Actually, one doesn’t have to have any detailed anatomical knowledge to see that the body is not, should not, be aligned in any sense of the word. Although the human body is fairly symmetrical laterally, it is certainly not so in depth – if it were, you’d have a butt in front to balance your butt (you’d have a front rear-end). You would have a foot which extends behind your heel, and you would have muscles equivalent to your calves in front of your shins.
Starting at the top, it is obvious that the head does not balance on top of the spine like a ball on a stick. The center of gravity of the skull is well forwards of the atlanto-occipital joint at the top of the spine. Note the origin of muscles, even those which attach to the sternum and collarbone, is at the rear of the skull. In a standing human, the pull of gravity on the skull stimulates action in muscles posterior to the skull, helping to extend the spine. In a well organized body, posterior muscles support the weight of the organs which are in front of the spine. Large muscles, including the gluteus muscles, prevent the trunk from falling forwards from the hip joints, in much the same manner as posterior neck muscles prevent the head from falling forwards. We see the same thing at the lower leg – in healthy standing, weight is not centered under the ankle, but is well forward on the foot, making the calf muscles work constantly to support standing.
Through this inherent instability, the muscular system integrates. Through it, we not only sense where we are in relation to gravity, but the muscular action necessary for proprioception is stimulated. Remember, the only way that you can sense where your limbs are in relation to each other is through constant change in muscle length. You don’t feel where your arms are in space – your body calculates the degree of change in muscles and knows where you are because of movement. (This is the same with all senses, in fact, which require movement for their functioning. Try feeling texture without moving your hand. If an image does not move upon the retina of the eye, we cannot make sense of it.)