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What does "a change of 1% in 20,000 years" mean? You assume a positive change that can facilitate evolution, but all your examples are hypothetical and you give no statistics on the percentage of USEFUL mutations as compared to undesirable ones -- meaning those that NO environment is going to favor..
I’m talking about net change (see below) - notice that I used the dog example, there is a 1% difference between, say, a dog and a wolf (depending a bit on the breed, of course).
The labels “good” vs. “bad” mutations, as I mentioned, are misleading. The vast majority of mutations (over 90%) are neutral - they don’t do anything at all. For instance, say your instruction book contained pages of random gibberish - randomly changing a word of that doesn’t change the instructions.
OK, now, let’s think about the mutations that do change something. Most changes could be either “good” or “bad”, depending on the environment. Take a second to step back and look in a mirror. Consider changing any aspect of your body. Darker skin? Is that “harmful”? Well, it is if you are a female living in northern areas, and you need to get enough sunlight to provide vitamin D when pregnant. Or instead do you live in Africa, where it is a good mutation, since you need protection from too much sunlight, which can cause skin cancer? Larger nostrils? Do you live in a windy desert, where larger nostrils will allow more sand into your lungs (ouch)? Or instead do you live in a forest, where being able to pull in more air when running from a predator will help you escape?
We could look at examples like this all day - the point is that mutations aren’t usually inherently “good” or “bad” - that depends on the environment, which will either cause them to help the bearer have more kids, (hence, “selected for”) or not (“selected against”).
OK, now look at the 1% I mentioned for dogs. I meant the net total of the mutations that WERE SELECTED FOR over 20,000 years. The number of mutations selected against is completely irrelevant, since those mutations all disappeared with their unfortunate owners. See why the ratio is unimportant? If half of the mutations that have an effect are selected for, then the ration you want is 1:1, and you end up with only the "selected for" mutations. If there is only 1 helpful, "selected for" mutation in 5, then you ratio is 1:5, and you still have exactly the same number of mutations at the end of the day, since the ones that weren’t selected for are gone anyway. That's why the number of non-selected for mutations is irrelevant.
If you want to discuss extremely harmful mutations, such as those that cause an quick death or some such, that's fine. Again, they are completely irrelevant, since that animal dies, the mutation (new allele) is gone, and we are back to square 1.
In fact, “harmful” mutations are very often selected for by humans. Look at the pathetic bulldog. We have selected the mutations that slowly made his snout all smashed in, resulting in hampered breathing. Have you ever been near a sleeping pug? It sounds worse than Darth Vader! Whether a mutation is “good” (selected for) is a function of the environment as much as it is a function of the mutation.
So, the % is the net change in the genome due to the accumulation of mutations that were selected for. It took thousands of beneficial mutations to get to a poodle from a wolf - and that change is only “beneficial” if you keep the poodle out of the wolfpack.
You mentioned how mutations work. Here are some basic types of mutations and how they work:
Duplication of a stretch of DNA. This is like accidentally copying part of a book twice. Example - when making a copy of a book that has chapters 1, 2, 3,4,5,6,7,8,9,10,11, 12, you end up with a book that has chapters 1, 2, 3,4,5,6,7,3,4,5,6,7,8,9,10,11, 12
Deletion of a base pair. AATCTGTC becomes ATCTGTC
Addition of base pair AATCTGTC becomes ACATCTGTC
Transposition (like a mirror) AATCTGTC becomes CTGTCTAA
All of these can have no effect, an effect which is selected for, or an affect which is selected against.
To add information, first, take a functional gene, and make an extra copy using the duplication mutation. That won’t hurt the organism, since the second copy is simply redundant. Then use any of the other mutation methods so as to make the second copy do something new. The organism still has the original copy doing whatever it is supposed to do, but now has the added ability of whatever the new gene does (such as digesting nylon, as in a species of bacteria).
The process can also add entire chromosomes, that’s how, over time, the total number of chromosomes changes. For that, simply copy a whole chromosome twice (it happens), then the rest of the process is the same as above.
I don't understand what you mean by "a mistake which is only destructive". Do you mean that all mistakes have to be harmful? Why? Many inventions have been found by people making mistakes. In genetics, if a group of animals is living in a valley and the climate changes to make it colder, then wouldn't a genetic "mistake" which made their hair grow a little longer be helpful?
Oh, I'll be out until next week. Have a fun weekend-
Equinox
Edited by Equinox, : No reason given.
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