Darwin's voyage provided an insight of evolution.
Darwin postulated a concept that all the species get modify with time as those that are best amended with their surrounding possess the tendency to survive and pass on their traits to their inhabitants. This became the theory of evolution.
He noticed that identical species on distinct islands exhibited distinct characteristics. For example, he found that finches from distinct islands exhibited distinct shapes of the beak. In his voyage, he found that evolution is the phenomenon via which species change with time.