R
rossum
Guest
Evolution does not have to explore an infinite number of mutations. Firstly there is a physical limitation on the size of a genome. Beyond a certain size it becomes too large for the cell to hold; DNA takes up space. Secondly natural selection ensures that there are huge volumes of genomic space that do not need to be explored. For example we all have a protein called Cytochrome C, which is an essential part of the Krebs Cycle. If our Cytochrome C is non-functional then we die immediately, without having any offspring. Hence any genome with a major fault in its Cytochrome C is immediately rejected and all of the other possibilities in the rest of that genome never need to be looked at.Hello, Rossum:
I have two problems with the above:
1.) “…a succession of random mutations, rigorously sorted and filtered by natural selection is an adequate explanation” until we qualify the process further by expanding the “succession of random mutations” to infinity, which science has done in order to make sure that all possible mutations are accounted for.
Only possible genomes that can function well enough to reproduce are ever considered by evolution. This means that the genomes looked at are not a random selection but a highly non-random selection. Only genomes that already function reasonably well get to sit the test. Hence we only need to look at a small fraction of possible genomes.
Your model fails to take into account the effects of natural selection. Its effect is to amplify the beneficial mutations at the expence of hte deleterious mutations. Not all mutations are equal so using a flat probability calcualtion will not correctly model the combined effect of random mutations and natural selection.If we postulate that luckily, the right mutations occurred someplace along the finite a priori succession of mutations, well before said finite succession was able to reach infinity, we throw a monkey wrench into the adequacy of the explanation.
Yes. In very simple terms natural selection counts how many fertile children you have and the winners are the ones who have the most. The process is a bit like compound interest. As an example, take a stable population; on average each organism has one descendant in the next generation. Now let a beneficial mutation appear with a 1% advantage, so the mutated organism will have on average 1.01 descendants in the next generation. See what happens if we let the population reproduce for one thousand generations:2.) “…rigorously sorted and filtered by natural selection…” Who, or what, is supplying the rigor? Natural selection . . . alone?
Code:
Generation Normal Mutant
---------- ------ --------
0 1.00 1.00
1 1.00 1.01
10 1.00 1.10
100 1.00 2.70
500 1.00 144.77
700 1.00 1059.16
1000 1.00 20959.16
This is a very simple model, but it is enough to show the advantage a beneficial mutation has and how it can spread through a population. There is nothing “supplying the rigor”, just natural selection.
rossum