Joe McCormick

speaker

4,384 appearances 9 recordings 1 series first heard Sep 2026 last heard yesterday

Joe McCormick’s voice in public audio — every appearance, attributed to the second.

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recordings per month · last 12 months

Recordings per month over the last 12 months — 9 in all, peaking in Sep 2026 with 9.

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Stuff To Blow Your Mind · From the Vault: The Wallace Line, Part 2 · 22 Sep 2026 podcast

One example of this is the American interchange where land and freshwater animals from North and South America were suddenly able to migrate across into each other's territory and voice-verified

After Rob, you mentioned this earlier, the idea of the uh Panama Isth isthmus. voice-verified

Oh man, that word is so hard to say. voice-verified

Isthmus for me. voice-verified

That's it's difficult. voice-verified

Uh after the the Panama uh isthmus was raised by volcanic activity. voice-verified

Uh so that came up from the seafloor. voice-verified

And previously there had been a saltwater barrier between North and South America for some time. voice-verified

Uh but you have this volcanic activity. voice-verified

Now there's a land bridge in Central America. voice-verified

Uh that happens between two and three million years ago, and now there's all this exchange of life forms across the barrier, or across the former barrier. voice-verified

Another one of these great biotic mingling events is the Indo-Australian interchange, which arose when the Australian and Eurasian tectonic plates smashed together, forming some islands in between within the region we were talking about earlier known as Wallacea. voice-verified

Now we've already talked about how there are some barriers to exchange along this connection point. voice-verified

Uh the extent of that barrier to cross colonization was the original observation of the Wallace line. voice-verified

It's like what Wallace observed is hey, there's not a lot of animal species going across here. voice-verified

Uh unlike the American interchange, there there is not and was never a full land bridge between Sunda and Sahul. voice-verified

But as Wallace also observed, all boundaries are permeable, and we now know a good bit of exchange does happen across this uh this line, and there are some more faunally mixed transition zones in between in the islands of Wallacea. voice-verified

But the authors of this paper point out something interesting. voice-verified

Biotic interchanges are rarely symmetrical, they're rarely totally even. voice-verified

Usually you have more life flowing in one direction across the new corridor than flowing in the other direction. voice-verified

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