Monday, April 18, 2005

Haldane's Dilemma

Haldane’s Dilemma is a paradox that relates to evolutionary theory. Let me try and explain as best I can ....

Imagine you have a population of 10000 weebles. A new, beneficial mutation occurs in one, which means that it has a selective advantage. This mutation is obviously not present in all of the generation in which it first appears – in fact it is only present in one organism. But offspring of that organism which have this mutation will have a selective advantage, so more of the next generation will have the mutation, and more of the following one ... and so on, until the presence of this mutation becomes a mark of weebles – a characteristic of the species. It is possible to work out how many generations exactly this “fixing” of characteristics would take, based on the number of offspring and the population size.

Now, evolution is supposed to work through mutation and natural selection. Take the example of a hypothetical creature that is an ancestor of both modern chimpanzees and humans. There are (let’s say) 100,000 differences in DNA bases between chimpanzees and humans. So Haldane’s Dilemma argues (in its strongest form) that each of these differences has to be “fixed” in the population; each taking some significant number of generations; and that the staggering number of generations required to fix this total number of DNA bases basically means that geological timescales are way too short. Those aren’t exact – or even probably approximate! - numbers but hopefully you get a sense of the argument.

Evolutionists don’t regard Haldane’s Dilemma as an issue – see here for evolutionist commentary. However, Walter ReMine, who wrote The Biotic Message does not think the issues have been addressed – see the ARN bulletin board for a (long!) discussion of the issue, from both those who think it is an issue and those who think it isn’t.

As far as I can see, there are several problems. First, although evolutionists say you can fix more than one DNA base at once, and this gets evolution done at a faster rate than fixing one at a time, I’m not convinced that this could be an effective mechanism for macro-evolution – I think I need to look at this being modelled mathematically if I am to be convinced.

Second, almost all examples of evolution that seem to be quoted in papers (that I have seen) are modifications of existing functionality. Ultimately new functionality has to appear from somewhere – RNA polymerase didn’t presumably appear as a consequence of modifications to Cytochrome C. Whilst a new protein doesn’t have to be completely specified to have functionality, it has to have some level of specification. Where is the “testing ground” for new proteins? And what proportion of random new proteins have to be thrown away before useful ones can be found? And how does an organism fund this testing?

Thirdly, a modification to an organism would have to be pretty darn good to have a definite impact on the survival of the organism. Look at the range of genetically heritable differences that are considered normal for human beings. Do they really affect survival in a positive sense? If changes give advantages of the level of a couple of percent, then random events in the life of the organism are much more likely to dominate survival chances. You can see “survival of the fittest” a lot better in its negative sense – genetic changes that drastically reduce the chances of an organism’s survival will wipe out a line. But that’s not an engine of evolution – it won’t get you from monkey to man, let alone from prokaryote to eukaryote.

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