Question

Imagine an island inhabited by a large population of a certain kind of creature—let’s call them furberts. Let’s call our group of furberts “Population A.” Now, imagine that a powerful hurricane picks up about half of the furberts (remember, you’re imagining this) and blows them to another island. Let’s call this group “Population AB.” As everyone knows, furberts can’t swim, so there’s no way for the furberts in Population AB to get back to their old island.



Because all the furberts in Population AB are isolated from the furberts in Population A, they cannot interbreed. It turns out tha