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« The SOTU Address Post-mortem | Main | What Institution Is Working? »

February 02, 2010

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GaryA

Excellent summary george. Just one point on biogenesis; the idea of panspermia (molecules of life from space) is becoming much more tenable than it was 10-20 years ago. Extremophores resilience to vacuum/ heat/cold is well documented and its difficult to think of a darwinain reason other than as a residue of an inherited past bottleneck. having said that, biogenesis is perhaps the most difficult & problematic subject I have ever studied!

George Mobus

Thanks GaryA.

Since you brought it up, I should mention another, more recent, book by my hero, Harold Morowitz, that you may have already consumed. But if not, I highly recommend: "Beginnings of Cellular Life: Metabolism Recapitulates Biogenisis". It somewhat is a follow-on to "Energy Flow" but with the specific goal of seeking the origins of life in the biochemical 'fossil' record (highly conserved core of metabolism).

I have read some of the extra-planetary origins of semi-complex organic molecules which may have been precursors of life going on in space, esp. in dirty icy comets. Sounds convincing for some of the precursors. But the original panspermia dealt with life having originated somewhere else and got here on a comet or asteroid hit. That version only puts off the difficult question of how life began - it had to start somewhere. Using Occam's razor approach that only make the explanation more complex, not less.

Also, I've read a number of works that speculate that some of the extreme environments such as deep ocean vents might provide a better starting chemistry for metabolism than open pools on the surface. So extremophiles may represent some of the earliest forms of life rather than late opportunistic invaders.

You are right though. The origin of life is extremely difficult.

George

GaryA

Yes,the idea that life arose from the 'hades of hell has many things going for it...also any seeded life from space could in theory have been subducted into the earths crust so they are not mutually exclusive theories. More way out ideas include quantum biology..it has been found thet C60 (bucky balls) can give two simultaneous place results in the famous twin beam experiment and DNA is about the size of a bucky ball so maybe at molecular level genetic DNA does not necessarily obey laws of strict determination...the implications are mind bending!
More interesting still is the idea that the search for the original first replicating molecule is in fact a cultural assumption projected onto the science because there is no evidence than any RNA or DNA precurser could possibly exist now or in the past. The emergence of even the simplest imaginable replicating molecule is only plausible within a highly complex chemical system—a system that includes molecules generally only produced by living systems. Just about every RNA first scenario I have read are full of all kinds of highly contrived, ad hoc pre-conditions, based on the assumption that "something like this had to have happened."
Perhaps a way out is suggested by Stuart Kaufmanns work on autocatalytic cycles where spontaneous molecules co-operate together..of course this introduces elements of the dreaded 'T word' into biology but I think it is a direction more fruitful than the utter failure of the reductionistic logic of the first replicator (that last parts my personal opinion BTW)
Anyway I seem to have hijacked your post- I could go on about this subject for ages; Apologies George!

Reiel F

It was interesting to have an extended view of the topic "collapse", building on Tainter. But I wonder if the notion "social entrophy" may be brought into this field, as a supplement to "complexity". The German sociologist Manfred Wöhlcke is using this term, though in a little different perspective, with a stain of blck humour.
When do a critical mass understand this message, overriding The Cassandra Syndrome.

George Mobus

GaryA,

No worries. I post this stuff to elicit other ideas and comments. You weren't hijacking.

I think you are right about the RNA-first scenarios as they stand. Too much needed already existing complexity to be completely plausible. However, I do think a pathway exists from earlier nucleotides + protein combos that, in the presence of templates such as clays could give rise to replicating structures. My favorite molecule is adenosine and its relationship with phosphates (e.g. AMP, ADP, and ATP) for their energy characteristics (though other nucleotides could have played a role). Coupled with glutenous polypeptides I think this could form an initial core for the later development of both extended, but still short, single strand RNAs along with embedding proteins and perhaps some early lipids. In other words I would argue for a "ribosome-first" world! I see it starting with adinosine simply because of the five or more nucleic acids, it seems to be the least labile under presumptive conditions back then. Its been a pet theory of mine for many years and some of Morowitz's arguments tend to support the feasibility and I've yet to find arguments that destroy that feasibility.

By the dreaded 'T' word I suppose you mean teleology. Have you looked into teleonomy? (http://en.wikipedia.org/wiki/Teleonomy ) It seems a fruitful way to proceed.

Thanks for the stimulating conversation.

George

George Mobus

Hi Reiel F.

Thanks for the comment.

By social entropy do you mean having many possible states (the usual meaning of entropy in information theory)? If so then I think it is essentially the same as potential complexity, before actual organizations have obtained (reduction of entropy in that the setting in of specific organization reduces the number of potential states at any given level).

Unfamiliar with Manfred Wöhlcke's work. Perhaps a link would help. I'm not sure I have time to go searching.

Thanks again. Hope you continue to contribute here.

George

Reiel F

Dear George
The only I can do for now is to refer to Kenneth D Bailey: Social Entropy Theory. I will try to bring you a translation of the pertinent Wöhlcke text.
Reiel F

George Mobus

Reiel F,

Thanks.

George

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