Um, yeah, this.jimbob said:
Do they reproduce in complete isolation from other living cells?
Evolution and abiogenesis
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Do they reproduce in complete isolation from other living cells?
Why would that matter?
Curiousity ... I don't seem to be able to find definitive evidence that they are autonomous replicators(?)
Well, every replicator has a context in which it operates, so I'm not sure what the import (or meaning) of "autonomous" is going to be here. Were we trying to pin down the distinction between "life" and "not-life"?
I would think that the existence of collections of non-living autonomous self-replicating molecules would be an unstable state. If there is no life at the time, then eventually selection pressures would tend to push some of the descendants to life (as being more efficient at reproducing).
If there was already life, then they'd be food.
I wouldn't expect to see such collections of molecules independent of life in an environment where there is already life.
ETA: The examples Skeptic Ginger has quoted (and which I have also mentioned elsewhere) are self-replicating molecules that self-replicate within specific environments, namely cells or nerve tissue.
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Then, it wouldn't seem 'likely' to find self-replicating molecules where there are no more obvious signs of life then, eh?
Belz...
Fiend God
Ask truethat. I'm just taking her nonsense to its logical conclusion.
Except then what would be preventing the evolution of these molecules into true life? That's why I said it would be an unstable state.
Environmental changes.
jimbob said:
So, 'unstable' means unpredictable, or short-lived??
Tero
Philosopher
What stable state? Nothing is fixed in life so eveything is forever changing. Stability might be measured in generations with little change, but every generation adds change to the gene pool of a species.
C_Felix
Master Poster
Did you happen to ask Darwin where he thought natural selection first began?
Isn't it a given there had to be a beginning?
I tried to, but he was an ass about it.
Temporary - not necessarily short lived, but they'd either eventually evolve into true life demonstrating at least nutrition, respiration, and excretion as well as growth and self-replication (and probably followed shortly by sensing and movement), or they'd become food for something that has, or they'd stop replicating because the conditions have changed.
I have learned from the discussion that in the most probable abiogenesis theories, evolution works on prebiotic replicators to produce life, but I still cannot see that evolution and abiogenesis are inextricably linked. First of all, they deal with entirely different aspects, and there are abiogenesis theories such as panspermia, or goddidit that have no element of evolution in them at all.
Linking them still seems to me to bowing to the creationists and acknowledging that evolution is in deep trouble if we cannot make abiogenesis work.
Linking them still seems to me to bowing to the creationists and acknowledging that evolution is in deep trouble if we cannot make abiogenesis work.
I think you are being pessimistic. There is no need to have a theory of abiogenesis to understand evolution or to use it for looking at the history of the life within the last 3.8-billion years or so.
If you want a plausible theory of abiogenesis, then you need to include evolution by natural selection. That is where the link arises, when one wants to explain abiogenesis, not the other way round.
They are linked in three important ways. The first is in the (fuller) title: "evolution by natural selection" - the "natural" part in that. We understand evolution now as applying to any complex system with particular properties and life being one such system. This makes it meaningful to talk about the evolution of language or evolving a computer program, so the concept survives abstraction away from "natural" conditions that arose on our planet in the distant past. However, the evolution we are usually debating with creationists deals with nature as the context and earth as the petri dish - a particular concrete instance of evolution.
The second way they are linked has to do with the structure of the debate itself. Creationism is a broad idea about cosmology, geology, biology and many more "ologies." They are all bound up together in a cross-ology fashion. It is not disingenuous for a creationist to bring up objections that cross realms, since their position crosses so many categories. I am free to bring up evidence from geology that supports deep time because evolution by natural selection needs time to work. By the same token, they are free to draw in cross discipline material.
The third reason is the most important to me. It's about intellectual integrity.
If a creationist wants to object to evolution on the grounds that it violates entropy, I want to address this, even though "entropy" is an idea in physics. In other words, I believe my picture is intellectually robust and as true as I can make it. It must survive the challenge and where I do not have a good answer, I should acknowledge that - not elide away from such areas because I "lose" debate points. Insofar as abiogenesis is "gappy," I think we shy away from it, recognizing the weakness of not having so ready an answer. I think this is the wrong thing to do, even when an opponent is being dishonest.
