Another feature that is considered to be attractive for women is large eyes. Unlike blue eyes (discussed in the previous post), however, large eyes are considered to be attractive only for women, not for men. Why is it? Why are large eyes considered to be attractive for women, but not for men?
There are at least two separate reasons why large eyes are part of ideal female beauty. First, as briefly mentioned in a previous post, large eyes (along with fuller lips, large foreheads, and smaller chins) are indicators of high levels of estrogen. And women who have higher levels of estrogen have easier time conceiving than women who have lower levels of estrogen. Women with larger eyes therefore on average make better mates than women with smaller eyes.
The second reason is that large eyes are a neotenous feature (characteristic of children and babies). Because human eyes do not grow in size during development as much as the rest of the face and the head does, the size of the eye relative to the face decreases as we grow. As we all know, babies (and infants of other mammalian species) have relatively large eyes compared to older children and adults. And, as a result, people (both men and women) who have large eyes are often perceived to be younger than they really are. (How old do you estimate the woman in this picture is, for example?) Because, as I explain in a previous post, men prefer younger women, they tend to prefer women with neotenous features, such as large eyes. That is another reason large eyes (typical of babies and children) are part of ideal female beauty.
Now you may balk at this explanation for the appeal of women with large eyes to men. You may (correctly) point out that men are not trying to mate with babies and small children; that would be highly maladaptive because they are not fecund. So, you may ask, why do men prefer women who, in essence, look like babies?
This is a very good point to introduce an important concept in evolutionary biology: runaway selection, sometimes known as Fisherian runaway selection, after the British geneticist, Ronald A. Fisher, who first proposed the hypothesis. As an aside, if you have ever taken elementary statistics in college, you may vaguely recall something call the “F statistic” or the “F test.” The F in F statistic stands for Fisher, who invented the test and made other significant contributions to statistics. That is why, unlike the t statistic, z statistic, or the chi-square statistic, the F is always capitalized.
The concept of runaway selection suggests that, when one sex prefers mates with certain genetic traits, then, through the process of sexual selection, the other sex will come to possess the trait in increasingly exaggerated forms. The elk’s antler provides a good example. Female elks prefer to mate with male elks with larger antlers, because such males can defeat other males with smaller antlers in contests over territories and mates, and, since the size of the antler is largely genetically determined, their sons will also have large antlers that are attractive to potential mates. As a result, male elks will come to possess larger and larger antlers, to a point where their antlers are simply too large. They become so large that they present obstacles to feeding and survival, and even to fighting other males, which is the original purpose of having large antlers in the first place. Yet males continue to exhibit exaggeratedly large antlers because the trait is preferred by females and evolves by Fisherian runaway selection.
Probably the same process occurs with men’s preference for women with neotenous features. Because men prefer to mate with younger women, women come to possess more and more neotenous features, which make them look not only nubile and pubescent but eventually prepubescent, childlike and even infantlike. Men’s preference for blonde hair may have gone through a similar runaway selection. As PT Senior Editor Carlin Flora has pointed out to me before, many young blond children cease to be blond and their hair turns dark long before they reach puberty (as Carlin's did). So by preferring to mate with women with light blonde hair, men are often (maladaptively) attracted to prepubescent children. Their preference for women with large eyes may similarly be maladaptive. But men’s preference for women with neotenous features, and women’s possession of such features, may nonetheless have evolved via runaway selection.