NonHomogenized

I was arguing with a creationist (as per usual), and I had a point I have not dealt with before brought up. The issue was the appearance of all major phenotypes during the 'precambrian explosion'. He continued by mentioning the unlikelihood of this happening.
Now, I know that this casts no doubt on evolution (indeed, I thought he seemed a little suprised when I gave examples of evolution AND speciation, and was able to explain away "irreducible complexity", not to mention give him some decent info on abiogenesis (and how it's not part of evolution). ), and we can simply say "we don't yet know". Furthermore, I am aware of how flawed the creationist arguments from improbability usually are.
That being said, during the conversation, I was unable to find any good resources which gave a workable explanation for the 'precambrian explosion', from an evolutionary standpoint.

Can anyone give me some readings so I'll be able to converse knowledgably on the subject, if it comes up again?

Fedmahn Kassad

The explanation I have usually seen put forth is that this was about the time organisms began to develop hard body parts which would be easier to fossilize.

But ask him this: If this Cambrian explosion is supposed to represent "The Creation", ask him why there are no fish is Cambrian deposits. (Actually, I may have seen some references to 1 primitive fish fossil found there). Certainly there are no modern fish, no birds, no reptiles, mammals, humans, etc. Ask him how this can be if this represents the Creation.

FK

Valentine Pontifex

NO phenotypes? The only way that could be true is if there was no such thing as mutation since the precambrian.

It is the Cambrian explosion, not the Precambrian explosion.

You might point out that in the Cambrian when this "explosion" occured there were no birds, no mammals, no reptiles, no amphibians, no bony fish, no flowers, no trees, no grass, and no insects. All of these appeared after the Cambrian.

pz

Gould's Wonderful Life, despite the fact that it has some flaws and obsolete information, is at least a nice, readable introduction to the concepts.

Conway Morris's Crucible of Creation is a bit more current, but is terribly written (Conway Morris truly has a lead ear when it comes to the language), and he definitely has a bug up his ass about Gould, but that makes it a good counterbalance to Wonderful Life.

I've been hearing good things about McMenamin & McMenamin's Emergence of Animals, but I haven't read it yet --although it's on my list of summer reading. What I've seen of it looks like it might be exactly what you need, a summary of major hypotheses explaining the Cambrian.

There's also some good evo-devo stuff on this subject. Raff & Arthur & Davidson might be a bit much to digest as a first stab at figuring it out, though.

One thing I noticed in your first paragraph: the claim that "all major phenotypes" arose in the Cambrian is simply false. The roots of the major animal phyla appeared in the Cambrian, but their actual origin was much, much earlier for many of them. The interesting thing about the Cambrian is that there was a near-simultaneous (at least, as near simultaneous as a difference of millions of years can be) diversification of many animal lineages into the 'big, with hard parts, and relatively easily fossilized' niche.

NonHomogenized

PZ, thanks for the recommended readings. I'll read them as soon as I can get ahold of copies. Hopefully, they'll cover the info I'll need. If you (or anyone else) can think of more, I'll be happy to add them to my rather extensive list of future reading material.

Joe Meert

JM: The M&M book is not that great. I've read both of the books and found them to be mainly "Me and My Big Ideas" type books. One other question you might ask your creationist friend is for an explanation of the Cambrian explosion from their perspective. It surely cannot indicate sudden creation as the organisms that are fossilized were killed. If it marks the onset of the flood, then why so many paleosol horizons in the Lower Paleozoic?

Cheers

Joe Meert

Secular Pinoy

The book, The Crucible of Creation, might be what you want.

Oolon Colluphid

The ‘explosion’, as has been noted, was Cambrian, not Precambrian. But if it is when the ‘creation’ happened, it’s odd that there’s plenty of Precambrian fossils. The words to Google for are Ediacaran, Vendian, or simply Precambrian, and try here for starters. The earliest microfossils pre-date the Cambrian by rather a lot.

[Edited: this is useful too: www.ucmp.berkeley.edu/vendian/critters.html ]

Cheers, Oolon

ps418

I cringe whenever I hear the word "explosion" used to refer to the emergence of animal phyla.

Wrong! Phenotypes and phyla are not at all the same thing, and in any event it is incorrect that all phyla or all 'major phenotypes' appear during the early Cambrian.

Patrick

Oolon Colluphid

Yup, that’s a useful point in general. Ask your pet creationist why there’s no angiosperm pollen found before the late Jurassic -- that’s about 350 million years after the Cambrian ended. After that, pollen is bloody everywhere. And yet according to Genesis 1:11-13, flowering plants were created on the third day, ie even before watery critters on the fifth day (Gen 1:20).

So in the Cambrian (and Precambrian), we have “abundantly the moving creature[s] that hath life”. So it’s the fifth day. But not a smidge of pollen till (apparently) hundreds of millions of years afterwards. Not as scripture would suggest, before Cambrian fossils; not even with them. Nope, a lot, lot later. You won't even find pollen alongside Dimetrodon or Procynosuchus, and there's little chance of it with Diplodocus, Stegosaurus or Allosaurus. (Won't say 'no chance', since while pollen becomes ubiquitous in the Cretaceous, there have been traces in the late Jurassic.)

With the Burgess shale, we have a wonderfully fine-grained stone, so fine-grained that even critters’ soft bits have been preserved. But where are the Burgess angiosperm leaves? Where are the bat fossils, so equally wonderfully preserved in the Messel Shale? Where’s the cartilaginous fishes, the bony fishes, the crabs, the Great Whales™ ?

If the Cambrian was the point of creation, all I can say is that there was a bugger of a lot of evolution after it.

Cheers, Oolon