This research examines the ecology of human diet using archaeological evidence from a specific site in western North America, North Creek Shelter (NCS) near Escalante, Utah. I use ecological measures and theory to quantify human dietary change during the early to middle Holocene and in the context of local ecosystems that supplied plant and animal food resources. Vegetation sampling techniques are used to quantify the landscape and dietary palettes that may have been available to the occupants of NCS during the Holocene. According to my sampling, the pinyon-juniper woodland and cool desert scrub vegetation types would have supplied the majority ofdietary plant resources, while the other types were either devoid of, or had low cover by, dietary species. I also combine evidence from dietary plant macro- and microfossil remains with dietary faunal remains to examine this comprehensive dataset in the context of ground stone abundance and environmental change. Two periods ofincreased dietary species richness occurred at 9400 and 800014C BP, when people were focusing their subsistence on deer and Chenopodium seeds, respectively. The shift in emphasis between deer and Chenopodium was accompanied by a shift in stone tool technology. The assemblage of chipped stone tools in substratum 3e (9400 ¹⁴C BP) was dominated by hunting and bone-processing implements. Ground stone tools became dominant in substratum 5t (8000 ¹⁴C BP), simultaneous with a peak in Chenopodium abundance. Increasing aridity began by 9000 ¹⁴C BP and had progressed significantly by 8000¹⁴ C BP, indicated by a shift in vegetation from a mixed conifer forest of cool-adapted species to a semi-arid woodland and shrub mosaic. This coincided with a broadening of the diet dependent upon an intensified use of small seeds and ground stone technology. Intensive processing of small seeds on ground stone tools was not the only such practice at NCS. Underground storage organs were also processed and possibly roasted in pits uniquely found on the living surface of substratum 5t (8000 ¹⁴C BP). Although taxonomic assignments for the starch grains are difficult at this point, there are minimally two "taxa" ("centric" and "eccentric") that can be added to the tally of dietary species richness developed from macrobotanical remains (above). Adding these starch-producing plants to dietary species richness would accentuate a shift toward broader diet concurrent with a period of rapid environmental change during the middle Holocene.