Why was pottery developed and adopted? Food residues on ceramic material from three sites in the Upper Great Lakes region of North America suggest that there is no single answer, and contradict previous indications that pottery was created for the ritual processing of fish oil. Samples from two sites showed evidence of both plant and animal remains, but no fish oils were detected, even for the site believed to be a fishing camp. Nut oils dominated for the third site, being present on both fire-cracked rocks and pottery, and were suggestive of an acorn-rendering process. All of the vessels were ideally suited to slow simmering, but it seems that their applications were diverse.