Researcher Geoffrey Miller has hypothesized that many human behaviors, like humor, music, visual art, altruism, verbal creativity, and extended vocabulary are the products of sexual selection. Miller proposed that the apparent redundancy of words in the human lexicon is the result of individuals using vocabulary to demonstrate their intelligence and consequently their fitness to potential mates. In experiments, researchers have demonstrated that men make greater use of more unusual words when in a romantic mindset, compared with men in a non-romantic mindset. This suggests that at least one use of an extended vocabulary is likely to gain access to mates. Some scientists go a step further and have hypothesized that human language as a whole evolved through sexual selection.
Geoffrey Miller has also suggested that human culture evolved through sexual selection for more creative traits in humans. Under this hypothesis, many human artifacts may have actually started as attempts at mate attraction. For example, clothing may have been used to enhance sexually desirable traits. Some scientists suggest that human intelligence, like our exceptional capacity for abstract reasoning, musicality, artistry, language and social guise, are examples of the handicap principle. Just like the peacock’s tail, only those individuals in good health and with good genes should be able to produce such signals like high intelligence and musicality. An extension of the handicap hypothesis in humans posits that human intelligence is a courtship indicator of health, specifically resistance to parasites and pathogens. The logic follows that parasites and pathogens are often very deleterious to human cognitive capabilities, and therefore an individual with high intelligence is likely to be free of such infections. For example, Lyme disease, contracted most often through a tick bit, can severely impact the memory of victims of the disease, even years after the diseases has been cured.