In our ancestral environment, gender specific intersexual attraction cues served as a basis for differentiating potential mates. These cues were fairly reliable, since the ancestral environment was much less forgiving than the one most of us live in today, the mortality rate was much higher for infants and adults alike. The attraction cues were a good indicator of whether someone was able to successfully reproduce and/or provide for and raise offspring. In industrialized societies, reproductive potential now far surpasses the estimates indicated by attraction cues, since these cues did not have to account for modern health care, shelter and nutrition.
We are still guided by these attraction cues today, although our technologically advanced environment has produced a spiral of increasingly stringent definitions of what qualifies as attractive. People are no longer limited to the few hundred individuals (of varying ages and reproductive potential) that would be encountered during the lifetime of a hunter-gatherer. Comparisons can now be made between thousands of individuals, and those which become mass media representations are often subjected to a high degree of selection. Today we are bombarded with images of "ouliers" on distributions of selection criteria which set the standards or at least exhibit strong guidance for feelings of attraction.
Another form of evidence for the validity of the evolutionary explanation for gender-specific mate selection criteria is the social phenomena involved in mate attraction. Males and females enhance their attractiveness by playing up the characteristics each is valued for. Women use makeup and wear clothing that compliments their figure, and in extreme cases resort to surgery to give themselves a more youthful and fecund appearance. Males will exaggerate their social status and inflate their resource potential, as seen in modern day rap music and videos. Of course, humans are attuned to deception in mate selection criteria, and will guard against dalliances with those who falsify their status.
Natural selection is not considered a sufficient explanation for the tripling of human brain size in the past two million years. The human brain started a growth while other closely related hominids in the same habitat remained at their current level. Human brain growth stopped about 100,000 years ago, long before the Neolithic revolution in technology and art 40,000 years ago. At least two theories have arisen to explain this trend. In the runaway social competition model, rapid encephalization occurred so hominids could predict and manipulate each other's behavior, leading to a social intelligence arms race between mind reading and deception. In the runaway gene-culture co-evolution model, hominids got smarter to learn and use material culture.
Sexual selection is the clearest and best established case of positive feedback evolution in nature. Runaway sexual selection on production and discrimination of viability indicators could be responsible for our current level of intelligence. The runaway process is a good fit to the human evolution data because it begins and ends unpredictably, without much relation to the external environment, but it is extremely powerful and directional once underway (Miller, 1998). Ridley (1993, p. 20) reports that "most evolutionary anthropologists now believe that big brains contributed to reproductive success either by enabling men/women to outwit and outscheme other men/women or because big brains were originally used to court and seduce members of the other sex."
Before the development of the entertainment industry, we had to provide our own amusement. Two uniquely elaborated aspects of the human brain are its creativity and love of novelty (Miller, 1998). Pinker (1994) believes that the evolution of language was important because it allowed hominids to display complex ideas and images to one another using an increasingly complex, structured, open-ended, combinatorial system. Language allowed a more direct sexual selection for the mind, and permitted discussion/gossip about an individual, so resource displays did not have to be directly witnessed by the potential mate. The feedback loop of between sexual selection, language complexity, and mental complexity was probably the mainspring of human mental evolution (Miller, 1998).
Sexual competition has generally been overlooked as an explanatory principle. Sexual selection theory has provided the only coherent, non-circular account of gender roles in culture. It gives a parsimonious explanation for gender-based cultural dimorphism, that most economic behavior is mating effort by males to acquire material resources for attracting and provisioning females. Most cultural behavior is male mating effort to broadcast courtship displays to multiple female recipients. Since females have a lower reproductive ceiling than males, the mating benefits of public cultural displays are larger for males.
It has been estimated that males produce about an order of magnitude more art, music, and literature than women, mostly not far after reaching sexual maturity (Miller, 1998). Contests of male intra-sexual competition, which traditionally have involved resource acquisition, have largely been sublimated or transformed into a display of resources, general ambitiousness, willingness to take risks, or desire to compete in arbitrary cultural contests (Gould & Gould, 1989). This argument would also help explain a gender bias in the amount of recognition individuals receive for their works.
Men also produce about a magnitude more of violent death than females. Throughout evolutionary history, men have often gained reproductively through warring behavior, while women almost never seem to do so. Men can make enormous direct reproductive gains through access to power, status, and great amounts of resources. This may not be the case for women (Low, 1998). It is no mere coincidence that the majority of the gods of war are male.