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onioning t1_j1166c4 wrote

Reply to comment by Ruuhkatukka in TIL Lake Baikal is located in southeast Siberia and is the oldest and deepest lake in the world, at 25 million years old and 1,700 meters deep. It contains 20% of the world's unfrozen freshwater and is home to a rich and unusual freshwater fauna that is of significant value to evolutionary science. by wisely_lined56

It's pretty much a wholely different environment. Totally plausible for seals to travel short distances through rivers, but at that length it's almost certainly a multi-generational migration. Meaning whole generations were born in and died in rivers. That's a hell of a rapid adaption from being arctic sea-dwellers.

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Ruuhkatukka t1_j116vot wrote

Interesting. So there were river based sub species at some point? I don't know much about seals but I was always fascinated by the sub species that lives in lake Saimaa here in Finland.

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onioning t1_j117x28 wrote

This is all speculation. Just perhaps the most plausible explanation. There's literally no evidence of river going seals up there. Though that doesn't at all mean it didn't happen. Finding a river going ancestor somewhere would change things, but the fossil record can be really cruel sometimes.

If they came from the West this problem doesn't exist, because that would be a voyage of shorter rivers between larger bodies of water.

There's a good YouTube video on this. Can't recall if it's PBS or Moth Light Media or someone else, but details the various theories.

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