This isn't EoEO, so I haven't been taking this thread seriously enough to question you knowledge of the subject in a polite way. What you have studies is relevant to the discussion--if you're making claims you should know something about the subject, shouldn't you?
The time at which the human body is best able to produce an offspring. A woman's body is most able to support an offspring after it has fully developed (late teens, at the earliest), and at this point the most desirable genetic material is available. After a woman's reproductive peak birth defects increase either due to damage to her remaining eggs, or just that the more desirable eggs were released before the less desirable ones.
I don't mean sexual peak; I mean reproductive peak. A woman's sexual peak is in her mid-thirties. The function of hormones in the teenage years is to facilitate physical development.
Women in advertisements and pronography are usually in their late teens to early twenties--their reproductive peak. I'm critisizing your notion that it's acceptable for men to be attracted to girls in their mid-teens (sixteen, in your earlier example).