Despite the big differences in the size of baby back ribs and spareribs, they are really just two pieces of the same slab of meat. Baby back ribs (bottom of photo) are cut from the top of the rib cage, near the backbone. Spareribs (top of photo) are cut from the bottom of the rib cage, and sometimes they include the brisket, which is a bony piece of meat that hangs from the bottom. The farther down the rib cage you go, the meatier the ribs get. That is essentially why spareribs take longer to cook.