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Junior Member (Idle past 2681 days) Posts: 7 From: South Africa Joined: |
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Author | Topic: Extent of Mutational Capability | |||||||||||||||||||||||||||||||||||||||||||
Dr Adequate Member (Idle past 305 days) Posts: 16113 Joined:
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So, Gregory Rogers. Please show us the maths backing up your claims. From this thread it seems as if you are very reluctant to do it. Maybe it's because you don't have a clue? Gregory Rogers and CRR are two different people. I don't see Gregory trying to put up a quantitative argument, so the absence of math is not a problem. As a matter of fact, I like them both. Gregory is asking questions which seem perfectly reasonable coming from someone who doesn't know much about the topic --- which is exactly the sort of person who should ask questions. And CRR, while he may be a creationist, is at least trying to be right. There's been some work and thought put it there, and while he is mistaken his mistakes have on occasion been subtle.
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Dr Adequate Member (Idle past 305 days) Posts: 16113 Joined: |
That's an interesting example, and at first looks convincing. Now in previous posts you were clearly talking about mutations that had been fixed in the population (# 195, 176) and I was arguing that there wasn't sufficient time to fix the required number. In this example it is quite certain that the mutations I acquired independently will not be fixed in the population. I never said they would be. Indeed specifically said I was doing a different calculation; I wrote: "if fixation is too confusing, let's think about two individuals". But it still gives you an order-of-magnitude estimate of the difference between any given human and any given chimp. Can you find anything wrong with it? (Fixation would, as you point out, not happen to very recent mutations, but it would happen by the elimination of the diversity that existed before the split. It's a different issue.) Edited by Dr Adequate, : No reason given.
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Dr Adequate Member (Idle past 305 days) Posts: 16113 Joined: |
Douglas Axe has estimated the chance of a chain of amino acids forming a functional protein is ~1 in 10^77. Denton estimates that no more than 10^40 proteins have ever existed on Earth. So even with those vast probabilistic resources the odds are fantastically small that a protein could have formed by chance. (obviously there are lots of assumptions and boundary conditions in any estimates of this kind). Pro-evolution researchers have done estimates and come up with the chance forming a functional protein as ~1 in 10^50. However that still leaves the chance at ~1/10^10 so it remains fantastically improbable. Note this avoids the sharpshooter fallacy because any functional protein would be success. No-one claims that proteins were produced by amino acids being randomly strung together. I notice that you have not shown any working. Edited by Dr Adequate, : No reason given.
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Dr Adequate Member (Idle past 305 days) Posts: 16113 Joined: |
Nevertheless Doc, you've managed to disprove your first position. No. Why would you say such a bizarre thing?
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Dr Adequate Member (Idle past 305 days) Posts: 16113 Joined: |
At Message 176 you posted a copy of sfs's post claiming that genetic drift could explain the difference between human and chimp genomes. At Message 195 you showed that you were talking about fixed mutations. My argument was that taking mean time to fixity into account meant that less than half of the mutations could have been fixed in that time. And how very wrong you were. (And if you were right it would hardly matter, this is an order-of-magnitude calculation.)
At Message 203 you presented what appeared to be the same argument from a different perspective. It was not the same argument, nor did it seem to be so, since I explicitly said I was calculating something else. Can you find an error in the calculation?
You are going to have to do a lot more to show that genetic drift is a plausible explanation for the genetic difference between humans and chimps. Perhaps to show you that I would have to perform an actual miracle. Geneticists, on the other hand, consider the thing to be proven.
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Dr Adequate Member (Idle past 305 days) Posts: 16113 Joined:
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Well perhaps you will have to explain it again so that even I can understand it. Hmph. I'm not sure there is a simpler way to put it. I'll explain it again, and you point out where you stop understanding me. First, bear in mind that what we're doing here is getting a ballpark figure of the genetic distance between one human and one chimpanzee. It is not going to be an exact figure, for reasons I will explain at the end, nor are we calculating the fixations that differentiate the populations as wholes. So, I have μ mutations that my parents didn't have. My parents in turn each have μ mutations that my grandparents didn't have. I inherit half of each of these, and I have two parents, so my parents contribute μ + μ = μ mutations to my inheritance: put that together with my own mutations, and I have 2μ mutations that my grandparents didn't have. My grandparents in turn each have μ mutations that my great-grandparents didn't have. I inherit a quarter of each of these, and I have four grandparents, so my grandparents contribute μ + μ + μ + μ = μ mutations to my inheritance: put that together with my own mutations and the ones I got from my parents, and I have 3μ mutations that my great-grandparents didn't have. And so on. It follows that if there have been G generations since the chimp-human split, I have accumulated μG mutations, and so will any given chimp. The difference between us will be 2μG. This is an underestimate. Why? Because it doesn't take into account the diversity which existed before the split, which will have been lost in different ways on the way to me and the chimp. (Usually this will involve fixation in the two populations as a whole. ) But we're not striving for great accuracy. A ballpark figure would do for now. That figure is clearly of the same order of magnitude as the differences that actually exist.
