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.
If they were truly 3 unrelated origins, they would have had 3 different forms of basic triplet coding, each to a differing set of Amino acids. If, in fact, they even used the same fundamental DNA paradigm. Truly independent evolution would mean they could'nt usefully eat each other--clearly not the case.
As to being evidence for ID, even if this were as you stated, it is no more compelling evidence for ID than than for some other form of earthbased abiogensis we haven't thought of yet. Your threshold of evidence is set way too low to bust the current paradigm. If ID wants attention, ID better predict some positive event other than that evolutionary theory will fail to be perfect--being a natural science, that's a given. Pointing to unfilled knowledge holes in the current paradigm is the easy half of the battle--no evidence of the hard half being fought has yet come to my attention. Please use ID theory to predict some major positive material event that comes to pass, such as green aliens landing to harvest what they planted 4 billion years ago, then ID will get everyone's respectful attention.
I also predict that life does not necessarily have one common biological ancestor. Since it is not dependent on natural processes working through chance there is no limit on the number of 'first cells from non-cells'. If it were by natural processes the first cell seems a miracle. What are the odds of at least three miracles happening (in geologic terms) almost at once?
Are those ID-supporting predictions fair enough?
Not neccesarily. This was VR's point as well. It depends entirely on the constraints present for abiogenesis. For example, was there a physical reason for homochirality or was it a flip of the coin? If several forms of transcriptional molecular aggregates popped up several places on earth, I would be hard-pressed to call them related. Their only relationship would be a common set of conditions. This smacks of too much of Gaia for my tastes.
While disagreeing that leaving fossils has anything to do with evolution, including the Darwinian kind, I cannot provide that proof by definition. I would like to represent the Darwinians in this argument and concede that you have put the nail in Chuckie's theory, but I know the real acolytes will not allow me to do that. I was acting as a messenger in relaying that requirement.
Offhand I would reject the idea of a commune of molecules dedicated to mutual survival in an energetic environment, but the idea seems interesting. The reason I have the immediate doubt is that heat tends to destroy structure instead of building it. And yes, I know of the cells formed in heated liquids, but they disappear when the heat is removed.
One of these days I'll proofread before posting.
I suppose His proofs are everywhere for people so inclined, but you're reaching.
Its not a slam dunk, but it shows the facts are consistent with what would be expeceted if a common designer (interchangable parts) made several types of cells.
In Woese's idea, there's still a common ancestor of a sort; it just isn't a single, self-contained organism. It's the "RNA world." Search on it, read for five minues, and know as much as I do.
Curt.
So I take it you WILL NOT concede that the sudden, near simultaneous appearence of at least three types of cells from apparently different non-living to living events is a mark in favor of ID? If creating cells from non-living tissue were as easy as this, why has no one done it in the lab and clamied that Noble Prize? From everything we know now, and we know quite a bit, the appearence of even ONE cell from non-living material is a miracle we are unable to replicate. Now we have evidence that it happened at least three times. Presumably,those three filled the Earth in a hurry, given evolutionary assumptions, else we might have 33 types of cells, not three. If it is so easy, WHY HAVEN'T WE DONE IT. Evolution has no answer, ID does.
Eukaryotes appear 1.2 billion years ago. Against that, isotopic signatures of some kind of life appear about 3.8 billion years ago. "Near simultaneous?"
If it (making a cell) is so easy, WHY HAVEN'T WE DONE IT. Evolution has no answer, ID does.
By natural, unguided, parallel-experiment processes, it may take from a quarter to half a billion years. Have these conditions been met since the first experiments in 1953?
Having an answer for everything isn't science, especially if there's no reason to think the answer is right.
That is just the oldest fossil evidence we can find for them. The position of this article is that they, in some form, appeared at the same time as the other two types, and that perhaps there were even more types that did not survive until the present day. If so, the non-living to living cell transition occured somehow (either naturalistically or with the help of intelligence) at least three times in a very narrow time frame.
Against that, isotopic signatures of some kind of life appear about 3.8 billion years ago. "Near simultaneous?"
