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Author Topic:   On the Origin of Life and Falsifiability
Dr Adequate
Member (Idle past 79 days)
Posts: 16112
Joined: 07-20-2006


Message 4 of 108 (779857)
03-08-2016 11:00 PM
Reply to: Message 1 by Genomicus
03-08-2016 3:23 AM


There are a number of problems with this post, of which the most obvious is this:

If it could be demonstrated that the last universal common ancestor (LUCA) was a population of very simple cells that did not have the necessary protein parts to survive extensive radiation, then non-directed panspermia will have been effectively falsified.

No, you'd need to demonstrate that of FUCA, not LUCA. Do you have any ideas how we could do that?


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Replies to this message:
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Dr Adequate
Member (Idle past 79 days)
Posts: 16112
Joined: 07-20-2006


Message 11 of 108 (779904)
03-09-2016 10:04 AM
Reply to: Message 7 by Genomicus
03-09-2016 8:25 AM


Well, not exactly, unless you can provide strong reasons to suspect that the initial "seed" population of microbes would be under strong selective pressure to lose these genes necessary for radiation protection.

On the contrary. Someone who wished to falsify the proposition that FUCA traveled through space, only by referring to evidence that LUCA would not have been able to, must show for certain that the requisite genes could not have lost between FUCA and LUCA --- over a period of time, and under conditions, of which we know nothing. He would have to demonstrate the existence of a strong, indeed inexorable, selective pressure to retain these genes under these unknown circumstances. Which hardly seems likely, since most bacteria don't have them.

This is just the nature of falsification. One requires an experimentum crucis which, if it turns out a given way, will disprove the hypothesis.

Edited by Dr Adequate, : No reason given.


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Dr Adequate
Member (Idle past 79 days)
Posts: 16112
Joined: 07-20-2006


(3)
Message 12 of 108 (779905)
03-09-2016 10:06 AM
Reply to: Message 9 by Genomicus
03-09-2016 8:43 AM


Maybe, but only if we operate under the notion that the relative rapid emergence of biological life on Earth is reasonable. A model is more parsimonious because it includes as few unnecessary steps as possible, but a case can be made that the extra time and chemical resources afforded by the panspermia model means that it doesn't add a purely unnecessary step.

Well panspermia does admittedly remove a lot of steps. But only by leaving them behind on Planet X, where abiogenesis took place ...


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Dr Adequate
Member (Idle past 79 days)
Posts: 16112
Joined: 07-20-2006


(1)
Message 22 of 108 (779996)
03-10-2016 10:46 AM
Reply to: Message 1 by Genomicus
03-08-2016 3:23 AM


Second Problem
I said your post had a number of problems. Here's another.

You say that the lithopanspermia model is falsifiable because if the work of Cavalier-Smith could be shored up and made more rigorous, then lithopanspermia would in fact have been falsified.

But why is that not also true of the RNA world hypothesis and the criticisms of Bernhardt, Kurland, and Harish & Caetano-Anollés? The two cases would seem to be on a par.

After all, if you really think that the RNA world is unfalsifiable, why are you citing these people at all? For the RNA world to be unfalsifiable, these criticisms would not merely have to be wrong, rather they'd have to be either (a) in principle and by their nature undemonstrable or (b) irrelevant even if they were right --- neither of which you have argued for.

Instead, you seem to be in one paragraph citing these people to suggest that the RNA hypothesis is false, and in the next paragraph complaining that it's unfalsifiable. Well, one or the other. If it's unfalsifiable, then you should be able to demonstrate the logical necessity of the complete vacuity of the arguments of Bernhardt, Kurland, and Harish & Caetano-Anollés. If, on the other hand, these arguments are even conceivably valid and relevant, then they bear the same relation to the RNA hypothesis as you say (wrongly, as I have argued) that Cavalier-Smith's work (or an improvement on it) bears to lithopanspermia.

Edited by Dr Adequate, : No reason given.

Edited by Dr Adequate, : No reason given.


