Reviewing Nathaniel Jeanson's nuclear DNA arguments

(Blogging Graduate Student) #1

I published the latest in my series reviewing Nathaniel Jeanson’s book “Replacing Darwin” a few days ago. This time I looked at his chapter 7, wherein he argues that human nuclear DNA indicates recent special creation rather than evolution.

I thought I’d post it here, as I cover a range of subjects in this post that could be the seeds of a discussion with the various non-evolutionary creationists on the forum.

The meat of the post examines Jeanson’s claims about various human molecular clocks, but also touches on pseudogenes, human chromosome 2 fusion, and pre-existing heterozygosity, for example.

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(John Harshman) #2

Nice. There’s one possible explanation for differences in evolutionary rate between chimps and humans that you don’t consider. One factor, perhaps the most important, in sperm competition is the sheer numbers of sperm. Chimpanzees produce lots more sperm than humans, and this requires more cell division in spermatogenesis, and thus more mutations in the male germ line. Of course this would affect the Y chromosome most strongly, but it would also affect autosomes. Partially countering that is the difference in generation times, as sperm accumulate more mutations with age of the host. Still, male-driven evolution seems an important factor to consider, especially as it affects all sequences, not just genes directly involved in sperm competition.

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(Blogging Graduate Student) #3

I did include a mention of sperm competition and male-biased autosomal mutations in an early draft, as Venn et al. (2014) indeed concluded that chimps had a stronger male bias in mutation rates than humans. However, Basenbacher et al. (2019) found no such statistically significant difference between great ape species, so I decided not to mention it as it’s status as an explanatory mechanism is currently unclear at best.

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(Dave Carlson) #4

Well done. With regard to the mitochondrial mutation rate - is there any evidence of a human lineage slowdown like there is in the nuclear genome (as shown by Besenbacher et al)?

(John Harshman) #5

Not that I can see. Look at Figure 1 here. There does appear to be a slowdown, but it’s at the base of the ape clade, i.e. between apes and Old World monkeys, not humans and chimps.

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(Dave Carlson) #6

Thanks, John.

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(Chris Falter) #7

Hi evograd,

When I tried to read post 2 in the series, an ad kept posting pop-ups, changing the URL prefix slightly/randomly each time. As a result, I was not able to read your post on my phone.

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(Blogging Graduate Student) #8

Sorry to hear that. I’m not sure how to solve that problem - I don’t control any of the ads, wordpress does. I just tried to access it on my phone and it seemed to work fine.

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(Chris Falter) #9

So I read most of the series on my work laptop over lunch break. The discussion of good vs. poor models in part 4 was especially poignant, and the discussion of why pedigree mutation rates are expected and observed to be much faster than long-term molecular clock rates truly educated me.

The whole series is extraordinarily instructive and well-written! Thanks for sharing.

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(Blogging Graduate Student) #10

Thanks, I appreciate those kind words!

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