Harvesters gather acorns, chia seeds, pine nuts and anything else. In a place like this one can't be choosy. Being people, they leave tracks. Some, being made of the nearly everlasting stone, record many years of use. Others remain only because of their location.
People make art .
Even in an environment where survival is a matter of constant work, there's some time for expression. Maybe it was someone waiting for someone else. It could have been an expression of a belief in magic, inviting a bountiful harvest or peaceful days. Reasons don't matter. The art is here, someone's heartfelt labor hidden on overhanging huge fallen blocks of enduring Sierra Nevada granodiorite.