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Dr Adequate
Member (Idle past 79 days)
Posts: 16112
Joined: 07-20-2006


Message 39 of 108 (780266)
03-13-2016 11:01 AM
Reply to: Message 37 by Genomicus
03-13-2016 8:18 AM


Re: Second Problem
This is an argument that has been levied several times, so I will address it here. "The two cases would seem to be on par," writes Dr Adequate, yet this glosses over this fundamental insight: that attempts to refute abiogenesis scenarios are based on arguments regarding the implausibility of these scenarios, whereas potential falsifications of panspermia are mainly arguments resting on historical reality.

But this distinction in how a proposition has been falsified makes no difference to whether a proposition has been falsified. I can, for example, perfectly well falsify the proposition "This elephant was in my house while I was out shopping" by observing that it's too big to fit through any of the doors. An argument that it's physically impossible is a splendid argument that it didn't happen.

Moreover, the argument against lithopanspermia requires its own implausibility argument --- besides requiring that LUCA (actually FUCA, as I have pointed out) should have certain genes, it also requires the proposition that FUCA couldn't have survived travelling through space without such genes. It requires one to say "X couldn't have happened, because chemistry". Take that away, and where's your argument against lithopanspermia? So why shouldn't "X couldn't have happened, because chemistry" be acceptable as a form of argument against the RNA world?


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Dr Adequate
Member (Idle past 79 days)
Posts: 16112
Joined: 07-20-2006


Message 41 of 108 (780270)
03-13-2016 11:14 AM
Reply to: Message 32 by Genomicus
03-13-2016 7:14 AM


You are somewhat mistaken when you say that "most bacteria don't have them."

You seemed, stop me if I'm wrong, to be suggesting that the bacteria in lithopanspermia would have required special extraordinary resistance to radiation to survive their space voyage; the sort of high radiation resistance found in (e.g.) Deinococcus radiodurans and B. subtilis. If you just meant that they need the genes for radiation resistance that bacteria usually have, then sure, I was wrong to say "most bacteria don't have them" but then on the other hand having such genes is not particularly indicative of survival in space.

So which way do you want to go with this?


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Replies to this message:
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Dr Adequate
Member (Idle past 79 days)
Posts: 16112
Joined: 07-20-2006


Message 45 of 108 (780306)
03-14-2016 12:02 AM
Reply to: Message 43 by Genomicus
03-13-2016 8:48 PM


Re: Second Problem
It is a splendid argument, because if something is impossible, then the probability of it happening is 0 -- or, at least, extraordinarily close to 0. So, for example, you can argue that your door has x*y dimensions, and the elephant would be too large to fit through this doorway. You can then point to the structural integrity of the walls surrounding the doorway, citing its Young's modulus and so on. Then you can say that the elephant's musculature and biomechanics would not have allowed for this Proboscidean creature to generate sufficient force to squeeze through the doorway. All of these would be very rigorous arguments that would rule out the possibility that the elephant was in your house while you shopped.

So this sort of argument is a perfectly valid method of falsification.

If you can propose or cite equally rigorous experiment or series of experiments that could potentially falsify the RNA world or metabolism first scenarios, then I will gladly concur that these models are falsifiable.

If you can show that in principle no such discoveries could ever be made, even if the RNA world did not exist and could not have existed, then I will gladly concede that it is unfalsifiable.

Because in the case of lithopanspermia our reasoning is very well-grounded in the radiobiology of microbes.

Now all you have to do is learn an equal amount about the biochemistry of RNA, and you're all set.

If all your argument boils down to is that we should prefer lithospermia to the RNA world because in our present state of knowledge we'd be better able to falsify one than the other, then from the point of view of epistemology that's hardly significant.

Before the invention of the microscope, was the hypothesis that Jews caused epidemic diseases preferable in principle to the idea that tiny little organisms caused epidemic diseases? The former was potentially much easier to falsify in practice, given the state of science in that era, because it was much easier to observe the activities of Jews than of these tiny organisms ... but did that make it somehow more scientific?


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Dr Adequate
Member (Idle past 79 days)
Posts: 16112
Joined: 07-20-2006


Message 46 of 108 (780307)
03-14-2016 12:07 AM
Reply to: Message 44 by Genomicus
03-13-2016 8:58 PM


A progenote population lacking proteases, ABC transporters, nucleases, and a variety of catabolic enzymes would be rather quickly exterminated by galactic cosmic rays.

