In the scene where the boys of the tribe are about to be circumcised, they are ordered to remove their loin-clothes. The camera only shows from the waist up on the closest boy. You are to assume this is because he's a bit "exposed" right then. If you look down the line of boys, because of perspective, the camera shows down to the knees on the last boys. They haven't removed anything! I guess they want to stay boys forever.