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EvC Forum Science Forums Biological Evolution

# How long would it take for a novel alelle to be fixated in a population?

Author Topic:   How long would it take for a novel alelle to be fixated in a population?
CoolBeans
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 Message 16 of 64 (692902) 03-08-2013 12:38 PM

Well. then about how much time .
How many generations would it take for allele frequencies to change.specifically mammals with low offspring.
 Replies to this message: Message 17 by Dr Adequate, posted 03-08-2013 12:52 PM CoolBeans has not yet responded Message 19 by Taq, posted 03-08-2013 1:09 PM CoolBeans has responded

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 Message 17 of 64 (692909) 03-08-2013 12:52 PM Reply to: Message 16 by CoolBeans03-08-2013 12:38 PM

Re: Well. then about how much time .
 How many generations would it take for allele frequencies to change.specifically mammals with low offspring.

Well, that depends.

If you look at what Haldane did (according to your quote) he tried to produce a ball-park figure for how many deaths would be required due to the less-adaptive trait being selected against. It turned out that in his math that could be answered in terms of a multiple of population size no matter how strong the selective pressure was, and no matter what the population size was.

But the question of how much time it would take to achieve fixation does in fact depend on the strength of the selective pressure, and quite possibly on population size as well (I'll have to think about that). That's a different question.

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CoolBeans
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 Message 18 of 64 (692914) 03-08-2013 1:07 PM Reply to: Message 7 by PaulK03-08-2013 11:02 AM

Re: Thread Copied from Proposed New Topics Forum
On your soft selection answer. The author says he adressed that already. He says that the cost of substitution is unnavoidable. He says that when an organism reproduces by 1 per birth. It would require that this organis will have to rerpduce to 2.25 rate. Its in his paper.

Though to be honest. The other organism is not reproducing then the cost is lower.

Edited by CoolBeans, : No reason given.

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Taq
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 Message 19 of 64 (692915) 03-08-2013 1:09 PM Reply to: Message 16 by CoolBeans03-08-2013 12:38 PM

Re: Well. then about how much time .
 How many generations would it take for allele frequencies to change.specifically mammals with low offspring.

A single generation is all it takes. A generation with 1 million A alleles and 1 million B alleles followed by a generation with 999,999 A alleles and 1,000,001 B alleles is a change in allele frequencies.

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 (3)
 Message 20 of 64 (692916) 03-08-2013 1:09 PM Reply to: Message 5 by CoolBeans03-08-2013 10:38 AM

 Haldane calculated that no more than 1,667 beneficial substitutions could have occurred in the supposed 10 million years since the last common ancestor of apes and humans. This is a mere one substitution per 300 generations, on average.

If any of this is true then it would be a problem.

Well of course Haldane did not calculate that as such, the creationist is simply lying.

But in the second place, why would it be a problem? It may well be the case that only 1,667 beneficial mutations separate humans from chimps. It might be a lot less, I wouldn't be at all surprised. ReMine doesn't know --- nobody knows at present --- how many beneficial mutations actually make the difference.

What ReMine is doing (implicitly or explicitly, I don't know how stupid he is) is assuming without the slightest shred of justification that every genetic difference between chimps and humans is the result of a beneficial mutation favored by natural selection rather than a neutral mutation fixed by genetic drift. And there is no reason at all for thinking this except that he wants to come up with some crappy creationist argument.

Now it can be shown mathematically (I've done this myself, I'll dig out the working if you're interested) that genetic drift would account for all the differences between humans and chimps over the last seven million years or so, if all the variations were neutral (which they aren't). If we wish to introduce Haldane into the argument, we need to know how many of these differences are beneficial and favored by natural selection, rather than neutral and fixed by genetic drift. And ReMine doesn't know that any more than anyone else does.

Edited by Dr Adequate, : No reason given.

