Evolution: mutational clocks vary with size (Evolution)

by David Turell , Tuesday, April 26, 2022, 23:43 (940 days ago) @ David Turell

Amazing new finding:

https://www.livescience.com/mutational-clocks-aging-in-different-mammals?utm_source=Sma...

"Animals carry "mutational clocks" in their cells that dictate how quickly their DNA picks up mutations. And across species, animals tend to die once they've hit a certain number of mutations, new research finds.

"It turns out that, in long-lived mammals like humans, these mutational clocks tick slower than they do in short-lived mammals like mice, meaning humans reach that threshold number of mutations at a later age than mice do. This discovery, the researchers said, could help solve a long-standing mystery in biology.

"This mystery, known as Peto's paradox, describes a perplexing phenomenon that has defied explanation since the 1970s. At that time, scientists knew that animal cells accrued mutations in their DNA over time, and that as the number of mutations increased, so too did the risk of those cells turning cancerous. On paper, this suggests that the world's longest-living and largest animals should face the highest risk of cancer, because the chance of picking up cancer-causing mutations increases over time and as the total number of cells in an organism goes up.

"But oddly enough, large, long-lived animals develop cancer at similar rates as tiny, short-lived creatures — this is Peto's paradox. Now, in a new study, published April 13 in the journal Nature, scientists offer a partial potential solution to this puzzle: They discovered that short- and long-lived mammals both accumulate a similar number of genetic mutations over their lifespans, but the long-lived animals do so at a far slower rate.

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"Through their analysis, the authors discovered that, just like in humans, the crypt cells [of colonic mucosa]of other mammals also accrue mutations at a constant rate, year to year. But what was striking was that this mutation rate differed drastically between species. Human crypts accumulated the lowest number of new mutations each year, at only 47, while mouse crypts picked up the most, at a whopping 796 per year.

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"Overall, the mutation rate of each species showed an inverse correlation to its lifespan, meaning that as an animal's lifespan increased the rate of new mutations per year decreased. That ultimately meant that "the total number of mutations at the end of an animal's life was roughly similar across species," Naxerova and Gorelick noted.

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"'Our reasoning was that cells from long-lived species may cope much better with a mutagen than cells from short-lived species," said Jan Vijg, a professor and chair of the Department of Genetics at the Albert Einstein College of Medicine.

"And that's just what they found. "Cells from a short-lived mouse quickly accumulated a lot of mutations, while in the very long-lived naked mole-rat or human, the same dose of mutagen did not even induce any mutations," said Vijg, who was not involved in the new Nature study. This suggests that long-lived animals may be better at repairing DNA damage and preventing mutations than short-lived animals, and this may partially explain why they accumulate mutations at a slower rate."

Comment: Iv find this discovery fascinating. I don't know how God speciates. but I have assumed He has kept tight control of DNA coding to change species. In this case the mutation rates appear to relate to random minor mutations that do not cause changes. God does not control these but it might be posed that He set the mutation clocks as described to produce the results seen here.