A short while back, I wrote about the problems associated with assuming that sites containing historic-era artifacts are necessarily related to Non-Native American use of a location. While it is true that, as of the mid-19th up through the early 21st century, Native Americans were a distinct minority among the European, Asian, and African-descendant settlers who occupied California, they nonetheless remained a present and active community (or, rather, set of communities) within California (and the United States more broadly). And, contrary to what a surprisingly large number of people seem to think, Native American communities have historically been very open to adopting new technologies and practices from other cultures - this is, in fact, a common human trait - and as such, after urbanization began in the American west, it becomes much more difficult to differentiate a Native American home from a non-Native American Home.
In an area such as the southern Sierra Nevadas, where I currently do much of my work, it becomes a bit more difficult to differentiate Native and non-Native sites. Many of the towns in this area have large Native American populations, many descended directly from the people who occupied the same locations a century or more ago. And European settlement was slower in this area than in other parts of California, resulting in the Native peoples of the area being better able to adapt to a slow creep of Euro-American settlement rather than the sudden rush brought on by the Gold Rush and, earlier, by the establishment of a local Spanish mission. Moreover, the culture of the settlers had changed over the course of the 19th century, so while the Native peoples of this region still had numerous problems with the settlers - some of them quite horrific in their own right - they were not quite the same as the trauma experienced by those in the central Sierras and also along the coast.
As a result, it is not unheard of to find Native American village sites that were known to be occupied as late as 1914 and with histories stretching back centuries, in the hills and mountains of this region. What this means is that the people of the area were making use of tools and goods that are typically associated with non-Native settlements, creating sites that are a mix of artifacts typically thought of as historic, as well as those typically thought of as prehistoric. The problem is that for most archaeologists, and I have to confess that I have been one such myself, we tend to assume that the presence of metal, glass, concrete, etc. are indicators of "historic" (that is, non-Native) settlement and land use, while the presence of flaked stone, ground stone, and similar materials is evidence of "prehistoric" (that is, Native) land use and settlement. As a result, we tend to describe sites that have both "prehistoric" and "historic" traits as being "mixed component" - we assume that they were occupied at two different periods of time by two different sets of people - both Native and non-Native.
I had to reflect on this while I excavated a site this last week that had been recorded as a mixed-component site. It contained bedrock milling features and flaked basalt and obsidian, and it also had metal and glass artifacts in fairly large numbers. Although I am aware of the problems associated with assuming two different settlements of the area, I had nonetheless fallen back into the habit of thinking of these types of materials as representing just that...until one of the field techs walked up to me with a piece of amethyst glass (a distinct type of glass that usually dates to the late 19th and early 20th century) that had been bifacially flaked - that is, someone had taken the glass and very carefully knocked flakes of glass off of it in a distinct pattern to make the larger shard into a cutting and scraping tool. This is not a behavior one sees from non-Native Californians, but Native Californians were masters of producing flaked stone/glass tools, and I have seen many examples of them being produced from bottles, porcelain, and thick old window panes.
Suddenly, this site looked different. We now had pretty convincing evidence that Native Californians were living here and making tools during the late 19th and early 20th century, which was the same period during which the other historic artifacts had been deposited here.
Now, there is still some evidence from the distribution of artifacts to suggest that there was a dump of industrial materials here after the site was used by the Native Americans who made use of the milling stations and flaked the stone and the piece of amethyst glass. But it was nonetheless a valuable lesson to be reminded that the Native Californians never left, and that we should be cautious in assuming that a site, or site component, doesn't belong to them simply because it has glass, metal, and porcelain. In fact, when we make that assumption, we buy into and perpetuate the belief that Native Americans are of the past and not part of the modern world, though they very clearly are still here and still part of the world that you and I inhabit.