The peacock’s dazzling tail feathers do not exist for them to carry out everyday activities such as eating or sleeping, but because their colourfulness is attractive to peahens: the more brilliant the feathers, the greater the chance the peacock has of finding a sexual partner. Tail feathers, to peahens, can be powerfully attractive. Scientists have long been interested in unravelling the subconscious processes that influence partner choice, since heritable characteristics that are favoured in sexual partners will tend to increase in frequency in subsequent generations. That’s why the peacock’s tail feathers are so radiant: over many generations, more beautiful tail feathers have been selected. This means that partner preferences tell us something about the evolutionary pressures that shape a species – including us. So what do we find attractive in each other, and why?