Survival of the Fittest

Survival of the fittest is a simple way of describing how evolution (the process by which gradual genetic change occurs over time to a group of living things) works. It describes the mechanism of natural selection by explaining how the best-adapted individuals are better suited to their environment. As a result, these individuals are more likely to survive and pass on their genes.

The theory of natural selection was first offered by English naturalist, Charles R. Darwin (1809–1882), during the 1850s to explain how evolution worked. Darwin suggested that all living things were connected to one another because they had evolved from a few common ancestors. He used the mechanism of natural selection to explain how this could be possible. Natural selection is based on the idea that although the individuals that make up a given species all seem alike, there are in fact many important characteristics that make each slightly different from the other. These differences were inherited from the individual's parents. Organisms would pass these differences on to their own offspring if they lived long enough to reproduce.

Darwin's idea proposed that since each individual was different from any other, certain ones possessed particular traits, or characteristics, that favored individual over another. For example, a single pair of rabbits can produce up to six litters a year. Darwin realized that if each of these offspring of every species of rabbits survived to reproduce, the entire world be overrun with rabbits, to the point where there would not be enough resources to keep them all alive. Since there was a limited amount of resources, Darwin argued that each individual had to compete with others for what it needed to stay alive, grow, and reproduce.

Darwin explained that it is the environment or nature itself that "selects" which individuals are best adapted to it or are best "fit." For the six litters of rabbits, those whose particular traits give them an advantage in their particular environment are the ones who most likely will survive. These offspring also will grow strong, and pass on these "fit" traits to their offspring. Depending on the environment, it may not always be the fastest rabbit that survives. Instead, it could be the one with a certain coat color that allows it to be easily camouflaged that has the "fit" advantage. This point was recognized by scientists who adopted the term "fitness" to refer to the members of a group whose traits made them the best-adapted. For this reason, natural selection is often called "survival of the fittest." Darwin did not use these words. Instead, they were first used by the nineteenth-century English philosopher, Herbert Spencer (1820–1903), to help explain Darwin's theory of evolution.

[See alsoEvolution; Evolutionary Theory; Natural Selection ]