The land bridge linking North and South America rose from the sea three million to five million years ago, forming a migratory pathway between the two continents. On this land bridge, species such as South American sloths and North American raccoons encountered each other for the first time. Microclimates, isolated topography, and the mingling of the abundant and varied life that funneled through this narrow land bridge caused new species to develop over the millennia. As a result, Mesoamerica and its biosphere reserves, such as El Triunfo, now hold some of the earth's highest biodiversity as well as a unique sampling of species, which is why El Triunfo is so essential to preserve.