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rocksfly t1_j0xyd44 wrote

Reply to comment by onioning 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

The river connections get pretty close to the lake, and likely connected to the southern part of the lake.

Pinnipeds have been found in inland California when they swim upstream in the rivers and canals.

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onioning t1_j0zlxoa wrote

Yah. Like I say, that's a long ways to go, especially since those rivers stay frozen for much of the way. As far as I know, there aren't seals that do well in rivers, and it's rather unlikely that the lake was populated by individuals making the entire journey themselves.

The other major theory is they came from the West, plausible because the Caspian was far far larger, as was the... Um... The sea that Ukraine borders. Whatever that one's called.

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rocksfly t1_j0zmdz0 wrote

A key to answering this question is genetic analyses, which can help narrow down how long that population has been there. Then you have a broader sense of the climatic variability that could play into the migration.

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onioning t1_j0zn6zo wrote

I'm speaking from memory here, so may have the details wrong, but if I am remembering correctly they haven't been there that long. It would be easier to explain if they had been around before the last ice age, because that would make the northern river route more plausible, but the timing doesn't add up. If they were a bit older than even that the western route would be more plausible, as those waterways were yet greater. But the timing doesn't add up, and they seem to have arrived after those easy routes were dried up or frozen.

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