166. The Evidence of Archæology
There is left as a final check on the problem of age a means of attack which under favorable circumstances is sometimes the most fruitful: archæological excavation, especially when it leads to stratigraphic determination, that is, the finding of different but superimposed layers. Unfortunately archæology affords only limited aid in California—much less, for instance, than in the Southwest. Nothing markedly stratigraphical has been discovered. Pottery, which has usually proved the most serviceable of all classes of prehistoric remains for working out sequences of culture and chronologies, is unrepresented in the greater part of California, and is sparse and rather recent in those southern parts in which it does occur.
Still, archæological excavation has brought to light something. It has shown that the ancient implements found in shellmounds and village sites in Southern California, those from the shores of San Francisco Bay in Central California, and those along the coast of Northwestern California, are distinct. Certain peculiar types of artifacts are found in each of these regions, are found only there, and agree closely with objects used by the modern tribes of the same districts. For instance, prehistoric village and burial sites in Northwestern California contain long blades of flaked obsidian like those used until a few years ago by the Yurok and Hupa. Sites in Southern California have brought to light soapstone bowls or “ollas” such as the Spaniards a century ago found the Gabrielino and Luiseño employing in cooking and in jimsonweed administration. Both these classes of objects are wanting from the San Francisco Bay shellmounds and among the recent Central Californian tribes.
It may thus be inferred (1) that none of the four local cultures was ever spread much more widely than at present; (2) that each of them originated mainly on the spot; and (3) that because many of the prehistoric finds lie at some depth, the local cultures are of respectable antiquity—evidently at least a thousand years old, probably more. This fairly confirms the estimate that the differentiation of the local cultures of the Third Period commenced not later than about 500 A.D.