I never said I had the answer, I was just pointing out that in ancient societies, something called teenager did not exist
My guesses would be :
Girl become woman when married
For the boy???
In some Jew society (maybe a real Jew could enlighten me) : the passage from boy to man comes from a special initiation.
In Canada or USA, for example, a child/teen becomes adult when he reaches 18/21 (age for drinking, to vote) Why 18? No particular reason, which is the flaw of such system. Something based on education would be much better (we can’t use the old marriage system, we could use something in the line of an initiation. When one reaches the minimum education, he is considered ready for life in society. I suppose this minimum of education could include knowledge of society, of its judicial system, of philosophy as well as standard studies from sciences/history/literature/culture. Could be after high school, thus making all those who skip high school not citizens, which in turn could motivate the so called “teen” to finish high school.)
I just fail to see the use of teenager. If its only used to describe the person between 11-19 (or whatever the numbers are), sure I have no problem with this. But there is an entire industry around this moment of teenager. Ideally, one could only hope that industry exist to prepare the teenager for adult age, which is not the case in our modern societies. Magazines about stars, how to do sex, sex tips etc.