Unless they had something else that would fulfill the same function. Do we really know enough about metabolism to say that only the things you've listed would suffice, and nothing else? And can we say that this something else, the nature of which we can't even guess at, must necessarily have been conserved from FUCA to LUCA under conditions of which we know almost nothing?


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Dr Adequate
Member (Idle past 79 days)
Posts: 16112
Joined: 07-20-2006


Message 51 of 108 (780430)
03-15-2016 10:34 AM
Reply to: Message 48 by Genomicus
03-15-2016 9:08 AM


Re: Second Problem
By your argument, however, it seems that only the weight of difficulties can bring down the edifice of a hypothesis. But this seems like a pretty poor criterion of demarcation between science and pseudoscience. A "weight of difficulties" can be found in creationism (for which there does not appear to be a compelling falsification scenario), so is creationism therefore science in some way?

No, but it had the potential to be. The proposition that there is an elephant in my house is not science, but it is a meaningful proposition, it's the sort of proposition that had the potential to be a scientific fact, and it is susceptible to scientific investigation. Like creationism, it is falsifiable and false.

Edited by Dr Adequate, : No reason given.


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Dr Adequate
Member (Idle past 79 days)
Posts: 16112
Joined: 07-20-2006


Message 59 of 108 (780478)
03-15-2016 1:49 PM
Reply to: Message 58 by Genomicus
03-15-2016 1:33 PM


Re: Second Problem
Well, that's the Duhem-Quine thesis made flesh, isn't it? We can save the appearances for any hypothesis by postulating the existence of an omnipotent being who used his miraculous powers in such a way as to lead us to false conclusions.

For example, whatever we discovered about LUCA's ability to resist radiation, we could say: "But maybe lithospermia is still true, but maybe there is a God who in his infinite wisdom used his mighty powers to screen FUCA from radiation in its passage through the cosmic void". And now lithospermia is unfalsifiable too. Likewise, the proposition that there was an elephant in my house, which you agreed was falsifiable, becomes unfalsifiable --- because what if God teleported the elephant in and then out again without it having to pass through any of the doors?

In order to use the idea of falsifiability at all, we have to rule out, methodologically, such things as a (willfully or inadvertently) deceitful God, the Cartesian demon, and the brain-in-a-jar hypothesis as the sort of auxiliary hypotheses that people are allowed to propose.

Edited by Dr Adequate, : No reason given.


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Dr Adequate
Member (Idle past 79 days)
Posts: 16112
Joined: 07-20-2006


Message 67 of 108 (780553)
03-16-2016 2:04 PM
Reply to: Message 66 by Blue Jay
03-16-2016 11:17 AM


I don't really understand why you think LUCA and FUCA should be similar. After all, in the panspermia model, FUCA is supposed to have come from an alien planet ...

And not only that, but one sufficiently different from Earth that abiogenesis was plausible there but not here.


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Dr Adequate
Member (Idle past 79 days)
Posts: 16112
Joined: 07-20-2006


Message 75 of 108 (780796)
03-21-2016 8:48 PM
Reply to: Message 74 by Genomicus
03-21-2016 8:35 PM


Re: @Dr Adequate
Well, unless I'm missing something, and I do have a nasty headache right now, this is somewhat beside the point. The point is that creationism is falsifiable, unless you allow the creationists the sort of auxiliary hypotheses that we don't allow anyone.

Once again, then, it is not a matter of the "weight of evidence." This is not a very good line of demarcation between science and pseudoscience, as no matter how heavy the weight of evidence might be against a particular hypothesis, auxiliary hypotheses can always be conjured. Thus, what matters here is falsifiability: do auxiliary hypotheses increase the degree of falsifiability or do they simply function as a kind of quarantine?

Well, no. Falsifiability is a very low bar, it just identifies the sort of thing that could be science. It doesn't mark off science from pseudoscience: there are any number of things which are eminently falsifiable and would be science if they were true, but are pseudoscience because they are false --- or, strictly speaking, because the weight of the evidence is against them. Homeopathy, for example, is practically the paradigmatic pseudoscience, and is readily falsifiable: we can test whether homeopathic medicine works better than placebo. It's a pseudoscience because it doesn't.


