Summary: Oregon Prehistory

The NW Coast, Columbia Plateau, Inter-Mountain, Great Basin, and California chaparral eco-zones merge in present-day Oregon. The cultures, technologies, and economies of prehistoric Oregon reflect each one of these regions. The temperate climate and fertile environment allowed Oregon's prehistoric cultures to thrive for thousands of years.

Pleistocene Adaptation

The hallmark of the PaleoAmerican period is that this is the within, but near the end of the Pleistocene Era--the Ice Age. The term "Paleo-American" refers to human adaptation to, and exploitation of, Pleistocene environments and associated plants and animals.

Here is my prediction about the Western Stemmed/Clovis hypothesis: 1) That Western Stemmed technology represents an early eastern old world movement into the new world along the kelp highway and coastal refuge zones; 2) that Clovis technology represents a western old world movement along the ice into the eastern new world; 3) as the ice retreated the eastern route slowed and stopped; 4) populations in the new world were hit hard by the Younger Dryas climactic shift; and 5) as the western ice withdrew it opened up a population movement into the new world that swamped the remnant genetic populations out of western Europe.

Very little data is available for this period of time. There are several reasons for this. First, there were very few people around this early. Populations grow over time. The initial occupation of North America was relatively late in comparison to the Old World, where the hominid species evolved. Second, time erases evidence through acts of nature. The older the archaeological site, the greater that chances that random events will destroy the site. In addition, all sites slowly decay. Their organic remains tend to be the first to go. Any features (soil stains, firepits, post molds, etc.) tend to erode away as artifacts and features are moved around by burrowing animals and plant roots. Artifacts and features in shallow soils are smeared out by freeze-thaw or moist-dry cycles. Third, the Willamette Valley is slowly filling up with sediments. Before the dams were built, the rate was about nine inches per thousand years. A site over 11,000 years ago would thus average about 8.25 feet below current surfaces. The chances of finding such sites are very remote. Continue with Pleistocene »

Holocene Adaptation


This period marks the beginning of the Holocene where modern flora and fauna were used by prehistoric groups. The hunting of giant mega-fauna was no longer possible, as the giant animals had either died out or were hunted into extinction.

The temperatures rose, and the Pleistocene lakes began to shrink and wither away into alkali basins. The grasslands of the Great Basin were replaced by desert grasses, juniper and sage. The glaciers in the Cascades, Wallowa and Steens mountains rapidly disappeared. The flow of water from the Harney-Malheur Lake basin fell below the connection with the Malheur River, and became an internally drained basin.

Mt Mazama erupted about 6,800 year ago, throwing out roughly 11 cubic miles of pumice over vast areas of the NW. Ash has been identified as far north as Alberta, British Columbia and as far east as Montana. About 20 miles from the crater (now Crater Lake) the ash was one foot deep. The ash changed the landscape, and filled the rivers and streams for a long time. Ash may have impacted runs of anadromous fish such as the salmon, causing them to drop in numbers. The ash deposit is now used to date occupations of sites, as the date for this event is known, and the ash was deposited over such a large area of the NW. When artifacts are found under a primary deposit of Mazama ash, it is known the site is more than 6,800 years old.


The plants and animals were now modern in form. Hunters switched to deer, elk, antelope and small game such as rabbits and birds. Fishing also became important along the coastal streams and in the Columbia River system, with an increasing emphasis on the annual runs of the salmon. Coastal land forms continued to be buried under raising sea levels, so little is know about adaptations. The few sites that have survived demonstrate that shellfish were an important part of the diet as well as other river, estuary and near beach fish. Hunting of seals, sea lions and other pennipeds was also done.

Archaeologist roughly divide the climate history of this region into three periods: the Anithermal, the Altithermal, and the Medithermal. The first of these was a period of increasing warmth and dryness roughly similar to climates of today. Around 4,500 years ago, the temperature increased into the Altithermal, reaching a maximum warmth and dryness. This was followed by the Medithermal coming back to modern conditions. The Early Archaic roughly corresponds to the Anithermal.

The Archaic periods cover human activities during the Holocene after the end of the Pleistocene. The Holocene Archaic is divided up into three sub-periods: Early Archaic and Middle Archaic. These represent changing cultural adaptations to changing environmental conditions. Continue with Holocene »

Pyroculture Adaptation

The period of "pyroculture" began roughly 2000 years ago and extended to historical times. This period is marked by the presence of the bow and arrow. The climate was modern within fluctuations. There were droughts and periods of wet conditions, but these fell within modern patterns.


The time period covered is roughly from 2000 years ago to contact with Euro-Americans. The climate was modern within fluctuations. There were droughts and periods of wetter conditions, but they fall within modern patterns.


Plants and animals distributions were essentially modern with small variations in relative density and abundance. Large scale manipulation of plants and animals through fire as a tool to reduce plants tied up in climax vegetation and to increase valued plant (and animals that depended on them) diversity and availability. The use of fire, what I call "pyroculture", started perhaps 3500-3000 years ago at the end of the Middle Archaic. Burning out climax vegetation, reduces the biomass tied up in cellulose (trees), and increases the diversity of the natural habitat. In the Willamette Valley, burning created an open grassland/oak mosaic between gallery riverine forests. The open grassland was the favored habitat for camas (a root "crop") and tarweed ( a seed "crop"). Oak expands with burning, so acorns (a nut "crop") also increased in relative abundance. Other plants used for food, medicine and fiber also increase in relative abundance with the use of fire. The oak/grassland mosaic was also favored habitat for deer and elk. The gallery forests along the streams were too wet to burn. The wood in these forests became the fuel source for camas processing ovens.

In the 2009 report on Sunken Village: "The site is on Sauvie Island, where a major aquifer pumps under the natural levee into Multnomah Channel, providing a unique 125 m wide beach area where acorns placed in shallow hemlock bough-lined pits were leached in huge numbers by ancient Multnomah peoples" (Croes, Fagan & Zehendner 2009: 15).

"The approximately one hundred pits recorded at 35MU4 were identified on the surface, sometimes because of the presence of acorns, but the more obvious marker of the leaching pits at the surface is a circle of branches protruding from the beach" (Croes, Fagan & Zehendner 2009: 85).

Based on the average size of the leaching pits they concluded that the pits contained roughly "2.5 million acorns leaching for use every year, these leaching pits on Sauvie Island could provide over 59 million calories to the group or groups who owned them" (Croes, Fagan & Zehendner 2009: 93).

They also concluded that people could harvest about 325,000 acorns per hectare of Oregon white oak (Croes, Fagan & Zehendner 2009: 93).

This supports my conclusion that acorn harvesting was an important part of the plant gathering process for western Oregon groups. While reading the section on pyroculture adaptations, if you FIND the word acorn, it will take you to the sites where acorn processing has been recorded archaeologically. Continue with Pyroculture »