Sexual selection: Physical performance and language

The biocultural success of the human species depends on mating, reproduction, and effective care of offspring. Charles Darwin identified two types of biological selection that make these possible: natural selection and sexual selection. Both are likely to be involved in the evolution of human adolescence. Sexual selection is all about opportunities for mating, while natural selection is, in part, about making and parenting offspring. Darwin, in his 1871 book The Descent of Man, and Selection in Relation to Sex, defined sexual selection as, «[…] the advantage which certain individuals have over other individuals of the same sex and species, in exclusive relation to reproduction.» Today we would replace the word reproduction with mating, as not all sexual encounters result in offspring. Females of many species of birds and mammals, for example, use mating as a way to elicit protection for themselves and care for offspring not sired by the male. Darwin also wrote of the many structures and instincts developed through sexual selection, including, «[…] weapons of offence and the means of defense possessed by the males for fighting with and driving away their rivals —their courage and pugnacity— their ornaments of many kinds —their organs for producing vocal or instrumental music— and their glands for emitting odors; most of these latter structures serving only to allure or excite the female.»

It is known today that sexual selection also works for females, meaning that female-specific physical and behavioral traits may evolve to allure or excite males. Some human examples are shown in the photographs above. Dance is practiced in all human societies. The style of dance movement is learned, as are the styles of clothing and other body ornamentation, including facial makeup. Singing is another pan-human behavior. Singing exemplifies and exaggerates the human capacity for symbolic language. Language is learned, beginning at birth and perhaps even prenatally, for example when mothers talk to their fetuses. During the adolescence stage of development there are important advances in language use, including an increase in speech-breathing capacity and increases in speech fluency. Linguistic content, including vocabulary, becomes more nuanced, grammatical operations and idiomatic phrases (slang) become commonplace. The adolescent develops more refined logical expression of thought as well as the capacities for joking, deceiving, mollifying, negotiating, persuading, and the use of sarcasm. By the end of adolescence women and men have greater socially relevant use of language from gossip to storytelling and greater use of language and cognitive skills in social competition. Rap music reflects these linguistic skills. Types of rap are known since the earliest historical records and are known in human cultures around the world, even those without formal systems of writing. Fluency and artistry in dance, singing, and speaking are central signs of physical, mental, and reproductive health. Effective teachers use the power of language and linguistic performance to transfer knowledge, especially from adults to adolescents, juveniles, and children. Much research evidence supports the view that these human behaviors have been sexually selected. [Barry Bogin]