Darwin also noted the historical context of Salvador, which was still permeated by slavery, a practice that abolitionists in Britain (like himself) were deeply against. The main takeaway from Darwin’s stop at Salvador is the shock he experienced by being exposed to a habitat that cannot be found in Britain.

He found that some of these fossils were similar to the structure of animals that were alive, such as the armadillo, and he also found that some of the extinct animals had physical traits that they seemed to have passed to animals that were not extinct. For example, the bones of an animal called Toxodon had the proportions of an elephant but the teeth looked like those of a rodent. The fossils were essential evidence of his belief that species change and mutate, which he would later publish on his evolution theory.

As part of the scenery, he explained there were various volcanoes including active ones such as the Osorno volcano. In Chiloe, he discovered new species of animals such as the Rhinoderma Darwinii, common name being Darwin’s frog, and the Lycalopex Fulvipes or Darwin’s fox. Darwin’s frog is notably famous because this is one of the rare species in which male frogs can have offspring. He also studied birds and their resemblances, beetles, slugs, snails, among others. 

Apart from the mockingbirds, one of the most cited examples of Darwins’s evolution theory are Darwin finches. These are 13 different species of finches that Darwin found in the Galapagos islands and seemed like they had a common ancestor from which they acquired common traits and modified based on their living space. The finches for example, had beaks with different sizes, which pointed to them eating different foods. Information gathered in the Galapagos made it into Darwin's book called the Origin of the Species published in 1859. Here, he disproved the theory of divine creations with multiple arguments, one of them being that species in the Galapagos must have acquired their traits from species that migrated from other parts of the world, and reached their recent versions through natural selection. 

He described that Australian platypuses and potoroos had similar roles than those of the European water rat and the rabbit, respectively. Through his observations he challenged the monotheistic concept of creation and even wrote that there must be two creators. From his perspective, it did not make sense that a perfect creation would include animals that are physically extremely different but behaviorally akin.