If hair greying was mostly caused by UV damage, I would expect that the pattern of greying would be even, and begin on the top of the head. In contrast (based

If hair greying was mostly caused by UV damage, I would expect that the pattern of greying would be even, and begin on the top of the head. In contrast (based on my own unscientific observations!) greying typically begins in small areas, and often on the temples - not what I'd expect if caused by UV damage.