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PaulK
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 Message 21 of 64 (692919) 03-08-2013 1:21 PM Reply to: Message 18 by CoolBeans03-08-2013 1:07 PM

Soft selection
quote:

On your soft selection answer. The author says he adressed that already. He says that the cost of substitution is unnavoidable. He says that when an organism reproduces by 1 per birth. It would require that this organis will have to rerpduce to 2.25 rate. Its in his paper.

In soft selection the cost of selection is paid by deaths that would occur anyway (that's what makes it "soft"). And I have to point out that all species DO produce considerably more offspring than would be needed to replace the population if all of them survived. Which is all that soft selection needs.

Edited by PaulK, : A more reasonable title

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CoolBeans
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 Message 22 of 64 (692922) 03-08-2013 1:32 PM Reply to: Message 20 by Dr Adequate03-08-2013 1:09 PM

That is batten's paper, not ReMine's. He argued that it doesnt matter if they are beneficial.

Edited by CoolBeans, : No reason given.

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CoolBeans
Member (Idle past 1787 days)
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From: Honduras
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 Message 23 of 64 (692923) 03-08-2013 1:37 PM Reply to: Message 21 by PaulK03-08-2013 1:21 PM

Re: Soft selection
.ell I wouldnt say that all the population needs to be replaced .
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PaulK
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 Message 24 of 64 (692924) 03-08-2013 1:41 PM Reply to: Message 23 by CoolBeans03-08-2013 1:37 PM

Re: Soft selection
quote:

ll I wouldnt say that all the population needs to be replaced .

It is necessary to maintain a stable population. In fact it is necessary for any species to be capable of producing more offspring than are needed to replace the population, if it is going to survive. If it did not then any disaster would result in a permanent reduction to the population, eventually leading to extinction.

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CoolBeans
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 Message 25 of 64 (692926) 03-08-2013 1:45 PM Reply to: Message 19 by Taq03-08-2013 1:09 PM

Re: Well. then about how much time .
What I meant is that this change would need to replace the old one in the population. Please read the paper.
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 (1)
 Message 26 of 64 (692927) 03-08-2013 2:05 PM Reply to: Message 22 by CoolBeans03-08-2013 1:32 PM

 That is !atten's paper, not ReMine's. He argied that it doesnt matter if they are banafitial.

Then he's wrong, because the math clearly shows that he's wrong.

It can be proved with some elegance that the rate of fixation of neutral mutations in the population is exactly equal to the rate of occurrence of neutral mutations in the individual. In fact, if I remember rightly, this was first proved by Haldane.

And of course it matters. Haldane's result (the so-called "dilemma") is specifically about fixation by natural selection. It refers to the number of deaths that would need to occur if selection was operating, because of those individuals dying because selection was operating against them. If natural selection isn't operating, then Haldane's result doesn't apply.

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CoolBeans
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 Message 27 of 64 (692929) 03-08-2013 2:22 PM Reply to: Message 26 by Dr Adequate03-08-2013 2:05 PM

This Walt ReMine's website with responses to rebutals.
http://saintpaulscience.com/Robert_Williams.htm

Edited by CoolBeans, : No reason given.

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CoolBeans
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Posts: 196
From: Honduras
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 Message 28 of 64 (692932) 03-08-2013 2:33 PM Reply to: Message 26 by Dr Adequate03-08-2013 2:05 PM

So what you are saying is that alot of the changes are due to neutral mutation.

I would be happy if you read his paper.

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PaulK
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 (1)
 Message 29 of 64 (692933) 03-08-2013 2:35 PM Reply to: Message 27 by CoolBeans03-08-2013 2:22 PM

And it immediately opens with a lie. Williams claimed to be rebutting internet postings by ReMine, not ReMine's book.
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CoolBeans
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 Message 30 of 64 (692935) 03-08-2013 2:47 PM Reply to: Message 29 by PaulK03-08-2013 2:35 PM

http://www.gate.net/~rwms/haldane1.html

 Haldane's Dilemma is based upon the substitution cost introduced by J.B.S. Haldane in his classic 1957 paper "The Cost of Natural Selection" (Haldane, 1957). ReMine addresses these issues in his book "The Biotic Message" (ReMine, 1993).

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