Posted 14 November 2010 - 09:30 AM
Here's a link for a Nova program I caught last night. Very interesting research using artificial selection on wild foxes. It was found that, first, there is an actual "tame" gene in the foxes. The wild foxes have more adrenalin in their systems, which keep them aggressive.
What is insightful is that when the tame gene is selected in the research, over several generations the tame foxes' phenotypes begin to change, to give a more "doggish" breed-like look. It is believed that past humans did this with wolves and other canines--bred the less aggressive ones, to make initial tame wolves. As their phenotypes also changed, they began to cross breed. Wild wolf populations were kept down by man, because of obvious reasons. Meanwhile tame dog populations thrived, because of man's love and use of the dog.
As a result, we see the natural variation capability God put in the genes, and that it doesn't require millions of years for natural variation to change things quickly. But that change is limited--it is still within "kind" parameters. None of he dogs started to look like another type of animal.
That all said, the point I want to make is that of pleiotropy--that is that genes are not isolated, but are part of groups of genes, and one change affects a group. Or one gene can affect more than one thing. The behavior of the fox was selected for, but phenotypical change came shortly afterward. As the tame foxes interbred--it isolated certain gene groups in their population. However they could still cross breed with wild foxes.
It is this pleiotropy which is believed to be antagonistic to major evolutionary changes by evolutionary unbelievers. Any comments?
Posted 14 November 2010 - 11:40 AM
I knew about that experiment, but not the genetic mechanisms involved. I always used the experiment to prove that rapid changes can occur within decades instead of millions of years. I'm very intrigued by pleiotropy, I didn't know one gene can effect the entire group changing the phenotype as well.
The important thing to consider is that NS is invalid once again. No fixation of mutations was involved and if these foxes are released they will revert back to their original pheno.
I think this also firmly establishes that foxes are a created kind and cannot microevolve into Wolves, Hyenas, etc.
Posted 17 November 2010 - 05:47 PM
This one is falling quickly. I guess such an illustration of natural variation and plieotropy it empirically demonstrates is hard for evolutionists to counter.
Basically, the plieotropic principle shows the difficulty of finding the "right" mutation for change. One mutation, or even selection for one trait can bring more change in another area--even rapid phenotypical change. And that other area may not be good for the organism.
For instance, if you changed a gene that was for some biochemical molecules that are used in several processes you now affect ALL the processes. Some of them might be nuetral, but if one is bad you decrease fitness, or cause death. So now you have gone from mount improbable to get to the moon without a rocket improbable.
Antagonistic pleiotropy WIKI
Antagonistic pleiotropy refers to the expression of a gene resulting in multiple competing effects, some beneficial but others detrimental to the organism.
This is central to a theory of aging first developed by G. C. Williams in 1957. Williams suggested that some genes responsible for increased fitness in the younger, fertile organism contribute to decreased fitness later in life. An example is the p53 gene, which suppresses cancer, but also suppresses stem cells, which replenish worn-out tissue.
Whether or not pleiotropy is antagonistic may depend upon the environment; for instance, a bacterial gene that enhances glucose utilization efficiency at the expense of the ability to use other energy sources (such as lactose) has positive effects when there is plenty of glucose, but can be lethal if lactose is the only available food source.
Note: Not all pleiotropy is antagonistic. It is a natural principle and was evidenced in the foxes. But antagonistic pleiotropy could be the enemy of macro evolution.
0 user(s) are reading this topic
0 members, 0 guests, 0 anonymous users