Isn't the thinking that in agrarian societies the age of menarche is lower while in hunter gatherers it's usually later? And that puberty seems to be earlier these days compared with the past?

Well you have to reach a certain body fat percentage in order to menstruate. Typically poor girls and girls who had less food would start their period at 16 or 17. Richer girls with more access to food would start at 12 or 13 like today.