In the Yellowstone region, the last major ice age ends about 14,000 years ago. The valleys are ice-free and vegetation has returned by about 13,000 years ago. The post-glacial environment is gradually drying and warming, and the animals that were adapted to the cooler glacial environment are dying out or becoming smaller. The mammoth, mastadon, camel, short-faced bear, and horse all disappear (horses would be reintroduced to North America by the Spanish in A.D. 1523), while the Pleistocene bison, Bison Antiquus, which was some eight feet at the shoulder downsizes to the modern bison, Bison bison, which is some five to six feet at the shoulder. People during this early period are sometimes referred to as Paleoindians and they used large (compared to later points) points hafted to spears.
The form of the projectile points changed as people adapted to different environmental conditions and as technology changed. The earliest points are lanceolate and fluted (which helped in hafting an unnotched, lanceolate tool). Lanceolate refers to an artifact that is long and slender in comparison to the length. Fluting refers to the removal of a flake from the base extending towards the tip that thins the base. Late Paleoindian points have shoulders, contracting stems, and square or concave bases. In the park, Paleoindian people hunted bison, bighorn sheep, rabbits, deer, and bear. While people probably are berries and fresh greens, there is little evidence at any time for the cooking and processing of plants as part of the diet.
The earliest evidence of humans living in Yellowstone is a Clovis point that was found near Corwin Springs, 12 miles north of the park. This artifact is made from Obsidian Cliff obsidian that is found only in Yellowstone National Park. We know the obsidian came from Obsidian Cliff in the park because it has been “sourced” to Obsidian Cliff. Obsidians from different rhyolite lava flows can be chemically fingerprinted using x-ray fluorescence, a non-destructive analytical technique. Obsidian Cliff is the remnant of the Obsidian Cliff rhyotite flow 180,000 years ago and is the predominant stone for tool manufacture in the park. At least 16 different sources of obsidian in the Greater Yellowstone Ecosystem have been identified in prehistoric tools from the park. Nevertheless, each year we find evidence of new obsidian sources for stone tools.
The next people or culture in western North America is known as Folsom. An Obsidian Cliff obsidian Folsom point dating about 10,900 years ago was discovered on the Bridger-Teton National Forest south of the park. A second Obsidian Cliff Folsom point was found about 15 miles northwest of the park. As time goes on, the number of distinctive point types (assumed to equal cultures), such as Agate Basin and Hell Gap dating to about 10,000 years ago, increase and these are taken as evidence of an increasing population.
While there are Agate Basin and Hell Gap points found on the ground’s surface in the park, the earliest intact cultural deposits are related to the Cody Complex which dates 9,400-9,600 years ago. The Cody Complex is named for a Bison antiquus kill site near Cody Wyoming. It is believed that these Paleoindians visited the park during the summer to hunt and while they were here, they collected obsidian for tools. The Osprey Beach site is a 9,400 year old camp at nearly 7,300 feet where several families spent time on Yellowstone Lake repairing and manufacturing tools. They used blocks of local sandstone to shape their wooden shafts. The large number of obsidian tools found Osprey Beach is changing the view that Paleoindians did not use obsidian, which had been thought by some archeologists to be too brittle a stone from which to make these lanceolate points.
About 9,000 years ago, an archeological tradition developed that is characterized by lanceolate spear points with contracting stems and concave bases. Outside the park, there is evidence that these people utilized more plants, as well as large and small mammals for food. The emphasis on a diversity of food resources is called a broad based economy. It has been suggested that a climatic shift to warmer and more arid conditions on the plains may have caused this increased utilization of the mountain environment or possibly the increasing population expanded from the plains into the mountains on a summer seasonal basis. While we know these people hunted in the park and used local obsidian sources for tools, there are many other questions about their way of life that remain to be understood.