I've been watching a Brian Cox documentary again. One that pointed to the idea of these hydrothermal vents being the origin of life. He also presents the (qualified) position that life is basically an inevitable consequence of the physics and chemistry of the universe under certain conditions. Basically given the right conditions, life will have no choice but to emerge.

So given that, and given the fact that hydrothermal vents are present in many areas of the world, why is all life related? Why have these vents not been churning out biologically unique specimens throughout the earth's history (even if there was a period in deep history where conditions were more receptive)? Or have they and only one strand survived? Perhaps it would be impossible, once our ancestors got a foot hold, for anything else to be allowed to evolve beyond that earliest stage whatever it might have been?

Any thoughts?

Obviously I know that hydrothermal vents aren't exactly a proven theory at this point.

As Charlie D (and myself, independently c. 150 years later for which I did in fact NOT win an award for extreme original cleverness) put it, paraphrased: any new "protobiotic" molecules produced would now be instantly devoured or absorbed, which would not have been the case before life first appeared on the planet.

ETA: from the abiogenesis wiki, Charles Darwin wrote: "at the present day such matter would be instantly devoured or absorbed, which would not have been the case before living creatures were formed."

I think this was brought up recently somewhere else. Largely, because the niche that new life would occupy is already filled.

I'm With Stupid wrote:I've been watching a Brian Cox documentary again. One that pointed to the idea of these hydrothermal vents being the origin of life. He also presents the (qualified) position that life is basically an inevitable consequence of the physics and chemistry of the universe under certain conditions. Basically given the right conditions, life will have no choice but to emerge.

So given that, and given the fact that hydrothermal vents are present in many areas of the world, why is all life related? Why have these vents not been churning out biologically unique specimens throughout the earth's history (even if there was a period in deep history where conditions were more receptive)? Or have they and only one strand survived? Perhaps it would be impossible, once our ancestors got a foot hold, for anything else to be allowed to evolve beyond that earliest stage whatever it might have been?

Any thoughts?

Obviously I know that hydrothermal vents aren't exactly a proven theory at this point.

To answer your questions:

Assuming the model is right, then all life is related because the first basic life-forms would have evolved there and then propagated out from there evolving to colonize new niches, but still maintaining their common ancestry.

These ecological and behavioral niches are also the answer for your other question. The first life forms would not have had to compete with other life forms. New life forms have no 'history' of competitive evolution, or of evading predators. A new life form evolving in an already complex niche needs to come out running, so the existence of life makes new life forms less likely to survive, those existing life forms having the benefit of an evolutionary history bestowing on them capabilities that make them outperform in every appreciable way a de novo life form.

Spearthrower wrote:

I'm With Stupid wrote:I've been watching a Brian Cox documentary again. One that pointed to the idea of these hydrothermal vents being the origin of life. He also presents the (qualified) position that life is basically an inevitable consequence of the physics and chemistry of the universe under certain conditions. Basically given the right conditions, life will have no choice but to emerge.

So given that, and given the fact that hydrothermal vents are present in many areas of the world, why is all life related? Why have these vents not been churning out biologically unique specimens throughout the earth's history (even if there was a period in deep history where conditions were more receptive)? Or have they and only one strand survived? Perhaps it would be impossible, once our ancestors got a foot hold, for anything else to be allowed to evolve beyond that earliest stage whatever it might have been?

Any thoughts?

Obviously I know that hydrothermal vents aren't exactly a proven theory at this point.

To answer your questions:

Assuming the model is right, then all life is related because the first basic life-forms would have evolved there and then propagated out from there evolving to colonize new niches, but still maintaining their common ancestry.

These ecological and behavioral niches are also the answer for your other question. The first life forms would not have had to compete with other life forms. New life forms have no 'history' of competitive evolution, or of evading predators. A new life form evolving in an already complex niche needs to come out running, so the existence of life makes new life forms less likely to survive, those existing life forms having the benefit of an evolutionary history bestowing on them capabilities that make them outperform in every appreciable way a de novo life form.

I get this. I guess my question is why didn't separate lifeforms evolve to fill these niches in their own tiny corners of a vast ocean? Or did they, and once they met, one had clearly evolved more successfully than all of the others?

The chemical composition of Earth's oceans have significantly changed since our planet's earliest history. The earliest oceans are thought to have contained a lot more carbon dioxide, almost zero oxygen, and very high concentrations of Iron and a host of other transition metals. These changes in turn have had significant consequences for the kinds of chemistry Earth's ocean waters can facilitate.