RecoveringYuppy
Penultimate Amazing
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But the reason behind saying that abiogenesis is irrelevant to evolution isn't that abiogenesis is a different branch of science, it's because it's irrelevant. You don't need to understand abiogenesis to understand how life works now.
Creationists don't have a leg to stand on if they think they are damaging the theory of evolution by pointing out we don't understand abiogenesis. Lack of understanding of abiogenesis only becomes a valid objection to claims that the theory of evolution completely eliminates any role for a god. But that's not a problem for the theory of evolution.
Bram Kaandorp
Master Poster
I keep seeing the discussion circling back to debating creationists, and acknowledging to them that abiogenesis is linked to evolution, because it's the intellectually honest thing to do. It is the intellectual thing to do, but it will only be fuel to the fire.
The problem I see is that creationists see this link differently than "we" do.
In reality, abiogenesis would be dependent on the principles of evolution to some degree at least, but even if abiogenesis were disproven, there is still plenty of evidence that evolutionary theory works.
In creationist reality, if you can show that abiogenesis doesn't work, then evolutionists have to go back to the drawing board, because until you can explain how life arose, you can't (or, aren't even allowed to) explain how it evolved.
This seems to be a result of the creationist reasoning that, if you doubt Genesis, you have to doubt Revelation (and since they need the idea of the Jesus sacrifice, they also need the idea of the first sin). So, similarly, if you doubt abiogenesis, you also have to doubt evolution.
The problem I see is that creationists see this link differently than "we" do.
In reality, abiogenesis would be dependent on the principles of evolution to some degree at least, but even if abiogenesis were disproven, there is still plenty of evidence that evolutionary theory works.
In creationist reality, if you can show that abiogenesis doesn't work, then evolutionists have to go back to the drawing board, because until you can explain how life arose, you can't (or, aren't even allowed to) explain how it evolved.
This seems to be a result of the creationist reasoning that, if you doubt Genesis, you have to doubt Revelation (and since they need the idea of the Jesus sacrifice, they also need the idea of the first sin). So, similarly, if you doubt abiogenesis, you also have to doubt evolution.
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If they stopped replicating, then Evolution would sort of be a moot point in this case then, eh?
Also, if we cannot decide which of the three alternative outcomes above will happen each time autonomous self replicating molecules appear, then perhaps the theory (Evolution) producing these alternative outcomes, is not yet sufficiently explicit for making its predictions (or consequences) from amongst these alternatives, in this particular case?
IMO, its the intitial conditions of Earth-life's instance that enable Evolution's predictability, and only for Earth-life's consequential development. If the nature of the initial condition alternatives submitted to Evolution theory, is fundamentally unpredictable, then where does Evolution's normal predictability then stand in the case of an autonomous self-replicating molecular second abiogenesis beyond Earth?
What sort of predictions are you talking about? The theory of evolution can assign likelihoods for particular traits arising, and can rule out certain ones as being highly unlikely.
For example the mammalian retina is not going to loose its blind spot by having its light receptors move in front of the nerves as the intermediate stages would be far less beneficial than the status quo and thus would be selected against, even though the final configuration would be superior.
One can also make the prediction that if there is a selective pressure in an environment, and organisms can still reproduce in that environment, then traits will arise according to that selective pressure. For example, we know that flight has a metabolic cost, so birds on large enough isolated landmasses will tend to loose the power of flight. One can also predict that antibiotic-resistant bacteria will arise and spread in response to the use of antibiotics. Organisms might evolve and fill empty ecological niches, but it would be unlikely to evolve to fill a niche that is already full.
Beyond that sort of level, I don't know of predictions that can be made by the theory of evolution. I would argue that this is because the future fitness landscape itself is not predetermined. It might remain similar for a long time, or it might be subject to change - either due to an organism acquiring a particular trait due to a mutation and affecting its competitors (see the long term evolution experiment for an example of that) or because of a random event (for example an asteroid strike killing off the dinosaurs).
What sort of predictions were you talking about?