The Brazil Mound Page 26

California wild grape (Vitis californica )

Shellfish

Before the historic period, when much of the lower Sacramento River/Delta was drained for agriculture, the area was a vast seasonal wetland, full of marshes and sloughs. It is not surprising, then, that the Brazil Mound faunal collection includes the remains of several species of freshwater shellfish, mostly clams and native oysters. Substantially more shell was found in the lower levels of the excavation units than in the upper ones; this suggests that the earlier occupants of the site ate more shellfish than the later ones did. It may be that food preferences changed over time, or that the local environment was somehow altered (became drier?), so that shellfish were less plentiful during the later period. It is precisely these kinds of changes through time that the archaeologist seeks to identify, and to understand. Such changes could help to explain, for example, why a site like CA-SAC-43, located in such an ideal spot, might have been abandoned.

Plant foods

Plant foods - seeds, berries, nuts, and roots, for example - must have made up a large part of the diet of prehistoric Californians, just as they do today. Unfortunately, plants do not survive well over time, compared to things like bone and shell. Essentially the only plant remains recovered from the archaeological record in Central California are those that have been charred, either accidentally or during cooking, because charring converts the organic plant parts to carbonized material, which is more resistant to decomposition.

These charred plant remains are collected from archaeological sites through a process called flotation . A large sample of soil from the site, preferably from a hearth or other feature where plant parts were discarded, is first passed through a large-mesh sieve to remove the bigger rocks. The screened soil is then placed in water to separate the "light fraction" (the material that floats) from the "heavy fraction" (the material that sinks to the bottom); most charred plant remains are very light and will float. These are skimmed off, allowed to dry, and then analyzed by an archaeobotanist , who specializes in the identification and interpretation of archaeological plant remains. The archaeobotanist sorts the sample under a microscope, counts the various plant parts, and identifies the different plant species represented by the charred seeds and shells. We assume that some of these parts represent plant foods, while others may represent medicines or even building materials (for example, tules used to construct canoes, or willow for the making of baskets).

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