This might actually constitute an even more significant explanation for why life does not continue to bubble out of Earth's hydrothermal vent systems on the ocea floor, than the idea that new life would be quickly consumed by microbes, as some of the crucial chemistry hypothesized to be require for life's hydrothermal origins, isn't possible at the ocean's current chemical composition.

I'm With Stupid wrote:
I get this. I guess my question is why didn't separate lifeforms evolve to fill these niches in their own tiny corners of a vast ocean? Or did they, and once they met, one had clearly evolved more successfully than all of the others?

I think I see what you mean. Essentially, in the earliest period of life on Earth prior to the radiation of any species why didn't numerous unrelated organisms evolve in different parts of the world around abouts the same time?

Perhaps they did - we simply cannot know. It's also possible that there are some organisms extant today that don't share a common ancestor with all the other organisms. This idea is wrapped up in a concept called 'Shadow Biosphere'. The closer back we get to the origin of life, the less evidence we have about it and consequently the less clear the picture is. The evidence of the earliest life forms is in trace fossils, basically the imprints organisms left behind rather than fossils of the organisms themselves.

So to the best of my knowledge, we honestly don't know the answer to your question. It could be that it just didn't happen as while life may well be inevitable, that doesn't mean it will necessarily happen at any given time - maybe just one organism evolved and then underwent rapid speciation filling and adapting numerous niches and resulting in such diversity that no new type of life could have succeeded. Maybe on the early Earth there were dozens of unrelated clades of organisms, and one simply out-competed or out-lucked the others. It's even possible that some as-yet undiscovered extant bacterium-like organism will turn out to be the only remaining sample of its entire tree of life, and it may even take us decades or centuries before we find it as we tend to have a necessary set of biases when we run tests that might detect life.

The tree of life may have roots.

Roots that may have died off or even possibly merged.

Even if so, and we may never know, what would that actually change about life or lifes past?

It was doing an astrobiology course that originally lead me to the interesting what-if of a shadow biosphere. The point is that if we're out there looking for life on other planets, that life is probably not like our own. We have to be aware of our (quite rational chemically speaking) biases, looking for free oxygen for example. So the idea follows then that if we could feasibly overlook life on other planets because of unexpected bio-chemistry not leaving the tell-tale signs we'd predict and create experimental missions to detect, then couldn't we also be doing the same on Earth in places very nearly as remote for us as the surface of other planets.

https://www.astrobio.net/retrospections ... biosphere/

All living things that have so far been found share the same highly complex method of protein synthesis, with DNA sequences of nucleotides being copied to RNA sequences of similar nucleotides, which are then the basis for protein sequences of amino acids, amino acids being completely different from nucleotides. This presumably took millions of years to evolve through natural selection, and there is only a very low chance of this exact mechanism appearing twice from separate lines of evolution in different parts of the world (also, there are other universal similarities between the living things which have been discovered). It's more likely that this particular process evolved only once, then eventually outcompeted other early life forms.

It's thought that ribosomes, the protein-RNA complexes where the genetic code made up of nucleotides is translated to proteins made up of amino acids, evolved at about the time of the Last Universal Common Ancestor (LUCA), as stated baldly in the first sentence of a 2015 paper here: "The modern ribosome was largely formed at the time of the last common ancestor, LUCA." This would be explained if organisms with modern ribosomes outcompeted the rest. ("Modern" here is relative to the earlier forms of ribosomes that presumably existed, estimated dates for the LUCA range between 3.5 billion years and 4.5 billion years ago, going by Wikipedia here.)

As Spearthrower says, it's likely that life forms which evolved entirely separately, on other planets, would have markedly different basic biochemistry.

zoon wrote:All living things that have so far been found share the same highly complex method of protein synthesis, with DNA sequences of nucleotides being copied to RNA sequences of similar nucleotides, which are then the basis for protein sequences of amino acids, amino acids being completely different from nucleotides.

<snip>

Except for the recently discovered anaerobic complex life form that doesn’t have RNA.

Macdoc shared a recent find that’s reported in the following. I’d link to the thread, but it turned into a complete waste of time. This find has major implications for life sciences.

https://www.sciencealert.com/this-is-th ... ource=digg

RS

theropod_V_2.0 wrote:

zoon wrote:All living things that have so far been found share the same highly complex method of protein synthesis, with DNA sequences of nucleotides being copied to RNA sequences of similar nucleotides, which are then the basis for protein sequences of amino acids, amino acids being completely different from nucleotides.

<snip>

Except for the recently discovered anaerobic complex life form that doesn’t have RNA.

