Wall-dog wrote:
The Cambrian explosion produced fully developed phyla, as evidenced by Doctor Wells:
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Darwin knew the fossil record failed to support his tree [of life]. He acknowledged that major groups of animals - he called them divisions, now they're called phyla - appear suddenly in the fossil record.... His theory predicts a long history of gradual divergence from a common ancestor, with the differences slowly becomming bigger and bigger until you get to the major differences we have now. The fossil evidence, even in his day, showed the opposite: the rapid appearance of phylum-level differences in what's called the 'Cambrian explosion.' Darwin believed that future fossil discoveries would vindicate his theory - but that hasn't happened. Actually, fossil discoveries over the last hundred and fifty years have turned his tree upside down by showing the Cambrian explosion was even more abrupt and extensive than scientists once thought.... This is absolutely contrary to Darwin's Tree of Life. These animals, which are so fundamentally different in their body plans, appear fully developed, all of a sudden, in what paleontologists have called the single most spectacular phenomenon of the fossil record.
I'll grant you that the Cambrian doesn't bring out the species we see today, but it did bring out far more than worms.
http://www.ucmp.berkeley.edu/cambrian/camblife.html
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Almost every metazoan phylum with hard parts, and many that lack hard parts, made its first appearance in the Cambrian. The only modern phylum with an adequate fossil record to appear after the Cambrian was the phylum Bryozoa, which is not known before the early Ordovician. A few mineralized animal fossils, including sponge spicules and probable worm tubes, are known from the Vendian period immediately preceding the Cambrian. Some of the odd fossils of the "Ediacara biota" from the Vendian may also have been animals in or near living phyla, although this remains a somewhat controversial topic. However, the Cambrian was nonetheless a time of great evolutionary innovation, with many major groups of organisms appearing within a span of only forty million years. Trace fossils made by animals also show increased diversity in Cambrian rocks, showing that the animals of the Cambrian were developing new ecological niches and strategies -- such as active hunting, burrowing deeply into sediment, and making complex branching burrows.
The Berkeley article I just quoted tries to call the Cambrian period evolutionary, but as Dr. Wells illustrated, that just isn't the case. These were not worm-like creatures. They were fully formed phyla.
Dr. Wells:
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Imagine yourself on the goal line of a football field. That line represents the first fossil, a microscopic, single-celled organism. Now start marching down the field. You pass the twenty-yard line, the forty-yard line, you pass mid field, and you're approaching the other goal line. All you've seen this entire time are these microscopic, single-celled organisms.
You come to the sixteen-yard line on the far end of the field and now you see these sponges and maybe some jellyfish and worms. Then - boom! - in the space of a single stride, all these other forms of animals suddenly appear. As one evolutionary scientist said, the major animal groups 'appear in the fossil record as Athena did from the head of Zeus - full blown and raring to go.'
Now, nobody can call that a branching tree! Some paleontoligists, even though they my think Darwin's overall theory is correct, call it a lawn rather than a tree, because you have these separate blades of grass sprouting up. One paleontologist in China says it actually stands Darwin's tree on its head, because the major groups of animals - instead of coming last, at the top of the tree - come first, when animals make their first appearance.
Either way, the result is the same: the Cambrian explosion has uprooted Darwin's tree.
An image of evolution that does fit the fossil record would be one of a guided micro-evolutionary model, where a designer created the major phyla and used evolution as a tool to forward species. That model however utilizes intelligence and the theory of evolution clearly calls for an unintelligent system.
As for the molecular evidence you use to try to show a common ancestor prior to the Cambrian, Dr. Wells discusses this as well:
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You can't get molecular evidence from the fossils themselves; all of it comes from living organisms. You take a molecule that's basic to life - say ribosomal RNA - and you examine it in a starfish, and then you study its equivalent in a snale, a worm, and a frog. You're looking for similarities. If you compare this one molecule across different categories of animal body plans and find similarities, and if you make the assumption that they came from a common ancestor, then you can construct a theoretical evolutionary tree.
But there are too many problems with this. If you compare this molecular tree with a tree based on anatomy, you get a different tree. You can examine another molecule and come up with another tree altogether. In fact, if you give one molecule to two different laboratories, you can get two different trees. There's no consistency, including with the dating. It's all over the board. Based on this, I think it's reasonable for me, as a scientist, to say that maybe we should question our assumption that this common ancestor exists.
Of course, descent from a common ancestor is true at some levels. Nobody denies that. For example, we can trace generations of fruit flies to a common ancestor. Within a single species, common ancestry has been observed directly. And it's possible that all cats - tigers, lions, and so on - descended from a common ancestor. While that's not a fact, it might be a reasonable inference based on interbreeding.
