Joined: Sep. 2007
|Quote (Alan Fox @ Sep. 23 2007,06:40)|
|We are very lucky to have fossils at all. After an animal dies many conditions have to be met if it is to become a fossil, and one or other of those conditions usually is not met. Personally, I would consider it an honor to be fossilized but I don't have much hope of it. If all the creatures which had ever lived had in fact been fossilized we would be wading knee deep in fossils. The world would be filled with fossils. Perhaps it is just as well that it hasn't happened that way.|
Because it is particularly difficult for an animal without a hard skeleton to be fossilized, most of the fossils we find are of animals with hard skeletons - vertebrates with bones, mollusks with their shells, arthropods with their external skeleton. If the ancestors of these were all soft and then same offspring evolved a hard skeleton, the only fossilized animals would be those more recent varieties. Therefore, we expect fossils to appear suddenly in the geologic record and that's one reason groups of animals suddenly appear in the Cambrian Explosion.
There are rare instances in which the soft parts of animals are preserved as fossils. One case is the famous Burgess Shale which is one of the best beds from the Cambrian Era (between 500 million and 600 million years ago) mentioned in this quotation. What must have happened is that the ancestors of these creatures were evolving by the ordinary slow processes of evolution, but they were evolving before the Cambrian when fossilizing conditions were not very good and many of them did not have skeletons anyway. It is probably genuinely true that in the Cambrian there was a very rapid flowering of multicellular life and this may have been when a large number of the great animal phyla did evolve. If they did, their essential divergence during a period of about 10 million years is very fast. However, bearing in mind the Stebbins calculation and the Nilsson calculation, it is actually not all that fast. There is some recent evidence from molecular comparisons among modern animals which suggests that there may not have been a Cambrian explosion at all, anyway. Modern phyla may well have their most recent common ancestors way back in the Precambrian.
As I said, we're actually lucky to have fossils at all. In any case, it is misleading to think that fossils are the most important evidence for evolution. Even if there were not a single fossil anywhere in the earth, the evidence for evolution would still be utterly overwhelming.* We would be in the position of a detective who comes upon a crime after the fact. You can't see the crime being committed because it has already happened. But there is evidence lying all around. To pursue any case, most detectives and most courts of law are happy with 2-3 clues that point in the right direction.
Of course I am not surprised at all that Dawkins would minimize the importance of the fossil record. Surely if it teemed with evidence for his theory, he would feel differently about it.
I am a bit surprised that he thinks the theory of evolution via RM+NS is essentially beyond reproach. I read through his lecture (which I mistakenly referred to as a book earlier) and I looked for this "utterly overwhelming" evidence he speaks of, but did not find it.
From the same lecture:
|These are all domestic dogs (Slide 1) except the top one which is a wolf. The point of it is, as observed by Darwin, how remarkable that we could go by human artificial selection from a wolf ancestor to all these breeds - a Great Dane, a Bulldog, a Whippet, etc. They were all produced by a process analogous to natural selection - artificial selection. Humans did the choosing whereas in natural selection, as you know, it is nature that does the choosing. Nature selects the ones that survive and are good at reproducing, to leave their genes behind. With artificial selection, humans do the choosing of which dogs should breed and with whom they should mate.|
These plants (Slide 2) are all members of the same species. They are all descended quite recently from the wild cabbage Brassica olearacea and they are very different cauliflower, brussels sprouts, kale, broccoli, etc. This great variety of vegetables, which look completely different, has been shaped - they have been sculpted - by the process of artificial selection from the same common ancestor.
The problem with Dawkins' logic here is that it doesn't match reality:
(As you and I have discussed before), artificial selection is not "analogous to natural selection", as Dawkins argues. Artificial selection only works by shielding organisms from natural selection.
Throw all domesticated dogs back into the wild and watch as all these breeds go away - to be replaced by mutt dogs which will gradually lose many of their unique, bred-for characteristics and more and more closely resemble the wolf from which they came.
The same goes for these cultivated plants. Throw them back into the wild and eventually they revert back to the original wild cabbage species - all the domesticated varieties would disappear.
These things can be verified in your own back yard.
"If we all worked on the assumption that what is accepted as true is really true, there would be little hope of advance." Orville Wright
"The presence or absence of a creative super-intelligence is unequivocally a scientific question." Richard Dawkins