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Evolution without mutation

 
 
Reply Fri 29 Jul, 2005 10:42 pm
How much potential variation is built into the genome of mammals?

Let's say for the sake of argument, that all mutation were to stop completely, but other than that, reproduction and selection would continue in populations just as it always has. Would new species still develop over millions of years just due to the proportional accumulation or reduction of pre-existing variables, or would the lack of mutation hinder or alter the result of evolution sufficiently to prevent new species from developing?

I'm tring to understand the relative importance of actual mutation as an evoutionary mechanism, versus existing variation of genetic material within populations.

I'm also trying to understand how much of an organism's evolutionary history is still present in its DNA. For instance, if at one point in our history, we were a small shrew-like animal, how much of what it takes to build that shrew-like animal is still present in our DNA (junk DNA?).
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Type: Discussion • Score: 2 • Views: 6,136 • Replies: 60
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Brandon9000
 
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Reply Sat 30 Jul, 2005 03:38 am
You'd just optimize the current population and then stick there in equilibrium.
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satt fs
 
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Reply Sat 30 Jul, 2005 03:45 am
Probably horseshoe crab is the one surviving without mutation.
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farmerman
 
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Reply Sat 30 Jul, 2005 07:30 am
Mayr's opinion was that there is sufficient diversity in a genome to achieve genus evolution. Remember, entire genic complements of various phyla are often the same. Of course mutation adds new means and fuel to the mix, but as we learn that there is some controller mechanism in the"junk" DNA that the genomeeffectively is rather large after all. Remember 25% of a mouses genome is in a humans without any repeats or changes.
A genome is like a large bar code with lots of economy therein. Once a controller sequence is "invented" it is passed on to other genera without modification.
Look at a chimp and a human male. Our chromosomes are exactly the same because chriomsome 2 in humans is actually a fuised 2 and 2R of the chimp. SO to say that we have 98% of a chimps genes is not correct, we have 100% but its been rearranged by chromosomal fusing.
Im sure anybody that has taken genetics has spent time over the microscope drawing chimp and human male chromosomes.

AS far as mutations go, lethal mutations occur and that recipient is taken out. Netral mutations accumulate in the junk all the time. These occur in the interons and are often "moved up" by recombination , so that new gene lengths are made available for a new environmental expression, should the environmental change meet up with the "hopeful" gene.
We accumulate mutations at a fairly constant rate so that our own wanderings could be almost timed from "out of Africa" to Eastern Europe. These rates are usable that forensic scientists can track members of populations to their ethnic origin areas (even as small as a small region of a country) if the data base is kept in some international repository.

As Goul;d said, genes are just the "bookkeeping of evolution" not the driver. The driver is the environmental change that favors or weeds out the adapted.
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rosborne979
 
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Reply Sat 30 Jul, 2005 09:05 am
farmerman wrote:
Mayr's opinion was that there is sufficient diversity in a genome to achieve genus evolution.


Amazing. So much of what has gone before us is still recorded in our DNA, and available as raw material for design change.

I hope they are teaching this in biology classes these days, because it's really a significant aspect of the process, one which they neglected to mention in my high school classes in the 70's.

This explains why there is such an acceleration in the diversity curve over the last 4billion years. Mutation isn't the primary driver; it's reshuffling and reuse of prior genes which is the primary force now.

Back in the precambrian, when there was less raw material (Genes) to work with and atmospheric conditions were different, I wonder if Mutation was the primary force for change?
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rosborne979
 
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Reply Sat 30 Jul, 2005 09:15 am
Brandon9000 wrote:
You'd just optimize the current population and then stick there in equilibrium.


I don't think so. Populations would continue to change due to re-shuffling of genetic material, and natural selection would act on the new combinations as it always has.

