Evolution Requires Reduction in Genetic Diversity

Both Denisova and PaulK responded to this, but I think they may have arrived at different interpretations, and I'm not sure what you mean either, so some further clarification would be very helpful. Let me describe what you seem to be saying and you can correct as necessary.Assume we have a population of 10 individuals. Every individual has unique and different alleles for a particular gene (i.e., heterozygotic) for a total of 20 different and unique alleles in the population. The genetic diversity for this gene could not be any higher. These alleles produce working proteins in each individual.Now 8 individuals die, leaving just 2 individuals in the population for a total of 4 alleles. How does the absence of the other 16 alleles cause the 4 remaining alleles to stop working (stop producing proteins) to turn the gene into a pseudogene?Of if you meant that the gene would only become a pseudogene in later generations, then when the 2 remaining individuals mate (assuming they're of the opposite sex, and note that they could have mated whether the other 8 individuals were alive or not) why would the alleles of this gene in the offspring no longer produce proteins? Or in any later generation?In other words, how does the removal of alleles from a population cause the remaining alleles to stop working, whether right away or in later generations?

Unclear. Alleles don't contribute something to a gene so that it is functional; the alleles ARE the gene. I assume you realize this, but the way you word these statements at times makes it seems like you think alleles and genes are different things. Alleles are different FORMS of a gene. If a gene is functional then there must be at lest one allele; if there is at least one allele, the gene is functional. Losing alleles in and of itself does not affect gene function. Just a clarification. Inbreeding itself does NOT change the proportion of alleles (ie. it does not eliminate alleles), it only shuffles them into homozygotes. An extreme inbreeding event (such as selfing which humans are not very good at) would result in 1/2 the population homozygous for allele A and 1/2 homozygous for allele B. Unless there is now some barrier generated, these populations will eventually begin to outcross and will restore the heterozygous proportion rather quickly. A change in allele frequency requires drift or selection, both of which can result from inbreeding, but are not necessarily a consequence. So, diversity is reduced by the bottleneck but would then remain stable unless acted on by drift or selection.In the case of cheetahs and elephant seals it is mostly selection that is causing a lack of recovery. In the case of humans after the flood, it doesn't seem to me that the population had any difficulty recovering. Do you have an argument as to why selection was acting on the post-flood population and it was unable to recover rapidly? This is a statement that you should be able to back up with evidence. Show us some subpopulations where it has been demonstrated that the subpopulation has increased in the number of fixed alleles. A more accurate way of saying this is that to ensure that a trait always breeds true then the trait needs to be homozygous in both breeding individuals. You want the traits you are selecting for to be homozygous, but traits not being selected for you want to have variability. Another statement you should be able to provide some evidence for. What "fixed loci" characterizes human populations today? There has been quite a bit of work done looking at the diversity of human populations and "races." Also, if you have a population of say 1000 individuals, all homozygous at a particular loci, how many destructive mutations (mutations that deactivate a gene) would there need to be for that deactivated gene to propagate throughout the population - that is, until the entire population lost function of that gene? Or another way to phase the question, what would have to happen for that deactivated gene to become fixed in the population? Yes, here we are... Faith's assertion of what happened without evidence. You have described your observations but have not provided empirical support that your conclusions about those observations are valid. Case in point! What percentage of the human genome is "disabled genes?" How would you detect a "disabled gene," what would it look like. What are some examples of "disabled genes" from the literature. What is your estimate of the number of "disabled genes" and how do you arrive at that estimate?Unless you provide answers to questions like these, all you have is an observation from which you have drawn an unsupported conclusion.HBD

My eyes are bad again, haven't been able to read the last few posts, only skimmed parts of them. I'll have to come back when my eyes are better.But do want to say I've thought through the idea that junk DNA was a result of the Flood and now agree that it couldn't be. I hate to give up on it, I really liked the idea. But if it's the result of mutations that destroy gene function it's got to have come about individualy over the generations. At least the Flood accounted for such a huge loss, now it's a bigger loss than I thought. But of course to me it IS a loss, no way these are just genes we didn't need or some such nonsense.Back when I can.

Interesting article!
It much parallels the genetic mechanisms of loss of hind limbs in cetaceans (FYI): Just a moment....

OK, be careful with your eyes and see you back!

