Question about evolution...

[Exonerate]

Somebody on a forum is using the argument that DNA codes for proteins, and proteins produce DNA, so that evolution couldn't have happened. Does anybody know the current scientific theory on how this happened, or am I going to have to say they came into existence concurrently?

[Sokar]

Okay , there is NO definitive answer to this ultimate chicken and the egg question. One of the leading theories, is that the base components for life existed in the primordial soup that was the Earths nascent oceans, through chance interactions with tides, and combined with the heavy geologic and electrostatic phenomena(lightning) induced the first amino-chains into being.(Theres a process for this, but its been way to long since Bio class) Thoes amino-chains combined to form the first protiens and then onward to eiether the early DNA or RNA world.

[Enforcer Talen]

we got lucky . . punk.

[InnerBrat]

The 1953 Stanley MIller experimetns produced basic amino acids and nucleic acids, so although there's no proff which one came first, they have been observed to arsie together from the relevnat gaseous mixture.

[Sokar]

AHA!! Miller! Thats what I was thinking of, thank you innerbrat

[InnerBrat]

AHA!! Miller! Thats what I was thinking of, thank you innerbrat

You're welcome.
I knew kleeping my first year notes would come in useful one day.

[Kenny_10_Bellys]

What's this assholes counter-argument then, we were made out of clay by a giant superbeing in a day? I love when these guys try to use science against scientists, it's like putting a one legged man in an ass-kicking contest.

[Yuri Prime]

What's this assholes counter-argument then, we were made out of clay by a giant superbeing in a day? I love when these guys try to use science against scientists, it's like putting a one legged man in an ass-kicking contest.

One of them tried to overturn atomic theory with me the other day by claiming the nucleus of an atom would repel itself and lost because he didn't know about this neat little thing called the Strong Force. His argument was based on the Rutherford model anyway. Not surprising seeing as that's what they teach in 7th grade.

[Lagmonster]

Not to put too difficult a chore on your shoulders, but I wouldn't use the Miller experiments in an argument. The experiments and their results have been heavily criticized since then and, in many ways, have been shown to be very inconclusive. There is a SHITLOAD of more modern research that is far more likely to show how simple protiens, etc., came into being on their own.

As another aside, the 'primordial soup' theory is being held onto in some circles, even though it is almost certainly *wrong*. A better, and newer, theory is the 'primordial sandwich' or 'open-faced' theory (don't have the originator's name handy, sorry), which proposes that life began between chemicals on flat crystalline or other specific surfaces, not floating about. The exciting implication to this newer theory is that life is likely 'originating' today at places like undersea sulfur vents.

[InnerBrat]

Not to put too difficult a chore on your shoulders, but I wouldn't use the Miller experiments in an argument. The experiments and their results have been heavily criticized since then and, in many ways, have been shown to be very inconclusive. There is a SHITLOAD of more modern research that is far more likely to show how simple protiens, etc., came into being on their own.

Can you give an example? Just out of interest.

[Darth Wong]

I'm interested too.

[Lagmonster]

The gist of the criticism is that Miller's results don't show the exact 'origin of life' due to the fact that his knowledge of atmospheric conditions on primordial earth was a guess, and probably inaccurate. Thus, the creation crowd tends to point out that his results don't show the 'origin of life' because of the current belief that his conditions were wrong. I'm fairly sure you can find some mention of that on the more clever creationist sites if you look (I found two with a brief search). The funny part is that Miller still proved that abiogenesis was *possible*, under specific conditions (in other words, even if he was dead wrong about conditions on early earth, he STILL showed that life can originate without God).

Above all, abiogenesis has nothing to do with "the origin of life". We should not necessarily be looking for a single method. A number of abiogenetic mechanisms might have been working simultaneously - atmospheric gas reactions, hydrothermal vent reactions, cometary/meteoric impacts, thermal copolymerization, solid-state catalysis, and other things I probably couldn't explain to you on a bet - in different ways to create first biomolecules, then metabolic systems, then replicating systems and finally life.

Below are some references below that I dredged up and shamelessly copied from other people and sites. Feel free to quote them as examples of experiments which qualify as abiogenesis, yet use more updated conditions and differing models and methods. The basic point of the matter is that we point out that we CAN simulate abiogenesis, not that we know which, if any of these, actually transpired on primordial earth. If the origin of life occurred as Miller proposed, then most or maybe all of these examples would not have anything to do with the origin of life, which is why we say that abiogenesis does not necessarily have anything to do with the origin of life on earth.


Amend, J.P. and E.L. Shock, 1998. "Energetics of Amino Acid Synthesis in Hydrothermal Ecosystems," <Science> 281:1659-1662.

Fox, Sydney W. 1995, "Thermal Synthesis of Amino Acids and the Origin of Life"_Geochimica et Cosmochimica Acta_59(6): 1213-1214.

Holm, Nils G. 1992, "Why are Hydrothermal Systems Proposed as Plausible Environments for the Origin of Life?", _Origins of Life and the Evolution of the Biosphere_, 22:5-14.

Huber, C. and G, Wachtershauser 1998. "Peptides by activation of amino acids with CO on (Ni,Fe)S surfaces: Implications for the origin of life," <Science> 281:670-672.

Joyce, G. 1988, "Hydrothermal Vents too Hot?", _Nature_, <334>:564.

Marshall, W.L. 1994, "Hydrothermal Synthesis of Amino Acids", _Geochimica et Cosmochimica Acta_, <58>:2099-2106.

Miller, S.L. and J.L. Bada, 1988, "Submarine Hot Springs and the Origin of Life," _Nature_, <334>:609.

Miller,S.L. and J.L. Bada, 1991, "The origin of life did not take place in submarine hot springs," _Eos Trans. Amer. Geophys. Union_, 72(suppl.), p. 59.

