For several years I worked for an archaeologist named Tom Jackson. Tom was, and remains, a very intelligent man and a very good archaeologist. And, like many archaeologists, he had a particular type of artifact that he was particularly interested in - bedrock mortars.
A bedrock mortar is just what it sounds like, a mortar for grinding stuff (usually assumed to be acorns, although they likely were used for other things as well) that is carved into a rock outcrop.
Tom introduced me to two ideas that have really stuck concerning bedrock mortars:
1) Who Owns the Mortars? Who Owns the Lifeway?
In a paper that he published in 1991, Tom described a research project in which he combined archaeological observations on bedrock mortars with ethnographic information regarding the processing of acorns, both from the southern Sierra Nevadas. He came to some interesting conclusions. The first is that models of prehistoric settlement in the southern Sierra Nevadas based on both archaeology and ethnography indicate that the settlement patterns were centered around areas of acorn production. This is not the least bit surprising, as acorns were a reliable and nutritious staple food, and there is an economy of scale at work so that once a people come to rely on acorns, the time and effort necessary to gather, store, and process them in any meaningful amount means that it is easier to become more dependent rather than less.
Ethnographically, southern Sierran people thought of acorns as belonging to women - everyone ate them and everyone helped gather them, but the acorns were processed by women and therefore were thought of as the property of women. More importantly, there is some evidence that the oak trees - the very features on the landscape that produce the acorns - were thought of as women's property. This means that, in a very real sense, women owned the settlement pattern.
However, the native peoples of the Sierras were generally patriarchal, like most hunter-gatherer societies. The ethnography suggests that there was a sort of cognitive dissonance, with men as the decision makers (the chiefs and other officials) having to base their decisions on the staple resource controlled by women. Tom suggested his own ideas for how this was sometimes resolved (and I'd refer you to the paper - see the link above to find out what books it's in - to read his thoughts), and since the publication of the paper there have been many other potential resolutions proposed. My personal favorite, though it is one that is damnably difficult to test in any meaningful way and is likely to always remain supposition, is that the men in positions of authority claimed ownership of the settlement pattern (though not the resource that created the settlement pattern) either through ritual or mythology, and used rock art to physically mark the landscape.
Regardless of how, or even if, the contradiction of male authority and female ownership of important resources was resolved, Tom's observations made for an interesting issue to ponder. The basic point of the article was that our usual models of male/female power relations amongst hunter gatherers are far too simple, which shouldn't surprise us really, and that we are looking not so much at power relations as ongoing and fluid power negotiations. Anthropologists (including archaeologists) talk a big game about studying how people actually live, in all of its complexity, rather than just using streamlined models that simplify and look pretty, but in too many of our reports and papers we fall back on overly simplistic models (patriarchy, clear social rank, etc.) when the reality is invariably much messier and much more interesting.
2) Hidden Meaning.
One interesting fact about bedrock mortars to which Tom introduced me: on a rock with multiple mortars, the distance by which the mortars are separated from each other tends to fall into a few patterns. For example, he and I spent a few days measuring BRMs in Tulare County, and he pointed out that when we measured the distance between mortars within the canyon, we routinely found them to be between 20 and 25 centimeters apart. He said that there are other places where they are routinely around 15 centimeters apart. What does this mean? I don't know. It may mean that these distances were ideal for certain types of acorn processing - ethnographic data indicates that acorns would be moved from one mortar to another, differently shaped mortar during processing. Perhaps acorns from different species of oak were more easily moved about depending on the distance between mortars. Perhaps the distances could tell us something about "personal space" norms within a culture - socializing during acorn pounding may have been facilitated by having the mortar operators at a distance that was appropriate for the society.
We just don't know. The distance between mortars may tell us something profound once we figure out what it is the result of, or it may not. But the fact that there does seem to be a pattern but, to date, no clear way to make sense of it makes it one of those odd little mysteries of archaeology that rarely makes onto the Discovery Channel, but does grab the imagination of those of us who work with these objects.