@steven-miller: surely you have seen countless people in the gym doing dead lifts, power cleans and power snatches that are really more like standing back extensions, sometimes with a flourish (the latter two). maybe i've got a biased sample because i go to a crossfit-happy gym and some of the form there is just, well, it's just awful.
of course your low back muscles can't extend your hips, but they sure can take your upper body from parallel to the ground to perpendicular.