How biogeography finds proof evolution theory?
The biogeography, i.e. study of the distribution of the individual species provides an enormous amount of evidence for the evolution of species of fauna and flora through gradual branching off from a common ancestor. If the individual species of organisms were to be formed independently at the same time or one after another, the distribution of their occurrence over the surface of the Earth should also be independent or this distribution should reflect only the differences in natural conditions in various parts of the Earth. However, reality is quite different. Species belonging in a particular taxon very frequently occur in the individual areas of the Earth, although species belonging in other taxa could also be very successful there. The reason why, for example, there are no local species of big cats in Australia is certainly not that there were not suitable conditions there for them, but that they did not have any species from which they could evolve, there was no species of cat that they could gradually evolve from. On the other hand, it is clear why there are a great many local species of bats there – their ancestors could quite easily get there by air. This phenomenon is particularly obvious on islands. As soon as an island is far from the mainland, there is a lack of the members of taxa for which the ocean represents an obstacle to spreading. In contrast, these species are present on islands located at suitable distances from the mainland and they very frequently form separate species that are different from the species occurring on other islands or on the mainland.
Another obvious phenomenon that is encountered on islands and groups of islands consists in radiation of taxa, whose members have only a very narrow niche on the mainland. Darwin’s finches are mostly given as a typical example; in actual fact, these are a group of closely related buntings occurring on the individual islands of the Galapagos Islands. The individual species became morphologically differentiated in the local environment and divided up various ecological niches that are occupied on the mainland by birds of various taxa. Numerous species of Drepanididae on the Hawaiian Islands represent a similar case (Fig. XXVII.3). The theory of evolution predicts the formation of species with this character of distribution of occurrence the individual species. Local species of woodpeckers cannot exist in the Galapagos simply because no common ancestor got there. If the relevant niche were to be filled, a species of bird that got to the island in the past, in this case a bunting, would have to (at least imperfectly) adapt to it. In contrast, other theories of the origin of species would encounter substantial difficulties in explaining similar data. If the species were to have been formed independently, for example by autogenesis, or if they were to have been formed in a single instant, either in one place or in a great many places by a rational being, either there would be woodpeckers on the Galapagos, or they would not be there; however, they would apparently not be replaced by a local species of bunting and quite certainly closely related species of this species of bunting would not replace several other unrelated groups of birds in their very different ecological niches in the Galapagos.