|
Mountaineer -> RE: Stasis as criticism of evolution (2/12/2008 8:25:27 PM)
|
quote:
ORIGINAL: Jhud
The problem with this approach is that is cuts both ways. It is true we cannot by observing phenotypical changes really know what is happening genetically – but that is exactly where evolutionists claim to derive most of their historical evidence – from observed phenotypic differences in the fossil record which they claim is evidence for certain kinds of genetic changes.
What we can know by observing phenotypes of horseshoe crab fossils (and the other organisms in historical stasis) are that if there are genetic changes, those changes had no observable affect on the organism despite 500 million years of presumably significant selective events.
I assume you mean selective pressures. It isn't necessary that because one sea creature changed as a result of, say, a snowball Earth that another creature changed. There's plenty of reason to suspect that a major global or regional event would have a profound effect on relevant species (in the case of a global event, the relevant species would be all of them), but there's little reason to say that these relevant species would all necessarily be impacted. If you wish to contend that there have been selective pressures that would radically (or even minorly) alter the horseshoe crab, you're going to need to present evidence.
What are the major events you contend are relevant to the horseshoe crab?
How is the horseshoe crab affected?
quote:
There is no reason to think that there would be more or fewer ‘beneficial’ mutations (or deleterious ones for that matter) in a horseshoe crabs (or jellyfish, or army ants or platypuses, etc) than any other organism.
There quite specifically is a reason to think this. I already cited it. An organism which is highly adapted to its environment has a smaller range of all possible beneficial mutations when compared to less well adapted organism. Let's set a max number of 100 possible beneficial mutations that could occur to an organism. The actual number of possible mutations is so near infinite we may as well call it that, but that isn't important. Our hypothetical states 100 possibilities. A poorly adapted organism can have 90 of these. The other ten would be deleterious because of what it happens to be. In other words, five mutations could be five different kinds of claws, but because of the cumulative effect of natural selection selecting another 5 mutations, our organism is some sort of finned sea creature. Claws are no good.
Now we take a well adapted organism. It only has a possible range of 10 mutations because it has already gone through 90 others (or maybe a combination of, say, 60 which canceled out the benefit of another 30). The total set of possibilities is smaller. This means the probability of a beneficial mutation is less for the well adapted organism than the poorly adapted organism. The point is assisted if we consider 100 possible neutral mutations, 100 possible deleterious mutations, and, of course, the 100 beneficial mutations.
All these numbers are arbitrary, but the point should be clear. A more well adapted organism has less room with which to improve. If it has fully exploited its niche, why would it need to evolve? The horseshoe crab has done this, at least insofar as its body is concerned.
quote:
In fact, one of the claims of evolution is that mutational change is rather ordinary and constant – not that it occurs especially in some species sometimes, and not at all in other species. The whole idea is that incremental changes accumulate over time and add up to large changes – not that they don’t happen at all in some species at any time, while happening dramatically in other species at certain times.
Most mutations are neutral. Many are deleterious. Neutral mutations do no lead to large scale changes unless a separate beneficial mutation occurs which exploits the formally neutral genes (natural selection can also act upon this). Biologists don't claim this to be the way in which the vast majority of large scale changes occur. Deleterious mutations obviously are weeded out.
That "mutational change is rather ordinary and constant" doesn't prove any point because mutations do not always (nor usually) lead to change in species. You can say mutations are as constant and common as you wish. This does not mean we should expect change. Furthermore, a critical flaw in your point is that it assumes beneficial mutations are constant and ordinary. Mutation is random. Why would anyone assume anything is constant concerning something which is random?
quote:
It is increasingly evident that stasis is not all that unusual for overarching forms. As I pointed out, the major groups of flowering plants and beetles – two groups which make up a large part of all living things – were established long ago, and have not changed in major ways since.
I saw your claim that planets and beetles have remained constant. Do you have an way of substantiating this claim?
|
|
|
|