Nisbet, E.G. 1989. "Origin of Life," _Nature_ 337:23.

Shock, E.L. 1990, "Geochemical Constraints on the Origin of Organic Compounds in Hydrothermal Systems," _Origin of Life and Evolution of the Biosphere_, <20>:331-367, 1990.

Shock, E.L. 1992, "Hydrothermal Organic Synthesis Experiments," _Origin of Life and Evolution of the Biosphere_, <22>:135-146.

[Exonerate]

Thank you very much to all of those who responded

[Admiral Valdemar]

You'll never get them to go with abiogenesis, they'll resort to quoting some garbage from a certain Christian based anti-talkorigins.org website.

[Ignorant twit]

.

Somebody on a forum is using the argument that DNA codes for proteins, and proteins produce DNA, so that evolution couldn't have happened. Does anybody know the current scientific theory on how this happened, or am I going to have to say they came into existence concurrently?

Current theory is that the first "lifeform" was a self-replicating ribozyme. We've manufactured a self-replicating ribozyme in the lab, I think it was in Science 2000 or 2001 somewhere. Basically RNA can be used as information storage, like in HIV; and for chemical catalysis like in VEGF inhibitor.

So the leading current theory is that somehow, somewhere you got poly ribonucleaic acids. One of em was self-replicating. There replication method wasn't perfect and every now and again a new sequence was "born". Somewhere along the way these ribozymes begin working on nonribonucleaic substrates, like say metal ions and amino acids. Eventually this gave rise to more efficient protein catalysts. Later more efficient and robust data storage came when certain polypeptides began using de-oxy forms exclusively (this is thought to be the case because some whack archeobacteria uses deoxy uracil).

Most of this is still massive conjecture, with massives portions unexplained, but several good labs are working on it. Best model I know of thus far. RNA can do what proteins do ... catalysis and what DNA does ... information storage. The answer to the chicken or the egg is the lizard
[/i]

[Darth Servo]

Somebody on a forum is using the argument that DNA codes for proteins, and proteins produce DNA, so that evolution couldn't have happened. Does anybody know the current scientific theory on how this happened, or am I going to have to say they came into existence concurrently?

DNA is self replicating. Proteins just speed up the process. DNA simply tells what order to place the amino acids in to generate a specific protein. A random sequence is easy to generate with simple chemistry.

[Ignorant twit]

DNA is self replicating. Proteins just speed up the process. DNA simply tells what order to place the amino acids in to generate a specific protein. A random sequence is easy to generate with simple chemistry.

Not any DNA I know of. DNA tends to be double stranded, "unzipping" it to get a template for replication requires proteins. Getting the proteins to unzip the DNA requires a template ...

Further the reaction rate for that 3' hydroxyl sucks. Waiting for DNA to replicate without some form of catalysis would be a SERIOUS exercise in futility. Loads of crap will react before that will.

Best theory is Ribozymes, jack of all trades ... master of none.

[Admiral Valdemar]

DNA is self replicating. Proteins just speed up the process. DNA simply tells what order to place the amino acids in to generate a specific protein. A random sequence is easy to generate with simple chemistry.

Not any DNA I know of. DNA tends to be double stranded, "unzipping" it to get a template for replication requires proteins. Getting the proteins to unzip the DNA requires a template ...

Further the reaction rate for that 3' hydroxyl sucks. Waiting for DNA to replicate without some form of catalysis would be a SERIOUS exercise in futility. Loads of crap will react before that will.

Best theory is Ribozymes, jack of all trades ... master of none.

Ah ribozymes, how often people get them mixed up with ribosomes in my bio class.

[Darth Servo]

DNA is self replicating. Proteins just speed up the process. DNA simply tells what order to place the amino acids in to generate a specific protein. A random sequence is easy to generate with simple chemistry.

Not any DNA I know of. DNA tends to be double stranded, "unzipping" it to get a template for replication requires proteins. Getting the proteins to unzip the DNA requires a template ...

Thats because the DNA strands are too long to do it by themself. Get a short strand and you have much less hydrogen bonding to overcome.

Further the reaction rate for that 3' hydroxyl sucks. Waiting for DNA to replicate without some form of catalysis would be a SERIOUS exercise in futility. Loads of crap will react before that will.

Yes it does suck but that doesn't mean its non-existant. But we're looking at time frames much longer than typical human observation here. And there are other things that can speed up the process besides the specific proteins our cells use.

[Ignorant twit]

Thats because the DNA strands are too long to do it by themself. Get a short strand and you have much less hydrogen bonding to overcome.

Actually its the pi stacking you need to overcome, but hey. The statistics of using a short strand template and then looking for spontaneous ligation of the next base makes this a dubious process.

Yes it does suck but that doesn't mean its non-existant. But we're looking at time frames much longer than typical human observation here. And there are other things that can speed up the process besides the specific proteins our cells use.

No but it is NOT shorter than the time frame it would take for the template-substrate complex to randomly dissassociate. It is also not longer than it would take for the DNA to be cleaved by other chemical processes. This isn't happening in a vacuum, the ligation process has to be faster than BOTH disassociation and cleavage. It is only a matter of time before you get hit with that nasty UV photon which breaks the template, the substrate, or both.

In a nutshell the replication has to be faster than any other chemical process. Given the lack of reactivity in that 3' hydroxyl and the numerous other things that can happen(like photocleavage and mismatch ligation); the statistics argue that any DNA sequence of consequence will not self replicate before something else happens, unless conditions are damn near perfect. The longer your DNA sequence is, the abysmally less likely it is you beat the odds.

Ribozymes have ORDERS OF MAGNITUDE better kinetics, and better thermodynamics to boot.

DNA is a poor, poor choice for the origins of life.