PZ Myers. 2005 Aug 28. Evolving motors. <http://pharyngula.org/index/weblog/evolving_motors/>. Accessed 2008 May 17.
Posted on M00o93H7pQ09L8X1t49cHY01Z5j4TT91fGfr on Sunday, August 28, 2005
Evolving motors
As we are so often reminded by proponents of Intelligent Design creationism, we contain molecular "machines" and "motors". They don't really explain how these motors came to be other than to foist the problem off on some invisible unspecified Designer, which is a poor way to do science—it's more of a way to make excuses to not do science.
Evolution, on the other hand, provides a useful framework for trying to address the problem of the origin of molecular motors. We have a theory—common descent—that makes specific predictions—that there will be a nested hierarchy of differences between motors in different species. Phylogenetic analysis of variations between species allows us to reconstruct the history of a molecule with far more specificity than "Sometime between 6,000 and 4 billion years ago, a god or aliens (or aliens created by a god) conjured this molecule into existence by unknown and unknowable means".
Richards and Cavalier-Smith (2005) have applied tested biological techniques to a specific motor molecule, myosin, and have used that information to assemble a picture of the phylogenetic history of eukaryotes.
Myosin should be a familiar protein to all of us: it's an important component of muscle, and is the motor that drives muscle contractions. Like most biological machines, its function can actually be reduced to something fairly simple, and the complexity arises from the multitude of permutations, the many little tweaks that have been made to it, in a long, long history of random changes filtered by selection.
Myosin is a ratchet. It has a globular head that has enzymatic activity: it hydrolyzes a molecule used for energy storage, ATP. When it burns the energy released from the breakdown of ATP, it undergoes a conformation change, bending the head relative to the tail. It's a small thing, really, a tiny shift in the shape of the molecule.
A small thing repeated many, many times by a large number of molecules can add up to a fair amount of force, however. These small shifts in shape are coupled into a contraction cycle in the muscle. The myosin burns ATP to ADP to change shape, it binds to another molecule, it releases the spent ADP, it flexes back, shifting the other molecule; then it burns more ATP, binds again to the molecule, flexes, and releases. Burn, bind, flex, release…over and over again, shifting sliding strands of protein a tiny fraction of a millimeter at a time. That's the engine that drives every contraction of your muscles.
You have 12 different forms of the myosin gene. Why the diversity? Because they have slightly different properties: what they bind to best, how fast they change shape, when and where they are expressed. There's a special myosin for your heart muscle, a different one for slow muscles for endurance, another for fast twitch muscles that generate lots of power quickly. There's a smooth muscle myosin and a fetal myosin.
Myosin is present in other organisms, too, not just animals with muscles, so don't think of it as simply a muscle component. Amoebae, plants, and mushrooms also have essential myosins. Myosin is a general purpose ratchet that shifts proteins, especially cytoskeletal proteins, relative to one another. Our cells use it to transport organelles and proteins from one part of the cell to another, and we wouldn't be able to sustain long nerves without myosin to move essential components from the cell body to the periphery. Amoebae use it to push out pseudopods; amoeboid movement depends on it. They drive cytokinesis, the process of cell division. If you're a eukaryote, it doesn't matter whether you are capable of pumping iron or not—you've got myosin or a member of the related kinesin gene family to power physical movements within cells.
All of these diverse functions in diverse organisms use the same recognizable core module to do their job, that ATP-binding globular head, but they vary in activity and binding properties to other molecules and in that associated tail you can see in the cartoons above. That means one can fish within genomic data and find the recognizable part of the myosin, and also catalog the differences and assemble a picture of the molecule's evolutionary history. Richards and Cavalier-Smith identified 37 different types of myosin in their investigation, used characters from each to put together a table of similarities and differences.
For instance, plants have a feature in their myosin called the TH1-FYVE-like insert, which is not present in any animals, fungi, or amoebozoa, which suggests that this element evolved after the plant and animal lineages diverged. Likewise, animals and fungi share a MYTH4/FERM duplication that isn't present in any of the other groups, linking them together and almost certainly evolving well after the plant-animal separation. Putting all the information together yields a eukaryotic family tree.
Schematic tree showing myosin-derived synapomorphies (green bars) and three previously published shared characters (grey bars). Yellow bars indicate synapomorphy plus secondary loss. MYSc, myosin head domain.
