Explanation: This implies that as humans grow or age in life, they get to have more experience and understand life better. By living more on earth, the concept of living and the "meaning of life" is revealed to us.

This is similar to reading a book. As each page of the book is being read it reveals more answers into the plot.

The readers get to understand the message of the book better as they read into the book. In the same way, humans tend to understand the purpose of life as they age older on earth.

An older man is full of wisdom and understanding of the way of life, the same way a reader who has read more into a book is full of understanding the message in the book