Can life begin today as it did 4billion years ago

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  • #26
MATLABdude
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Because I don't think those conditions were necessary for life. I think life formed as it did because of the environment (there's no advantage to tolerating free oxygen if it's not around). I don't see anything inherently difficult about surviving in an oxygen- (or methane-, or nitrogen-) rich environment, unlike (say) in a high x-ray emission environment.

But I could be convinced otherwise. Why do you think that abiogenesis requires conditions like the early Earth?
Miller-Urey and Miller-Urey-like experiments (which managed to produce nucleic and amino acids) have always been performed in a reducing atmosphere. Sure, that was to try to replicate the early conditions on our earth, and with an end goal of producing the biochemistry we have today, but are there any oxidizing equivalents?
 
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Most bacteria can't leave fossils. Cyanobacteria (your blue-green algae) have thick enough cell walls that they can sometimes leave fossils. The easiest explanation would be that the precursors to cyanobacteria, like most bacteria, lacked these thick cell walls.
Can't leave fossils.? The scientists studying that Mars meteorite are going to be disappointed to hear you say that.

However, the blue-green alga has over a hundred different proteins that make up just the cell wall alone. That's a lot, I admit, but to say that evolution jumped from an extremely simple something to this cyanophyte is quite a step. Evolutionists usually try to insert an evolutionary tree between quantum steps. Perhaps, say only 95 proteins. Even earlier, perhaps only 85. Where's the fossil remains.?

"Sometimes leave fossils".? Please know that these specific fossils are on every continent. I've got a driveway lined with these same fossils (I gathered them from the Missoula, Montana, area).
 
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But I could be convinced otherwise. Why do you think that abiogenesis requires conditions like the early Earth?
,

That's not the point. You can posit any "what-if" scenario you want. You're saying what if all life, including bacteria disappeared, then......? It's a completely unscientific proposition.

There's good reason to believe that life began sometime between 3.5-4.0 Gya and that there was some form of pre-biotic chemistry perhaps up to 4.2 Gya, following the final bombardment. Since the first known bacteria were anaerobic, it's safe to assume that anaerobic conditions existed. No? Since anaerobic bacteria produce free O_2 as a waste product, it's probably likely that the demise of most anaerobic species was to due to O_2 poisoning with the exception of a few organisms that adapted (perhaps even just one).

Yes, you could say that maybe aerobic bacteria came about by a new abiogenesis rather than by natural selection. You could say they all came from extraterrestrial sources like James Watson apparently believes. You can say almost anything you want, but science is based on evidence. The current evidence points to life beginning in a mild reducing environment with very little free O_2 and natural selection eventually leading to aerobic life.
 
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CRGreathouse
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That's not the point. You can posit any "what-if" scenario you want. You're saying what if all life, including bacteria disappeared, then......? It's a completely unscientific proposition.
Let's hope that propositions stays in the non-science section. It's experimentally verifiable, but that would be B-A-D.

There's good reason to believe that life began sometime between 3.5-4.0 Gya and that there was some form of pre-biotic chemistry perhaps up to 4.2 Gya, following the final bombardment. Since the first known bacteria were anaerobic, it's safe to assume that anaerobic conditions existed. No? Since anaerobic bacteria produce free O_2 as a waste product, it's probably likely that the demise of most anaerobic species was to due to O_2 poisoning with the exception of a few organisms that adapted (perhaps even just one).
We're in complete agreement here.

I don't care to speculate about the fraction of organisms that adapted vs. those that died out; for one I'm not even sure how that would be measured in principle. You don't happen to have any numbers or information on that, do you?

Yes, you could say that maybe aerobic bacteria came about by a new abiogenesis rather than by natural selection.
But I'm not saying that at all! If I gave that impression, I'm sorry to have mislead you; if your point was some kind of analogy, I missed it entirely. (Sorry.)
 
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CRGreathouse
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Can't leave fossils.? The scientists studying that Mars meteorite are going to be disappointed to hear you say that.
Why? They expect only that some would, not that all or even most would. And they'd be hoping for some fairly advanced bugs, which would be able to produce such structures as cell walls and various organelles.

However, the blue-green alga has over a hundred different proteins that make up just the cell wall alone. That's a lot, I admit, but to say that evolution jumped from an extremely simple something to this cyanophyte is quite a step.
But I didn't say or even suggest that they did.

Evolutionists usually try to insert an evolutionary tree between quantum steps.
There are of course different schools of thought here (the PE crowd, for example), but I'll not go into that. I'm more of a gradualist anyway.

Perhaps, say only 95 proteins. Even earlier, perhaps only 85. Where's the fossil remains.?
Simpler bacteria with thinner walls, plus being older and hence more worn. I'd think most wouldn't have lasted and the balance would be difficult to tell from modern ones. How can we tell the # of proteins just from a fossil? We're mostly looking at gross anatomy AFAIK.

"Sometimes leave fossils".? Please know that these specific fossils are on every continent. I've got a driveway lined with these same fossils (I gathered them from the Missoula, Montana, area).
This fits with my understanding very well. Say 10^10 generations of bacteria with maybe 10^27 (now) to ? (then) bacteria per generation... what fraction would you expect to leave fossils? To put it another way, what fraction of Earth's mass do you think is bacterial fossils?
 
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Let's hope that propositions stays in the non-science section. It's experimentally verifiable, but that would be B-A-D.
OK, your "hypothesis". What do mean experimentally verifiable? Say you completely sterilized some marine/tide pool environment (and were able to keep it sterile somehow). You say aerobic life might start de novo in a million years. That's an instant in geologic time, but a bit long for a government grant. I don't think we've seen a proton decay yet, but that experiment is a microsecond affair compared to waiting around for new aerobic life to start.

I don't care to speculate about the fraction of organisms that adapted vs. those that died out; for one I'm not even sure how that would be measured in principle. You don't happen to have any numbers or information on that, do you?
Of course not. I just said that a mutation in just one individual might have been sufficient to get an aerobic species going. Obviously some anaerobic species survived since they're still around, producing nasty purulent infections (probably revenge against us aerobes).

But I'm not saying that at all! If I gave that impression, I'm sorry to have mislead you; if your point was some kind of analogy, I missed it entirely. (Sorry.)
(RE: Early Precambrian aerobic abiogenesis) I'm just saying that if (natural) aerobic abiogenesis were possible, it most likely would have happened then (as the anaerobes were dying off creating locally sterile environments) as opposed to now.
 
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