Yes, for sure. Take care of your eyes! Sounds like it is happening more frequently recently (or maybe it is just that you are now mentioning it?) Good. Very reasonable.But then you go on to say this: So, I am unsure of what you mean... do you mean that you thought the flood explained it? What genes are these? There have been no genes identified which we can make an informed decision as to whether they were needed or not. I think you mean pseudogenes... so what are the homologs of these pseudogenes that they appear they might have at one time been that you feel we did or didn't need?HBD

I shouldn't be here. Quick and gone I hope. Both. I haven't mentioned other times when I've had to avoid the computer for this reason, but it's definitely worse lately, getting scary. Well, yes, huge loss of life, huge area of pseudogenes. Even thought I understood how it happened, accumulation of fixed loci, vulnerability to destructive mutations. But there's no more reason for that sequence to have happened as a result of the Flood than in any other population split that led to decreased genetic diversity. Those that became junk DNA. I'm merely responding to various statements that interpret them as having been lost because they weren't needed, which seems to be a common evolutionist interpretation. Sometimes sounds positively Lamarckian, as if these mutations increased BECAUSE the gene was slated for junk DNA, like a sort of retirement when no longer needed. The Wikipedia article on Pseudogenes gives this interpretation as Irecall but I'm gone now, not going to look it up.

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I'm merely responding to various statements that interpret them as having been lost because they weren't needed, which seems to be a common evolutionist interpretation.

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I thought that was your argument - that they were only useful with alleles of other genes, and those alleles were lost.

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Sometimes sounds positively Lamarckian, as if these mutations increased BECAUSE the gene was slated for junk DNA, like a sort of retirement when no longer needed.

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That's because your interpretation is wrong (ironically that view would be more consistent with your idea - you needed genes to be mutated to the point of being unrecognisable as genes in a few thousand years).Unnecessary DNA is not subject to a higher rate of mutations. It is, however, not subject to selection. Mutating a useful gene to be non-functional would have a significant affect on fitness and should be removed by selection. Mutating a useless, or nearly useless gene to be non-functional would not be removed by selection.So, over generations unnecessary DNA changes faster than that that is needed or useful (at least where the sequence matters). But not because more mutations occur - it's because more are retained in the gene pool.

Nicely done. Giving up on a favorite idea is hard for any of us. But your taking it one step further and explicitly admitting changing your mind (rather than letting us guess) is surely something to celebrate. But the Flood loss could not represent any loss of function that Noah and his sons still possessed right? Surely those eight people possessed all of the vital functions for humans. Besides the silly notion that the people missing after the flood could have done something to the genes of living people, the flood itself could not have possible eliminated any essential human functions or else Noah and family would have had to be sickly.

But that isn't what I thought. Really I hadn't thought it through at all, I just liked the idea, and when I finally did actually think it through I realized it wouldn't work. But what I sort of vaguely thought I thought was something like this: I thought the surviving eight, really the surviving three reproducing couples, had so little genetic diversity left (though they had enough to generate everyone living today, it's relative of course) that when later population splits occurred and some genes were reduced to fixed loci, that they'd become vulnerable to further loss and therefore keep adding to the junk DNA. But I finally realized that doesn't happen with population splits in general so there's no reason to expect it to happen as a result even of the Flood bottleneck. And as someone said here, it would only happen through mutations anyway.So in reality it had to happen as a result of random mutations completely unrelated to the Flood. Yes, although I didn't really have that idea as such it was as if I was equating the enormous loss in the Flood with the enormous accumulation of the pseudogenes somehow or other.Noah and family themselves didn't lose anything genetic of course, they still possessed the same genetic strengths people generally had before the Flood so the losses would have occurred to their descendants over the following generations.I still think junk DNA is genes that used to do something useful so we are now without those anyway. Are we sickly? Compared to Noah's generation I think we must be. We are certainly vulnerable to quite a collection of maladies from the mild to the lethal that they no doubt weren't.Edited by Faith, : No reason given.Edited by Faith, : No reason given.Edited by Faith, : No reason given.Edited by Faith, : No reason given.

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But that isn't what I thought. I thought the surviving eight, really the surviving three reproducing couples, had so little genetic diversity left (though they had enough to generate everyone living today, it's relative of course) that when later population splits occurred and some genes were reduced to fixed loci that they'd become vulnerable to further loss and therefore keep adding to the junk DNA. But I finally realized that doesn't happen with population splits in general so there's no reason to expect it to happen as a result even of the Flood bottleneck.

