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How did the Isthmus of Panama enable the Great American Interchange?

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Messinian Stage — Tertiary Period Gypsum cones, which resulted from the evaporation of the Mediterranean Sea during the Messinian Salinity Crisis, in the Sorbas basin, Spain.

The Great American Interchange was made possible by the elevation of the Isthmus of Panama, which occurred between 5.5 million and 3 million years ago.1

Prior to this event, the region was occupied by a seaway that had existed since the first half of the Cretaceous Period, effectively acting as a barrier that forced the faunas of North and South America to evolve in isolation. When the isthmus emerged, it created a terrestrial land bridge that allowed for a massive migration of land mammal faunas between the two continents.1

This interchange facilitated the movement of South American species, such as ground sloths, into North America as far as the Great Plains, California, and Florida. Simultaneously, various North American mammals—including cats, horses, elephants, and camels—migrated southward, reaching as far as Patagonia. This event fundamentally reshaped the biodiversity of the Americas, resulting in the rich intermixture of species observed in the region today.12