The more physically attractive you are, the more likely you are to have lots of sex, reproduce and pass these traits on to the next generation. Or so the theory goes. So how come we don’t all look like movie stars and supermodels? Or so it seems from looking round the train this morning.
• Three things work together to prevent all of us from looking like supermodels. First, standards of beauty change constantly. For one generation, it is Twiggy and Marlon Brando, while for another it is Pamela Anderson and Michael Jordan. As a result, even if the assumption about “beautiful” people being more likely to reproduce were true, it wouldn’t lead to a population that met today’s beauty standards.
Second, genetic inheritance doesn’t produce slightly improved models of one’s parents. Instead, there are myriad combinations, and it is possible that none of these may meet or exceed the beauty standards of the time.
Finally, when two people at the end of any distribution of attributes reproduce, their offspring will almost always move back towards the middle of the distribution, known as “regression to the mean”. If the two tallest people in the world have a child, that child will almost certainly be shorter than their parent of the same gender.
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Stephen Johnson, Eugene, Oregon, US
• To some extent, heterosexual humans behave like other animals in seeking a mate that will guarantee the highest lifetime reproductive success (LRS), as measured by the number of grandchildren they have. Certain physical features act as honest signals of “good genes” that will be inherited or indicate the capacity for parental care. Studies have shown that such features are widely perceived as attractive.
In general, men prefer women with more symmetrical faces and larger breasts, for instance, which have been linked to healthy genes and higher oestrogen levels.
Women’s mate preferences are more complicated and vary with the menstrual cycle. At their most fertile, women prefer “masculine-looking” men with prominent jawbones and a “dominant” odour. These features are linked to higher testosterone levels and good genes. At other times, women prefer more “feminine-looking” men because they are perceived to promise better parental care. Women therefore choose feminine men for a long-term relationship and child-rearing environment, but may seek extra-pair relationships with masculine men when ready to conceive to ensure their children inherit good genes.
If physical attractiveness has a heritable basis and more attractive people did have greater LRS, then physically attractive traits would indeed spread through the population. But we exhibit a great variety of sizes, shapes and appearances, which suggests this idea is incorrect.
The term “physically attractive” is highly subjective and physique is only one of myriad traits we consider when choosing a partner, including extrinsic traits such as wealth. Social circumstances could also constrain mate choice.
In addition, humans can consciously choose whether or not to have kids, and how many to have, and being physically attractive may be irrelevant in making this choice. In fact, certain traits that some may consider attractive can be detrimental to reproduction: very thin women tend to have lower fertility, for example.
Finally, some “attractive” physical traits have a non-genetic element, such as muscularity, which varies with exercise, or are “false signals”, such as the use of make-up, Botox and implants, which are unrepresentative of genetic stock.
Sam Buckton, Cambridge, UK
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