Many of the observations that led Charles Darwin elaborating his evolutionary theory occurred during the voyage around the world as a naturalist of the English ship H. S. S. Beagle.
During the five-year voyage that began in 1831, Darwin visited various places in South America (including Brazil) and Australia, as well as several tropical archipelagos.
During the travel of BeagleDarwin excavated in Patagonia, where he found fossils of already extinct mammals. Darwin discovered the fossil of a gigantic animal, with its skeletal organization very similar to the armadillos that currently inhabit the South American continent.
In the Galapagos Islands, a cluster of small, arid islands situated in the Pacific Ocean about half a mile off the coast of Ecuador, Darwin found a highly peculiar fauna and flora that varied slightly from island to island.
Darwin becomes a fan of evolutionism
Darwin did not become truly evolutionary until several months after returning from his voyage in about 1837. Only then can he understand the evolutionary significance of his observations in the Galapagos and elsewhere by reviewing his notes and submitting the material collected on the trip to various experts. .
The question Darwin was asking was whether animals and plants had been reared as they are today, why are distinct but strikingly similar species, such as Galapagos birds and turtles, placed by the breeder and nearby islands, and not evenly distributed throughout the world? It was really surprising that islands of similar but distant climate and physical condition (such as the Galapagos and Cape Verde, for example) had no similar species.
Darwin eventually concluded that the flora and fauna of nearby islands are similar because they originate from common ancestors from nearby continents. In each island, the colonizing populations undergo specific adaptations, resulting in different varieties of species. For example, the various species of Galapagos fringilid birds probably originated from a single ancestral species from the South American continent. The diversification of the original species, which would have originated the different current species, resulted in the different islands of the archipelago.