This tree corresponds well with similar trees generated from other kinds of data; it doesn't place fungi closer to plants than animals, for instance, despite the fact that you might superficially think mushrooms and trees have more in common than mushrooms and monkeys. This is another strength of the scientific approach: we get answers that are consistent with one another and with the idea of relationships by descent.
They were also able to infer some of the properties of the last common ancestor of all eukaryotes. It had three kinds of myosin, that differ mainly in the structure of the tail.
Richards and Cavalier-Smith propose that there were three ancestral myosins in the earliest eukaryotes, each with distinct tail domain structures. Listed are examples of organisms or cells expressing members of each myosin group and their known functions. The TH1 domain would probably bind to charged lipids and target these myosins to membranes. The SMC domain would promote dimer formation and the DIL and MyTH4/FERM domains would target myosins to their cargo or subcellular location.
In addition to three myosin types, it would have also had a single cilium, mitochondria, and pseudopodia, and would probably have been a motile cell. This is one of the powers of modern evolutionary biology: although we weren't there, and although we don't even have fossils of these organisms, the chain of evidence and logical inference can give us a fuzzy glimpse of a creature that lived over 2 billion years ago.
Richards TA, Cavalier-Smith T (2005) Myosin domain evolution and the primary divergence of eukaryotes. Nature 436(7054):1113-1118.
Titus MA (2005) A treasure trove of motors. Nature 436(7054):1097-1099.
Posted by PZ Myers on 08/28 at 01:02 PM
Science • EvoDevo • Organisms • 0 Trackbacks • Other weblogs • Permalink
Science • EvoDevo • Organisms • 0 Trackbacks • Other weblogs • Permalink
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Ha! And all along I thought it was teeny-tiny-little red truck in the cells saying "choo-choo"!
Brilliant paper. -
This tree corresponds well with similar trees generated from other kinds of data; it doesn't place fungi closer to plants than animals, for instance, despite the fact that you might superficially think mushrooms and trees have more in common than mushrooms and monkeys. This is another strength of the scientific approach: we get answers that are consistent with one another and with the idea of relationships by descent.
And this also shows that the theory of evolution is falsifiable because we did not know a priori that the trees we draw from different data would come out consistent with each other. -
No, no, coturnix, it's the teeny-little black engines that go "choo-choo." The teeny-tiny-little red trucks go "toot-toot."
That's where the scientific evidence for the expression "to get steamed" comes from. Normally the teeny-tiny-little trucks do the work, but when we get angry, the teeny-little black engines get revved up. That's where all the steam comes from of course!
Isn't it wonderful how PZ's writing makes this all so clear to everyone? Go PZ!!!
PS: I want my gravatar back. -
Of course Behe's response would be, "Yes, but how did those three myosins get there in the first place? You haven't explained anything." Thus moving the bar to a more protective hight.
#: Posted by on 08/28 at 03:23 PM
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Bill: Sorry. Gravatars just ate up too many resources. You can get an avatar by registering here, going to your account info, and adding an avatar.
JSB: To Behe, I would say look at MukB. It's a putative prokaryotic homolog to myosin/kinesin -- sequence similarity isn't very good, but it has a very similar structure, with a globular head, pivot joint, and tail. -
"—it's more of a way to make excuses to not do science."
That's a great line.
The actual science is pretty impressive too - hey, my unimaginably distant nth cousin is a fungi . . . -
I would add to Arun's comment regarding the testability of the theory of descent. Tests of hypothesis that all organisms are related using the congruence of evolutionary trees has been conducted before - initially in the early '80s by David Penny. A nice summary is presented in:
Penny D, Hendy MD, Poole AM.Testing fundamental evolutionary hypotheses.
J Theor Biol. 2003 Aug 7;223(3):377-85.
In the '82 (if I remember correctly) Nature paper Penny and colleagues used the limited amount of data then available for mammals, but the basic idea was the same.#: Posted by Edward Braun on 08/28 at 05:13 PM -
Myosin and skeletal muscle - all those years in a muscle lab and finally.............
a different one for slow muscles for endurance
A classic no-no from the non-muscle folks among us scientists (and the way skeletal muscle is described in virtually every text one can read). Here you are mixing contractile speed and metabolic properties and while combining the terms "slow" and "endurance" is generally true, skeletal muscle is not really broken down into categories such as you have mentioned. Skeletal muscle properties are not discrete units rather the properties of muscle fall along a continuum – “fast” fibers can and do have some of the properties of “endurance” fibers. Remember, it is not only myosin that determines the characteristics of the fiber in question other variables such as, for example, oxidative enzyme content and non-myosin contractile protein isoforms play a role. (although myosin is the major factor). It is easier for skeletal muscle to be described in the manner that you have above but that would provide, as my old colleagues would say, only a half-truth.
