Oh Grow Up!
A few questions first
Before we begin to try to ask the past to be perfectly clear about the stages of life, let's look to our own ideas and vocabulary. What does it mean to be a "grownup?" Does that signify a specific age? Does the word mean one thing to you but something different to someone else?
Once you think about it a little, you'll see there are a number of age-related words in our vocabulary and that you can apply the same questions to each of them. What's it mean to be "little" or a "kid"? What is "young" or "old" or "middle-aged"? Do the words have other connotations to them besides the purely chronological? Do they have particular meanings to institutions such as the government?
Take the time to write down a list of such words. Go ahead and use a thesaurus or the Net; there's no cheating on this one.
Go ahead. I'll wait.