https://phys.org/news/2023-04-woolly-mammoths-evolved-smaller-ears.html
Phys.org has a news article on this research.
https://www.cell.com/action/showPdf?pii=S0960-9822%2823%2900404-9
The mammoth had already separated from the Asian elephant a couple of
million years before the 700,000 year old mammoth genome existed. The
claim in the article is that 700,000 years was soon after the mammoth
separated from the Steppe mammoth. The research article claims that
they used 22 wooly mammoth genomes (16 of which they constructed for
this paper) and 28 genomes of modern Asian and African elephants.
Figure 1 indicates that Mammoth were more closely related to Asian
elephants than they were to mastodon that shared the same ice age
environment, and also did not survive the current warm period.
The paper is about the genetic changes that occurred within the mammoth
lineage to adapt them to ice age conditions. Mammoth seems to have the
basic gene set to be cold adapted by 700,000 years ago, but became
better at arctic survival until they went extinct.
My take is that better selective advantage during the cold periods left
them more vulnerable during the relatively short warm periods. They
note that some of the variation was not fixed in the mammoths. This
type of variation may have helped them cope with the warm periods even
though segregation in the cold periods would have some disadvantage.
These would be the alleles that would be maintained by being selected
for during the warm period, and being selected against during the cold
period. As more of the warm period alleles were lost during the
extended cold periods, the mammoth would be less able to cope with the
warm periods.
Ron Okimoto
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