I have it on good authority that the cause of hair turning gray is that the hair follicles finally tunnel down through the skull and start leeching out brain cells (also known as "gray matter"). This not only turns your hair gray, but also explains the coincidental memory loss and onset of old-timers' disease.
Of course, I've also been known to blame all my gray hair on my ex-wife. When I married her 30 years ago I didn't have a gray hair on my head!
Fly fishing - it's cheaper than a bass boat!