What human qualities count at metaphysical versus the man-made?

Many human qualities -- including simple ones such as handedness -- seem to be influenced by a person's genetic makeup. Often, such qualities develop substantially before the person can make conscious choices. In the case of handedness, every person with the use of his hands develops a dominant hand. Does that mean that handedness is metaphysically given, rather than a man-made fact which can vary with each individual? More generally, what kinds of qualities of a person are "metaphysical" versus "man-made"?