Some mutations sound too good to be true

Recombination generally only reshuffles genes. That can't increase genetic diversity at all. The diversity is measured by the number of variants of a given gene (the alleles) so it really does require that the genes change over time.

Well, this is problematic it seems to me, as natural selection reduces genetic variability, which is what the species is trying to recover from in this example, as this condition of low diversity ultimately strands it on the brink of extinction. (That's the problem with all the "processes of evolution" -- and bottleneck and natural selection are listed among them -- that most of them tend to reduce genetic variability which reduces the variations available to be selected.So now we're talking about a population that finds itself out there in a condition of extremely low diversity because of a severe bottleneck, and the question is how can it recover from this condition as it is not conducive to further variation or selection. If breeding with another population of the same kind is not possible then mutation is all there is available to increase variability, and at this point it is this increase, not selection, that is desired.Hence the question, has it actually been observed that by mutation alone, genetic variability has been increased in a bottlenecked population, and therefore its viability also increased (rescue from the brink of extinction)?

Random mutation will increase variability by definition.AbE:There is no other mechanism to increase variability than mutation.This message has been edited by jar, 09-27-2005 10:27 AM

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Aslan is not a Tame Lion

But doesn't recombination (re)introduce variants to a population in which variants have been severely reduced? That is, a bottlenecked population may have NO variants for particular genes, but variants may be reintroduced by breeding with another population that has them.

Yes, by definition, but the question is about observation, not definition.

Well, I only brought up recombination because I understood it to be a possibility and it has to be ruled out if we're going to focus only on what mutations actually do.So now whether in fact mutation has been observed to increase variability is the important question.

You are claiming that mutation alone increases genetic variability but only over great great periods of time -- in 10,000 years it has not rescued the cheetah, and you consider 10,000 years to be a small period of time, or recent. And yet you also say that each human child has 100 mutations that its parents don't have, which suggests a very high increase in genetic variability being introduced in each generation. I would think 10,000 years would produce enough generations to restore genetic variability to the cheetah if that is really how it occurs.This message has been edited by Faith, 09-27-2005 11:39 AM

How many variants of a given gene can there be in a population?This message has been edited by Faith, 09-27-2005 11:41 AM

It is impossible for mutation to NOT increase variability. If two things are identical and you change one, then there is increased variability.

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Aslan is not a Tame Lion

Unless the change is deleterious or produces disease. That's a kind of variability but we have to be talking about VIABLE variability don't we? This is why I'm asking if a severely bottlenecked population has ever been OBSERVED to recover by mutation alone from its condition of severely reduced genetic variability.

1) If we consider the genetic variation within a species rather than a local population the sort of recombination you suggest cannot occur (ignoring hybridisation which can occur between some species).2) The main bottleneck in the cheetah population is beleived to be a single pregnant female. There are no other populations.3) Likewise in the Bible story of the Flood the inhabitants of the ark are supposed to be the sole survivors - again there are not other populations to consider. The effective human population under the usual interpretation, then, would be 5. "Unclean" species would be reduced to 2 individuals - a situation nearly as bad as the cheetah bottleneck (and even worse under some YEC interpretations, where multiple species would be descended from a mere 2 individuals living 4500 years ago).

In a diploid species there can be an absolute maximum of two variants of a gene per individual.

No, of course not. Mutation has nothing to do with viability. Viability is determined by Natural Selection.Whether something is viable or not depends on the environment it lives in. If something lives long enough to reproduce it suceeded. If it lives long enough to reproduce more than one critter, then the population expands. But that is a function of the filtering process.

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Aslan is not a Tame Lion

We've been talking about bottlenecked populations, and in some cases there are other populations of the same species from which the bottlenecked group has become isolated, with which breeding is still possible. But I'd rather focus on mutation alone as the mechanism for increasing genetic variability. I merely mentioned recombination as the only other way a bottlenecked population might recover genetic diversity. Yes, which is why it is dependent on mutation alone to increase its genetic variability. But in 10,000 years, according to Graculous, this hasn't occurred. This is why YECs have to postulate a greater inbuilt genetic diversity in these few than we normally see these days. More genes for one trait for instance.This message has been edited by Faith, 09-27-2005 11:55 AM

And how many per population?This message has been edited by Faith, 09-27-2005 11:53 AM