As we well know, every animal and plant species seems perfect for its environment: nothing, not even a single detail, should be there by chance. For centuries that was the certainty of natural history: species are fixed, created once and for all. Then Charles Darwin arrived and that certainty, however solid, was no longer enough. In its place he proposed an idea with truly unique characteristics: species are not fixed. They change, they evolve. They have a history. The intuition dates back to 1859. Darwin combined the observations from the voyage on the Beagle with the selection of breeders and discovered that, in nature, not everything survives. Individuals are born in excess and differ from one another: those who have a useful trait in that environment survive and reproduce, those who do not disappear. Seen from the outside, that difference is an engine. It is called natural selection. The more the environment changes, the more it pushes; the more it pushes, the more species diverge, until they can even become something else. The theory explains phenomena that the mere fixity of species left unresolved. Fossils have a stratigraphic order, Darwin's finches in the Galápagos have different beaks within the same family, humans share bones with a whale: it is one of the most beautiful results of nineteenth-century science and it raises a still open problem, the origin of variation: if selection chooses, who creates the new? Darwin himself changed his mind more than once. The question is alive. It is not a laboratory accessory and it is not worn. It is a map of the living: it is for those who study biology, for those who seek to unite genetics and environment, for those who want to understand whether even "perfection" can arise from chance. It is more than a hundred and sixty years old and continues to be debated. Few human theories can say the same. If you are therefore interested in publishing one of your own (and wish to protect it in the best way first) contact us at the telephone numbers indicated at the end of the page or write to us using the appropriate ELECTRONIC FORM. We remind surfers that the texts present in this section are protected by copyright, which prohibits total or partial reproduction. The scientific theories disclosed here belong to the heritage of knowledge; their exposition in these pages is protected as an original elaboration.