In Western Europe at least back to the early medieval period it was common for anyone who wasn’t nobility to have their first child around 22. The younger you are the more likely you’re going to have serious (fatal, back then) complications. It was the nobility that was marrying off barely pubescent kids.
No idea, I’m not as read up on that. It would shock me if it was significantly different just because risk of death from complications is a hard biological line the younger you get, pre-modern medicine.
There are definitely cultures who have practiced polygyny to get around this issue. Some still do today, for example in many different countries in Africa where people still practice a pastoral life.