About 3.86 billion years ago, give or take a couple of hundreths places, is my information. At that time there was A LOT more debris floating around the solar system. Earth got walloped by impacts that made the tiny speck that extincted the dinos look like nothing by comparison. These impacts generated heat that raised temperatures planet-wide to the crustal melting point. I wish I had the RealPlayer file on this. Maybe I can find it. This is why the oldest Earth rocks found date to that time and no older. When is that time? 3.85 million years ago, give or take a couple of hundreths place.
You will note that the first date overlaps the second. Neglecting the error bars, the time for the first trace of life comes BEFORE the last TOTAL EXTINCTION EVENT which melted Earth's crust. With the error bars stretched to the limit those two events happen on top of each other. That is not the "quarter billion years" that you say is needed to go from soup to cell. That is a maximum of 10 million years.
If natural processes can make at least three types of cells from soup in a maximum of 10 million years then scientists should have been able to show how it was done. Indeed, we should be catching nature in the middle of doing it all the time, as we "catch" nature in the various phases of stellar evolution. Every time a nutrient rich environment is sterelized the mythical "RNA World" should start self-assembling. The fact is we don't see that. Naturalism has no rational explanation, even though we now know enough that one could reasonable expect any such explanation to be well known.
Are you willing to concede that the sudden, near simultanious appearance of more than one kind of cell is, to some degree, evidence favorable to the ID hypothesis?
Apparently not. And the real point of Woese's argument, a point donh earlier chided me for missing, is that Woese's theory does not have instantaneous abiogenesis moments. The RNA world is acting like a long-lived, slow evolving common ancestor in Woese's scenario, and there was some shadowy something-else evolving before that.
You're doing the creationist hand-wave on Woese's RNA world, while retaining Woese's idea that archea, bacteria, and eukaryotes are siblings. Then you go "Tah-dah!"
Cheap trick. Is Woese credible? You're throwing away the first half of his story, then announcing the second half appears from nowhere.
Read the first paragraph of the main article. Try not to just see what you want.
Just as Newton's version of gravitational theory only applies to the appallingly slow and small, Darwin's version of evolutionary theory only applies to the appallingly cold and energy-starved.
Hmm. Than I presume you think the best temperature environment for evolution to take place in is absolute zero. Every sustained mean temperature regime the earth passes through is going to face life, or life-like entities, with distinctly different opportunities for structuring toward optimum survival.
It's not so mind boggling as you seem to want to make it--if the "life" I am proposing is pre-cellular, than why should it give a rat's ass if cells dissolve "too easily"? Maybe that's a feature, not a problem, for pre-cellular co-operating communities of RNA. The fact that mRNA, with it's curious short lifetimes became the lynchpin of DNA reproduction might have to do with utilizing evanescent cells as temporary factory floors for building temporary RNA machinery.
There are lots of viable amino acids hanging around that we don't employ in our DNA-RNA-protein paradigm, & an effectively infinite number of long-chain molecules to be built from them to experiment with--AND, questions of efficiency or compactness have been amply demonstrated, at least to my satisfaction at this point, not to have been necessarily the selecting criteria. The chirality argument gets better press than it deserves. Other chirality-compatible sets can be constructed, and it's not obvious why nature would prefer one to another. So far, there is no dragonslayer argument that has come to my attention saying our current fundamental design was in any way compelling.
I think we neglected our duty in not mentioned to you the second restraint of an ID test, aside from prediction. ID must be a far better explanation of whatever phenomena it proports to explain than a corresponding natural phenomena that might be possible-to-likely in the evolutionary paradigm, but, like the little green men of ID, has yet to be observed in the flesh.
hmmph. It's not even as efficient as 3-redundant Hemming code. It double-books several of the triplets for the exact same amino acid, and there are only a few scattered instances of re-entering a genome chain at just one or two removes from the initial starting point to give a different, but equally useful protein. It is, to a compaction geek, a very sparse information-packing design. I could do better, and I'm a fair remove from having Godly powers.
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