For the human animal, the question of commitment has a long history, as mammals by their nature commit to mates, offspring, kin and kindred. But being by nature emotionally complex and having been granted increased intelligence makes for painful dilemmas. Where an ape makes the call based almost entirely on emotions, essentially driven by their hormones, the naked ape weights in with possibilities. Feeling protective of a woman he is bedding, a man does not simply accept this as a concomitant of sexual desire, he starts to worry about how to put the kids they may have through college. Sharing vegetables from their garden, neighbors may not accept this as simple bonding but begin to worry about future intrusions. Might the neighbor show up for dinner one day, uninvited, or perhaps park himself on the doorstep and demand to be taken in? The ape shares food without these worries, as a simple life without possessions doesn't complicate the picture.
At the base of a fear of involvement is the inability to say no. If every contact melts all the borders then conquest cannot be resisted. It's all or nothing. Those who fear involvement are either fearful of losing this fight to retain their individuality, or desire this consumption and would start on a slide with no stop. The desire to be possessed, to lose oneself in another, is a form of hero worship but also a sign that the individual thinks little of himself and wishes to augment the package he represents. In either case, a stronger self image is the answer, as when reaching across borders, one must have a country to extend a hand from.