The depth of recombination could be almost infinite, all without any new mutation.
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farmerman
 
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Reply Sat 30 Jul, 2005 04:23 pm
well, one thing has been discovered about cyanobacters that live in hydrothermal vents. These guys have genes for oxygen respiration but the O2 has been surpressed and theyve adapted to H2S and NO O2 environments.
Ive always looked at gene compliments as a sort of data base o how long species have been around. I dont think theyve decoded the Limulus yet (horshoe crab), but Id be really interested in its genome
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rosborne979
 
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Reply Mon 1 Aug, 2005 09:14 pm
Will anyone ever teach this nuance of evolution in Kansas? Will it matter if we do or don't?
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farmerman
 
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Reply Mon 1 Aug, 2005 09:36 pm
Kansas, at its present rate, will be depopulated by 2025. (That is unless some population of immigrants moves in, then at least they will have the intelligence to teach evolution)
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Ray
 
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Reply Mon 1 Aug, 2005 09:43 pm
I was taught that we have 98% of our genetic sequence are the same as chimps... So it's the fusing of certain chromosomes that made the difference?
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farmerman
 
  1  
Reply Mon 1 Aug, 2005 09:53 pm
ooh oooh oooh
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rosborne979
 
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Reply Tue 2 Aug, 2005 06:18 am
Ray wrote:
I was taught that we have 98% of our genetic sequence are the same as chimps... So it's the fusing of certain chromosomes that made the difference?


You must have been reading your Farmerman (from above) Smile
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GrinCDXX
 
  1  
Reply Wed 3 Aug, 2005 03:00 am
rosborne979 wrote:
Will anyone ever teach this nuance of evolution in Kansas? Will it matter if we do or don't?


I dont think there are really all that many people in places like kansas that actually deny the reality of evolution...I think many of them are probably waiting for someone to come up with a realistic scenario where self replicating molecules can spontaneously be created.
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Mr Stillwater
 
  1  
Reply Wed 3 Aug, 2005 03:21 am
Ray wrote:
I was taught that we have 98% of our genetic sequence are the same as chimps... So it's the fusing of certain chromosomes that made the difference?



Not really - BIG, big morphological differences in terms of size and sexual characteristics. Probably due to a positive feedback loop - the more we became less like chimps the better our ability to expand our niche. It is also very likely that the original 'human' population was very tiny indeed and may have had a smaller gene pool to speciate with.

The population of chimpanzees also probably outnumbered that of humans until... what.... a quarter of a million years ago?. Maybe even as recently as 100K BP. Impossible to tell - they are a very successful species.
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patiodog
 
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Reply Tue 9 Aug, 2005 09:35 pm
There's a school of thought -- I'm not sure how popular, but it seems very feasible to me -- that the chief difference between humans and chimps is our arrested development. Anatomically, we're pretty much underdeveloped chimpanzees -- the foramen magnum (the big hole at the base of the skull through which our spinal cord passes), for instance, is oriented at the same angle relative to the spinal column as that of late foetus/early infant chimp. (There's a bunch of other stuff, too, that have been noted for at least a century.)

Humans are pretty unusual in being born without a fused cranium. It leaves our brains very vulnerable, but it also gives them the opportunity to continue developing for a long time after birth. So, if we're born premature, and our brain is allowed to grow as it interacts with the external environment -- could be a very big determinant.

And such a developmental shift might require an infinitesimal alteration to the genome.
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satt fs
 
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Reply Tue 9 Aug, 2005 10:05 pm
It is quite a disturbing fact that any fossils of chimps are not found yet.
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patiodog
 
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Reply Tue 9 Aug, 2005 10:50 pm
Perhaps they be we, and not we, they.





Course, we don't really know that we've found any human bones of that vintage, either, when it comes down to it.
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rosborne979
 
  1  
Reply Wed 10 Aug, 2005 05:20 pm
satt_fs wrote:
It is quite a disturbing fact that any fossils of chimps are not found yet.


Why?
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satt fs
 
  1  
Reply Wed 10 Aug, 2005 05:27 pm
rosborne979 wrote:
satt_fs wrote:
It is quite a disturbing fact that any fossils of chimps are not found yet.


Why?

Multiple fossils of Australopithecus to Cro-Magnons have been found, but fossils of chimps are not. I think this is very strange.
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Vengoropatubus
 
  1  
Reply Wed 10 Aug, 2005 05:29 pm
rosborne979 wrote:
satt_fs wrote:
It is quite a disturbing fact that any fossils of chimps are not found yet.


Why?

because how can we know that they ever existed unless there is solid evidence in the ground to support the theory of chimpanzee existance.
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