Hi all
I mentioned eye color as a trait with no apparent adaptive value and folks jumped in to refute it. Honestly, I just picked that trait out of the hat because I thought it was uncontroversial. 

> In our study we focus on eye color, a feature variable mainly in European populations. Eye color does not seem to have any association with an individual’s fitness. Notwithstanding changes in the brightness of coloration caused by ageing and health condition, eye (as well as hair) color have been considered ‘neutral features’, unlikely to reflect mate quality. According to Edwards et al., iris coloration might be the result of pleiotropic effect associated with selection on pigmentation genes primarily engaged in determining skin or hair color, but not iris coloration. It has been hypothesized that not only natural selection but also sexual selection contributed to recent variations of skin, hair, and eye color. Frost offers an explanation of the geographical distribution of various eye and hair colors. 

1) no association with fitness
2) pleiotropic effect
3) aesthetic attraction

Interestingly, there seems to be a trend toward being attracted to the less common eye colors in a given population (novelty effect). Novelty may increase the prevalence of a trait, but only until it's widespread and then it's no longer novel.

PLB

Tomáš Kočnar. The Evolution and Functional Role of the Colour of Iris in Humans, Its Biological Role, and Cross-Cultural Perception - Evoluce a význam barvy duhovky u člověka, její biologická role a mezikulturní percepce. Doctoral thesis. Prague, 2021

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