Millions of years ago, Central America became an almost unparalleled highway for organism migration.

Millions of years ago, Central America became an almost unparalleled highway for organism migration.
Is there a connection between the avocados in your guacamole and extinct giant ground sloths? The answer may surprise you.
While sloths today are lethargic tree-dwellers, their ancestors were different beasts entirely. But what happened to these wonderful animals? And what does Thomas Jefferson have to do with them?