Perce inhabited the Clearwater and Salmon River basins and the Snake river through Hells Canyon. The Cayuse homeland is the Blue Mountains and the valleys of the rivers that flow from them. The Molala inhabited the eastern side of the cascade mountains in Oregon. The Klamath people inhabited the upper Klamath River basin and had close contact with people from the California cultural area, though their lifestyle and language were more characteristic of plateau culture. The Columbia River below Celilo Falls was inhabited by Chinook people. Chinook people on the lowest portion of the Columbia are considered part of the Northwest Coast. Sahaptin groups also lived in Western Washington on the Mashel River and upper Cowlitz River. The Willamette Valley was inhabited by the Kalapuya people. Having no major salmon run, their culture was somewhat different from other plateau people, maintaining oak savannas similar to many California natives. History While plateau people kept no written records, the prehistory of the plateau region can be partially reconstructed by a combination of oral traditions, linguistics and archeological evidence. There is archeological evidence of human presence on the plateau for at least 12,000 years. The Marmes Rockshelter and Kennewick Man are two examples of early human presence. Over time human technologies adapted to the unique environment. Earth ovens near camas meadows have been found that are up to 8,000 years old. Around 4,000 years ago, there was a shift in the archeological record from small bands to larger semi-sedentary villages, and a shift towards root processing tools, hallmarks of plateau culture. Linguists and oral traditions point to several comparatively recent movements of people. According to language comparisons, the interior Salish peoples expanded onto the plateau from the vicinity of the lower Fraser River. This expansion reached as far as Montana, was complete around 1,500 years ago. Likewise, Athabaskans on the plateau are part of a relatively recent expansion from northern Canada and Alaska, as recently as 1,000 years ago. The Kalapuya people spread into the Willamette Valley, likely from the south, in the last 1,000 years. The recent expansion of Numic people across the Great Basin displaced several groups on the southern edge of the plateau. This process was still occurring at the time of European contact. Around 1730, horses were introduced onto the plateau from the Great Basin and were first adopted by the Cayuse and Nez Perce. This greatly changed the