Hundreds of split-twig figurines have been recovered from caves in Grand Canyon and are associated with a hunting ritual that dates from 4200–3100 ¹⁴C yrs before present (BP). The caves chosen for this ritual all have Pleistocene remains of big game animals visible in packrat middens or surface deposits at the entrances. Presumably, Archaic hunter-gatherers identified these sites as entrances to the Underworld where the fossil remains represented ancestral animals. We examine the known chronology for these sites in Grand Canyon and postulate that the origin of this ritual is correlated with a period of rapid climate change that occurred on both global and regional scales beginning at ∼4000 BP. Increasingly variable conditions and the onset of modern El Niño Southern Oscillation (ENSO) patterns in the eastern Pacific at that time probably negatively affected productivity of big game species in years with decreased winter precipitation. Thus, the caves became foci for a hunting ritual with figurines serving as a kind of offering. Most dates on the figurines or associated artifacts occur between 4100–3530 BP and many cluster to specific periods that suggest this ritual was not continuous, but may correspond with episodic droughts. Additional radiocarbon dates on figurines can test this hypothesis.