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The framing you have here is an attractive one, but I don't think it makes much sense in the context of reproducing molecules. There is no reason to posit rand

by Cogito 6y ago

The framing you have here is an attractive one, but I don't think it makes much sense in the context of reproducing molecules. There is no reason to posit random DNA chains. The statement that "the number of DNA chains that produce valid/useful protein in the space of all possible DNA chains is vanishingly small" seems reasonable (however I'm not sure how we would know these chains are the only ones that produce valid/useful proteins). The idea that we need to choose randomly from the space of all possible DNA chains is not reasonable. ---- Once we have a reproducing molecule, we expect to see a multitude of valid reproducing molecules as descendants of that first molecule. We expect (at least some of) these descendants to eventually be extremely different from the original molecule, and by their nature valid reproducing molecules. Once we have a reproducing molecule (like DNA) that creates other molecules (like RNA and proteins) we can expect the same of its descendants, and the descendants' by-products. If these molecules form an ecosystem, where the reproduction of one relies on the validity of the other, the only succesful variations within the ecosystem will be valid variations of the ecosystem. ---- The space that we are choosing from is not the space of all possible DNA chains, it is the space of all DNA chains adjacent to existing valid chains (or chains in a valid ecosystem). It's analogous to taking a valid x86 program that can reproduce, randomly adding/removing/mutating some bits on reproduction (with low frequency, very quickly, and in a ginormous space - think on the scale of molecules in the Earth's oceans), and asking if that new program is also valid. And then, after millions of years of this, asking if one of the programs is a valid mathematical function. ---- There are still big questions here. Questions like "how do we get the first reproducing molecule?" and "is DNA likely to arise once you have reproducing molecules, or just one out of many options?" None of those questions give reason to evoke the number of all possible variations of DNA as evidence that the variation we see in proteins is somehow unlikely. Once we know that there exists one valid DNA/protein system (which we do, as it exists), and we know that variations of DNA/protein ecosystems can be functional (which we do, as we've observed it), it is reasonable to expect a multitude of valid, functional DNA chains, and the proteins produced by them.

erichocean 6y ago
Like you, I can imagine hundreds—maybe thousands—of ways to resolve these issues. That's hardly relevant though, what matters are resolutions that actually work. I agree that we are (very) likely to find the mechanisms involved, but so far, we haven't. In fact, we don't even have a theory on how DNA was originally developed, or how non-functional DNA/proteins self-replicate, or really anything at all. We only have the end product (which does—as you point out—work). The question is how did it get there, and previous hand waving about a huge, old Universe and random chance isn't sufficient. It's going to have to be something similar to what you (and other commenters) describe: mechanisms that preferentially and relatively quickly produce valid, self-replicating DNA/protein chains. To date, no one has found anything even close to that.
- Cogito 6y ago
  You see the difference between this argument and what you wrote above though? Perhaps I'm reading your original post too strongly, so please correct me if so. In the first post you compare the number of valid DNA chains to the space of all possible chains, you mention the number of different proteins in the human body, and you draw an analogy to a random sequence of bits forming a valid program. None of these talk to the probability of a reproducing molecule arising through physical processes, nor do they talk to the probability of DNA as a descendant of that original reproducing molecule (or potentially multiple original molecules). I get that you understand the gaps in our knowledge of how these systems came to be; my point is that your original argument is misleading in the exact same way you claim the argument "Billion of years passed since the Big Bang. If some chemical process can create life it's very likely that somewhere it did." is a "kind of hand-wavey statement [that] seems to convince most people. Universe is hella-old, and really big. Ergo, incredibly rare stuff has happened basically infinitely many times. Life everywhere, etc." (this was a reply to a different post, but I think it holds to the comment you originally replied to). In fact, I find the argument that "things reproduce, and have been reproducing for a long time in a large environment, so we expect to see complexity in those things" much more reasonable than "most random arrangments of this molecule are useless, and we can see lots of useful arrangements, therefore time and randomness can't explain them".
  - erichocean 6y ago
    We're discussing how to get those "things that reproduce" in the first place. I agree that once you have useful things that reproduce, it's easy to keep it going. Similarly, if I have a running copy of Linux, I can use the tools (and source code) to produce another copy of Linux. But how do we get the first copy, the "original reproducing molecule" as you put it? The usual explanation is that the "first copy" arose randomly, and then kept going. Do you believe that? I suspect not—but most people do. We know that it can't have been random (which is the argument I gave, and I suspect you agree with). We should tell people "it wasn't random, something about the fundamental nature of these molecules caused better and more complex molecules to emerge." But we have no mechanism for that, just a (valid) belief that it has to be true. I think we should find those mechanisms, and simultaneously, stop telling people that random chance + vast universe + long timespan is sufficient.

by Cogito 6y ago

erichocean 6y ago

Like you, I can imagine hundreds—maybe thousands—of ways to resolve these issues. That's hardly relevant though, what matters are resolutions that actually work. I agree that we are (very) likely to find the mechanisms involved, but so far, we haven't. In fact, we don't even have a theory on how DNA was originally developed, or how non-functional DNA/proteins self-replicate, or really anything at all. We only have the end product (which does—as you point out—work). The question is how did it get there, and previous hand waving about a huge, old Universe and random chance isn't sufficient. It's going to have to be something similar to what you (and other commenters) describe: mechanisms that preferentially and relatively quickly produce valid, self-replicating DNA/protein chains. To date, no one has found anything even close to that.

Cogito 6y ago
You see the difference between this argument and what you wrote above though? Perhaps I'm reading your original post too strongly, so please correct me if so. In the first post you compare the number of valid DNA chains to the space of all possible chains, you mention the number of different proteins in the human body, and you draw an analogy to a random sequence of bits forming a valid program. None of these talk to the probability of a reproducing molecule arising through physical processes, nor do they talk to the probability of DNA as a descendant of that original reproducing molecule (or potentially multiple original molecules). I get that you understand the gaps in our knowledge of how these systems came to be; my point is that your original argument is misleading in the exact same way you claim the argument "Billion of years passed since the Big Bang. If some chemical process can create life it's very likely that somewhere it did." is a "kind of hand-wavey statement [that] seems to convince most people. Universe is hella-old, and really big. Ergo, incredibly rare stuff has happened basically infinitely many times. Life everywhere, etc." (this was a reply to a different post, but I think it holds to the comment you originally replied to). In fact, I find the argument that "things reproduce, and have been reproducing for a long time in a large environment, so we expect to see complexity in those things" much more reasonable than "most random arrangments of this molecule are useless, and we can see lots of useful arrangements, therefore time and randomness can't explain them".
- erichocean 6y ago
  We're discussing how to get those "things that reproduce" in the first place. I agree that once you have useful things that reproduce, it's easy to keep it going. Similarly, if I have a running copy of Linux, I can use the tools (and source code) to produce another copy of Linux. But how do we get the first copy, the "original reproducing molecule" as you put it? The usual explanation is that the "first copy" arose randomly, and then kept going. Do you believe that? I suspect not—but most people do. We know that it can't have been random (which is the argument I gave, and I suspect you agree with). We should tell people "it wasn't random, something about the fundamental nature of these molecules caused better and more complex molecules to emerge." But we have no mechanism for that, just a (valid) belief that it has to be true. I think we should find those mechanisms, and simultaneously, stop telling people that random chance + vast universe + long timespan is sufficient.