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That doesn't sound like you thought it through. Selection won't "break" a gene - and the gene would have to be actually harmful before selection would even prefer a "broken" version.

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I still think junk DNA is genes that used to do something useful so we are now without those anyway. Are we sickly? Compared to Noah's generation I think we must be. We are certainly vulnerable to quite a collection of maladies from the mild to the lethal that they no doubt weren't.

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If the "junk" is even mostly pseudogenes, we'd have had to have lost a huge number of them - many times what we have now. If the junk was contributing in any other way that is dependent on sequence we'd have still lost a huge amount of functional DNA. And then we have the role of selection which would have favoured the functional versions if they added to fitness. Worse still, it looks like you need a lot of mutation AFTER the junk versions became fixed.So really, your "best" explanation would be to say that Noah and family had most of this assumed functional DNA reduced to junk. The bottleneck is both the easiest place for drift to influence the genome, and relatively long ago. It's still nowhere near a good explanation though.

It is enough that junk DNA cannot be related to a loss of diversity caused by the bottleneck that is an inevitable consequence of a global level hear extinction event 4500 years ago. Given things like lack of toleration of transplanted organs even for family members, there is plenty of evidence that the current genetic diversity of humanity, even within single single families, exceeds than which can be explained by the number of alleles present in just 8, not so diverse people absent some mechanism to ADD diversity.And as you have acknowledged, junk DNA has nothing at all to do with that. As I see it, if you want to pack diversity into the non-diverse group of Noah, sons and their wives, only some kind of super genome is left to you as explanation.As for whether we are more sickly than Noah. I note that every one of us humans are considerably weaker and more frail than Achilles and Hercules are claimed to be.

Apart from the obvious nonsense of people growing 5 meters or taller or ageing 500 years or older, which is directly contradicted by archaeological finds, there is hardly any indication that extant humans are fainter than people 4,500 years ago.With ups and downs, longevity has increased throughout the past millennia. Archaeologists can estimate the age of death from buried people for instances. Also written attests from old cultures help. For instances, in the Ptolemaic era, Egyptians began to pretty systematically note the age of death of the deceased. It yields an average age at death of 54 years for men and 58 for women.However, note that these merely were the elite of whom we know this. As the elite always tends to live longer than "ordinary" people, the actual, population-wide age at death should have been lower. If we take the differences found between elite and common people in medieval England, this may subtract 7 years or more from the average, population-wide age at death. These differences in longevity between elites and common people persist even today in developed countries.Moreover, in ancient cultures not all child deaths were recorded. It is not possible to calculate these effects but it must have had a considerable effect on the average life expectancy at birth (which is quite distinct from average age at death).What about Sumer? Examination of 17 skeletons from al-Ubaid, of fourth millennium date, learned that humans were not living longer than ~60 years. At a burial site in Kish the average age at death was even lower. Again, these are mere the numbers for the elite.Now what will happen when the average age at death rises?
Then you will get ever more people who are old. And, the older a person is, the more medical problems he or she will experience. For instance, cancer still MAINLY is an age related disease. Only some 10% of all new cancer cases involve people younger than 45 years.This also applies for most other diseases. In other words, the raise in health care costs and the increasing incidence of all kinds of diseases, mainly is just due to an ageing population.

Interestingly, there are estimated to be ~20,000 pseudogenes in the human genome which matches up nicely with the roughly 20,000 - 25,000 protein producing genes. The protein coding genes make up less than 2% of the human genome so it would mean the amount of pseudogenes take up roughly the same amount of space in the genome <2%.In addition, many (maybe most?) of the pseudogenes that have been identified have homologs that are functioning genes within the human genome. You may be aware of this but others may not, one hypothesis is that vertebrates have undergone two whole genome duplications during the course of their evolutionary history. 2R hypothesis This idea seems to fit well with the pseudogene pattern and also fits with what we know about duplications and subsequent adaptation of gene copies.A diagram illustrating this hypothesis using theoretical gene patterns:

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Pattern predicted for the relative locations of paralogous genes from two genome duplications

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HBD

Denisova, realise that Faith rejects all scientific dating methods as inaccurate. To her all genetics is a result of what happened after The Flood. So, to mention a date, for example the 3500 year old Otzi living around what's now the Italy/Austria border, to her is the same as claiming that Otzi lived on the sun 14 billion years ago. No matter whether Otzi has been genetically sequenced or not.Edited by Pressie, : No reason given.