Macdoc shared a recent find that’s reported in the following. I’d link to the thread, but it turned into a complete waste of time. This find has major implications for life sciences.

https://www.sciencealert.com/this-is-th ... ource=digg

RS

Wow, I'd no idea there's a life form with no RNA. How does it make proteins? Is there a link to an article about it?

I know some viruses only have DNA (Wikipedia article here), but I wasn't counting them as life forms, in the same way that a computer virus isn't a computer?

Found the actual paper, and of course behind a damned pay wall. Still, here ya go.

https://www.pnas.org/content/early/2020 ... 1909907117

RS

theropod_V_2.0 wrote:Found the actual paper, and of course behind a damned pay wall. Still, here ya go.

https://www.pnas.org/content/early/2020 ... 1909907117

RS

Thanks, I hadn't taken in that all previously known multicellular organisms need oxygen, that finding does improve the chances of complex extraterrestrial life, though RNA's not mentioned. I suppose it's still an open question whether the storage of inherited information in some sort of nucleic acid is a requirement for evolved life.

I suppose it's still an open question whether the storage of inherited information in some sort of nucleic acid is a requirement for evolved life.

Here in 2020, I want to go on record that I am skeptical that would be the case. In centuries to come, this post will be rediscovered and people of the future will revel at my foresight and genius.

*cough cough*

zoon wrote:

theropod_V_2.0 wrote:Found the actual paper, and of course behind a damned pay wall. Still, here ya go.

https://www.pnas.org/content/early/2020 ... 1909907117

RS

Thanks, I hadn't taken in that all previously known multicellular organisms need oxygen, that finding does improve the chances of complex extraterrestrial life, though RNA's not mentioned. I suppose it's still an open question whether the storage of inherited information in some sort of nucleic acid is a requirement for evolved life.

This is an organism that inherited almost all of its structure and function from an organism that evolved with an aerobic metabolism which then devolved to abandon aerobic metabolism in an anaerobic environment. Evolution of multi-cellular animals from unicellular or colonial forms in anaerobic conditions has not been demonstrated and I do not think anyone posting in this thread or in the other is equipped to evaluate the chances of complex extraterrestrial life based a study focused only on a single species that has merely shed features belonging to organisms with aerobic metabolism.

Nope, no reason to consider the demonstrated fact that, no matter the pathway, an organism arose that does not employ oxygen in its metabolic processes. No such example has ever been observed before. Nothing to see here. Move along.

Until this critter was discovered suggesting its existence would be met with laughter. To not now see how having a living example of an anaerobic complex organism, no matter how it became so, just might inform an exobiologist of a “possibility” that, until this discovery was laughable, I am boggled.

On a planet 10 billion years old (orbiting a red dwarf), that lost most of its free oxygen over a VERY long time, this very mechanism could come into play. Life arises, and evolves complexity, in an free oxygen rich environment, slowly loses that free oxygen and life gradually evolves to become anaerobic. In a universe as vast as we can observe such a thing surely has happened, and is happening. Had we not this example we might not even bother to look at an apparent “dead” planet devoid of oxygen. Instead of limiting exobiologists search for extraterrestrial life forms, it expands it. So, I feel justified in declaring that an exobiologist should get a charge out of this. Cito, having taken an extensive survey of exobiologists across the globe, has informed us they disagree.

To the curious, or OCD, among us, just go look. Point out where I made any other assertion than exogeeks would cum. They cum at the crack of dawn! This is a full length triple X 8K 3D splash fest. Good for them!

I am sorry that my comments are not formulated well enough to convey the intent with enough clarity, but perhaps instead of dismissive two word declarations, the use of less arrogant tone might return more positive results. If anyone wants to take a position in opposition to mine, and can correct me, I thank them. Look back across the forum. You know my ID. I’m a damned straight shooter. This ain’t what’s going on. Cito jumped the gun.

If the above doesn’t clarify my throw away post in another thread Cito felt compelled to deride, (then laughably directed me to a wiki page) and totally rebuts his sweeping declaration he has not earned the right to make, nothing would.

RS

I'll just pull in this passage from wiki as it's very "hydrothermal vents are where it started" expoundy, also that life gets going ASAP where it can, even on a largely molten and erupting planet Earth.

The earliest known life forms on Earth are putative fossilized microorganisms found in hydrothermal vent precipitates.[1] The earliest time that life forms first appeared on Earth is at least 3.77 billion years ago, possibly as early as 4.28 billion years,[1] or even 4.5 billion years;[3][4] not long after the oceans formed 4.41 billion years ago, and after the formation of the Earth 4.54 billion years ago.