Darwin's theory consisted of two main points; 1) diverse groups of animals evolve from one or a few common ancestors; 2) the mechanism by which this evolution takes place is natural selection. This SparkNote will first take a look at Origin of the Species, and then more closely examine Darwin's theories.
Natural selection is a nature-made selection, and artificial selection is a man-made selection. Artificial selection is the process by which humans select certain naturally occurring variations to use in breeding new plants and animals. Darwin thought that a similar process in nature could explain how organisms change over time.
