Discussion of everything related to the Theory of Evolution.
I would like to start by clarifying the terminology for this post so that everyone is on the same page…
1. Molecular evolution – refers to molecular changes over time (ex. Genetic mutations, lateral gene transfer, etc.) that have been proven to be able to affect phenotype changes (ex. Diseases, deformities, trait variations, etc.)
2. Natural selection – refers to survivor of the fittest phenomenon, a negative selection process that eliminates/limits reproduction of the “unfit” individuals.
3. Positive selection - a process of stimulating reproduction of individuals with particular trait over others.
What I would like to discuss is the idea of evolution as it commonly refers to evolution of human kind (along with other species). Evolution as such is used to describe the process of change from simple to more complex organisms. Evolution of all life forms from bacteria as represented by the phylogenic tree of life.
I, however, have a fundamental problem with this idea. This theory at its core has an implied assumption that was (to my knowledge) ever discussed. The assumption is that we (and any other species of today) are MORE advanced than our predecessors. And I don’t believe that that is the case.
First fact that points toward the idea of our superiority is that our brain is larger than that of our ancestors. However, we should know by now that it’s not quantity but quality that matters. Now that larger than normal brains have been linked to autism, I think it’s time to rethink this conclusion. (http://www.ncbi.nlm.nih.gov/pubmed/16151044).
My second problem is the idea of genome duplication. At first the genome duplication was said to be the driving force of evolution by providing the genetic material for mutations leading to additional function development. Now they are saying that idea could not be substantiated and opted to conclude that genome duplication prevented extinction (http://mbe.oxfordjournals.org/content/2 ... l.pdf+html). That is actually more consistent with the observed genome deterioration over time (take Y chromosome as an example). But does it mean that new polyploid species are superior when compared to their predecessors PRIOR to genome deterioration over time??? OR was it more like recouping the original vigor???
Lastly, selective breeding and domestication of animals for a single trait via positive selection process can bring about variety of other changes by allowing other recessive traits (traits that natural selection process would have eliminated). Thus, we, humans, are primarily responsible for variation in domestic animals and not nature.(https://johnwade.ca/attachments/article ... mstudy.pdf). This raises the question of how can we eliminate evidence of evolution that results of our efforts from natural changes in plants and animals on this planet?
So, evolution or de-evolution? Are we moving toward perfection or away from it?
What do you think?
Who said that it's the other way?
Cis or trans? That's what matters.
People who use "evolution" of domestic animals to ascribe positive selection to nature (http://www.biomedcentral.com/1741-7007/8/20).
I think when we are using positive selection for one trait other traits related to survival start deteriorating quickly. For example, when antibiotic resistant transgenic plants grow in absence of antibiotic, they lose function of antibiotic resistant genes on a few generations (http://www.gmo-safety.eu/database/884.h ... nisms.html). If unneeded, it's discarded. And so are survival related traits of domesticated animals...
..but hasn't ...
It hasn't because we prevented it from doing so. I don't think that many domestic dog or cat breeds would be able to survive long in abscence of humans...
But getting back to my original question:
1/ If it was a hidden recessive ( as seemed to be the implication ) which was exposed through domestication and breeding, then it was there, Nature had not eliminated it - you just didn't ever get to see it.
2/ Black fur in wolves is thought to be a trait from domesticated dog.
1. Based on the evidence available and until proven otherwise, I would say that associated recessive phenotypes are NOT due to variety of genetic changes. You have to remember that there is no “aggression gene”. So far, only mutations in the serotonin 5-HT1A and 5-HT1B receptor genes were implicated in aggressive behavior (http://jhered.oxfordjournals.org/content/95/3/185.full). Considering that receptor is part of the cascade signaling mechanism there is good possibility of recessive allele activating/deactivating a totally different subset of downstream genes that would otherwise. If the other recessive phenotypes that emerged (coat color, tail shape, etc.) were due to direct genetic differences, you would expect to see them crop up in the aggressive population as well, but they don’t… (http://www.terrierman.com/russianfoxfarmstudy.pdf)
2. Based on this study (above) I would conclude three things:
a) Tame (along with other phenotypes) is recessive
b) Aggressive is incomplete dominant
c) Heterozygous is preferable in nature as the middle ground
3. I wonder if this is actually a nature’s way to prevent tame phenotype. Would those tame individuals exhibiting new coat colors, etc. be shunned by their wild type counterparts as ugly ducklings???
1/ My reply
was a reply to what you were saying
which seemed to be indicating that recessive traits are just showing up with domestication as they are not eliminated as would be in nature. So I replied that they actually had not been eliminated, if it was that they were there, only hidden until domestication allowed them to be found by humans.
2/ I disagree with your assessment in the post above, as well. When they selected for tameness , they selected for lower stress hormone levels, when under stress.
Whatever controls development of the animal that translates into lower adrenaline levels when stressed, also translates into developmental shifts so that patterns and many other things are affected. Just some change in timing, is enough to make major changes in appearance or behaviour.
Actually we have a misunderstanding. You actually agree with my assessment that genes are eliminated overtime NOT created...
When I talk about “traits”, I mean “hereditary characteristics” present in the population. For example coat colors in tame animals do not appear in the wild type population, so they are new. However, the GENES responsible for new traits ARE there. If I had to explain this scenario, I would say that those genes (let’s call them reserve genes) are being actively suppressed in wild type population by epigenetic mechanism (which is a wild type hereditary characteristic). Hypothetically, the loss of key genes responsible for significant survival characteristic triggers new hereditary characteristic – the loss of suppression of the reserve genes to increase variety of traits to insure survival of the species. If one of those genes was accidently activated out of turn, the individual would probably be selected against by nature (there is no knowing for sure of cause)…
I doesn’t really matter what you select for or the exact mechanism of the process. But it stands to reason that there is a large reserve of unused genetic information…
No, I do not say genes are not created.
NO, it doesn't take all that much to do this kind of major effect. Just a shift in timing during development can do all this.
It may not take much or even any of unused genetic information, to make all those changes.
Please, elaborate. I would like to hear your detailed explanation of the events (as opposed to just few sentences of general ideas). Keep in mind that possibility of “developmental shifts” and “shift in timing” are genetically predetermined.
Also, I would like a possible explanation of the fact that “in 40 years, no offspring of an extraseasonal mating has survived to adulthood” (http://www.terrierman.com/russianfoxfarmstudy.pdf). Could you offer one?
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