Quick Definition: In Darwin’s own words, “the struggle between the individuals of one sex, generally the males, for the possession of the other sex.”
In biology, females often prefer to mate with males that have external ornaments or males that defeat other males in competition. There are a few reasons these exist:
- It is hypothesized that these can plausibly arise because of an arbitrary female preference for some aspect of male morphology initially increased by genetic drift, creating selection for males with the appropriate ornament. This is known as the sexy son hypothesis.
- Some species, such as the robin (bird), have longer tail feathers, a trait that is genetically close to disease resistance (on the DNA strand). In this case, the genes that enable males to develop great ornaments may simply show off greater disease resistance or a more efficient metabolism, all which are biological features that increase S&R value. This idea is known as the good genes hypothesis.
In both cases, biologists today distinguish between “male to male combat” (it is usually males who fight each other) versus “mate choice” (usually female choice of male mates) and sexual conflict. In today’s modern world, subtle male to male competition still exists, while mate choice is still strong in women. Women prefer physically strong men, taller men, and more symmetrical looking men.
In The Mating Mind, Miller explains sexual selection in part due to intelligence and art. For example, the expression of the greatest artists and inventors of our time were largely inspired (on an unconscious level) by the desire to mate and (on a conscious level) for a woman. In a less physically driven world, art, power, wealth, and the expression of one’s personality and intellect drive sexual selection. The idea behind these theories is that, in the modern world, survival and replication require more than just ornaments and good physical traits; it requires a strong and healthy mind.
In Sperm Wars, Baker illustrates various scenarios where females are biologically wired to promote sperm competition, often devising (consciously or unconsciously) situations where she cheats on a long term partner, only to return on the same night and obtain his sperm as well. Baker states, “worldwide… about 10% of children are in fact not sired by the men who think they are the fathers. This is also the average level found in Western industrial societies.”
Sexual Selection in Pheasants:
Sexual selection is often evident in a woman’s behavior but not her words, as it is often driven by the unconscious female mind.
- Sexual Selection on Wikipedia
Source: Charles Darwin, Evolutionary Biology