What should the Legal Adult age be and what should the drinking age be?

In Today's society 18-21 year olds are treated like children little kids.Biologically speaking the word "Adult" is a "society" created term.You either become a "man" or a "woman,in animals and other species you become a man or woman when you have the appearence of secondary characters.Parents and Society encourages immaturity,Young children are capable of knowing about and what goes on in the world maybe if they were taught RESPONSIBILITY maybe they would REALLY be men or women when they reach ual maturity.I think when it comes to mental maturity I think that the brain can finish developing way before age 25 but because of society overprotecting young people it encourages immaturity which probably stunts mental developing leading to the brain not finishing development till the age of 25.Society has created these tv rating laws and movie rating to protect children from Humour and entertainment which is not meant to harm anyone period.I wish society would change so bad but how can it?