Member (Idle past 4033 days)
Message 1 of 2 (409664)
07-10-2007 6:09 PM
As I finished up a book about evolution today, I learned a surprising fact. Until today, I had assumed that mutations were totally random and there was no way to predict what would "show up" in any given mutation. I learned, however, that the processes by which mutations arise are actually nonrandom; rather, they are affected by many other factors. The only thing that's random is the effect that the mutation has on the organism's fitness.
In addition, the book indicated that the primary causes of mutation are physical events like X-rays, chemicals, and other genes. I had always thought that mutations occured by a random "shuffling" of the parents' DNA; instead, it appears to be caused by nonrandom, physical causes. When do these physical causes actually happen? While the embryo is developing or something?
Another way that mutations are nonrandom is that it can only effect the existing processes of embryonic development. Doesn't that limit the potential effects of mutations? Does each organism have a certain number of potential mutations, and no more? If this is true, then as a population evolves more mutation "possibilities" should become available. Is that correct?
And, are some evolutionary "pathways" so ridiculous that they'll never be "walked upon"? For example, and I feel stupid typing this, but we don't see any fire-breathing dragons. And yet we see plenty of amazing features in the animal kingdoms which have staggering complexity. With slight, successive mutations and natural selection, why can't an animal breath fire? (God, I feel stupid!)
Thanks for putting up with my questions! And for reference, the book I read was The Blind Watchmaker by Richard Dawkins, and the chapter that inspired these questions is called "Doomed Rivals" (specifically pgs. 434-445).