Panama Isthmus

Islands and shallow seas changed gradually; the final land bridge formed about 2.8 million years ago, connecting continents and restricting exchange between oceans. Relatives of horses and camels spread south; ground sloths and glyptodonts spread north. Some animals crossed before the land bridge was complete. At a separate historical date, the Panama Canal opened in 1914. Locks raise and lower ships to cross a lake; this did not restore the ancient seaway.