Darwin, Charles. «Chapter IV. Natural selection; or the survival of the fittest. 2. Sexual Selection.». The Origin of Species by means of Natural Selection. «This leads me to say a few words on what I have called sexual selection. This form of selection depends, not on a struggle for existence in relation to other organic beings or to external conditions, but on a struggle between the individuals of one sex, generally the males, for the possession of the other sex.»
