Evolution Requires Reduction in Genetic Diversity

Oh yes it does. Figure it out.ABE: Sorry, it can't add alleles but the rarest alleles may drop out.Edited by Faith, : No reason given.

I just did all that work in Message 598 to demonstrate what inbreeding actually does and how allele frequency doesn't change by inbreeding alone. I guess you need to explain to me how inbreeding can create new allele frequencies. All you have done so far is to say that it does but you don't know how.You apparently understand this so well, explain where my calculations of frequencies in Message 598 are wrong.HBD

What? You want to trade insults? Naw. I'll provide the discussion you can stick to insults.HBD

No, it doesn't create new allele frequencies, although very rare (low frequency) alleles do get dropped, so I've read. But I never claimed it creates new frequencies, it creates new combinations of the new mix of alleles that occurred at the population split. I believe that's all I've said.

HOWEVER, I might have said something like that as now I remember thinking that inbreeding isn't guaranteed to preserve the original proportions. Even without intentional sexual selection random pairings can favor certain combinations over others and offspring aren't guaranteed to occur in equal numbers or follow perfect Mendelian allele combinations, so yes you could very easily, perhaps always, get an increase in some alleles and vice versa which would be a change in gene frequencies.. This would be a form of genetic drift but in a small population it could make a big difference. However, I don't care.Edited by Faith, : No reason given.Edited by Faith, : No reason given.

Just a subset of the original mix. A pre-existing subset of a larger set. Depending on how large the set is, it might actually contain all of the original alleles in different proportions among the population than the original set. Now what does inbreeding accomplish absent some selection? And what makes us require inbreeding at this point? Is this really the only scenario we need to consider in order to rule out or in evolution?I'll answer the last question. Obviously not.

PARDON????
Did you say "rather than address my arguments?"
See post Message 1758349[/mid].
Where did you address those then?

Is everyone aware that you're using this very technical and highly specific definition of inbreeding? It's possible that, like me, others are using a definition more along the lines of a small population just breeding with each other. In a population "breeding completely at random," is it reasonable to assume no drift?Also, I think at times that you and Faith are talking about two different things, that sometimes when Faith is talking about the population a short time after the isolating event, you're responding about the population after a lengthy enough period of isolation to result in equilibrium according to Hardy-Weinberg. I only quoted your concluding paragraph, but I read and understood everything that preceded it. I think you've demonstrated what I said, that changing genotypic frequency without affecting allelic frequency is very unlikely. In order to keep allelic frequency constant while changing genotypic frequency you need the highly idealized conditions of no mutation, selection, drift or migration. Do you really require allelic frequency to remain constant, something that seems highly unlikely in the real world, in order to make the point that genotypic frequency has changed but not affected interfertility?Sorry to get this far into the details, but I'm trying to keep this at a level everyone can understand, and I'm sort of using my own comprehension level as a yardstick.

HBD, if I'm not wrong, inbreeding also "artificially" declines the population size by closely related individuals mating among their own kin alone. Isn't it that under such conditions of a small population, the effects of genetic drift are stronger? After all, genetic drift may cause gene variants to disappear completely and thereby reduce genetic variation. If so, did you include this factor into your calculations in post 598?

HBD's comments do not warrant this response. Could I suggest that if you have comments about how slavish, sophomoric or brickheaded any other participants are, or about the positive aspects of your own contributions, or about your own emotional state, that you should keep them to yourself.There *is* a moderator on duty here. If you have concerns about conduct in the discussion you should raise them with me rather than trying to deal with them yourself, otherwise the one engaging in misconduct is you.Why don't you try to understand why HBD thinks it's necessary to deal with gene flow in both directions, among other things?

You appear to be attempting the discussion board analog to "suicide by cop" (though of course here it's usually very temporary). There *is* a moderator here.I am, as always, reading the thread in order, responding as I go, and I don't know what comes next. If I decide upon any moderator actions I'll hold off until I finish reading to the end.

Yes, genetic drift would be a way to change allele frequency and it is especially efficient in small populations. The role inbreeding plays is it moves alleles into homozygotes and so individuals removed from the population at random are more likely to be homozygotic and thus two alleles are removed with the death of that individual. But really, the key in this effect is population size, not specifically inbreeding (although there is certainly more inbreeding in small populations than there is in large populations)Here is a figure that shows the results of an experiment using different population sizes of Tribolium beetles. (I lifted it from Rich, Bell and Wilson (1979) Genetic drift in small populations of Tribolium. Evolution 33:579-584. but you would need a JSTOR subscription to view the whole paper) Each population started with an equal proportion of alleles (b⁺ - 0.50) and only varied by the number of founding individuals. Notice the general upward trend of each population; that indicates that selection is acting to favor the b⁺ allele. Also notice the magnitude of fluctuations and the number of subpopulations that go to fixation is reduced as the population size increases.Therefore yes, your founding population would experience drift because of the small population size and allele frequency would change, probably rather rapidly, but this is a known effect (founder effect) not something new you came up with.So, I will echo a question NoNukes posed"Is this really the only scenario we need to consider in order to rule out or in evolution?"HBD

Really?I shouldn't need to say any more, but just to be very specific, you should be working toward making your position clear instead of telling others to do your work for you. To everyone else it seems impossible that mere genotypic change in two originally interfertile subpopulations could negatively affect interfertility, because without new alleles or genes any genotypic permutation in either subpopulation could have occurred in the original population. Without new alleles how is a subpopulation to arrive at a genotypic permutation that couldn't have occurred in the original population? People are seeking an explanation from you.I'm not taking a position in the discussion, but being neutral doesn't mean imposing some kind of artificial ignorance or stupidity upon myself. Others have made the genetic considerations very clear. If they're wrong then you have to show how they're wrong.

Hi Denisova,I think others have answered your questions. I'll just add that I think you can tell that I'm no shrinking violet, but you can't push on a string or herd cats. I don't think there's any forum anywhere that has ever solved the problem of how to turn on the light bulb for creationists. Just the fact that they've arrived at their position and likely maintained it for many years means that they have developed a complex catacomb of misconceptions and obscure justifications that defies simple facts and rational thinking.

The reason a small population inbreeds is that the individuals in that population are more likely to breed with a close relative than random chance would expect because there is so few choices of mates. It becomes more difficult to find a mate that is not closely related.I suppose it is unfortunate that I had to get so technical about this from a such a simple comment I originally made; that inbreeding alone would not change allele frequency but requires drift, selection, mutation of migration. Absolutely not. Faith originally wanted to exclude other evolutionary factors and claim that in a founding population inbreeding alone was sufficient to explain the differentiation of the populations. That's how this line of argument got started. So, in order to examine how a particular factor effects population structure you need to exclude other factors. Highly likely. I try really hard to understand what she is talking about but I may be missing the mark sometimes. I was only demonstrating what inbreed itself does. I totally agree that under real world conditions, allelic frequency will be affected. I would be completely satisfied with a statement such as "inbreeding will cause the allelic frequency to shift." but not at the exclusion of the other evolutionary factors. It is not inbreeding itself that causes allelic frequency to change it is drift and selection. I got the impression that Faith wants to exclude those factors (she does because those are "evolutionary forces") - that's not OK. Often what seems like a simple and straight-forward comment turns into a big fiasco. Here's my original comment: It could have helped some had she responded to my Message 558 where I stated this again So I am not relying on allelic frequency to remain constant at all. I tried to avoid all the detailed technicalities, but sometimes feel forced into it when the simple, straight-forward point is called ridiculous.HBD