Above: This bone from a deer has been sawed to expose the marrow. The marrow in bones of healthy animals has the consistency of peanut butter.
Below: Here the bone has been roasted and the marrow removed. Native Americans roasted bison bones and then broke them open with stones. Sticks were used to remove the marrow so it could be eaten (much like a cheese stick). Although this marrow was important part of their diet, the purpose of boiling bones was to extract another kind of fat, which some archaeologists refer to as "bone grease".