Over the course of a thirteen-generation experiment with stalk-eyed flies, Wilkinson and Reillo selected for males with long (L males) and short (S males) eye stalks.

When females produced in the long and short eye treatments, were given a choice between males, they preferred males from their own selection treatment group.

This suggests that female preference was genetically linked to the male trait being selected (stalk length), resulting in runaway selection..