The Paleo-Indian period is the era from the end of the Pleistocene (the last Ice Age) to about 9,000 years ago (7000 BC), during which the first people migrated to North and South America. This period is seen through a glass darkly: Paleo-Indian sites are few and scattered, and the material from these sites consists almost entirely of animal bone and stone tools. Available information from Paleo-Indian times documents hunting of several animals that became extinct in North America at the end of the Pleistocene, spectacularly skilled stone working by artisans who made beautifully crafted stone tools (especially spear points), and the beginning of a reliance on bison hunting that persisted on the Great Plains for 10,000 years.
Although Paleo-Indians were more than just flintknappers and big-game hunters, those have been the most visible aspects of their lives since archaeologists first recognized this period in the early twentieth century. From animal kill sites to tool caches, some of the most important clues to the Paleo-Indian past have been found in Colorado.
First People: Clovis and Pre-Clovis
Europeans have debated the origins of the indigenous people of North America ever since the Spanish conquest of Mexico. If human beings did not evolve here, where did they come from and how did they get here? Traditionally, it has been argued that humans migrated here out of Asia, either moving in boats down the west coast or walking through a corridor between the continental glaciers onto the northern Great Plains, although the timing of this migration has always been uncertain. This theory has been complicated by recent arguments that the earliest North Americans were biologically distinct from more recent people and that they may have arrived from Europe.
However, chemists have now extracted DNA from very ancient skeletons in Montana and the Yucatan Peninsula. Most (not all) of the skeletons of the earliest people in North America do look slightly different from those of many recent people. Similar skeletons are well known on the northwestern Great Plains from many periods of time. This new genetic work leaves no doubt that the earliest migrants to this continent were the biological ancestors of recent people, and that these migrants were unambiguously Asians, not Europeans.
But even if the first people in the New World (and Colorado) arrived here from Asia, it is less certain when they arrived. People were certainly in what is now Colorado by 11,500 BC, producing the distinctive and beautiful spear points and other artifacts classified as Clovis. But it is also possible that people were here earlier. Sites dated as early as 39,000 years ago, including the Dutton and Selby sites near Wray and the Villa Grove site in Saguache County, contain the bones of large, extinct animals broken in ways that suggest human action. However, these localities produce no stone artifacts at all, and very few archaeologists accept them as definite evidence of human occupation.
By about 11,500 BC, though, discoveries of Clovis artifacts in sites with the bones of at least some of these animals leave no doubt that people were here. The best-known Clovis sites in North America are mammoth kills, and this has led many to view Clovis people as specialized big-game hunters. The Dent site near Greeley is the only Clovis site in Colorado (Figure 1). By themselves, however, these sites are misleading since large bones like those of mammoths always attract archaeological attention, and digging around them can hardly tell us about activities other than hunting.
Clovis campsites (best known from Texas) tell a very different story. Clovis people relied on a wide array of large and small animals. They also cached tools on the landscape. Most often understood as “insurance” to guarantee access to the tools in areas without natural stone sources, these caches also may have served as offerings or for other reasons. Three of these tool caches are in Colorado: the CW and Drake caches from northeastern Colorado and the Mahaffy cache from within the city of Boulder (Figure 2). The CW cache includes tools made from stone that outcrops north of Sterling, but the other two include material from the Texas Panhandle (the Drake cache) and from across the Continental Divide as far away as Utah (the Mahaffy cache). These discoveries suggest movements over very large areas, although it is uncertain whether families, individuals, or larger social groups made these movements.
By some time after 11,000 BC, most large mammals in North America, including mammoths, mastodons, camels, horses, and many others, were extinct. A handful of archaeologists think these were simply exterminated by human hunters. However, the overwhelming majority sees no convincing evidence of this and suspects that a combination of environmental change and some degree of human hunting is more probable. In fact, no one knows for certain what caused this extinction, although recent work in modern and ancient animal DNA is beginning to offer fairly detailed answers. So far, this new work does not suggest extinction by overhunting.
Plains and Mountain Hunters and Gatherers
Knowledge of human ways of life after 10,800 BC has increased dramatically. Later Paleo-Indian sites are subdivided by types of spear points: Folsom in the plains and mountains from 10,800 to about 9700 BC and a variety of types (Agate Basin, Hell Gap, Scottsbluff, Eden, and so on) after that on the plains. Many plains types also occur in the mountains alongside a number of distinctive mountain points (often labeled Foothills-Mountain and Western Stemmed).
It is known that Clovis people passed through the high country in Colorado, but essentially nothing is known about what they did there. Later Paleo-Indian groups, though, lived throughout Colorado. On the eastern plains and in the mountain parks, Paleo-Indians hunted bison and other animals. People undoubtedly hunted in a variety of ways, but large bison kills at sites like Olsen-Chubbuck and Jones-Miller on the eastern plains were communal events that involved large numbers of people and sometimes killed hundreds of animals at a time.
Archaeologists have often viewed later Paleo-Indian groups much like those who lived during Clovis times as wide-ranging nomads who rarely or never reused particular places on the landscape. This is clearly wrong. Paleo-Indian sites throughout the plains, and throughout Colorado—for example, Folsom-age Lindenmeier, near Fort Collins, and Cody-age Jurgens on the plains near Greeley, as well as sites in the mountains—document nearly total reliance on local raw material to make all of their tools other than spear points, implying that they did not travel over particularly large areas. Lindenmeier, perhaps the most spectacular Paleo-Indian site in North America, also shows thick accumulations of debris that mark a place where people camped over and over again for centuries. Paleo-Indians did not always do that—the Folsom-age Cattle Guard site in the San Luis Valley is a single encampment near a bison kill—but enough is known to say that Paleo-Indian ways of life were quite variable, often at a local level.
Within Colorado, this variation especially involved the obvious differences between the eastern plains and the western mountains and Colorado Plateau. Bison ranged into the mountains and Paleo-Indians hunted them there, in Middle Park and elsewhere, just as plains Paleo-Indians hunted them (and many other animals) on the open grasslands. But mountain groups seem more local in their habits. For example, there is little evidence that they imported stone from the plains or from distant parts of the high country, and they seem to have occupied the high country year-round. Folsom groups in western Colorado built stone foundation houses at least sometimes (these are unknown elsewhere), and later Paleo-Indian groups in the area roasted food (probably but not definitely plants) in pits, using pre-heated rocks as heating elements. Unsurprisingly, mountain sheep and other high elevation species were important in the diet of high country Paleo-Indians.
End of Paleo-Indian Times
The Paleo-Indian period began near the end of the Ice Age, when glaciers were melting as climate warmed. It was punctuated in the middle by a climatic interval called the Younger Dryas, a return to cooler and wetter conditions that began fairly abruptly at 10,800 BC and ended even more abruptly at 9700 BC. For the remainder of the period, the climate warmed and dried. On the Great Plains in general, as upland range conditions deteriorated and bison herds declined, hunters preyed on animals like deer and antelope more often, and families took more small animals. After 8000 BC, human populations seem to have thinned on the Colorado plains, with some people perhaps joining their neighbors in the high country; by 7000 BC and after, people throughout the state began to make new styles of spear points and to experiment with new kinds of hunting, marking the end of this period.