Posted on 06/17/2002 4:40:34 PM PDT by Nebullis
CHAMPAIGN, Ill. — Life did not begin with one primordial cell. Instead, there were initially at least three simple types of loosely constructed cellular organizations. They swam in a pool of genes, evolving in a communal way that aided one another in bootstrapping into the three distinct types of cells by sharing their evolutionary inventions.
The driving force in evolving cellular life on Earth, says Carl Woese, a microbiologist at the University of Illinois at Urbana-Champaign, has been horizontal gene transfer, in which the acquisition of alien cellular components, including genes and proteins, work to promote the evolution of recipient cellular entities.
Woese presents his theory of cellular evolution, which challenges long-held traditions and beliefs of biologists, in the June 18 issue of the Proceedings of the National Academy of Sciences.
Cellular evolution, he argues, began in a communal environment in which the loosely organized cells took shape through extensive horizontal gene transfer. Such a transfer previously had been recognized as having a minor role in evolution, but the arrival of microbial genomics, Woese says, is shedding a more accurate light. Horizontal gene transfer, he argues, has the capacity to rework entire genomes. With simple primitive entities this process can "completely erase an organismal genealogical trace."
His theory challenges the longstanding Darwinian assumption known as the Doctrine of Common Descent – that all life on Earth has descended from one original primordial form.
"We cannot expect to explain cellular evolution if we stay locked in the classical Darwinian mode of thinking," Woese said. "The time has come for biology to go beyond the Doctrine of Common Descent."
"Neither it nor any variation of it can capture the tenor, the dynamic, the essence of the evolutionary process that spawned cellular organization," Woese wrote in his paper.
Going against traditional thinking is not new to Woese, a recipient of the National Medal of Science (2000), and holder of the Stanley O. Ikenberry Endowed Chair at Illinois.
In the late 1970s Woese identified the Archaea, a group of microorganisms that thrive primarily in extremely harsh environments, as a separate life form from the planet’s two long-accepted lines – the typical bacteria and the eukaryotes (creatures like animals, plants, fungi and certain unicellular organisms, whose cells have a visible nucleus). His discovery eventually led to a revision of biology books around the world.
The three primary divisions of life now comprise the familiar bacteria and eukaryotes, along with the Archaea. Woese argues that these three life forms evolved separately but exchanged genes, which he refers to as inventions, along the way. He rejects the widely held notion that endosymbiosis (which led to chloroplasts and mitochondria) was the driving force in the evolution of the eukaryotic cell itself or that it was a determining factor in cellular evolution, because that approach assumes a beginning with fully evolved cells.
His theory follows years of analysis of the Archaea and a comparison with bacterial and eukaryote cell lines.
"The individual cell designs that evolved in this way are nevertheless fundamentally distinct, because the initial conditions in each case are somewhat different," Woese wrote in his introduction. "As a cell design becomes more complex and interconnected a critical point is reached where a more integrated cellular organization emerges, and vertically generated novelty can and does assume greater importance."
Woese calls this critical point in a cell’s evolutionary course the Darwinian Threshold, a time when a genealogical trail, or the origin of a species, begins. From this point forward, only relatively minor changes can occur in the evolution of the organization of a given type of cell.
To understand cellular evolution, one must go back beyond the Darwinian Threshold, Woese said.
His argument is built around evidence "from the three main cellular information processing systems" – translation, transcription and replication – and he suggests that cellular evolution progressed in that order, with translation leading the way.
The pivotal development in the evolution of modern protein-based cells, Woese said, was the invention of symbolic representation on the molecular level – that is, the capacity to "translate" nucleic acid sequence into amino acid sequence.
Human language is another example of the evolutionary potential of symbolic representation, he argues. "It has set Homo sapiens entirely apart from its (otherwise very close) primitive relatives, and it is bringing forth a new level of biological organization," Woese wrote.
The advent of translation, he said, caused various archaic nucleic-based entities to begin changing into proteinaceous ones, emerging as forerunners of modern cells as genes and other individual components were exchanged among them. The three modern types of cellular organization represent a mosaic of relationships: In some ways one pair of them will appear highly similar; in others a different pair will.
This, Woese said, is exactly what would be expected had they individually begun as distinct entities, but during their subsequent evolutions they had engaged in genetic cross-talk – they had indulged in a commerce of genes.
How so? This saves Darwinian hours of public time trying to answer the thesis that you can't expect random interactions to suddenly create a prokariote. The "whirlwind can't build a 747" argument.
Think about it. What is necessary for Darwinian evolution?
