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Overall, the vegetation represented by the pollen spectra from Lehner Ranch suggests a desert-grassland, which today occupies slightly wetter sites nearby. Mehringer and Haynes concluded that the climate at the Lehner site 11,000 years ago was only slightly wetter and cooler than today, followed by a rapid shift toward drier conditions. As many palynology studies have found, only a small shift in temperature and/or precipitation was required to produce dramatic differences in the environment at the Lehner Ranch site. And it may have been that slight change in rainfall and temperature that caused mammoths, horses,and a range of other animals to disappear from the southern Arizona landscape forever.One major contribution of pollen analysis to archaeology is the reconstruction of environmental change. Properly applied, pollen studies can also help archaeologists understand past human behavior (see “Looking Closer: Palynology of Shanidar Cave: Why Formation Processes Matter”). Pollen can also play a role in figuring out what plants were important in prehistoric diet. An example from Nevada’s Stillwater Marsh shows how and introduces other sources of paleoethnobotanical information.What Plants Did People Eatin the Stillwater Marsh?You recall from Chapter 3 that floods exposed dozens of archaeological sites and human burials in the Stillwater Marsh of Nevada’s Carson Desert. We discuss the burials in the next chapter; here we focus on the plant remains recovered from one site. Site 26CH1062 sits on a low clay dune and contains pits, postholes, and at least two ephemeral houses. People lived there at least twice, about 1400 and 1000 radiocarbon years ago. We water-screened all the sediments, and recovered a large number of stone tools, manufacturing waste flakes, shells, and faunal remains. We also floated sediment samples from several of the features and retrieved many carbonized macrobotanical remains. We sent these to paleoethnobotanist David Rhode (Desert Research Institute). Looking at the samples under a microscope, Rhode identified the carbonized seeds and charcoal using a comparative collection; most of the charcoal was reed (Phragmites australis), greasewood (Sarcobatus sp.), and willow (Salix sp.). These plants are found today in the Carson Desert, and they could have been firewood, or used in housing or tools.Rhode also found the carbonized seeds of cattail, dock, seepweed, chenopods, pickleweed, silverscale, heliotrope, saltbush, and goosefoot. The site’s inhabitants could have gathered any of these as food, and all, again, occur in the area today. One of the most abundant seeds was that of bulrush (Scirpus sp.), one of the many plants that the indigenous Paiute Indians gathered and ate in the nineteenth century. Experimental data show that bulrush seeds are an efficiently gathered and nutritious resource. But did people collect bulrush for food? Maybe the seeds were attached to bulrush plants that were used to uild shelter or baskets, and were accidentally burned. Were bulrush plants, and not just their seeds, present on the site? To answer this question, we looked at another source of plant data in archaeological sites.PhytolithsPhytoliths, literally “plant stones,” are microscopic plant opals. As plants take in water, they also take in silica and deposit it between cells, within cell walls, or in the cells themselves. Phytoliths occur in various grasses, as well as in rushes, sedges, palms, conifers, and deciduous trees. When plant material decays, the almost indestructible phytoliths are left behind. Phytoliths take the shape of the cells in which they wer deposited, and because different grasses have different cell shapes, their phytoliths also have different shapes. This means that we can identify the presence of certain kinds of plants long after those plants have decayed and disappeared. Phytolith analysis, therefore, is similar to pollen analysis, although phytoliths are not quite as identifiable to species as pollen. Phytolith analysis was extremely useful in the Stillwater Marsh. Our sediment samples contained abundant, wellpreserved phytoliths. Most of these were from Phragmites, a common marsh grass. What was most intriguing, however,was the absence of sedge phytoliths (phytoliths produced by plants such as bulrush). This means that no bulrushplants decayed on the site. Perhaps, then, there was no bulrush in the StillwaterMarsh 1000 years ago. Perhaps a visitor brought some bulrush seed cakes from another wetland, such as Winnemucca Lake to the west. This is a question about the regional vegetative environment, and it is best answered through pollen data. So, we also took pollen samples from several of the site’s features. Analysis showed these to contain pollen that is little different from the modern pollen rain; in fact, bulrush pollen was abundant. So, now we know (1) that burnt bulrush seeds were present on the site, (2) that bulrush plants were not on the site, that bulrush seeds were brought to the site to be eaten. The macrobotanical remains were also interesting because of what was not present. Completely missing were the seeds of upland plants such as ricegrass or piñon pine nut hulls, both important food sources to the nineteenth-century Paiute. This suggests that when people lived in the Carson Sink, they got their plant food exclusively from the wetland. They did not travel even a few kilometers into the low foothills to gather ricegrass, nor did they hike another 20 kilometers into the hills to gather piñon.Site SeasonalityThe seasonality of the Agate Basin site was determined using faunal remains, but we used the macrobotanical remains at 26CH1062. Establishing seasonality from plant remains is a matter of determining the plant foods’ seasons of availability. Recall that we found seeds of bulrush, cattail, seepweed, dock, chenopods, pickleweed, heliotrope, silverscale, saltbush, and goosefoot. We know that most of these seeds ripen in mid- to late summer and into the early winter, although dock and heliotrope are gathered throughout the summer only. All of these resources, therefore, are only available in the late summer, and that is probably the best estimate of when the site was occupied, although an occupation from midsummer into the late fall cannot be ruled out.
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