So as we go up these different levels in the taxonomic hierarchy - species, genus, family, order, class - common ancestory is certainly true at the species level, but is it true at higher levels? It becomes an increasingly uncertain inference the higher we go in the taxonomic hierarchy. When you get to the phyla, the major animal groups, it's a very, very shaky hypothesis. In fact, I would say it's disconfirmed. The evidence just doesn't support it.
He was talking about the red letters you posted earlier...
I agree with you that creatures with a common ancestor would likely follow similar developmental routes, but when you look at different embryos of different species you don't see that. The embryos you see compared are not early-stage embryos but rather embryos in the middle of their developmental stages. Earlier on they don't look similar at all.
Wells:
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Remember Darwin claimed that because the embrios are most similar in their early stages, this is evidence of common ancestry. He thought that the early stage showed what the common ancestor looked like - sort of like a fish.
But embryologists talk about the 'developmental hourglass,' which refers to the shape of an hourglass, with its width representing the measure of difference. You see, vertebrate embryos start out looking very different in the early cell division stages. The cell divisions in a mammal, for example, are radically different from those in any of the other classes. There's no possible way you could mix them up. In fact, it's extremely different within classes. The patterns are all over the place.
Then at the midpoint - which is what Haeckel claimed in his drawings was the early stage - the embryos become more similar though nowhere near as much as Haeckel claimed. Then they become very different again.
The use of molecular evidence is back-peddling too. Also from Wells:
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As I said, it's just false that embryos are most similar in their earliest development. Of course, some Darwinists try to get around Haeckel's problems by changing their tune. They use evolutionary theory to try to explain why the differences in the embryos are there. They can get quite elaborate.
But that's doing the same thing that the theory-savers were doing with the Cambrian explosion. What was supposed to be primary evidence for Darwin's theory - the fossil or embryo evidence - turns out to be false, so they immediately say, well, we know the theory's true, so let's use the theory to explain why the evidence doesn't fit.
But then, where's the evidence for the theory? That's what I'd like to know. Why should I accept the theory as being true at all?
Similarities in design are often used as 'evidence' for evolution, including in your posts. Sadly though similarities prove nothing. Wells:
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The explanation can go either way: design or descent with modification.
And:
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Actually, these homologies were described by Darwin's predecessors - and they were not evolutionists. Richard Owen, who was the most famous anatomist of Darwin's time, said they pointed to a common archetype or design, not toward descent with modification.
More on common developmental pathways and similar genes (from Wells):
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One is called 'common developmental pathways,' which means if you have two different animals with homologous features and you trace them back to the embryo, they would come from similar cells and processes. This happens to be mostly untrue.
I mentioned frogs earlier. There are some frogs that develop like frogs and other frogs that develop like birds, but they all look pretty much the same when they come out the other end. They're frogs. So the developmental pathway explanation is false - I don't think anybody who studies development and takes it seriously.
A more common explanation nowadays is that homologies come from similar genes. In other words, the reason two features are homologous in two different animals would be that they're programmed by similar genes in the embryo. But it turns out this doesn't work very well either. We know some cases where you have similar features that come from different genes, but we have lots and lots of cases where we have similar genes that give rise to very different features.
My favorite Wells illustration about the folly of genetic similarities as proof of evolution comes when he is asked about Mankind sharing 98 or 99% of our genes with apes:
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If you assume, as neo-Darwinism does, that we are products of our genes, then you're saying that the dramatic differences between us and chimpanzees are due to two percent of our genes. The problem is that the so-called body-building genes are in the ninety-eight percent. The two percent of genes that are different are really rather trivial genes that have little to do with anatomy. So the supposed similarity of human and chimpanzee DNA is a problem for neo-Darwinism right there.
The biggest problem with the theory of evolution though is in the fossil record. Fossils, while problematic for usage in proving theories, are never-the-less useful to disprove theories. Theories should at least be verified as plausible within the fossil record. Dr. Michael Denton, in his book 'Evolution: A Theory in Crisis,' illustrates the fossil record's debunking of evolution:
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The univeral experience of palentology... [is that] while the rocks have continually yielded new and exciting and even bizarre forms of life...what they have never yielded is any of Darwin's myriads of transitional forms. Despite the tremendous increase in geological activity in every corner of the globe and despite the discovery of many strange and hitherto unknown forms, the infinitude of connecting links has still not been discovered and the fossil record is about as discontinuous as it was when Darwin was writing the Origin. The intermediates have remained as elusive as ever and their absence remains, a century later, one of the most striking characteristics of the fossil record.
Denton concludes that the fossil record "provides a tremendous challenge to the notion of organic evolution."