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Dr Adequate Member (Idle past 305 days) Posts: 16113 Joined:
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This assumes the same number of generations in humans and chimps. Yeah, when I said we're not striving for great accuracy, I meant it. Ballpark is all we're going to get.
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Dr Adequate Member (Idle past 305 days) Posts: 16113 Joined: |
As you said Usually this will involve fixation in the two populations as a whole. We are talking about fixed mutations. NO WE ARE NOT. That was an addendum, a footnote, referring to a different process to the one I was discussing. The 2μG figure I just derived comes without any consideration of fixation. You are in fact wrong about fixation as well, but is hardly worth going into since you are being wrong about the wrong thing. Can you find any error in the calculation that I just presented, the one that involves neither fixation nor the human and chimp populations considered as a whole?
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Dr Adequate Member (Idle past 305 days) Posts: 16113 Joined: |
Taking into account the diversity which existed before the split is not going to save the situation. It would, in fact, but since we got to 2μG without any consideration of fixation, using only mutations which happened after the split, none of your quibbling about how fixation would work will "save the situation" for you. Can you find anything wrong with the calculation I just presented, the one that doesn't involve fixation in any way shape or form? The calculation that I prefaced with the words "nor are we calculating the fixations that differentiate the populations as wholes"? Edited by Dr Adequate, : No reason given.
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Dr Adequate Member (Idle past 305 days) Posts: 16113 Joined: |
No problem with your second calculation. Good. Then you must admit that mutation is sufficient to account for the genetic distance between me and a chimp.
However you started talking about fixed mutations and now you're talking about a gross number of mutations of which only a minority are fixed, so there has been a significant shift in your position during the conversation. No there hasn't. Both things I said are still true. I have not shifted my position one inch: I have merely talked about two different things consecutively.
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Dr Adequate Member (Idle past 305 days) Posts: 16113 Joined: |
Then I think you don't understand your own argument. Try going back to taws and work through it again. I do understand my own arguments. I do not understand what you mean by taws. One thing you don't seem to understand --- despite me explaining it repeatedly with a patience that would do credit to a saint --- is that I have in fact presented two completely different arguments. The second of these does not involve fixation, and so cannot possibly involve time to fixation, and so is entirely unaffected by population size and all the other semi-digested ideas by means of which you hope to misunderstand the first argument. Can you find anything wrong with the second argument? If not, you must admit that mutation is sufficient to account for the genetic distance between me and a chimp. Edited by Dr Adequate, : No reason given.
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Dr Adequate Member (Idle past 305 days) Posts: 16113 Joined: |
If the mean time to fixity is 100 generations then we would expect 50 of those mutations to be fixed in the time available. I'm not sure that that can be right, even if it was relevant.
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Dr Adequate Member (Idle past 305 days) Posts: 16113 Joined: |
I was right. The correct figure appears to be approximately 61%, independent of population size.
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Dr Adequate Member (Idle past 305 days) Posts: 16113 Joined: |
Would this also apply to the fixation of alleles? Each human is born 50 mutations. In a population of just 1 million, that is 50 million mutations in a single generation. With that many mutations isn't it possible for many of those mutations to reach fixation in a much shorter time frame than the mean fixation rate? Well, ~61% do. This is because there is a lower limit on how long an allele can take to fixation, but no upper limit. Some of them are going to take a really long time. Because the time is large, they will contribute a lot to the mean time even though they are few in number. Here's the results of a computer simulation of 10000 fixation events. The blue line shows where the mean time to fixation is.
CRR is making the not uncommon mistake of supposing that the mean must be the median.
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Dr Adequate Member (Idle past 305 days) Posts: 16113 Joined:
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While some would go to fixation quicker than the mean, wouldn't a larger population mean it's harder for any mutation to go to fixation? Note that in the end every new mutation will either be lost or fixed. Now the chances of it being lost are proportional to the population size. But so is the number of new mutations in the population per generation. Hence the rate is independent of population size: the rate at which mutations are fixed in the population is equal to the rate at which they occur in the individual. (Of course, this only applies to neutral mutations, but quantitatively those are the important ones.) Edited by Dr Adequate, : No reason given.
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