Keep up the good work#: Posted by on 08/28 at 07:06 PM - But, I have a list of 253 scientists with PhDs ranging from sociology to economics who have signed a statement that the theory of black engines is just a theory, an unproven one, too, and that the red-engine theory has to be included in science classes for balance! Furthermore, it is a self-evident fact that a belief in black engines inevitably leads to atheism, immorality and Nazism.
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Ooops, forgot to put a lot of words in ALL CAPS....
- OK, muscle, I'm guilty, guilty, guilty. As amends, though, let me say that when I teach physiology, I hand my students a great big complicated table of muscle properties, and tell them they have to memorize all of it -- I don't take shortcuts there.
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Excellent stuff. I'm usually easily lost in the articles on molecules and molecular systems, but your write up was fantastically clear.
-Schmitt.#: Posted by on 08/28 at 09:00 PM -
Before continuing, I would like to reveal: 1) I think IC is probably wrong; and 2) I have a Ph.D. in Ecological Entomology from a reputable institution. I say these things only to preempt the flame throwers.
First, contrary to what many have said, IC <b>IS<b> a scientific hypothesis. I say this because IC can be falsifed.
Second, contrary to many disparaging comments about "raising the bar" or "moving the goalposts", <b>THERE IS NOTHING WRONG<b> with modifying a hypothesis if it fails a test. Hypotheses evolve. If all hypotheses had been totally ash-canned on failing their first tests, we wouldn't have many left. It's a 'baby and the bathwater' situation. Ultimately many hypotheses must be discarded, but this should happen only when they are no longer tenable even in our imagination.
So when Behe says (as he is certain to): "Ok. So where did the three 'original' motors come from?" he is not committing any sin against the scientific process.
Nay, and verily I say unto you, his only 'sin' is that he has challenged orthodoxy! But is this REALLY a sin?
Ernst Mayr has said: "Orthodoxy must be challenged. But this does not mean that orthodoxy is wrong."
With this in mind, I would like to opine that IC has provided a valuable service to evolutionary theory (as have many earlier challenges) in that it has defined the limits of our knowledge (the frontiers of our ignorance?) and forced us to look more critically at our own views. He has challenged us to explain puzzling aspects of biochemistry without resorting to 'just-so' stories.
He was incorrect in asserting that the blood coagulation system is 'irreducably complex' (falsified by observation of reduced cetacean systems and crustacean precursors), and he is probably incorrect in asserting that the flagellum is 'irreducably complex' (I see a partial rebuttal but no knockout blow yet). etc.
Of course, each such falsification of a specific case of IC will unveil a deeper possibility of IC. The challenge is to continue to falsify these possibilities. Great progress WILL be made as a result of this challenge.
On a closing note, I have to reveal a long-held source of puzzlement: How can the DNA-processing apparatus have originated from a simpler system?
I bailed out of biochem as soon as I could, but this much I recall: the cistron ("gene") contains coding sections and non-coding sections. One enzyme makes an RNA copy (mRNA?) of the specified cistron; another cuts out the non-coding bits and attaches a poly-A tail. This processed mirror-gene is then conveyed to a ribosome, where it is converted to protein by accumulation of tRNAs.
My question: how could this evolve from simpler precursors? Especially, how does the splicing enzyme recognize the difference between coding and non-coding DNA? A half-assed one would be no better than none at all!
I expect that there is an answer, but does anybody know?
yours in science:
Derek Lactin#: Posted by on 08/29 at 05:09 AM -
Behe doesn't have a hypothesis about IC, all he (and you) have is anargument from incredulity. "I can't figure out how it evolved, therefore the designer did it". That doesn't challenge any orthodoxy, all it shows is laziness.
