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Monday, 5 September 2011

This is not a Knock-Down Argument against Darwinian Evolution

I am genuinely curious about this.

How does the neo-Darwinian synthesis account for the startling similarities between some marsupials and some placental mammals? There are pairs of animals – in each case with one in the marsupial group and the other of the placental persuasion – which the untrained eye would assume to be closely related.

One of Darwin's principal arguments for his theory was "homology". If two organisms look similar then there is a reason for supposing that they are related. He certainly did not say that butterflies, bats and birds are related because they all have wings. He did point out that the similar structure of a human limb, of a mole's digging apparatus and of a dolphin's flippers was a good reason to put these creatures in the same broad category – mammals, especially in view of other shared characteristics (hair, lactation etc). All modern taxonomies concur, I think. A Baptist, a Muslim and an atheist will agree that that there are indeed many many diverse animals which should be classified as mammals. And they are very very different from reptiles and arthropods.

The evolutionary theory then goes on to construct the "tree-of-life". It explains homology in terms of common descent. In other words, humans, moles and dolphins share a common ancestor – a proto-mammal.

This is persuasive – to a degree. It persuades me that dolphins are my cousins many times removed and that sharks are too, though many more times removed.

As with many modern Darwin doubters, my problem is not with common descent but with the mechanism. Also with the lack of evidence from the "fossil record" – but that is another issue.

You have the placental mole and you have the marsupial mole. They are as similar to each other as the field mouse and the house mouse – in appearance. Obviously cousins, right?

But they aren't. Placental mammals and marsupials have radically different reproductive systems. Both groups employ sex; but the development of the foetus takes place according to wholly different schemes. You would have to do an awful lot of tinkering with a marsupial mole to turn it into a placental mole. David Berlinski goes into a fair amount of detail in speculating on the number of morphological changes which would enable a grass-eating mammal to evolve into a sea-going mammal. Many tens of thousands of coordinated changes in every physiological system. He admits that we have a few fossils which look like possible way stations. But not the tens of thousands that the theory requires. Darwin said, "Seek and ye shall find." We have sought; we have not found.

So, the question is: do marsupial wolves and placental wolves share a common (proto-wolf) ancestor, or do marsupial wolves and kangaroos share a common (proto-marsupial) ancestor?

I understand that the standard answer is something called "convergent evolution". My objection to this refinement to Darwin's theory is what Dawkins sneeringly dismisses as, "The argument from personal incredulity"! I find it a really good argument. Dawkins is, in my view, quite breathtakingly credulous. He does, after all, seriously consider the idea of life having been seeded on Earth from outer space as a solution to the origin-of-life problem.


  1. Dear Chris, thank you for including me in your list.

    You say you are interested in the “mechanism”. Maybe I am too analytic, but if you want to understand mechanisms you have to look at simple systems: i.e. bacteria. Now, with bacteria we have hundreds of confirmations of the goodness of Darwinism on daily basis. Bacteria resistance to antibiotics or insect adaptation to agrochemicals, are all examples of the same Darwinian evolutionary mechanism. Now, if evolution works well with bacteria and insects on weeks/months time scale, why shouldn’t it working as well with mammals at million years time scale? We don’t have the complete fossil records because the vast majority of fossil deposits have been buried, destroyed, eroded. The “coordination” of the genetic changes is striking only if you remove the time factor (many millions of years).
    The answer to your question is that “marsupial wolves and kangaroos share a common (proto-marsupial) ancestor” and the similarity between mammals and marsupials is linked to the similarity of the ecological niches they have.
    The evidence that does not fit in the theory is the basic motor of scientific progress; if we start to use it as a proof of the existence of God, then the scientific progress stops and we go back to the pre-Galilean era. I am very happy that there are a lot of things the Science does not explain, because it means that there is a lot of room for doing more research.

  2. Umba!
    Thanks for your visit and for your thoughtful comment.
    Think about becoming a "follower". I would be interested in your views on my other opinions: on Science and Economics
    We may disagree.
    Back to Darwin.
    When a strain of bacteria encounters antibiotics, most will die. A few may have "natural immunity" - just as some humans have natural immunity against some diseases. Those immune bacteria will thrive - they have the organism to themselves; but no new information is created. They do not turn into a new strain of bacteria. I think the analogy fails.
    When fruit flies are stressed by radiation, you get either: normal fruit flies, mutant fruit flies or dead fruit flies - not another species of fruit fly.
    I certainly believe that scientific knowledge makes belief in God reasonable (not proven). I also believe that Science grew out of Christianity. Copernicus, Galileo, Kepler and Newton were all devout Christians. Many contemporary scientists are Christians (not many biologists, I admit). It doesn't stop them making scientific progress.
    All the best