© Trey Ratcliff
Further, radio-carbon dating shows that some of the unearthed artifacts are thousands of years older than expected.
Archeologists began excavating the site last summer after the Wyoming Department of Transportation made plans to widen Highway 26/89/191.
Now, after two summers of digging, the artifacts are beginning to develop a picture of life at the site that ranges over thousands of years, from a roasting pit dated at 10,100 years old to a .38-caliber bullet that is likely from the early 1900s, said Michael Page, a senior archeologist with the Wyoming state archeologist office.
During some periods, the abundance of projectile points crafted from local sources could mean that people lived in the region year round, Page said. By contrast, projectile points from outside the area could suggest people migrated out of the region during some part of the year, most likely winter.
"A lot of the obsidian turns out to be fairly local, and a lot of it probably came from cobbles," he said. "They could have walked down to the Snake River and found all the obsidian they needed.
"We also found other material types - cherts and quartzites and quite a bit of petrified wood," Page said.
The petrified wood is probably local, Page says, explaining that a rock hunter found a match in the Gros Ventre drainage.
The idea of year-round inhabitants in Jackson Hole isn't so far fetched. Climate models show that, 5,000 to 7,000 years ago, Jackson Hole was warmer and wetter in the summer, and colder and drier in the winter. Warmer, wetter weather in the summer means more forage, and more forage means more animals for humans to eat. Drier weather in winter also could mean more available forage for animals.
"The more food sources there are, the higher the carrying capacity - the more people who could live here," Page said.
But those are just guesses at this point, and further analysis of the materials will either prove or disprove Page's theory.
Laboratory analyses of the artifacts already have produced some surprises. A roasting pit thought to be roughly 2,000 years old came back from the lab dating more than 5,000 years old.
"I sent off a bunch of charcoal for radio-carbon dating, and I found out I was wrong," Page said. "I definitely had to rethink the whole thing."
Another roasting pit dates just after the ice age.
"We found a fire pit down at the very bottom that turned out to be older than we thought, 10,100 years, plus or minus," Page said. "But, we still hadn't found these diagnostic point types down at that level."
Those diagnostic point types - arrowheads and spear heads of the Agate Basin variety - would help confirm the roasting pit's age and perhaps provide information about the people who made it. For now, the evidence points to prehistoric humans from the Great Basin and Columbia River, which makes sense, because the Snake River flows into the Columbia. Ancient people may have followed the river system up into Jackson Hole.
Next summer, Page aims to excavate more on the west side of the road, where archeologists have discovered a treasure trove of new artifacts.
"We were finding twice as much in half the soil," he said.
Diggers have found a bison skull, a fox skull and elk, beaver and probably deer bones. One large bird bone could have come from a trumpeter swan. Animal artifact experts might be able to determine what time of year the animals were killed by looking at things such as emerging teeth. Carbonized seeds also can point to seasonality because seeds only ripen at certain times of year.
The in-depth look at Jackson Hole's prehistory is exciting, said J.P. Schubert, an archeologist for the Bridger-Teton National Forest.
Forest Service archeologists typically assess what's on the surface, and that information is later used for planning purposes, Schubert said.
"It's neat when people can actually spend some time," he said. "There's stuff way down in there that is super fascinating."
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