The northern Great Basin environment during the late Pleistocene was significantly more humid than today — the presence of Lake Chewaucan demonstrates this plainly — but it was not as persistently wet as the environments of many other regions where organic preservation is poor.

The caves above the lake shoreline experienced seasonal variation in humidity, but the consistent temperatures and the protection from direct precipitation provided by the overhanging rock created microenvironments that were, in the relevant periods, substantially drier than the surrounding landscape.

Desiccation is the most important single factor in the preservation of biological material like feces.

When biological tissue desiccates rapidly — when the water content drops below the threshold needed for microbial activity — the decomposition process is essentially suspended.

The organic molecules that would otherwise be metabolized by bacteria, fungi, and other decomposers remain intact in the desiccated structure, including both the physical components of the feces (plant fiber, bone fragments, seed coats) and the molecular components (DNA, lipids, proteins).