On the temple to Athena at Athens this saying is inscribed. It's a notion that's just as true today as it was in ancient Greece. Inspired by the moon and heavens early civilizations such as the Mayans created circular calendars. Moon cycles and lunar phases tracked time long before clocks came to be.
The continuity of life and time is symbolized commonly by today's wedding ring. With a more evil meaning, a serpent eating it's tail embodies the renewal of life as the snake sheds it skin and appears anew.
We have an innate curiosity as humans, and a profound desire to observe. The world around us both physically and through the passing of time is circular. Are all human things a circle or are we simply reflecting the world around us.
"All human things are a circle."