Ah! There we go, lebasiara! Theories and Facts! (Those ideas can be considered facts nowadays, but since it's proven wrong at some points by other cultures, many still consider it to be a theory)

Sorry, didn't mean to get irked... it was a long day yesterday.

As for that... well, in my opinion, the ages are a number for that still. Maturity levels are grown through the ages, true, but again, without experience, nothing appears to show that age creates a determining factor other than a form of measuring the stages of a life cycle.

Back in the day, the age 15 was considered to be adult... a man (15 years old) could leave home and make a living, marry and etc. People's obvious complaint about that was and still is: They died at 40 years old and under, so they had no choice but to grow up quickly.
Well, consider that maybe, just maybe, the reason why most TEENS are so rowdy and rough and purely immature, isn't because they're going through a changing phase... could it possibly be the fact that around this stage in life, they should be allowed to be adults? And their extravagant behavior is a form of rebellion from being allowed to be what they're supposed to be? (Well, nowadays, it wouldn't be smart to allow teens to be adults, since most aren't taught correctly on important things in life)

So what does that mean?

Stages in life differ from age.
An infant can be given an age range, but a person can still remain an infant until the day they die (let's say... 70 years old) if no one teaches them how to grow up. Even if their body generates more chemicals on some areas of the psyche and physique, their mental state is the true calling of their stage in life.
If one hasn't matured by the age of 40, that is their mental inability, and henceforth, you cannot consider them being an adult. You may consider their age, but here's the thing:

If we suddenly say that the age of 18 (people are now asking if they should turn it to 21) is adulthood, and then we change it once more... wouldn't AGE be determined by the people and NOT the individual?
How we see ages are from the media, from what our parents taught us, what our friends told us, how the news portrays them, and what we experience from them.

If a child raised in an area where 13 year olds are taught to be adults and are in a very effective manner (with no sign of negative reaction due to a "revolutionary" "breeding" pattern) was somehow transported to this world and saw several teens walking around...
The first thing in his mind would be "a mature adult" (by the way, one of the things to keep an adult from being a robot, is a sense of humor... just wanted to say that)...
But on further investigation, he finds that these... KIDS, are completely unruly and practically primitive, or in our language "totally retarded". -_- What a suprise for a kid like this.

The stages in life physically depend on our adaptation and how our bodies react to certain chemicals and environments... while the stages in life mentally depend on our experiences and thought patterns caused by our physical stage.
The age was given so we could measure these stages to make more accurate decisions on how to raise someone or how to treat them.

In that form, age is a number.
In my opinion.

And nice, fled. You made a good point, but it sounded like you had a lot more to say before you lost that train of thought.