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A Conversation With Richard Dawkins: This Is My Vision Of "Life"

#1
C C Offline
http://edge.org/conversation/richard_daw...on-of-life

EXCERPT: [...] Over the years Dawkins has been among the most frequent (and valued) Edge contributors, and our pages are filled with his elegant writing and brilliant thinking. On a trip to England this month, it occurred to me all of his contributions on Edge had been the result either of his public speaking or his writing. I realized that I had never asked him to sit down for a one-to-one videotaped interview. After making arrangements, we met at noon on Saturday, April 11th, in the Enthoven Room of New College to have an Edge conversation. I am pleased to present the video and the transcript below...

[...] My conjecture is that if there is life elsewhere in the universe, it will be Darwinian life. I think there's only one way for this hyper complex phenomenon which we call "life" to arise from the laws of physics. The laws of physics—if you throw a stone up in the air, it describes a parabola, and that's it. But biology, without ever violating the laws of physics, does the most extraordinary things; it produces machines which can run, and walk, and fly, and dig, and swing through the trees, and think, and produce the whole of human technology, human art, human music. This all comes about because at some point in history, about 4 billion years ago, a replicating entity arose, not a gene as we would now see it, but something functionally equivalent to a gene, which because it had the power to replicate and the power to influence its own probability of replicating, and replicated with slight errors, gave rise to the whole of life. If you ask me what my ambition would be, it would be that everybody would understand what an extraordinary, remarkable thing it is that they exist, in a world which would otherwise just be plain physics. The key to the process is self-replication....

[...] My vision of life is that everything extends from replicators, which are in practice DNA molecules on this planet. The replicators reach out into the world to influence their own probability of being passed on. Mostly they don't reach further than the individual body in which they sit, but that's a matter of practice, not a matter of principle. [...] There are two kinds of unit of selection. The difference is a semantic one. They're both units of selection, but one is the replicator, and what it does is get itself copied. So more and more copies of itself go into the world. The other kind of unit is the vehicle. It doesn't get itself copied. What it does is work to copy the replicators which have come down to it through the generations, and which it's going to pass on to future generations. So we have this individual / replicator dichotomy. They're both units of selection, but in different senses. It's important to understand that they are different senses....

[...] One of the things that I've always done is not make a clear separation between books that are aimed at popularizing, books that are aimed at explaining things to other people, and books that explain things to myself, or explain things to my scientific colleagues. I think the separation between doing science and popularizing science has been overdone. And I have found that the exercise of explaining to other people, which I suppose I've been fairly successful at, is greatly helped by the fact that I first have to explain it to myself....
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#2
Yazata Offline
Dawkins Wrote:My vision of life is that everything extends from replicators, which are in practice DNA molecules on this planet.

I think that the view that life originated in simple chemical replicators is a widely held view on the origin of life. The simplest existing cells, bacteria and archaea, are already so complex that it seems to me that they must have had simpler ancestors that presumably were themselves capable of evolving by natural selection, which suggests that they would have had to have been replicators.

I'm doubtful about whether the original chemical replicators were the nucleic acids that we know today. (DNA and RNA of various sorts.) The same complexity problem exists with them as well. Our DNA and RNA are probably the end result of long processes of elaboration.

Quote:The replicators reach out into the world to influence their own probability of being passed on. Mostly they don't reach further than the individual body in which they sit, but that's a matter of practice, not a matter of principle.

Reach out? I don't understand what he means by that. Nor am I convinced that the earliest chemical replicators had bodies. They might have just been naked self-replicating molecules. Perhaps one of the earliest quantum leaps in the evolution of life was the evolution of the ability for these replicating molecules to form membranes around themselves. That might have facilitated all kinds of new stuff regarding concentrations of chemicals necessary to the replication process. We would have also seen a spurt of evolution regarding selective permeabilities of the membranes to various things.

Speculating about this makes me wonder whether life really originated here on earth. If it did, wouldn't we expect to see the simple chemical replicators still around, busily reproducing themselves? Instead, what we see is a huge chasm with life on one side and non-living geology on the other. There isn't any continuity between them, except perhaps for viruses, which seem to be dependent on living cells in order to reproduce and seem to have originated after the genetic code was already established and elaborated.

What could have eliminated the hypothetical early chemical replicators? Competition with more advanced life for necessary chemicals? Did the oxygen holocaust oxidize them into oblivion? Or are they somewhere else? Did life find its way here through space in an already fairly advanced state in the form of something like bacterial spores? If bacterial life originated somewhere else, was its origin an interstellar exoplanet, or was it right here in our solar system, on early Mars or Venus, before their own ecologies became inhospitable to life?  
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#3
C C Offline
(May 13, 2015 09:27 PM)Yazata Wrote: Speculating about this makes me wonder whether life really originated here on earth. If it did, wouldn't we expect to see the simple chemical replicators still around, busily reproducing themselves? Instead, what we see is a huge chasm with life on one side and non-living geology on the other. There isn't any continuity between them, except perhaps for viruses, which seem to be dependent on living cells in order to reproduce and seem to have originated after the genetic code was already established and elaborated.

