A Thousand-Year-Old Social Network Revealed
An Artifact Connects the Dots
On the Uncovering the Mysteries of Ancient Colorado expedition in Cortez, Colorado, Earthwatchers are excavating a site occupied by ancestral Pueblo people (also known as the Anasazi) during what’s known as the Basketmaker III period (500 to 725 A.D.). The many artifacts they’ve dug up include 14 fragments of obsidian, a volcanic rock used to make arrowheads and other tools. “When it is made into a blade, that edge is so sharp; it can be even sharper than surgical steel,” says Dr. Susan Ryan, the archaeologist who leads the expedition. “It’s the type of material that you would prize, that you would want to keep around for a long time in your tool kit.”
Using chemical analysis, Dr. Ryan’s colleagues traced the sources of these finds. That’s where things got especially interesting for Earthwatch: four of the fragments turned out to have come from about 150 miles away in the Valles Caldera in New Mexico, where volunteers on the Encountering the Prehistoric People of New Mexico expedition, led by Dr. Anastasia Steffen, are excavating the very obsidian quarry where these fragments originated.
Some of the far-reaching places where artifacts made from Valles Caldera obsidian have surfaced.
Tracing Trade Across the Southwest
How did these bits of rock get so far from their source? “We consider it to be evidence of trade,” says Dr. Ryan. “It could be that people who are living closer to the quarries are getting the obsidian out of the ground, and through a series of trade networks, they’re ending up in other parts of the Southwest.” In other words, someone walked them there, or traded with a group nearer by who then passed the goods along.
Not only objects would have exchanged hands—information would have, too, just as it does along our much more wide-ranging social networks today. Information like, according to Colorado’s Bureau of Land Management: “What were other communities doing? How was the climate in other areas? How did others irrigate? How did other people make kivas? Such communication was involved in learning to make pottery, learning new farming techniques, acquiring the bow and arrow, and other important advances.”
The Obsidian Connection
According to Dr. Steffen, it’s no surprise that obsidian from the Valles Caldera—a crater formed by a massive volcanic eruption 1.2 million years ago—would make a sought-after trade item in this network. “This site has some of the best obsidian around—weapons-grade obsidian,” she says.
Colorado is hardly the farthest this valuable rock has traveled: it’s turned up in 12 states and Mexico, in sites as distant as Mississippi and northern North Dakota. Tracing the path of Valles Caldera obsidian suggests the mind-boggling extent of prehistoric social connections.
Clues to the Basketmaker Network
The Basketmakers—ancestors of the Pueblo Indians—were the first people to live in the Mesa Verde region of Colorado. They brought with them, or developed, a breadth of knowledge far beyond their boundaries: “When we see material from [the Valles Caldera] quarry show up, it indicates that the people living there have some type of knowledge directly about that source, or they know people who do,” says Dr. Ryan.
Artifacts like these obsidian fragments provide clues to how people moved throughout the ancient world and what they carried with them. They also show why forging connections in the present day, part of the Earthwatch mission, is so important: in science, collaboration is often the only way to put the fragments together and see the big picture.