They say beauty is only skin deep, which means that beautiful people are no different from ugly people except for their appearance. This is the second stereotype or aphorism that evolutionary psychology has overturned. It turns out that beautiful people are genuinely different from ugly people, because they are genetically and developmentally healthier.
In my last post, I explained that the standards of beauty are culturally universal and innate. There are three main features that characterize beautiful faces: the geometric feature of bilateral symmetry, the mathematical feature of averageness, and the biological feature of secondary sexual characteristics. They all indicate genetic and developmental health of beautiful people.
Bilateral symmetry. Attractive faces are more symmetrical than unattractive faces. Bilateral symmetry (the extent to which the facial features on the left and the right sides are identical) decreases with exposure to parasites, pathogens, and toxins during development, and with genetic disruptions such as mutations and inbreeding. Developmentally and genetically healthier individuals have greater symmetry in their facial and bodily features, and are thus more attractive.
For this reason, across societies, there is a positive correlation between parasites and pathogen prevalence in the environment and the importance placed on physical attractiveness in mate selection; people place more importance on physical attractiveness when there are more pathogens and parasites in their local environment. This is because in societies where there are a lot of pathogens and parasites in the environment, it is especially important to avoid individuals who have been afflicted with them when selecting mates.
Averageness. Facial averageness is another feature that increases physical attractiveness; faces with features closer to the population average are more attractive than those with extreme features. In the memorable words of Judith H. Langlois of the University of Texas, who originally discovered that the standards of beauty might be innate, “attractive faces are only average.” Evolutionary psychological reasons for why average faces in the population are more attractive than extreme faces are not as clear as the reasons for why bilateral symmetry is attractive. Current speculation is that facial averageness results from the heterogeneity rather than the homogeneity of genes. Individuals who have two different copies (or alleles) of a gene are more resistant to a larger number of parasites, less likely to have two copies of deleterious genes, and at the same time more likely to have statistically more average faces with less extreme features. If this speculation is correct, it means that, just like bilateral symmetry, facial averageness is an indicator of genetic health and parasite resistance.
Secondary sexual characteristics. Unlike the geometric concept of bilateral symmetry and the mathematical concept of averageness, the biological concept of secondary sexual characteristics differ for the sexes. For men, features that are considered to be attractive are indicators of high levels testosterone (such as large jaws and prominent brow ridges). For women, features that are considered to be attractive are indicators of high levels of estrogen (such as large eyes, fuller lips, larger foreheads, and smaller chins). This is probably why women instinctively tilt their head forward and look up (making their eyes and forehead look larger than they are and their chin smaller than it is) when they want to appear attractive. (Think of the way Princess Diana was typically photographed). Similarly, men instinctively tilt their head back (making their jaw appear larger than it is and their brow ridge more prominent than it is) when they want to look attractive. For both sexes, faces that typify higher levels of sex-typical hormones are considered to be attractive.
Far from being only skin deep, beauty appears to be an indicators of genetic and developmental health, and therefore of mate quality; beauty is a “health certification.” More attractive people are healthier, have greater physical fitness, live longer, and have fewer lower back pain problems (although some scientists dispute these findings). Bilateral symmetry measures beauty so accurately that there is now a computer program that can calculate someone’s facial symmetry from a scanned photograph of a face (by measuring the sizes of and distances between various facial parts) and assign a single score for physical attractiveness, which correlates highly with scores assigned by human judges. A computer program can also digitally average human faces. Beauty therefore is an objective and quantifiable attribute of individuals, like height or weight, both of which were more or less “in the eye of the beholder” before the invention of the yardstick and the scale.
译文:
【所有刻板印象都没错，除了……】三：“美丽是肤浅的”
人们说美丽是肤浅的，意思是除了外表之外，美人和丑人没什么区别。这是进化心理学所推翻的第二个刻板印象和谚语，事实上美丽的人确实和丑陋的人不同，因为他们的基因更为健康。
在我的上一篇文章中，我解释了美丽的标准是跨文化统一的，同时也是与生俱来的。美丽的面孔具有三个主要特征：左右对称的几何特征、平均化的数学特征和第二性征的生物特征，这些都表明他们在基因与发展上更健康。
左右对称：迷人的脸总是比平凡的脸更为对称。 左右对称性（左右两边的面部特征相同）会由于在成长中遭遇寄生虫、病原体和毒素，或者由于诸如突变、近亲结婚等基因破坏而降低。成长和基因上更为健康的个体，他们的面部和身体特征都会更对称，因此也更加吸引人。
出于这个原因，在许多社会中，寄生虫和病原体的流行程度都与选择配偶时对外表的重视程度成正相关，在当地环境中有很多寄生虫和病原体时，人们会更看重漂亮的外表，这对于在择偶时避开那些被感染的异性至关重要。
平均值：面部的平均化是提高吸引力的另一特征，那些面部特征接近人群平均值的脸要比有极端特征的脸更具吸引力。德克萨斯大学的Judith H. Langlois是第一个发现美的标准为天生的人，他有一句名言：“迷人的脸不过平平。”进化心理学没能像解释左右对称那样清楚地解释为什么平均化的脸比极端的脸更迷人，现有的推测是面部平均化是基因异质化、而非同质化的结果。拥有两个不同等位基因的个体对许多寄生虫都有更强的抵抗力，一对基因都有害的可能性较低，同时也更有可能具有在统计值上平均化的脸。如果这个推测是真的，这就意味着和左右对称一样，面部平均化表明了健康的基因和抗寄生虫的能力。
第二性征：与几何上左右对称的概念、数学上平均值的概念不同，生物上的第二性征概念是有性别差异的。对男人来说，有吸引力的特征意味着睾丸素水平较高（如下巴较大、突出的眉弓等）；而对于女性，有吸引力的特征是雌激素水平较高的体现（如大眼睛、饱满的嘴唇、较小的下巴等）。这也许就是女人总爱本能地将头前倾并向上看的原因（这使她们的眼镜和额头看起来大一些，而下巴看上去小一些）。同样的，男人们会在展露魅力的时候本能地将头部后仰一点（这使他们的下巴看上去大一点，而眉弓显得更突出）。无论是哪种性别，代表着较高水平性的激素的脸总是被认为更迷人。
美丽远不仅只是一层皮囊，它还是基因和生长健康的指示牌，表明了配偶的质量；美丽是一张“健康证明”。长相迷人的人更为健康，身体更为匀称，寿命更长，也较少受背疼的折磨（尽管有科学家对这些发现还有争议）。左右对称性对美丽衡量得如此精确，以至于现在出现了一种电脑程序，可以从扫描的面部照片中计算出其对称性（通过测量脸部不同部位的大小和之间的距离），并得出一个美丽评分，这个分数与人工得到的评价高度相关。电脑程序也可以用数字手段将人的面孔平均化。因此美丽成为了一种客观的、可量化的个体属性，就像身高和体重一样——而在码尺和秤发明之前，这两者也多多少少是“在观者眼中”的。