You can’t just look at the age of the mother when she has her first daughter. You also have to consider her age at the time of her last daughter. Even if she has her “prom night” daughter at 18, if she later has another daughter at 36, we’re looking at an average age of 27.
Plus talking about the deep past you have to consider infant mortality rates as well. If someone has 10 kids, but only the ones they had after 29 survived then that changes the math.
You can’t just look at the age of the mother when she has her first daughter. You also have to consider her age at the time of her last daughter. Even if she has her “prom night” daughter at 18, if she later has another daughter at 36, we’re looking at an average age of 27.
Plus talking about the deep past you have to consider infant mortality rates as well. If someone has 10 kids, but only the ones they had after 29 survived then that changes the math.