While monitoring grading in the Arroyo Grande Valley, John Parker spotted a rounded shape protruding from the soil. He suspected that it was an inverted mortar. He stopped the grader and asked field crew member Cheyanne Parker to expose the item while he took measurements, pictures and mapped its location. All pretty typical activities for an archaeologist. The crew was a little depressed when they discovered that the mortar was missing a chunk from its side.
Just another typical mortar he figured... But while cleaning the artifact back at the lab he discovered something that was very unusual. Yes, a chunk was missing from the side of the mortar.... but the face of the broken bowl where the chunk was missing was covered with "pismu" (asphaltum). Not only was there a thick layer of pismu on the broken face, but the remnants of a band of pismu encircling the mortar.
The site (SLO-2296) has been identified as a seasonal hunting and acorn gathering camp used sometime around 1,000 years ago. As a seasonal camp, it is likely that two or three families used the site each fall, bringing with them whatever necessities they would need for the stay (including a lightweight mortar). Unfortunately the mortar broke. But the break was in the side of the bowl and didn't effect the bottom of the mortar (the area where the actual acorn pounding takes place). Making a new mortar is a very time-consuming undertaking. The trip back to the main village to retrieve another mortar (probably the heavy one left behind) was also not seen as an option. But in the camp they had pismu and twine; used for hafting the stone tips on the long hunting spears. So, why not try to repair the bowl.
The pismu was heated by the fire to a thick runny consistency and spread on the broken face. The broken piece was held against the pismu until it cooled forming a glue-like seal. Then, to guard against the piece breaking loose during the pounding process, twine was wrapped around the repaired mortar and also cemented in place with heated pismu. Not perfect, but it must have served its purpose during the seasonal stay.
Necessity has always been the mother of invention... throughout time.