Yes, natural selection, and indeed any kind of selection whatever, the most common most likely being simple geographic isolation of a portion of a population, means a loss of genetic diversity to the new populationj as compared with the parent population. This reduction in genetic diversity means that evolution has a natural limit bewyond which no more genetic variation is possibl.
But they always think that mutation imakes up the difference, insofar as they notice there is a problem at all, which of course they don't, I've tried to point it out for years. Mutation is always the answer and my answer to that is that it doesn't matter what the cause of the variation is, natural selection MUST reduce genetic diversity, that's how it works. Mutation or not mutation there is a limitation to evolution built into the processes that bring about change.
But this idea that mutation could contribute anything positive at all is crazymaking. I just watched a couple of videos making that claim. Oh golly gosh, mutation is the CAUSE of variation. WSigh. If you have a population of black mice a mutation may occur that makes one white and on a white background that mouse will survive predatory birds while the black ones will be picked off, so the white mice will proliferate.
Sigh.
First the idea that mutations just popp up when need3ed is a biizarre article of faith. If mutations so easily cam along to save the day for any species surely they would have saved the dcheetah long ago by now, but no, the poor cheetah goes on generation after generation with no mutation coming to the resue, endangered as always by 8its genetic depletion.
No. Plain old Mendelian genetics is all we need to explain variation. In a word, heterozygosity. When you have two alternatives for a gene you get vriation. The recessive alternate may not appear in the phenotype for some generations but when it does if it is beneficial it will proliferate in the populationj. So once in a while black mice on a black background will get a white individual in its midles. It will be eaten by a big bir. but if a few more appear over time and they wander onto the white sand near the lava flow it is the black mice that will get eaten.
You don't need anything more than normal heterozygosity for this kind of variation to occur in any population. A And heterozygosity is really what genetic variability IS. It's when you get a population of homozygous genes for asalient traits that become the only genetic gype in the population that you can't get variation. This is the natural limit to evolution. It's the common situation in engangered species and it is alwso what used to be the definition of a purebred in domestic breeding. The more fixed loci or homoZygous genes the more a breed will "breed true.
And that's what breeders used to want, until it was disocvered that this genetic condition usually brings genetic weaknesses and diseases with it, so they've had to modify their standared.
Ha ha. They've got such an investment in their fake theory I guess there's no may to get them to see the truth.
Sigh.
No comments:
Post a Comment