Charles Darwin saw Cambrian explosion as one of the main objections that could be made against his theory of evolution by natural selection.
That's because the oldest fossils Charles Darwin knew were trilobites.
That was before The Burgess Shale was discovered by palaeontologist Charles Walcott in 1909. Although it was not until the time of Stephen Jay Goulds that Darwins theory was in the most trouble. So Gould came up with the theory of punctuated equilibrium to keep Darwins theory of slow gradual change over long periods of time from going down the tube.
Gould (and Niles Eldredge, let's not forget his co-author!) came up with PE to reconcile evolutionary theory with fossil evidence. PE isn't really anti-Darwinian, whatever Gould himself might want to believe. Darwin never said that all evolutionary change must proceed at the same rate - and also, the appearance of abrupt change is partly because of
migration, not simply sudden evolutionary events. The basic idea is that new species often form in small, isolated populations that evolve rapidly but aren't likely to leave fossils. Thus, we only get to see the new form if/when it spreads and replaces the parent species.
Again,
here is a good breakdown of what PE really says.
Talk about changing the rules and moving the goal post. Clearly they make this stuff up as they go along and I think they get more of it in their creative writting class then anywhere else. All ranting aside, the bottom line is if you want to make or break Darwins theory the Cambrian Explosion is where all the action is. "Evolution" tends to take the same proteins and put them together in the same way in many different species that do NOT have a common ancestor.
Wut?
This has got to be difficult for a theory of common decent to explain. I could go on but I have already started about five discussions here already.
Common de
Scent. I think I've corrected your spelling a few times before...
Creationists have an answer for you. God created them. As far as extinction Gould's theory is that Evolution is VERY random. According to Gould if you started all over again all the species would come out VERY different, even if conditions were identical.
Chaotic is probably a better word than random. Gould was big on the idea of
contingency, that is, coincidences of history determining the future. These aren't necessarily random - they are just unpredictable and unlikely to occur the same way twice.
There is another theory. That elements can only be assembled one way. So anywhere you go in the universe life is going to be pretty much the same as what we find here. This is supported by the fact that you have many proteins assemble in identical ways despite the fact that there is no common ancestor.
Hey hey hey, what "no common ancestor"? I think you are going to need some backing for such a radical claim.
As far as extinct Science has pretty well determined that conditions change so that they can no longer support the existing life and it then goes extinct.
What?
The Cambrian explosion does not falsify evolution, because there are fossils from before this rapid speciation event - and these earlier fossils are, suprise suprsise, simpler forms of life such as stromatolites and impressions of jellyfish.
Are any of the Ediacaran fossils convincingly from jellyfish?
I have a vague recollection that most of the Precambrian "jellyfish" fossils are more likely to be holdfasts of
Charnia type creatures. Not that those couldn't be
cnidarian, but I think the
oldest relatively secure actual
jellyfish is
Cambrian.
Also, sponges. Earlest branching living phylum of animals, one of the simplest animal body plans, and...
possibly the earliest fossil appearance?
Clearly there was life before the Cambrian, it just so happens that - for a variety of reasons, there was over a period of around 20 million years (hardly an explosion on any other timescale than geological) where life rapidly evolved into differing forms..
It's also worth nothing that it almost definitely had a "fuse" much longer than 20 million years. Both
molecular clock methods (which I somewhat mistrust) and Ediacaran fossils that can be classified into major subgroups of animals provide strong evidence that the main lineages that "exploded" in the Cambrian had started diverging way before that. (I think
Kimberella is the best-evidenced one, at least lophotrochozoan and probably stem mollusc.
And holy cow, I just found this paper and I'm totally downloading it. Mineralised sclerites??? [bless and do not curse][bless and do not curse][bless and do not curse] why didn't I know about this??? *cough* Got a bit carried away there...)
Punctuated Equilibriam is a description of the evidence, it would appear that there were times of stability and times of rapid change in earth's history. When looked at with geological upheaval, this is not suprising.
Continents move, climates change and natural disasters wipe out many forms of life in the blink of an eye (again in geological time).
Incidentally, I'm fairly sure that
Origin discusses some remarkably PE-like ideas. I know I was very surprised upon reading it, because I'd been "trained" to view Darwinism and PE as contradictory.
Most famously, the extinction event near the end of the K-T boundarty shown the demise of some rather famous large lizards...
I
hope you mean
mosasaurs. At least they really were large lizards. Non-avian dinosaurs...
definitely not lizards, and far from universally large.
I also would like you to back up your last statement with some evidence, as I am not aware of exactly the same proteins being found in unrelated forms of life. Perhaps you could enlighten us on this.
If
Doug Theobald can be believed, there is no such thing as "unrelated forms of life", anyway.
Yes but what you do not have is a record of common ancestors needed to show that something evolved. So the end result is still the same of something from nothing.
I don't think most people are aware how well-documented the origin of some major groups is. I'm an animal person, so I can give you examples from animals. Arthropods are probably the best case - the Cambrian is home to a whole range of creatures that range from essentially worms with legs, much like water bears and velvet worms today (e.g.
Aysheaia and other "lobopods"), through creatures with obviously jointed bodies and limbs (e.g. anomalocaridids), and a wide variety of definitive arthropods that are various distances away from living or better-known extinct groups (such as
these trilobite relatives). Echinoderms are another rich one, though I think people can't quite agree whether creatures like
helicoplacoids actually represent ancestral conditions or secondary modifications of the "classical" echinoderm body plan. Brachiopods and their possible
tommotiid ancestors also come to mind. And then there are molluscs, with
Kimberella appearing bang in the middle of the Ediacaran.
At least nothing you have a record of.
So... yeah, that's kind of dead wrong.
So this continues to be the biggest challange evolutions have to deal with. They keep saying that this is a result of that but they never produce the common ancestor that life was suppose to have evolved from.
Please tell me how you would go about finding
and identifying the remains of the universal common ancestor. The last universal common ancestor was just a simple (proto)cell without any special features, and its fossils, if preserved by some astronomically immense stroke of luck, would probably have nothing other than their age to suggest their significance. The evidence for universal common ancestry lies in molecular biology, not fossils. (Hello,
near-universal not-quite-optimal genetic code!)