Differential survival is an essential component of Charles Darwin's theory of natural selection. As an idea, it was partially inspired by Adam Smith's essay "On Population", which states that because food production increases linearly, but population increases exponentially, more human beings are born each generation than can possibly survive, and the excess need to be killed by war, famine, and disease. Evolution applies this principal to all other organisms, with some extreme figures: for existance, if every starfish and all of its offspring survived, in 16 years one individual would give rise to 10-to-the-79th-power offspring. (This is the same number of electrons in the visible universe.) In reality, limited quantities of space and resources lead to a struggle for survival results, everybody competing for environmental resources, and as a result those individuals in a population that are the most fit can survive.