Yes, you could draw past your ear or head if you just haul back with your drawing arm and the bow is light enough for you to do it. If you draw correctly, however, you will draw with your back muscles, such that the path of the draw is more of a J shape rather than a straight line. The J is formed by your drawing elbow tracing an arc backwards around your spine, and as you complete your draw, you bring your forearm in alignment with the arrow. Most people hit a wall at this point and can't draw much further if they are using their back muscles correctly. Some people may be able to overdraw, even when correctly using the back muscles, and have to learn to stop when they reach alignment of the forearm with the arrow.