If you really cared about the science you'd make the effort to learn biochemistry and do the research. Why don't you?#: Posted by on 08/29 at 05:49 AM -
Hope you guys didn't miss this article about some IDist having second thoughts:
http://seattletimes.nwsource.com/html/localnews/2002450329_danny24.html#: Posted by Mikko Sandt on 08/29 at 07:19 AM -
euan.
that was uncalled-for.
i expect intelligent replies on this board.#: Posted by on 08/29 at 08:19 AM -
Derek,
First, contrary to what many have said, IC <b>IS<b> a scientific hypothesis. I say this because IC can be falsifed.
. Really? Let's hear it. IC hasn't "forced us to look more critically at our own views". IC IDCists have been making wild claims about iology being full of "just-so stories" without bothering to read the literature. As H. Allen Orr pointed out in his critique, Behe is a decent biochemist but has a shallow knowledge of evolution and seems to have gleaned it from a quick reading of popular ,dumbed down (my addition) works on the subject. Bilogists, mathematicians and other scientists and intellectuals have forced IDCists to look at their own assumptions about biology with their replies. And that is why after a great big boast about driving back materialism to the Stone Age IDCists today stand exposed as little better than snake oil salesmen. Scientists don't waste their time 'debating' these charlatans and that is annoying isn't it? Every supposed lacuna that IDCists point out to turns out to be a thriving and intensely researched area. For every "expert" put forward by the IDC movement, it turns out that there are a few 100 scieintists and papers on the subject. Wells wrote about peppered moths and ran into a scientist who has been studying them all his life. Behe writes about the clotting cascade only to run into Dolittle who has studied them for decades. So with Dembski and the NFL theorems - this time from the person who wrote the proof. Since you have a PhD in the area and are surely familiar with the ways of science and are a credentialed expert in your field why not study the papers referred to here before drawing these unfounded conclusions? -
Derek -
The essential statement of ID is that some features of living organisms are too complex to have arisen without the intervention of an "intelligent designer."
That, by itself, is not falsifiable.
You can falsify such a claim with respect to particular features (e.g. extant molecular motors). But you can never falsify the general claim. You can't prove the negative.
Now, if ID gave us some positive predictions, it would be different. For instance, ID could claim "features that have the following characteristics could not have arisen through evolution," and then list the relevant characteristics. Then, we could go out, identify features that have those characteristics, and ask whether they could have evolved.
That would be a testable hypothesis. And in that case, I agree it would be entirely fair to modify the hypothesis if it failed initially. In principal, at least, the list of defining characteristics could be tweaked until it fit all the data.
But the current definition of ID only says there are "some" features somewhere that couldn't possibly have evolved "naturally." It's equivalent to me claiming that there are some flies somewhere that arise by spontaneous generation of maggots from rotting meat. No matter how many times you prove me wrong using a specific piece of rotting meat, you can never formally prove me wrong about every piece of rotting meat that exists.#: Posted by on 08/29 at 10:49 AM -
I expect that there is an answer, but does anybody know?
It is likely that many of the answers may be found outside of the biochemical realm.
A complete understanding of how the complex pre-biotic molecules (nucleotides, complex sugars, etc) formed and then evolved into more complex systems will likely be best understood through quantum mechanical principles.
For example, it is well understood that numerous pre-biotic complex molecules (including major intermediates of the carboxylic acid cycle, polypeptides, porphryins, amino acids) can be found it the gaseous clouds in far-away galaxies and/or in some extra-solar systemic meteors, indicating that they result from bifurcation and spontaneous symmetry breaking and molecular evolution, which themselves are remnants of the original cosmic symmetry breaking of the fundamental forces.
That is, much of the evolution of our little machines is (was) done at the quantum level, and thus was technically able to take "leaps" through complexity via the various symmetry breaking/bifurcations, which (presumably) first resulted in the organization of the periodic table.#: Posted by on 08/29 at 11:25 AM -
Maybe our host PZ might someday talk about what's been emerging about overall eukaryotic phylogeny (as reported in places like Cavalier-Smith and Stechmann and Patrick Keeling's pages.
To use Cavalier-Smith's terminology, eukaryotes are divided into unikonts and bikonts, that first branch in the tree that PZ showed us in his entry.
Unikonts = Amoebozoa + Opisthokonts (flagellum is rear-mounted)
Opisthokonts = Fungi + Choanoflagellates (incl. Animals)
Bikonts = Plants sensu vere lato + Chromalveolates + Cercozoa + Excavates (named after their "excavated" feeding grooves)
Plants s.v.l. = Green Algae (Chlorophytes + (Charophytes + Land Plants)) + Red Algae + Glaucophytes
Chromalveolates = Chromists + Alveolates
Chromists = Golden Algae + Brown Algae + Oomycetes + etc.
