I found this interesting, so I thought I’d share it with you.
I’m not sure I buy that it would be 100% fatal to some species, but not others. If it killed off Megalodon, why wouldn’t it have killed off elephants? They had zero protection from water. Or mammoths, or giraffes… the list of large land animals that should have been heavily impacted isn’t small.
Still, it’s an interesting theory, and I’ve always wondered how far back we can follow our solar system’s history through the galaxy. If we can tell who past neighbors were for any length of time we should be able to associate galactic events with events on Earth.