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Dr Adequate
Member (Idle past 79 days)
Posts: 16112
Joined: 07-20-2006


Message 78 of 108 (780800)
03-21-2016 11:39 PM
Reply to: Message 77 by Genomicus
03-21-2016 9:08 PM


Re: @Dr Adequate
Well, here's why I disagree with the notion that creationism of the YEC variety is falsifiable: the auxiliary hypotheses which are proposed as a way around rather extraordinary problems do not increase the degree of falsifiability of the creationism scenario. So YEC isn't falsifiable because the further back you chase these auxiliary hypotheses, the less falsifiable the whole model is.

But as you can do that with anything, this is not a criticism of YEC as such.

The fact that some YECs do in fact add auxiliary hypotheses to deprive their central idea of any predictive power is a reason to criticize the people who do this. Nonetheless, the idea that (e.g.) the world and the universe are ~6,000 years old is meaningful and testable.

You're right in the sense that falsifiability isn't the only criterion that delineates science from pseudoscience. However, the caloric theory isn't pseudoscience. It's a dead scientific theory. Just because it's false doesn't make it pseudoscience. Pseudoscience exists in a rather particular social and political fabric.

Yeah, sure, in order for something to be pseudoscience someone has to promote it as science.


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Replies to this message:
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Dr Adequate
Member (Idle past 79 days)
Posts: 16112
Joined: 07-20-2006


(1)
Message 85 of 108 (780813)
03-22-2016 11:02 AM
Reply to: Message 84 by Genomicus
03-22-2016 9:18 AM


Re: @Dr Adequate
Yes, you can do that with anything, but YEC requires this array of auxiliary hypotheses which do not increase its falsifiability. In other words, there's no way for YEC to get around isotope data concerning the age of the Earth except through the invocation of increasingly unfalsifiable auxiliary hypotheses.

There's no way to get round the evidence that there wasn't an elephant in my house except through the invocation of increasingly unfalsifiable auxiliary hypotheses. That's 'cos it's false.

And you can in fact invoke auxiliary hypothesis to save any initial hypothesis from the evidence. (I think of this as the principle of Smacco's Rozar.)

Right. So what's the minimum threshold form an idea must take in order to be considered a properly constructed scientific hypothesis? I argue that the minimum threshold requirement is that it must be falsifiable and testable. Of course, these are not the only requirements, but they are the bare minimum. Do you disagree?

I think I would disagree somewhat with your characterization, as it has revealed itself through your posts and examples. For example, go back a few decades and we had no means to test whether other stars had planets. Was it then an unscientific hypothesis that exoplanets existed? What should we have said about someone who was in the process of building a device to test it, but hadn't finished yet? --- that he wished to conduct a scientific investigation of something that wan't even a properly constructed scientific hypothesis?

But the question of whether "There are exoplanets" is properly constructed should surely not be dependent on the state of our technology.

Now you might ask, if we admit this principle, where do we stop? Is someone allowed to say "Although we can't test this yet, we would be able to if we could construct a time machine or an omniscope"? Well, if not, where can we draw the line? If so, then the criterion of falsifiability looks more like a criterion of meaningfulness.


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Dr Adequate
Member (Idle past 79 days)
Posts: 16112
Joined: 07-20-2006


(1)
Message 94 of 108 (781061)
03-30-2016 11:04 PM
Reply to: Message 73 by Genomicus
03-21-2016 9:11 AM


Re: Fungi from spaaaaaaace!
The thing is that amino acids are falling out of the sky all the time, unaccompanied by alien space fungi. Consider, for example, the Murchison meteorite. It fell in 1969; analysis showed that it contained numerous amino acids --- including aminoisobutyric acid. The amino acids were racemic and have all been produced in the laboratory by Miller-Urey type setups.

Nonprotein Amino Acids in the Murchison Meteorite

Nonprotein Amino Acids from Spark Discharges and Their Comparison with the Murchison Meteorite Amino Acids

Edited by Dr Adequate, : No reason given.


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