The boiling is to get most of the fat off the ribs. I have boiled muskrat before. It's good to do that for about 15 minutes then lower the heat (or move the pot further away from the fire). If the meat is well marbled with fat then the boiling doesn't toughen it as much. Better to slow-cook as opposed to boil. Also, slow cooking 'keeps' more of the protein value of the meat (or vegetable).