Scientists agree that the Galapagos Islands never connected to the mainland. The ancestors of every plant and animal species native to the islands arrived in the archipelago from somewhere else. Most scientists accept the theory of long distance dispersal for bringing life to the Galapagos Islands . Flotation rafts of natural vegetation, wind and air currents and oceanic drift all contributed to this "sweepstakes dispersal". Organisms had to endure the hazardous voyage, survive in an unfamiliar environment and reproduce in order to survive.
Most of the animals in the Galapagos originated from North, Central and South America and the Caribbean . Land birds and California sea lions arrived from North America . Pink Flamingos and Darwin 's Finches arrived from the Caribbean . Land iguanas, giant tortoises, pelicans, cormorants and boobies all arrived from South America . Fur sea lions and penguins came north from the Antarctic.
Many animals are not found on the Galapagos. Amphibians and other aquatic animals, for example, are poorly represented. Large terrestrial mammals similarly failed to make the crossing. The lack of herbivorous mammals left a niche open for tortoises. These huge reptiles developed and became the large grazing herbivores on land, a position they enjoyed until the relatively recent arrival of humans with domestic livestock.
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