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Did MicroRNAs Shape the Cambrian Explosion?

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The fossil record reveals a history of life characterized by the abrupt appearance of new species followed by no change and eventual extinction in most cases. Needless to say, abrupt appearances and no change is not exactly what evolution expected. Much of this was known in Darwin’s time and he figured that the fossil record was incomplete. Today such speculation doesn’t work anymore. The evidence reveals even more clearly this pattern of abrupt appearances followed by stasis. As one recent paper explained:   Read more

"CannuckianYankee" (#5) asked: "Have you read Dr. Meyer’s book yet? Not yet, but it's in the queue. I went to my local Barnes & Noble in which "Signature" was out of stock - but they had a Harry Turtledove novel I hadn't read, so I bought it and started reading it. Then I went to a different Barnes & Noble and bought "Signature." But then Dan Brown's new book comes out today, so I might not get to "Signature" for a while. PaulBurnett
PaulBurnett, "In actuality it took place over tens of millions of years, possibly as much as a hundred million years. The Cambrian “Explosion” was not the “Biological Big Bang” that some folks make it out to be." Yes, Mr. Burnett, but in geologic time, it is a rather short time period for all that diversity and complexity to appear (according to the fossil record). Thus, 'explosion' seems appropriate. Darwinian processes appear (at first glance) to require much longer time periods, and that's why it's such a 'conundrum.' It's pretty significant, since before that time, and up to 600 million years ago, all that seems to have existed were single-celled prokaryotic organisms,(bacteria, plankton and algae). Then in a period of just 45 million years (not 100 million - according to Simon Cconway Morris)...., http://www.pnas.org/content/97/9/4426.full ...all those complex multi-celled organisms arose, and then eventually died out. And as Dr. Hunter pointed out "abrupt appearances and no change is not exactly what evolution expected." Have you read Dr. Meyer's book yet? I find it interesting that the Cambrian 'conundrum' was known in Darwin's time, and is yet to be satisfactorily resolved. I think the speculation involving RNA and development is way off track. If they are really interested in resolving the Cambrian issue, biologists would do well to leave all Darwinian speculation behind, and consider the requirements for the origin of life (not merely development), as Meyer discusses in his book, and as Joseph mentioned in #2. I also find it significant that (as it appears), ID people are the few that are looking into the probability problems with chance and necessity as far as the development of the first cellular organism is concerned. This to me seems to be a fundamental OOL question. Dr. Meyer states (pg 201) "There is a second reason for doubting the chance hypothesis as an explanation for the origin of biological information. Building a living cell not only requires specified information, it requires a vast amount of it.......It turns out that it was initially hard to quantify the answer to this question (how small the probability of the information arising by chance), because biologists didn't know exactly how much information was necessary to build and maintian the simplest living cell." 'Signature in the Cell' (parenthesis mine) It is significant that the ID people are the ones asking these questions, when they should have been asked long ago. Instead, what we seem to get are speculations founded on the 'fact' of Darwinian evolution - the absolute wrong direction, given the evidence at our disposal. BTW, Dr. Meyer's paper (the one that got 'expelled' from the science literature) was a treatise into the Cambrian explosion, and why it poses a problem for Darwinian evolution. It's not an issue of his not having a scientific argument, it's an issue of his daring to look where others are not looking. So is the issue in minimizing the Darwinian significance of the Cambrian explosion (as you appear to be doing), in order to continue with the speculation? Would it not rather be more prudent to look in another direction, when no satisfactory answer has been found for 150 years? CannuckianYankee
Words like "explosion" and "abrupt" lead many to assume the "Cambrian Explosion" was an instantaneous event. In actuality it took place over tens of millions of years, possibly as much as a hundred million years. The Cambrian "Explosion" was not the "Biological Big Bang" that some folks make it out to be. PaulBurnett
I am often a reader but only rarely a poster here at UD, mindful of the old saw, "Better to keep your mouth shut and be thought a fool, than open it and remove all doubt." I open it now, with the below hypothetical concerning the fossil record, because the question keeps rattling around between my ears, appearing to make sense. So, just in case any of the fine folks here care to comment one way or another, here goes: We look at the fossil record, and we assume that it is a record of life on earth. But what it actually is, is a record of is death on earth. Of course, for something to die it has to be alive first. But even though life on earth, as we know it today, all dies, that does not mean -- philosophically or any other way -- that for life to exist, there has to be death. So here come the question: What if of the fossils in the geologic column were a record, not of the rise of life, but of the rise of death? Progressing from "lower" organisms to "higher"? Pretty far out, I know. And it would be a difficult, although perhaps not impossible, hypothesis to pursue. (For one thing, it might better rationalize the "sudden appearance" problem.) jstanley01
DNA and RNA may influence development but that is not the question. Influencing something is not the same as determining it. The question is "What determines form?" What makes a fly a fly? In his book (English title) “Why is a Fly not a Horse?”, the prominent Italian geneticist Giuseppe Sermonti, tells us the following : Chapter IV “Why is a Fly not a horse?” (same as the book’s title)
”The scientist enjoys a privilege denied the theologian. To any question, even one central to his theories, he may reply “I’m sorry but I do not know.” This is the only honest answer to the question posed by the title of this chapter. We are fully aware of what makes a flower red rather than white, what it is that prevents a dwarf from growing taller, or what goes wrong in a paraplegic or a thalassemic. But the mystery of species eludes us, and we have made no progress beyond what we already have long known, namely, that a kitty is born because its mother was a she-cat that mated with a tom, and that a fly emerges as a fly larva from a fly egg.”
Cornelius, Thanks for the post. After reading the abstract below, is seems to me that "big words hide the fact that there is no content to the proposal" may be a bit generous. "One of the most interesting challenges facing paleobiologists is explaining the Cambrian explosion, the dramatic appearance of most metazoan animal phyla in the Early Cambrian, and the subsequent stability of these body plans over the ensuing 530 million years. We propose that because phenotypic variation decreases through geologic time, because microRNAs (miRNAs) increase genic precision, by turning an imprecise number of mRNA transcripts into a more precise number of protein molecules, and because miRNAs are continuously being added to metazoan genomes through geologic time, miRNAs might be instrumental in the canalization of development. Further, miRNAs ultimately allow for natural selection to elaborate morphological complexity, because by reducing gene expression variability, miRNAs increase heritability, allowing selection to change characters more effectively. Hence, miRNAs might play an important role in shaping metazoan macroevolution, and might be part of the solution to the Cambrian conundrum." Granville Sewell

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