It might be useful to think about the simple fact that if you're a hunter of small game, you're probably going to spend an awful lot of time sitting around staring at things, and that maybe evolution has a good reason for wanting it to feel good... not to mention developing your ability to concentrate, if your hunting pattern requires such concentration. What's more, it's a kind of exercise that humans haven't gotten much of since we switched to agriculture.

Note, too, that it's only since we've had agriculture that we started having religions offering salvation and release from suffering... maybe there's a connection there.