Alveolates = Ciliates + (Apicomplexans + Dinoflagellates + etc.)
Cercozoa = (Foraminifera + Radiolaria) + Cercomonads + etc.
Excavates = Discicristates + Jakobids + Trichomonads + Diplomonads + etc.
Discicristates = Euglenids + Kinetoplastids + etc.#: Posted by on 08/29 at 12:37 PM -
"...the London Times...."
Just as a bit of warning, truly fussy Britons have been known to irritatedly inform Americans that there is no such paper; there is, however, "The Times of London," also known as "the only Times."
Hey, just warning. But slightly seriously, I'm sure you can appreciate an interest in proper nomenclature.#: Posted by Gary Farber on 08/29 at 03:33 PM -
I don't agree with Derek. However, I don't believe the following is correct:
The essential statement of ID is that some features of living organisms are too complex to have arisen without the intervention of an "intelligent designer." That, by itself, is not falsifiable. You can falsify such a claim with respect to particular features (e.g. extant molecular motors). But you can never falsify the general claim. You can't prove the negative.
In principle, I imagine, one could prove that for each "feature" in a coding scheme, there exists a "reasonable" model in which that feature could be derived from a set of initial states. One could then prove something about "reasonable" models being likely to exist. On the other hand, I haven't seen any ID theorists moving in this direction. -
<quote>
#37854: coturnix — 08/28 at 07:20 PM
Ooops, forgot to put a lot of words in ALL CAPS....</quote>And lots of exclamation points. And if you really want to look like an idiot, use quote marks for emphasis. I was looking for that website which features photos of signs with such errors, but instead I found this moronic site where a writer actually advocates that. http://www.wedosites.com/website_powerful.html#: Posted by on 08/29 at 06:38 PM -
Now, if ID gave us some positive predictions, it would be different. For instance, ID could claim "features that have the following characteristics could not have arisen through evolution," and then list the relevant characteristics.
Behe did just that. And it was quickly falsified. IDers do not care. Their belief is religious, and impervious to logic.#: Posted by on 08/29 at 06:50 PM -
Here's my attempt to respond simultaneously to several postings.
As a philosophical preface: there's nothing we can know with absolute certainty. In science (except mathematics) we have no proof, only evidence. Furthermore, the Popperian paradigm of scientific inquiry suggests that the only sure answer is 'no': Evidence which does not falsify a hypothesis does not prove that the hypothesis is correct. Of course, hypotheses which continually survive attempts at falsifcation eventually reach the point where they are considered 'correct', but this acceptance remains conditional. Note that the theory of descent with modification (i.e., neo-darwinism) falls into this category. I SAY THIS EVEN THOUGH I MYSELF CONSIDER IT CORRECT.
some specific statements:
1) I do not conflate IC with ID. IMHO, ID is and always has been, psuedo-science. IC at least has SOME basis in obsevational science and is therefore worth responding to. (NOTE: I don't believe it is GOOD SCIENCE)
2) for Shiva:
IC is a valid FORM of hypothesis in that it makes specific assertions which can be tested empirically. That these assertions have been wrong when subjected to tests, is not relevant to my opinion.
By asking difficult questions of origin, Behe has obliged us to seek or present empirical evidence, rather than ignore/defer difficult questions.
Also, your assertion that scientists outnumber IDists is irrelevant. Science is not a democratic process.
Finally, Shiva said "why not study the papers referred to here before drawing these unfounded conclusions? "
I'm not drawing conclusions: I'm only saying that the formulation of the IC hypothesis allows testing. I also specifically stated that I believe it's probably wrong. (I say 'probably' because I don't believe ANYTHING in science absolutely.)
3) qetzal said:
"You can falsify such a claim with respect to particular features (e.g. extant molecular motors). But you can never falsify the general claim. You can't prove the negative."
I grant you this one; however, we can continue to disprove specific aspects until the whole idea becomes untenable.
