Dr. David Rhode digs deep to unearth mysterious existence of Ice Age people atop Tibetan Plateau

Heima He overview: A 13,000-year-old hunters' camp lay buried deep in this loess outcrop. Exposing the long stratigraphic profile opens a window on the prehistoric campsite and changing environmental conditions in the region since the end of the last Ice Age. (photo by David Rhode)

Dr. David Rhode, archaeologist and paleoecologist, knew what he was getting into as he and a team of students and fellow researchers followed guides across the Tibetan Plateau in China, retracing steps he had taken years before. Often called the "roof of the world," the Tibetan Plateau is the world's highest geological feature.

Its lofty altitude, thin, oxygen-poor air and harsh climate pose serious challenges and questions to scientists like Rhode: How could Paleolithic or Stone Age hunting people sustain themselves in such an extreme environment thousands of years ago?

Like a private investigator searching for clues, Rhode's eyes are trained to spot evidence of Ice Age hunter-gatherers who first colonized the area sometime between 10,000 and 35,000 years ago. During previous trips to Tibet, Rhode's research team had discovered firehearths and other signs of ancient hunters' campsites, and they made plans to return to unearth their finds.

His group's research will help answer questions about what evolutionary and ecological processes led hunter-gatherers to occupy these extreme environments and what behavioral strategies facilitated successful human colonization.

Fire hearth excavation: Archaeologist Dr. David Madsen, second from left, DRI, and students Haiying Zhang, University of Washington, and Jim Morrison, University of Arizona, attract the interest of a local Buddhist monk as they excavate the fire hearth at Heima He. (photos by David Rhode)

Late last June, Rhode packed his gear and returned to Tibet with targeted sites plotted and with high hopes of avoiding treacherous summer monsoons. The five-week trek took the team through high-altitude meadows bordering China's largest lake, across vast stretches of sandy desert and into deeply cut canyons with towering walls of gravel and loess—ancient deposits of windblown silt.

The expedition took them atop the broad high plain of the Tibetan Plateau—all places traversed for thousands of years by prehistoric hunters and herders. They crossed paths with yaks, antelope, gazelles, camels and even a Tibetan wolf in an effort to turn back the hands of time to the Ice Age.

The Tibetan Plateau reaches upward to more than 15,000 feet, surpassing the likes of Mt. Rainier in Washington and Mt. Whitney in California. The thin air can make the task of excavating tough on the body. Despite these inconveniences, the research team exposed the 13,000-year-old hunters' camp they had discovered previously near Qinghai Lake. Rhode and his team gathered remnants of stone tools, bones and plant remains, and took sediment samples from geological sections and small lakes to understand better when and how Ice Age people survived at high altitude in a cold, arid climate.

"We were able to accomplish everything we set out to do," Rhode says with a smile. "We cleaned up a big geological section of a loess outcrop to create a stratigraphic profile and dug down about two meters to get at the firehearth. We initially thought there were several separate individual hearths, but instead we found one main hearth and small associated ash scatters, suggesting a single short-term campsite used by a hunting party for only a few days."

Onlookers: Local herders and sheep shearers take time off to view the Heima He excavations from profile-side seats. (photos by David Rhode)

At this site, the team gathered evidence of Stone Age tool technology involving microblade cores-stones that Ice Agers chipped away at to form thin parallel-sided blades to be used as efficient tools. The blades, sharp as razors, were usually stuck in bone shafts or antler shafts to create knives or long spear points for hunting.

As part of the three-year National Science Foundation project, UCLA's Dr. Jeff Brantingham is analyzing the stone artifacts. For Rhode's part in the project, he will use clues such as seeds, charcoal and pollen from the site to shed light on what the hunter-gatherers were eating or using for fuel. Rhode will also study core samples from lake sediments to help reconstruct the changing natural environment of the area at the end of the last Ice Age.

"In this project, we hope to know when our human ancestors were first able to tackle extreme environments such as the Tibetan Plateau and to understand better how they were able to do so. Finding the artifacts of ancient mankind always fascinates me—retracing their steps to figure out how they survived with little more than rocks and simple tools in such a harsh environment," Rhode says. "Their adaptation to the environment is really tremendous when you appreciate how tough it still can be to travel those same paths today."

But the tough conditions don't deter Rhode—he's already planning his next trip back in time to the Ice Ages atop the Tibetan Plateau.

-Heather Emmons