Overview
At 12,000 feet along the Continental Divide in Colorado, the landscape is too harsh for permanent habitation. Yet, the Rollins Pass area is home to one of the most extensive prehistoric engineering projects in North America. These are not dwellings; they are an intricate system of stone walls and blinds designed to manipulate the behavior of large game.
Evidence at a Glance
Key signals, kept separate from interpretation.
| Key Signal | Archaeological Data |
|---|---|
| Maintenance Data | Lichen growth patterns prove 5,800 years of continuous use |
| Blind Density | Over 60 individual hunting pits at the Olson site alone |
| Structural Geometry | "V-shaped" funnel walls up to several hundred feet long |
| Environmental Challenge | Construction occurred above the tree line in sub-arctic conditions |
Forensic Breakdown: Alpine Persistence
Comparing the archaeological reality to natural environmental factors.
| Feature | Natural Slope Process | Archaeological Forensic |
|---|---|---|
| Maintenance | Weathering causes collapse | Evidence of clearing and restacking over 5 millennia |
| Target Species | General movement | Specific funnels designed for Bighorn Sheep behavior |
| Labor Cost | Zero | Extremely high energetic cost for seasonal food yield |
| Strategic Logic | Path of least resistance | Funnels that force animals toward concealed ambush points |
The Logic of the Drift Fence
The primary discovery at Rollins Pass is the Drift Fence. Unlike a trap, these walls didn't stop animals; they gently "drifted" them toward a specific location. Prehistoric hunters used the terrain and these low stone barriers—often only two or three stones high—to guide Bighorn sheep into the "kill zone" where hunters waited in concealed blinds.
5,800 Years of Maintenance
Lichenometry—the study of lichen growth rates on stone—reveals a startling fact: these walls were maintained. Generation after generation of hunters returned to the same sub-arctic ridges to restack fallen stones and clear the blinds.
This suggests a deep, multi-millennial continuity of cultural knowledge and landscape management that defies the "nomadic" label.
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