"I assume you're talking about 18-22, but my impression is that historically, most women had their first children after that age, even before widespread college

"I assume you're talking about 18-22, but my impression is that historically, most women had their first children after that age, even before widespread college education." In cities and in richer families, yes. In rural settings, everything was sped up a bit, and, until very recently, most population worldwide was rural. Even if we look at highly fertile regions today (Afghanistan, Niger, Chad...), the first-time mothers tend to be between 16 and 18 and live outside the few cities that are there. My own grandmother grew up in a rather underdeveloped corner of Slovakia in the 1930s (no electricity, wooden huts etc.), and a peasant girl who wouldn't be at least betrothed by 20 was seen as a bit weird. Quite a lot of our previous fecundity was driven by rural mothers having six or seven children. This was a major source of "kid surplus". The urban population was never as fertile, plus there was some extra mortality from diseases and higher cost of food.