Well, there's such a thing as similarity by convergent evolution, where in different places or times similar forces sculpt initially dissimilar life forms to outwardly similar adaptations. The classic case is Australia and Tasmania, where marsupials radiated into ecological niches we find held elsewhere by placentals. Thus there were small marsupial predators (the Tasmanian Devil), large marsupial predators (the Thylacine), a marsupial "flying squirrel," etc.
While the similarities between, say, thylacine and timber wolf can be striking, the underlying unrelatedness is also there to see. More importantly, the unrelatedness only goes so far. They still have a common ancestor way back there in time.
The less commonality the original organisms have, the more improbable any parallelism becomes. For instance, I'd be surprised if any alien lifeforms that we ever encounter use DNA for replication. All the lifeforms of earth use it, but that's generally considered a historical accident and an artifact of common descent. There figure to be other possibilities.
Woese's theory--that the archaea, bacteria, and eukaryotes evolved separately--struck me as improbable in the same way and for the same reason. (There's also the problem that the fossil record for eukaryote life doesn't go back very far at all comparted to the other two.) But there's a major difference between the Woese scenario and my alien example. Woese's life forms would still presumably have evolved from the same "ancestral" soup.
The first molecule to form a suitable basis for self-replication triggered three "abiogenesis" events, if I understand Woese correctly. It's nowhere near as big of a deal as the same parallelism would be in the alien example, where you have to believe that a different soup on a different planet did exactly the same thing as on earth.
Nothing related to the beginnings of cellular life as we know it. Darwin was quite explicit about this. Darwinian evolution applies to the fossil record. What might has set it all off was beyond Darwinian ken, and he was quite careful to say so quite often, to avoid being embroiled in the abiogenesis debates.
Of course something way different, to which the Darwinian rules do not all apply, was going on before Prokariotes and Thermatoga made their debute. The only people surprised by this are the staunch proponents of the "whirlwind kind build a 747" argument as applied to Prokariotes.--who are, alas, mired hopelessly in last century's active debates on this subject.
No, I'm NOT pushing creationism (or anything else)! I'm taking this as yet another opportunity to laugh (out loud) at the folly of darwin who, just like environmentalist wackos do, based his wasted life on junk (false) "science"!!!!
I'd like to humbly suggest that you are still hung up on a sudden miracle that probably never did occur. Never bet long odds. There was probably a smooth transition from some radically alternative form of self-replication that was neither highly accurate, nor highly centralized, into RNA world. As has been suggested before--it is the energy conserving chemical cycles that have to start the show--and these could have formulated around such non-cellular locations as enduring paint pot bubble clusters, or smooth crystaline rock faces, to give some initial locality to beginnings of the process of enduring maintainence and replication.
All natural science is based on assumption and inference. If you think otherwise, I'd like to see your deductive proof of the theory of gravity.
Credit where credit is due. You and Nebullis had a discussion maybe a year and a half ago in which some ideas similar to Woese's got bandied about. Among other things, you mentioned that viruses might be linear descendants of the soup rather than evolved from cellulars as more commonly thought.
Nothing about Woese's work refutes Darwinian evolutionary theory. The title of this thread is misleading.
Yet the evolutionists want you to believe it happened.
It's funny on how the evolutionists can't even seem to agree how life began, yet creationists all have the same (correct) answer.
I believe I can jump into the middle of that discussion right here:
http://www.freerepublic.com/forum/a3a8ef634710e.htm#99
Using a reference of yours I saved. Woese was, in fact, the subject of this particular part of the discussion. I believe the virus quandary was pointed out earlier in the thread, but I'm a little vague about all this now.
No, it's not. And any "calculation" that suggests it is, which fails to overwhelmingly demonstrate why I must accept it's state-space and selection criteria to do the calculation, is puffed up nonsense masquerading as science.
Besides, I don't have to prove anything; after all, how many years (and years and years and years) has it been since Darwin died, and his assumption and inference STILL can't be shown to have any basis in fact?
Who needs to prove what to whom, here?!! How many folks over all this time have worked tirelessly, and failed miserably, in trying to prove Darwin correct? All of them!
I'm not trying to make anyone angry here, merely stating the facts!
Well, that is, of course, errant nonsense. Evolutionary biology's evidence is exactly like Evolutionary astronomy's evidence. Induction on a tiny number of samples. Kindly show me all the examples of stellar evolution in action that we have observed. Kindly show me the examples of gravity in action in the vacuum between, say Milky Way and Andromeda? How do you know God doesn't specially re-create gravity over and over only in specific localities near galactic formations?
Or, possibly, you are not trying to state facts, just make anyone angry. The evidence for evolution is palpable, and can be located in any sedementary rock face, or natural history museum in the world. If you have grief with that evidence, than state it, but don't be representing a natural science as something it is not.
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