may well be true.
We don't know where exactly viruses came from, but one of the leading theories is actually that they are the descendants of bacteria which outcompeted other bacteria. When a parasitic bacterium sheds more and more of its own metabolic capabilities, because it's more efficient to steal those abilities from its host cell, it evolves in a way that looks more and more like a virus.
"More evolved" or "more advanced" in this case doesn't mean "bigger" or "more complex". You can say viruses are equally evolved as bacteria, meaning they've spent equally long being optimized for their ecological niche.
Re: Radical Study Suggests Life on Earth Arose Twice
#116Earlier 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…
> 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 dis…
Presence of metallic catalysts is just an environmental factor.
No, it isn’t quite that. For it to count as “environment” the organism must be able to survive for at least a time without it.
The issue here is, the metal wasn’t a nutrient. That would be fine and exactly like it is for all life now.
Instead the metal was the anchor. If an organism needed to grow on it to enable half its metabolism, it is at the least very distinct from current life.
The only issue with the “two origins” claim is both lineages, bacteria and archea, come from this, and even with an open metabolic chain, you already had the nucleic acid function etc all sorted out, and common between both kingdoms.
So it’s a stretch to say there were two origins to life, but not that this proto life is distinct from modern life. That we need things from our environment is not the same as what they found about proto life in the vents.
Re: Radical Study Suggests Life on Earth Arose Twice
#117Earlier quoted context omitted.
> 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 dis…
Presence of metallic catalysts is just an environmental factor. No, it isn’t quite that. For it to count as “environment” the organism must be able to survive for at least a time without it. The issue here is, the metal wasn’t a nutrient. That would be fine and exactly like it is for all life now. Instead the metal was the anchor. If an organism needed to grow on it to enable half its metabolism, it is at the least v…
> For it to count as “environment” the organism must be able to survive for at least a time without it.
How long can a cell survive without liquid water? It literally enables almost all of the chemistry inside the cell.
Cell requiring a specific metal to be present is not very different from cell requiring for liquid water to be present.
Initially life started in favorable conditions, then spread to less favorable ones. Lack of metal catalyst around was the initial less favorable condition. At some point lack of liquid water was one. But eventually life spread to various very dry or cold places because it found workarounds for environment infeasibilities.
Maybe in 5 billion years life that can't survive without liquid water around and can't substitute it with self-made polar solvents and thus is stuck to surfaces of very few, very particular planets is going to be considered proto-life.
Re: Radical Study Suggests Life on Earth Arose Twice
#118Earlier quoted context omitted.
The Great Filter is only one possible answer to the Fermi Paradox.
The Milky Way is almost 14 billion years old. The Milky Way is perhaps 100K light-years in diameter. If you can travel at 0.1c you could colonize the Milky Way in perhaps around a million years, less than 0.01% of the age of the Milky Way. So, either there's a filter that's blocked interstellar colonization... or it has occurred already, and we just aren't aware of it (some sort of dark forest thing / we are being se…
> If you can travel at 0.1c you could colonize the Milky Way in perhaps around a million years
There's no reason to believe a civilization is capable of million year projects.
Re: Radical Study Suggests Life on Earth Arose Twice
#119The 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…
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"?
Where there is chlamydia or microsporidia, there is undisputed life. How much of it one assigns to chlamydia or microsporidia is moot from the point of view above
Re: Radical Study Suggests Life on Earth Arose Twice
#120Earlier quoted context omitted.
Presence of metallic catalysts is just an environmental factor. No, it isn’t quite that. For it to count as “environment” the organism must be able to survive for at least a time without it. The issue here is, the metal wasn’t a nutrient. That would be fine and exactly like it is for all life now. Instead the metal was the anchor. If an organism needed to grow on it to enable half its metabolism, it is at the least v…
> For it to count as “environment” the organism must be able to survive for at least a time without it. How long can a cell survive without liquid water? It literally enables almost all of the chemistry inside the cell. Cell requiring a specific metal to be present is not very different from cell requiring for liquid water to be present. Initially life started in favorable conditions, then spread to less favorable on…
>How long can a cell survive without liquid water?
Depends on the cell, but it’s not instant death. By definition, a cell is a membrane with some water inside it.
Sure, move that cell to totally dry conditions and most will die. But not all, by any means. Bacterial endospores last millenia without water. Tardigrades can do years.
This isn’t quite the gotcha you think it is.
The metal use for multiple catalytic steps is distinct. The paper isn’t wrong about that at all. Trying to prove the closed loop metabolism of modern life is secretly open loop isn’t going to work because it isn’t open like that. An organism can survive without constant contact with any of its components. Sometimes not for very long, but nothing alive today is as dependent on something external as these proto cells were on reduced metal.