I've told this story a couple of times - I met this woman on a trail run and talked to her a bit.  We're both married so it wasn't that kind of thing but I do remember thinking that in another life I might have gone after that.  I find out later this woman is 58 years old and her oldest daughter is only 3 years younger than me and she herself is only 4 years younger than my own mother. Fifty eight.  I'm 34.  And why?  Because she runs several 100 milers per year and is incredibly fit and wears sunscreen.  I would have said she was 38, 42 tops.