The purpose of this study is to understand how prehistoric people moved around the landscape and used major stone tool resources throughout the last 10,000 yr. B.P. in southern Idaho. Similar research has been reported in the Great Basin and western Wyoming and this study continues to fill the map with data about how large regions of the western United States were used prehistorically. This study specifically examined whether or not prehistoric mobility changed according to wet and dry climatic shifts. Based on these shifts archaeologists expect the regions people used to expand or shrink using an economic model of decision-making when foragers were confronted with the choice to stay in one resource area or move to another while pursuing plants and animals for food. To measure this decision prehistorically, obsidian projectile points and tools left behind throughout time were analyzed to determine where the stone originated geologically, a concept known as conveyance. The data were gathered from many regional studies and new sourcing of 139 artifacts from southeastern Idaho regional collections and excavations at the Fox Site near Thatcher, Idaho. In the compiled dataset are 4,440 artifacts from 640 archaeological sites in southern Idaho that originate from 37 obsidian sources. Analysis of this dataset grouped archaeology sites based on the percentage of different obsidian sources used, creating conveyance zone sets that were encompassed by statistically created ovals in mapping software. Four trans-Holocene conveyance zones are proposed and described: the Malad Conveyance Zone (MCZ), Timber Butte Conveyance Zone (TBCZ), Big Southern Butte Conveyance Zone (BSBCZ), and Snake River Conveyance Zone (SRCZ). These zones are then separated into four wet or dry climate periods and changes in mobility are compared to the economic decision model. Overall the MCZ and TBCZ both met the expectations of the model, while the BSBCZ and SRCZ did not. Another test of the data reveals that the number of obsidian sources used and the evenness of their use is not correlated with conveyance zone size, which helps confirm that these zones reproduce prehistoric behavior and are not a statistical product of the availability of obsidian in a region. The conveyance zones described in this study are comparable in size to those proposed in neighboring regions. Research also finds that southern Idaho conveyance zones were firmly established in the Early Holocene and shows that conveyance zones can be created from large datasets in a statistically robust manner and enable researchers to look at changes in forager mobility across large spatial and temporal scales. Expectations for forager mobility are partially supported by the variability wet and dry climate during the last 10,000 years B.P.

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