In the farming era, people disapproved of sexual attraction, especially outside marriage, but weren’t much more offended by attraction to adolescent girls than to older women. Today, in contrast, we approve more of sexual attraction in general, even outside marriage, but we take great offense at pedophilia, i.e., older males attracted to pre-fertile females.
This trend is explained in part by rich folk reverting to forager ways, in particular to more sexual promiscuity. From Evolutionary Biology of Human Female Sexuality:
Adolescent females with exaggerated [fertility] ornaments in nonhuman primates exhibit and elicit from males relatively little sexual interest. Human adolescent females appear to differ in these respects. This difference is likely another manifestation of the profound implications of long-term pair bonding in humans. Human female lifetime reproductive success has historically been influenced by [their] ability to attract male attention during adolescence. Men’s sexual interest in adolescent females reflects the fact that, typically, their reproductive success achieved through pair bonds was not maximized by attending solely to cues of current fertility but also to cues of [future] reproductive ability. [p.124]
This is more about the long-term-ness of bonds, and less about whether they are pair bonds. Farmers look more to a female’s future fertility potential, while foragers and other primates with shorter-term relationships focus more on her current fertility. This turns farmer males into pedophiles, i.e., more interested in younger females. Pedophilia is a sign that a species or a culture has longer term sexual relationships. Which our culture considers to be a good thing. Which makes it ironic that we consider pedophilia a bad thing.
While we still praise marriage today, we are more accepting of sexual promiscuity. Of course neither farmers nor foragers are much offended by marriage-directed attraction to pre-fertile females. So why are we so offended? Perhaps the key is our extending kid dependency further via more years of school. Perhaps we mentally rate someone’s “adultness” via their economic independence, and assume that their sexuality should follow this rating. If so, we might think of a 21 year old today the way our ancestors thought of a 14 year old, as an acceptable if young marriage partner, while thinking of a 14 year old today as our ancestors did a 10 year old, as unacceptably young. Count this as another way we have not fully adapted to industry era novelties.