Also, note that you refer to ID; I did not.
and now for:
4)
[review: I asked a specific question regarding the origin of the enzymes which splice out non-coding DNA before conversion to protein..., concluding with:
///I expect that there is an answer, but does anybody know?//
Jeebus "replied":
///It is likely that many of the answers may be found outside of the biochemical realm./// [sez who?! --DJL]
///A complete understanding of how the complex pre-biotic molecules .... quantum mechanical principles...
...numerous pre-biotic complex molecules ... gaseous clouds in far-away galaxies... extra-solar systemic meteors
...bifurcation and spontaneous symmetry breaking ... remnants of the original cosmic symmetry breaking of the fundamental forces... quantum level, ..."leaps" through complexity via the various symmetry breaking/bifurcations, which (presumably) first resulted in the organization of the periodic table. /////
(sorry, I have to go to caps here)
WTF DOES THIS OBFUSCATORY PSEUDO-PROFOUND BAFFLEGAB HAVE TO DO WITH MY QUESTION?
Derek Lactin
"I may disagree with what you say, but I will defend to the death your right to say it." -- Voltaire#: Posted by on 08/30 at 01:22 AM -
been reading up on the genetic editing mechanisms (splicesomes).... it's even more complex than i thought.
(hold off on the flames until you read my bit at the end!)
following is an abstract:
"
The spliceosome: the most complex macromolecular machine in the cell?
Nilsen TW.
Center for RNA Molecular Biology, Case Western Reserve University School of Medicine, 10900 Euclid Avenue, Cleveland, OH 44106-4973, USA.
The primary transcripts, pre-mRNAs, of almost all protein-coding genes in higher eukaryotes contain multiple non-coding intervening sequences, introns, which must be precisely removed to yield translatable mRNAs. The process of intron excision, splicing, takes place in a massive ribonucleoprotein complex known as the spliceosome. Extensive studies, both genetic and biochemical, in a variety of systems have revealed that essential components of the spliceosome include five small RNAs-U1, U2, U4, U5 and U6, each of which functions as a RNA, protein complex called an snRNP (small nuclear ribonucleoprotein). In addition to snRNPs, splicing requires many non-snRNP protein factors, the exact nature and number of which has been unclear. Technical advances, including new affinity purification methods and improved mass spectrometry techniques, coupled with the completion of many genome sequences, have now permitted a number of proteomic analyses of purified spliceosomes. These studies, recently reviewed by Jurica and Moore,1 reveal that the spliceosome is composed of as many as 300 distinct proteins and five RNAs, making it among the most complex macromolecular machines known. Copyright 2003 Wiley Periodicals, Inc.
"
whoa! i'm certain that there will prove to be evidence of precursors, but this is pretty heavy stuff!
blue-skying a bit...
1) prokaryotes have no similar system to the spliceosome, as their DNA is intron-free.
2) there is good evidence that the eukaryote cell arose from a mutualistic assemblage of prokaryotes (search for 'margulis' and 'eukaryote origin') which ultimately proceeded to integration of the genomes.
3) with crossing-over and inversions and stuff during meiosis, the genomes would get scrambled; genes themselves would occasionally get interrupted. this would be bad news.
4) a proto-eukaryote with a system for recognizing which components of the genome came from which ancestor, and rescuing the components would have a tremendous selective advantage. (how could they recognize 'their own'? protein tags? might this also explain why eukaryote DNA is complexed with histones, whereas prokayote DNA is naked?)
5) the most likely (?) origin of such a system would be within the physiology of the component symbionts. i.e. prior to total genomic integration, each partner genome would have had to reproduce separately from the others and would have had systems in place to allow this. [details? sorry, i'm already beyond my depth in biochemistry/cellular physiology.]
i suggest then, that
6) the spliceosomes originated concurrently with (were a precondition for?) total genomic integration and thus arose by amalgamation of genome-rescuing systems of the protosymbiote partners...
??
but then i'm just an aging dilletante entomologist.
Derek#: Posted by on 08/30 at 07:29 AM -
I will start by quoting you, djlactin.
That was uncalled-for.
Your original questions seemed pretty open to conjecture, as the questions you ask were either purely theoretical,
I expect intelligent replies on this board.How could this evolve from simpler precursors?
or depend on mechanisms that biochemists don't necessarily have the highest ground,how does the splicing enzyme recognize the difference between coding and non-coding DNA? A half-assed one would be no better than none at all!
as every inter-molecular reaction is governed by the quantum laws. Yes, you can describe in detail the biochemical reactions between DNA and DNA-binding proteins, etc., because the interactions are basically classical in nature. I'm just saying that molecular binding is in nature a purely quantum mechanical process. Is that very "profound"? No, it is fact.
