The Descent of Man, and Selection in Relation to Sex
Charles Darwin first expressed his ideas on sexual selection and mate choice in his book "The Descent of Man, and Selection in Relation to Sex" in 1871 in response to questions surrounding the elaborate ornamentation that males of some species exhibit despite detrimental costs to survival and seemingly negative consequences for reproductive success. He proposed two explanations for such traits' existences: these traits are useful in male-male combat or are preferred by females.