Individuals develop at different rates and also _start_ at different points: a child born a month early will always be a month behind, though this is far less significant at 10yo than 10mo, and that month gets lost over time in the natural variation of development.

Also, the idea that girls mature faster than boys is a much more a myth; girls mature _physically_ faster than boys but not psychologically.

> There isn't great evidence linking that to anything behavioral though.

Ish. There are behavioral patterns which run parallel to it, most obvious with young male aggression which plateaus in the late 20s before trending down.