https://www.cnn.com/2023/12/21/world/octopus-dna-west-antarctic-ice-sheet-climate-scn/index.html
CNN has an article about how arctic octopus lend evidence to what has
been claimed about more ice melting during the last interglacial. Wiki
has up that the earth was warmer and more ice melted during the last interglacial than now. Sea levels did rise to 20 meters higher than
they are now, and those islands and low lying countries did flood the
last interglacial.
These octopi are separated by the large antarctic ice sheet, but when
more ice melted last time the ice sheet disappeared and the two
populations were able to get together and produce hybrids. They looked
at how the hybrid bits of DNA have recombined over the last hundred
thousand years to estimate that the hybrids were formed during the
previous interglacial period.
What is screwy is that they are not using the information to wake people
up about how the same thing will happen in the current interglacial if
the global warming predictions hold out. Instead of crying about how
terrible things are going to be, we should be putting up substantial
efforts to figure out how life survived the last example. The extant
species obviously survived, but a lot of them likely didn't make it
through with viable population genetics. A lot of the ice age mega
fauna went extinct during the beginning of this interglacial period.
The last woolly rhino paper that I put up had genetic evidence that the population did not recover after the last interglacial period and
remained an inbred population even after their population recovered to
over 100,000 individuals when the glaciers returned. It looks like not
enough animals survived the last interglacial to create a viable
population that could survive another.
We need to help the existing species most affected by global warming
have large enough populations so that purging deleterious genetics can
be accomplished. We know how this seems to have worked in the past. A
species exists as a large number of sub populations. The whole species population doesn't evolve into a future, but just bits of it make it and
the rest seem to go extinct. You keep hearing about over 90% of the
species that have ever existed are extinct, and it makes it likely that
just a small fraction of 1% of the sub populations that have ever
existed evolved into new species or kept the old lineage going until new species could evolve. Most populations are likely not genetically
healthy in that you might have to be pretty lucky to purge by founder
effects enough of the deleterious load to be the survivor of something
like the population reduction of the interglacials. If there are no
lottery winners the population goes extinct.
I've seen the current conservation efforts focusing on maintaining
genetic diversity to the point of mixing sub populations. This is a
stupid thing to do. Those subpopulations are adapted to their local environment, and they have a deleterious load that they are managing to
cope with. Mixing populations could make a less fit population for
their environment, and also adds new deleterious variants into both populations. All you have to do is look at the recombinant inbred
genetic mapping populations to understand that this is not a good thing
to do. What they did was interbreed 2 or more highly inbred lines, and
then backcross to each line, and full sib mate until you had 12.5% of
one genetic background dispersed into the other. You could produce
around 20 such lines and cover the entire genome of one line in 12%
portions. What they found was that even though the parent lines
survived and may have even produced more pups per litter than wild-type,
when they made the intercross many of the recombinant inbred lines
failed. A lot of them would have died out, but they would have to
increase the breeding population and start only mating cousins instead
of full-sib matings. Such lines never became as inbred as their parent
lines. There were obviously deleterious genetics in both lines, but
they were survivable as homozygous alleles in each line, but different combinations of these deleterious alleles were lethal, and these
combinations were created among the inbred hybrids.
The same thing will occur if you start mixing genetically isolated
populations.
What conservation efforts should likely be focusing on is increasing
population sizes and identification of deleterious variants, and working
on removing them from the populations so that they do not become an
issue. We even have the technology to fix genetic defects once they are identified. We know that there is a sperm trait in cheetahs that we
could fix and improve the reproductive capacity of that species. We
will soon have multiple genome sequences of all the endangered species,
and will have a better understanding of if they have a chance of making
it or not. Just using the human population should tell us a lot about
what variants are bad for existing protein genes.
Ron Okimoto
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