According to Darwin's theory of evolution, when the surrounding environment changes, individuals that have better characteristics to adjust to new conditions, are those that will survive and generate new living beings with similar features to theirs, while others less adapted will be extinguished before being able to reproduce. Consequently, the better adapted individuals, through the natural selection of the best characteristics, will create individuals with even better ones. Darwin believed that all species alive nowadays descended from a single common ancestor and thanks to the natural selection they were able to create new organisms that adapted to the requirements of an ever changing environment.