Then, I just decided to have a little fun.
You asked "How could this evolve from simple precursors, and I conjectured that this could be explained in other ways than the standard "evolution by natural selection" - when it comes to some of the complex biotic molecules such as DNA.
For, although DNA itself may be an evolved structure that is a cousin of some more "primitive" genetic material, the initial genetic material (some complex of nucleotides, for example, or with a different code) did not, for instance, start with just a few atoms and then built itself up to complexity. But instead, many complex molecules (such as the ones I mentioned in my earlier "obfuscatory" post) form simply out of the normal molecular interactions that are ubiquitous in the universe, some of which "evolve" (so as to "find" lower energy states within their complex forms) and stabilize into what just so happen to be pre-biotic materials for the animal kingdom on this planet.
So, basically, I don't have the biochemical answer you were looking for... I am not a biochemist, to say the least (although I do have a Biology degree).
I simply put forth an idea that may sound crazy and you may have never thought about, but it is not bafflegab and I was not trying to sound profound. It may not be applicable to medicine or even the current state of biochemistry, but the applications of quantum physics in biology (e.g. Frohlich excitations of proteins, quantum tunneling, etc.) are relevant to understanding how living things are different from non-living things.
Plus, at the very least, have an open mind or a fucking sense of humor. Especially since you apparently think that Intelligent Design is science. That's just too funny, IMO.
By the way, smart guy: That really well thought-out quote was not Voltaire.
It was Beatrice Hall [pseudonym: S.G. Tallentyre], 1907.
(Thanks to Dr. Myers' random quote list)#: Posted by on 08/30 at 07:57 AM -
you're right, jeebus. i did not see that it might be a joke. i apologize.
and by the way i have stated CLEARLY that i do not view ID as a science.
it is Irreducible Complexity that i consider to be a VALID HYPOTHESIS, in the sense that it makes testable assertions. i have also said that i don't thinks it's correct.
and thanks for clarifying the source of the quote. i've also seen it attributed to voltaire.#: Posted by on 08/30 at 08:27 AM -
By asking difficult questions of origin, Behe has obliged us to seek or present empirical evidence, rather than ignore/defer difficult questions.
Wrong. Behe has had no effect on the progress of science - quite apart from the fact that his assertions on ID/C have no scientific validity or utility, many of the 'problems' he refers to are long settled lines of enquiry. Apart from having missed out on the theory (inexcusable on the part of an academic) his books have been shown to have been written without as much as a cursory glance at the relevant literature. If anything the Behe process (a continuing one) shows that a scientist however well qualified and published, akes a mass of himself (him because women in science have so far shown a healthy contempt for this quackery) if he abandons the scientific method. PZ and the tons of scientists on this forum and other scientific ones will agree with me (a non-scientist) that even with all the genetic endowments and grades and diplomas; excellence in science is achieved and maintained by a scrupulous adherence to the methods of science. I am surprised that you - no slouch - forget this being a PhD yourself. Behe's homepage at one time used to be filled with interesting stuff, his papers, research and all that. Most of what we find there today is references to his raddi and the comical mouse trap. I am angry with the ID/C movement for having reduced a once good scientist to a caricature, even if Behe himself must bear most of the blame for this decline.#: Posted by on 08/30 at 08:28 AM -
jeebus:
i have found a version of the voltaire quote here:
http://quotes.liberty-tree.ca/quotes.nsf/quotes5/168492862be74cee85256cec006758b0#: Posted by on 08/30 at 08:41 AM -
Hartman and Fedorov have proposed a very interesting hypothesis for the origin of eukaryotic cells' complicated RNA processing.
They propose that the ultimate eukaryote ancestor was a RNA-protein organism that they call a chronocyte, after the Greek god Kronos, who swallowed his children. It was a RNA-protein organism, one that never developed DNA, but instead elaborated on its RNA processing.
The nucleus was the first endosymbiont, an archaeon.
This was followed by some gene transfer and some symbionts from Bacteria, notably the ancestors of the mitochondria and the chloropasts. And some eukaryotes even became some other eukaryotes' endosymbionts.#: Posted by on 08/30 at 02:53 PM