I discriminate adulthood 2 ways: "legal"/"federally protected" adulthood - 21 - can vote, drink, etc. "biological" adulthood - brain is not fully developed un

I discriminate adulthood 2 ways: "legal"/"federally protected" adulthood - 21 - can vote, drink, etc. "biological" adulthood - brain is not fully developed until ~25, and takes a few years to "activate/realize" those "powers", so ~30 for "actual, mature" adult processes to start taking place. ~40 seems appropriate within that as an outer boundary of "early" adulthood.