JACKSON — Underneath a white tent near Game Creek along Highway 89/191, University of Wyoming archaeology student Bryon Schroeder sits in a 6-foot-deep hole troweling out the winding path of a rodent burrow through a square of gray earth.
Schroeder excavates the burrows first so the rodent-churned dirt doesn’t contaminate the cake layers of history that jut out at perfect right angles from the walls and floor.
On one wall, the charred, fractured stones of a partially exposed roasting pit are visible at waist level. Given its location in the strata, the pit likely dates back 3,000 to 5,000 years, when it probably was used to roast tubers such as sego lily.
On the floor, another square of earth was scraped away to expose the tops of river cobbles.
“That’s the Ice Age,” said Rich Adams, a senior archaeologist from the office of the Wyoming State Archaeologist. “Right there, those river cobbles, that’s probably pre-human habitation of Jackson Hole.”
While some might think of Jackson Hole as untraveled before a handful of trappers made their way here in the early 1800s, the written history of the region is just a postscript on the 10,000 years or so that prehistoric and Native American tribes lived in this region.
This site, discovered in 2001 when the Wyoming Department of Transportation decided to widen the highway, adds a wealth of information to that narrative.
Adams and senior archaeologist Mike Page, the leader for this dig, have directed the unearthing of artifacts that give clues as to who visited the site and when. A small army of archaeologists sifts through every square inch of dirt. That dirt is then “water screened,” a technique that sifts material to detect artifacts as small as one-eighth of an inch wide.
What made the Game Creek site so attractive is its location.
“There are multiple ecosystems that coincide right here,” Page said, explaining that the south-facing hills near Game Creek were likely good habitat for deer and bighorn sheep, while the land around the Snake River was good habitat for elk and bison. The river itself, just a few hundred yards to the west, was a good source of water and, possibly, fish.
“There’s a reason why they called it Game Creek,” said Adams, who said the area is also relatively close to the “Path of the Pronghorn,” a 150-mile migration corridor through the Gros Ventre Mountains from the Upper Green River Valley to Grand Teton National Park that scientists believe dates back thousands of years. “The pronghorn migration corridor wasn’t just pronghorn.”
Another reason early humans visited the Game Creek site was its proximity to a source of stone for tools.
“That’s something they always had to think about,” Page said.
The Crescent H Ranch in Wilson, about eight miles to the northeast, is a good source of obsidian that, along with chert and quartzite, was used to make projectile points, knives and other cutting tools. Other obsidian sources exist in Yellowstone National Park and other mountain ranges around Wyoming.
“All five obsidian sources were used at this site,” said Page, who explained that some material is from the Absaroka Range and the Wind River Range. “Almost all of it, 98 percent, is obsidian.”
These projectile points and other stone tools give researchers some of the best information. Where animal skins, bones and wood usually disintegrate over time, the projectile points persist. The style of a given projectile point, especially the notches at its base, along with its location in the strata, can place the manufacture of the tool within its proper time period.
A detailed knowledge of the sources of the stone tells archaeologists how far a group of prehistoric hunters might travel over the course of a year. Stone tools made from exotic materials hint at trade among prehistoric groups.
“My guess is they had very large home ranges and they traveled thousands of miles on foot,” Page said. “They probably left for Idaho in the winter, although some people stayed here year round.”
The oldest projectile point likely dates back 9,000 to 9,500 years ago, to the Paleoindian time period.
Radiocarbon dating will be used on the charred remains of the old fire pit to get a more accurate date, Page said. If those dates come back from between 10,000 and 10,500 years ago, it points to people who lived in the region just after the latest ice age, when Jackson Hole’s mountains more closely resembled Alaska with lower tree lines and receding glaciers.
The next oldest set of artifacts dates back 5,500 to 8,000 years to what is considered the Early Archaic period. To the archaeologists, the evidence of Early Archaic visitors to Jackson Hole is perhaps the most exciting.
“We have two nice projectile points from that time period,” Page said. “It’s not well documented in Jackson Hole,” or anywhere else in Wyoming.
During the Early Archaic, there’s evidence of high temperatures, called the Altithermal, that could have caused drought conditions in places such as the Great Basin. “There are some who suggested that when it all turned brown, prehistoric hunters came to the mountains,” Page said.
The mountains were a sort of refuge from the oppressive conditions at the time, Adams said.
“Everyone was following the (mountain) rains,” he said.
Once the 2,500-year stretch of unusually warm weather ended, so did the Early Archaic time period.
In the Middle Archaic, from about 5,000 to 2,500 years ago, “things were just about how they are now,” Page said, explaining that artifacts from Middle Archaic people have been found near Jackson Lake and the Jackson National Fish Hatchery.
“We have a well-defined and heavy occupation. They were coming here for thousands of years and they left all kinds of stuff here,” he said.
The people of that time period were “enamored with the mountains,” Adams said. “They appear to be more conservative.”
That conservative streak in the Middle Archaic people is shown by more local materials, compared with their ancestors who were bringing in stones from other areas.
Finally, there’s also evidence of Late Archaic people, who probably lived in the area from 1,500 to 3,000 years ago.
“We have two different Late Archaic projectile points,” Page said. “The occupations haven’t been nearly as dense here.”
Evidence from skeletal remains shows that prehistoric people in Wyoming lived well. Any persistent infection, something like an abscessed tooth, would have proved life-threatening, yet archaeologists find skulls with nearly complete sets of teeth.
“If you avoided all that, you lived to a ripe old age,” Adams said. “And you weren’t working 80 hours a week to do that.”
For prehistoric people, as with wildlife, the toughest time was from late February to early April. After that, animals such as bison started to feed on new forage, which was also available for human consumption. Unlike prehistoric hunters who lived in the plains, there’s no evidence of traps to catch bison in the Jackson Hole area.
It was encounter hunting, Adams said, “one guy with a sharp rock and an ego.”
While the dig is expected to last two years, maybe longer depending on the extent of the find, an exposed hole is a hazard for people and wildlife that might wander here in winter. So, soon the highway department will bring in heavy equipment to bury in a few hours the five or so holes it took an entire summer to excavate.