Along lakes and streams that have long since disappeared, archaeologists working in southern Nevada have found nearly 20 sites used by ancient hunter-gatherers as much as 12,000 years ago.

And even though the sites are remote, they weren’t discovered by accident. Scientists expected to find them there.

About 160 kilometers [100 miles] northeast of Las Vegas, researchers from the Utah-based firm Logan Simpson discovered 19 separate sites containing a variety of stone points, biface blades, and other artifacts associated with the Paleoarchaic Period, an era ranging from 7,000 to 12,000 years ago.

Though scant and widely scattered, these pieces may help clarify the hazy history of human activity throughout the Great Basin, when the Ice Age gave way to a warmer and more stable climate.

To archaeologists like Jesse Adams, who led the new study, this period marked the transition from the Pleistocene epoch to the Holocene, a time of change that has been scarcely studied in the American West.

“The Pleistocene-Holocene Transition period is a little known but fascinating time period,” said Adams, a senior archaeologist with Logan Simpson, “especially to everyone in our office, as we have identified similarly aged sites during other projects in the Great Basin which piqued our interest.”

Adams and his team found these rare sites using a technique known as predictive modeling: By identifying the qualities that previously known locations had in common, the archaeologists predicted where other, similar sites might be waiting to be found. [See how predictive modeling led to another big find: “13 Ancient Villages Discovered in Wyoming Mountains May Redraw Map of Tribal Migrations“]

Previous research in the Great Basin had shown that signs of human activity from the late Pleistocene were most often found around certain kinds of land formations near water and marshlands — on the shores of lakes that have since dried up, for example, or on the landforms that overlooked them, or along the channels that led into or flowed out of them.

With funding from the Bureau of Land Management’s Lincoln County Archaeological Initiative, Adams and his colleagues used this kind of information to predict where signs Pleistocene-Holocene activity might be found in Nevada’s Lincoln County, using geographic information system (GIS) technology.

“The Lincoln County Archaeological Initiative offered an opportunity to create, and refine, a technique using GIS that would more effectively identify where these rare site types are located on the landscape,” Adams said.

Their model focused on the fact that the Great Basin’s climate was cooler and wetter at the end of the Pleistocene than it is today, with marshes and lakes that likely drew hunter-gatherers over the centuries.

After mapping the land with GIS, aerial photos, and other tools, the researchers pinpointed and then ranked the most promising locations in the study area.

“These areas were then ground-truthed and resulted in several landforms of interest,” Adams said. [See what boots on the ground found in the Mojave Desert: “Nearly 9,000 Artifacts Uncovered in California Desert, Spanning 11,500 Years of History“]

By surveying the top-ranked areas on foot, archaeologists turned up seven sites in Lincoln County’s Delamar Valley, along the traces of what had been an ancient stream channel.

The sites included scatterings of fluted and stemmed projectile points fashioned in styles — such as Clovis, Lake Mojave and Silver Lake — that are known to date to the Paleoarchaic epoch in the Great Basin, Adams said.

Likewise, at the nearby Dry Lake Valley, the team detected six more sites, along the shoreline of the extinct lake that gave the valley its name.

There, researchers found more stone points from the Paleoarchaic, but also many others dating from more recent periods, indicating that these lakeside sites were used many times over the millennia.

And finally, in the area of Lincoln County known as Kane Springs, yet another half-dozen sites were detected, with projectile points and flakes with an equally ancient profile.

[See more 12,000-year-old points, including the biggest point of its kind ever found: “ Over 1,000 Ancient Stone Tools, Left by Great Basin Hunters, Found in Utah Desert “]

Together, the newly found sites are providing the best view yet of the distant past in this corner of the Great Basin, Adams said.

And they also prove that GIS-based predictive modeling can work, he added, providing a potentially invaluable tool in the search for as-yet-undiscovered prehistoric sites, even in the increasingly developed American West.

“The Pleistocene-Holocene Transition is a fascinating, yet underrepresented, time period in the Great Basin,” Adams said.

“Through the creation, and later revision, of a model using GIS technology, we are able to successfully identify archaeological sites from this time period on the landscape.”