Why has grey hair evolved? A vast majority of humans get at least some grey hair as they age. As far as I know this applies to both genders and all races. Presumably this means that at least some grey haired humans have noticeable reproductive advantage, or maybe they had it in the recent past. Theoretically, because this feature is so prevalent, there must be a strong evolutionary pressure to keep it. Am I right? If so, what is it?

> Presumably this means that at least some grey haired humans have noticeable reproductive advantage, or maybe they had it in the recent past.

No it doesn't. Natural selection is not that strong, it doesn't optimize every single possible physical trait towards maximum reproducing.

And as others have mentioned, having lots of grey hair usually happens after reproduction is over. Historically, lots of women did a lot of reproducing before they had any grey hair.