What was the purpose of the deep mortar holes found in almost all shelters? Is there a significance of the various sizes?

Deep mortar holes, shallow mortar holes, natural concavities, and cupules have elicited a lot of interest over the years but much remains unresolved. There are round mortars and boat-shaped mortars, and mortars so deep they have broken through the rock, and mortars with little channels, mortars with lids, upside-down mortars, and sideways mortars, mortars on creek beds, in rock shelters, on uplands, in bedrock, in boulders, and so on. Such diversity in form and location probably reflects diversity in function as well. The use of natural concavities that strongly resemble mortar holes and some mortar holes as well is clearly related to storage or retention of water. This is particularly evident on the Eldorado Divide where petroglyphs are often found surrounding natural potholes and concavities on waterless uplands (including one at Lewis Canyon where water is easily available). In some of the more isolated spots, limestone lids were still lying next to the holes and a scouting report from Fort Concho describes the troopers coming across some lidded "potholes" such as these. The lids protected the water from bugs, dirt, leaves, and evaporation. Given the ease with which limestone dissolves in water, use might have promoted deepening of the hole, until in some cases, it broke through the rock. Some boat-shaped mortars in creek banks, for example, seem to purposefully penetrate the rock, perhaps to serve as siphons or small wells from which water could be extracted. So it is fairly certain that some of the deep holes were water storage or retention devices, both natural and artificial. The same properties would work for the storage of other materials as well if they were resistant to insects and moisture but those features are more likely to be high and dry than low and wet. There is obviously a difference between a shallow grinding facet, such as those seen on boulders, cave ledges, and stream banks, and deep mortars, and it is difficult to tell if it is a matter of degree - how long the facet was used - or if the shallow grew deeper over time and were adapted to other uses. Once a hole achieved a certain depth, it would be difficult to remove powdery material - seeds, pigment, pulverized roots, etc - so function may have changed with size. It has been suggested that some of the mortar holes were used to ferment alcohol, a process that could easily be discovered accidentally but, until we find the swizzle stick and olives, it will be a hard hypothesis to test. Cupules present yet another dimension of holes in rock. Cupules are small, bowl-shaped shallow indentations and can number in the hundreds on a single boulder. They are found all over the world, often as part of more complex compositions. Although they are not as common in the Lower Pecos as they are in many other parts of North America, I have seen boulders riddled with cupules in rock shelters with elaborate panels of Pecos River rock art, bedrock and boulder cupules in Red Monochrome pictograph sites, and of course amid the petroglyphs at many sites. Ethnographically, in California, the Plains, and the Northwest Coast to name a few examples, cupules are part of women's puberty, birth, and fertility rites. They therefore serve a spiritual rather than economic function. The people of the Lower Pecos, and most other arid regions, were eminently practical folks and I am sure they used whatever was at hand for whatever purpose it was needed and, in the case of mortar holes, those purposes may have changed depending upon the nature of the need. It is clear that some holes were used as storage facilities, especially for water, that others were grinding tools or implements, and that yet another category was symbolic and religious. The first two may well have been interchangeable to the degree made possible by the capacity of the hole but the latter have few practical applications. The lesson to be learned is, I suppose, that even the most mundane rock features can transcend a purely functional interpretation of prehistoric life. For those interested in further pursuing this topic re the Lower Pecos and environs, I wrote about the juxtaposition of petroglyphs and lidded water reservoirs in "Hunting Camps and Hunting Magic: Petroglyphs on the Eldorado Divide, West Texas" in North American Archaeologist V13:295-314 (1992) and mentioned them in "Lewis Canyon" the RAF publication. The Fort Concho scouting report is documented in "Grierson Springs" in the Journal of Big Bend Studies, (1998). La Tierrra, the Journal of the South Texas Archaeological Association, has run a number of articles on mortars, including one on boat-shaped mortars at Big Lake where they intentionally penetrated the streambed. Joe Labadie has written a couple of articles on petroglyphs, including cupules, in the Lower Pecos but they are not easily available. Contact him at Amistad National Recreation Area for more information. As an addendum to last month's discussion of mortar holes and cupules, I came across the following reference to self-sacrifice among the Indians of New Spain 1629 in Hernando Ruiz de Alarcon's "Treatise on the Heathen Superstitions" (University of Oklahoma Press): "Upon arriving at the place of the idol or at the pile of rocks, he (the penitent) prostrated himself where he was to place the offering, and after having placed it, he sacrificed himself by spilling his blood, for which purpose he carried a sharp needle made of a little sliver of cane, and with it he pricked his ears in the parts where woman put earrings until much blood was spilled. He poured it into some LITTLE VESSELS THAT THEY MADE IN THE ROCKS like saltcellars." (p. 57, my emphasis) This is another example of the role cupules played in ritual, not unlike the practice of placing part of the umbilical cord of a new born infant in a cupule in what is now the American northwest. The widespread distribution of cupules suggests that they too have some universal meaning, along the same lines recently proposed for geometric designs or entoptic phenomenon. Next time you take the tour to the White Shaman, observe the cupules in the boulders by the Red Monochrome paintings and imagine what sort of rituals were performed in front of this panel. Their presence adds another dimension to this style that is not always evident in its iconography.