Abundant petroglyphs in West Mexico dating from 900 to 1500 have been the
source of our understanding of the cultures of that period. These are rock
art on boulders or cliffs made by “percussion tools, flaking off the rock
surface to leave designs in relief.” The motifs in them are mostly “the spiral
and other geometric shapes; animal and human beings were less common.” Some of
these motifs “have been interpreted as elements of water and fertility cult;
others mark sacred spots in local mythologies; some were used as solstice and
equinox markers or as part of ancient computing system.”