What could have eliminated the hypothetical early chemical replicators? Competition with more advanced life for necessary chemicals? Did the oxygen holocaust oxidize them into oblivion? Or are they somewhere else? Did life find its way here through space in an already fairly advanced state in the form of something like bacterial spores? If bacterial life originated somewhere else, was its origin an interstellar exoplanet, or was it right here in our solar system, on early Mars or Venus, before their own ecologies became inhospitable to life?  

I sometimes wonder if anyone is really looking hard enough for lone, obscure molecules which they wouldn't dream of replicating. Those working in the life sciences would tend to only pay attention to full-fledged cells, viruses, or the familiar fragments arising from their decomposition. The hypothesis of prions and their eventual isolation / confirmation might never have occurred if there were not certain global brain dysfunction syndromes which suggested a mysterious, new agent being responsible.

Due to a lack of mobility or dependence upon arbitrary drifting, competition could very well have been an extinction factor for the most primitive replicators. It might be that the original replicators relied on a dense resource of raw materials that was more quickly gobbled-up by advanced competitors. Once those special pools of thick soup were gone, the scarcity of the right chemical units haphazardly coming into contact for growing and breaking off effective copies of themselves could have spelled doom.

OTOH, with planets being discovered that date back to less than a billion years after the big bang, there would be ample time for evolution on extrasolar planets and interstellar migration via comets, etc, to deliver extremophile cells to Sol's territory. If a shortage of heavy elements didn't prevent solid cores from forming, maybe another hat-trick enabled replicators to bypass the shortage, too, on those ancient planets.
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#4
Yazata Offline
CC Wrote:Those working in the life sciences would tend to only pay attention to full-fledged cells, viruses, or the familiar fragments arising from their decomposition.

I agree. It's especially true of astrobiology or whatever they call it. The search for life in outer space always seems to translate into a search for life that's essentially identical to the life we are familiar with, on the biochemical level at least. They look for X,Y or Z as 'evidences of life', because such things are evidence of present-day life here on Earth.

If panspermia is correct, and Earth bacteria originated elsewhere and something like bacterial spores seeded planets all over, then that might not be a bad strategy. But if life here or elsewhere had its origin in chemistry that's significantly different, its traces might not be anything like what we are expecting to find.

Quote:I sometimes wonder if anyone is really looking hard enough for lone, obscure molecules which they wouldn't dream of replicating.
If there are chemical replicators here on Earth, what would they look like? How would we recognize them?

It seems to me that one possibility would be that they would be fairly common. Maybe we are looking at them all the time and not recognizing them for what they are.

But alternatively, maybe competition or environmental change eliminated the chemical replicators from all but a few niche environments where (I'm speculating) oxygen is almost absent so that they don't oxidize, chemical raw materials are abundant and there's a source of energy. Maybe conditions remain right for them around a few deep sea hydrothermal vents.

Quote:The hypothesis of prions and their eventual isolation / confirmation might never have occurred if there were not certain global brain dysfunction syndromes which suggested a mysterious, new agent being responsible.

Yeah, prions do seem to be something located in the chasm between life and non-life, but my layman's guess is that, like viruses, they remain dependent on life n order to reproduce.

Quote:Due to a lack of mobility or dependence upon arbitrary drifting, competition could very well have been an extinction factor for the most primitive replicators. It might be that the original replicators relied on a dense resource of raw materials that was more quickly gobbled-up by advanced competitors. Once those special pools of thick soup were gone, the scarcity of the right chemical units haphazardly coming into contact for growing and breaking off effective copies of themselves could have spelled doom.

That's true. There would have had to have been satisfactory concentrations of precursor chemicals in the environment to enable simple replicators to form, the first ones probably essentially by chance. But as they multiplied, they would have quickly reduced those concentrations. That's why the ability to form a membrane around themselves might have been such a big step. It would enable them to essentially carry their primordial soup around with them, replenishing it from an increasingly depleted environment by some kind of selective permeability or even active transport process across the membrane. The earliest evolution might have involved elaborating the details of the membrane and enhancing the ability of the replicator's own self-copying structure to code and synthesize it.

I'm not convinced that the first replicators were RNA or DNA, but somewhere in there, very simple forms of RNA or DNA might have been especially good at those coding and synthesizing functions.
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