How did those old Greek sculptors put life into their statues?
To start with, they took a good look at the human body. Two things were noticeable right off: one, the way the frame adjusted to the shifting of the body’s weight. It was as if the shoulders were like a scales (the kind blind Justice holds) that dipped to one side or the other in response to what the hips did, which were another scales. For instance, if the weight of the body was on the right leg, the right shoulder fell, as though itself trying to rest on that hip.
That was what the bone support system did. The other thing that struck them was how the muscles acted. If a muscle was at work—if it lifted or pushed or supported a movement—it puffed up, contracted, stood out through the skin covering above it; whereas if it was at rest, it lenthened, shrank, all but disappeared under the skin.
So now if you made a figure resting on one leg instead of two and got the skeleton armature and muscles right, it would immediately look “realistic”—more so than figures had ever looked. One side of the statue would be tightened, would seem to be in tension, while the other side would look relaxed. Everywhere there would be variety and contrasts as the two sides approached or departed from symmetry. And all this “life” was given to the statue even before the sculptor tried to represent voluntary movement, i.e., the stone man’s action. This was so successful by itself that sculptors mostly didn’t even care anymore about the action. Many antique figures aren’t doing much of anything. They just stand there and show what gravity is doing to their beautiful anatomy.
This “tipped scales” device—one shoulder falling, the other rising; one hip up, the other down—gave such spectacular, such sure naturalism, to the figure, that it was copied thousands and thousands of times in the classical world.