One of the first questions that journalists and other civilians often ask me when I describe my repeated findings that beautiful people have more daughters is “So why do Posh and Becks have three sons?” Such questions, while understandable at some level, nonetheless betray ignorance of the danger of relying on manwho statistics, in other words, anecdotes.
For any given scientific generalization, it is always easy to recall an anecdote or example that is contrary to the general pattern, such as “I know a man who...” or “I know a woman who....” As I explain in an earlier post, science is empirical, not logical, which is why there is no such thing as a scientific proof. The existence of exceptions and counterexamples, which invalidate mathematical proofs, do not invalidate scientific conclusions and empirical generalizations. You may know a man who finds elderly, obese women sexually attractive, but that does not invalidate the conclusion that men in general find young women with low waist-to-hip ratios sexually attractive. The anecdotal fact that Posh and Becks have three sons cannot be used to refute the gTWH, any more than another anecdotal fact that Charlie Sheen and Denise Richards have two daughters cannot be used to confirm it. Scientific theories must always be tested with large representative samples or in controlled experiments.
This may also be a good place to explain the danger of relying on small convenience samples, such as samples drawn from the annual People magazine’s 50/100 Most Beautiful People lists, to test scientific theories in general, and the generalized Trivers-Willard hypothesis in particular.
As a source of data to test the gTWH, People magazine’s Most Beautiful People lists have two particular problems. First, most people on People’s Most Beautiful People lists are celebrities and other well-known people. If you are an incredibly good-looking waitress at a local truck stop, you will never make it to People’s Most Beautiful People list, because you are not famous enough and nobody knows about you. Well-known, famous people tend to have greater wealth and higher status. And, as I explain in an earlier post, the Trivers-Willard hypothesis (TWH), from which the gTWH is logically derived, predicts, and a large number of studies confirm, that wealthier people of higher status are more likely to have sons.
Second, and more importantly, many people on People magazine’s Most Beautiful People lists are actresses or actors married to actresses. And, as I explain in an earlier post, two evolutionary psychology megasuperstars, Steven W. Gangestad and Jeffry A. Simpson, have discovered 20 years ago that actresses are more likely to have sons compared to women in other occupations. This is probably because actresses are more likely to be extraverted and sexually promiscuous than women in other occupations.
Although it is always very difficult to explain individual cases, rather than aggregate patterns, if I have to venture a guess as to why Posh and Becks have three sons, I would point to the fact that Posh is an actress. Well, calling Posh Spice “an actress” might be a bit of a stretch. I cannot recall any movie or TV show that she has acted in since Spice World in 1997, and that wasn’t much of a movie to begin with. (Yes, I’ve seen it.) Fortunately, the precise category that Gangestad and Simpson use in their analysis is “actress/performing artist,” and in that Posh definitely fits.