Originally Posted by Somerdai
The literature on intellectual giftedness suggests strongly that the gifted tend to be children of older parents. In Terman's sample (Terman, 1925), the mean age of fathers at the birth of the subject child was 33.6 years, with a median of 32.6 years. The mean age of the mothers at the children's birth was 29 years with a median of 28.5 years. In the mid-1980s, Rogers (1986) reported that the mean age of mothers of children of average intellectual ability was 25.4 years.

Educated people, who tend to be smarter, tend to have kids when they're older.

(I'm not sure if there's an implication there that being older raises the IQ of your offspring or has a positive influence on it).