Consider the apparently received wisdom that we prefer symmetrical, evenly balanced features. The scientific explanation seems sound: disease and stress during childhood could subtly influence the body’s development, creating an “instability” that leads one side to grow slightly differently to the other. A slightly lopsided face should therefore be a sign of physical weakness – making them less appealing as the parent of your children.

The problem had been that many of the previous experiments had asked just a small number of subjects to rate different faces – making it easier for fluke results to jump out. When Stefan Van Dongen at the University of Antwerp conflated the results in a large meta-analysis, he found the effect almost disappears when you consider enough people. In fact, facial symmetry may not even say much about your health. Although previous research had found some evidence for the idea, a 2014 study took 3D scans of nearly 5,000 teenagers and quizzed them about their medical history. It found that those with the most symmetrical features had been no fitter than the others.