Testing Jeanson's Model: Y Chromosome Mutation Rates

3 posts were merged into an existing topic: Scientific Ethics, Enculturation, and Policy

We expect Y chromosome to have a bit higher mutation rate (not 50x higher, but maybe 1.5x) and X chromosome to have a bit lower mutation rate.

Can you explain why this is? Is it because the Y chromosome doesn’t contain genes necessary for survival? After all, women get along just fine without one.

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Thank you for providing this argument. I give you lots of credit for reading this book. I am very interested to see how the mutation rate argument shakes out.

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Well, in fact the Y mutation rate is higher than that in most of the genome, and the X rate is a bit slower. But the difference isn’t nearly as high as Jeanson needs. You can google “male-driven evolution” for information.

Oops, I see @swamidass has already answered this.

Not sure why you would expect such a thing. But again the X is a little less different than autosomes. So the prediction, whatever the reason for it, is wrong. And yes, chimps have Y chromosomes.

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How does 275,000 years line up with evolutionary timescales? You would have the invent the other million+ years needed to satisfy evolutionary requirements. What if someone claimed, based on your statement, that mankind simply began 275,000 years ago? That would leave you far short of evolution. And with such a recent number as 275,000 years, still another could claim that external factors may have affected internal genomic results such that hundreds of thousands of years may have been reduced to mere thousands years. How do you guarantee uniformity of mutation rates such that a range of 275,000 to 588,000 years becomes infallible science?

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That’s not true @r_speir. Mt-Eve and Y-Adam are expected to be a few hundred thousand years in the past. We get the mutation rate, however, this way:

The formula is pretty simple: Rate x Time = Distance.

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You should mention that the observed distance needs to be corrected for multiple hits, site-to-site rate variation, and different probabilities of different mutations. Though not so much within the human population.

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I believe that very few creationists have any notion of coalescence, and suppose that mt Eve and Y Adam must be placed at the beginning of the species at least, and likely at the start of the lineage. You should remind @r_speir that there is no correlation.

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Yes. That is definitely true. The formula Rate x Time = Distance is a simplified approximation.

Venturing a prediction far outside my own field, I think a mutation rate 50 times higher than expected would not only disprove evolution, but create serious problems with much of what we know about biology. This is the sort of prediction Jeanson could be making and testing to provide confirmation.

It is my observation that Creation Science never deals with the obvious consequences of YEC predictions, which is how we get silliness like Hydroplate Theory.

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Seems to me @John_Harshman is right and it wouldn’t. The balance of evidence would still be massively in favor of evolution even if the measured mutation rate deviated from expecatation by a large factor. It would just leave us with one source of evidence resulting in conflict rather than consilience. And it’s not like large variations in mutation rate are unheard of in evolutionary biology at all. Heck, in some of the lineages of the LTEE, the bacteria evolved something like a hundred-fold increased mutation rates because one of the mismatch repair pathways suffered deleterious mutation(s).

This is a stronger point, because a 50-fold increase in the human mutation rate would have massive implications for the probability of suffering both spontaneous heritable and somatic diseases, their subsequent worsening due to additional deleterious mutations, the probability and evolutionary rates of cancers, and so on. It would be extremely important to medicine.

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Yeah, but that is bacteria. This level of per-generation mutation in humans (or any large mammal) is unheard of at this time.

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For the between-species comparison, you also have to include the coalescence time within the ancestral population, which is a large effect.

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Sure, but there doesn’t seem to be any reason why such an increased rate couldn’t evolve in principle.

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It is hard to imagine a complex organism that wouldn’t be at a mutation catastrophe with such high mutation rates. In principle, I do see prohibitive negative selection against hypermutators.

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Yes that would increase their mutational load quickly, and thus would explain why such high mutation rates don’t persist for any extended period of time(either the species goes extinct, or selection manages to bring the rate back down). It is my understanding that the mutation rate of any given species reflects some balance between historical population size(and thus variance in the balance between selection and drift) and mutation load. Larry Moran had a good post about this on his sandwalk blog: https://sandwalk.blogspot.com/2016/12/learning-about-modern-evolutionary.html

Curiously(or, accordingly), even in the LTEE the hypermutator lineages are actually evolving reductions in their elevated mutation rates(*). But my only point was really that, biochemically speaking, the causes of hypermutability could happen in large multicellular eukaryotes such as humans, too.

(*) See https://www.pnas.org/content/110/1/222.short

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Isn’t that actually the contention of the “genetic entropy” clowns? Sanford, and that lot? I recall it being pointed out that if they were right, lineages with shorter generation times ought to have gone extinct a long while ago, so that we would be living in a rat-free world, among other things.

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It’s also being done because sequencing is so much less expensive and easier these days… It’s kinda like picking the low hanging fruit.

It works out all the time in the Marvel Universe. They frequently get superpowers plus side effects that make it difficult to get dates for a Friday evening. So, predominantly adverse mutations but with interesting phenotypes.

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This review paper from 2016 alone has 11 pedigree studies. We can certainly be sure that many more studies have been done since then. Notice that the date on Jeanson’s study is 2019, which means there is just no excuse for not including the 11 papers in this review.

These are whole genome studies, which will also include Y-Chromosome. Even if they don’t state the Y-Chromosome rates directly, the supplementary information or a simple email to the authors will usually be enough to get that subset of the results/data.

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