On this day in 1857, Darwin first outlined his theory of natural selection. He found that those organisms that were better able to adapt to their environments were more likely to survive and reproduce than those that had trouble or could not adapt. The favorable variations that allow members of the same species to survive are then transmitted to successive generations.
Darwin's theory of natural selection held that the origin and diversification of species results from the gradual accumulation of these individual modifications. This is the key element of his theory of evolution, as we learn from today's reading from "The Origin of Species."