Humans Thrive At High Altitudes Earlier Than Suspected

Jun 30, 2017

Credit courtesy of Randy Haas

A summer hike up to a 13,000-foot alpine meadow can be exhilarating. But what if you decided to stay up there for the rest of your life? The lack of oxygen, frigid temperatures, and sparse vegetation would make it tough. Archaeologists know hunter-gatherers traversed highland areas thousands of years ago, but presumed they also had to spend time in lowland areas in order to survive.

That idea is now being challenged by a team of researchers at the University of Wyoming who have made a rare discovery.

Archaeologist Randy Haas led the team of scientists, and has made numerous trips to the Andean Plateau in Peru over the years. He said upon arriving he’s immediately reminded why some of his colleagues are reluctant to believe his hypothesis that hunter-gatherers lived at high altitudes year round.

“I’ve seen people get off the plane in Juliaca, [Peru]

and just fall over, and people will rush out with oxygen tanks because of the lack of oxygen,” said Haas.

Not to mention it’s cold.

“If you don’t have fancy down jackets and sleeping bags, it’s very difficult to keep warm,” said Haas. “In other parts of the world where it’s cold you can keep warm by fire. But there are not a lot of trees up there. Not a lot of fuel to burn at this high elevation.”  

Haas added that the harsh environs means there’s not much of something else you need to live: “Your food. Not much of that either. All these things combined make it a challenging place to live.”

And that explains why this high-elevation region was one of the last frontiers for human settlement.   

“For a lot of scholars it was believed that it wasn’t until you had food production, where you could produce a lot of food in abundance and store it, that’s what made colonization or permanent habitation of these landscapes possible,” explained Haas.

We know that between 3,000 and 5,000 years ago agricultural communities emerged in the alpine valleys of the Andes. The descendents of these early farmers still successfully work the land today. If you’ve ever eaten quinoa it was likely grown in this southeastern region of Peru.

But Haas said, “Not many people had really examined the hunter-gatherers who kind of paved the way.”

Haas saw an opportunity to help fill a gap in the historical understanding of how humans came to settle at high elevations. He said there was, “this one particular site, Soro Mik’aya Patjxa, we knew about from surface remains and flakes from tools.”  

That was a pretty good indicator that evidence of hunter-gatherers might be buried underground at Soro, too. But first, he had to meet with the local community to get their blessing to dig right in the middle of their barley field. He also hired community members to help with the excavation.

“What I hoped to find was some house features, hearths,” said Haas. “But what I didn’t expect to find was a burial assemblage; 16 individuals in burial pits.”

He knew he'd hit the jackpot, but he was nervous about how the local community would respond to the disturbance of their ancient ancestors remains. He said they, too, were intrigued by the discovery and encouraged him to proceed.

“If you want to understand people of the past one of the best things that you can find is the people themselves.”

Now on his desk at the University of Wyoming sit plastic baggies with fragments of 7,000-year-old bones.

He’s spent last year at UW on a post-doctoral fellowship, after getting his Ph.D. at the University of Arizona.

When he first arrived in Wyoming he shared his find with his colleague at the university Melissa Murphy, an anthropologist who also studies human evolution in the highlands of Peru.

She immediately recognized that Haas was going to make an important contribution to the understanding of the occupation of the Andes.

Murphy said that’s because, “Hunter-gatherers and foragers — they don’t bury their dead in cemeteries. There’s not going to be large samples.”

Murphy studies the Inca, which she admitted makes her work a little easier.

“It’s much sexier if you are going to excavate a pyramid or fancy burials,” said Murphy.  

Hunter-gatherers were mobile, so they weren’t building large structures and accumulating stuff, which means they left behind

fewer clues. To find a body, let alone 16, is a big deal.

Murphy said this find offers a glimpse into, “important transitions . . . from being a hunter-gatherer forester to being a settled pastoralist or settled agriculturist.” And it can help answer questions, like: “How does that come about? And also when do we really occupy these higher elevations?”

Haas’s discovery offers a solid answer to Murphy’s question for several reasons.

“If this was a temporary camp monitored from a low-elevation base camp the old and infirmed would not have been coming along. The young would have been left alone. But it turns out our burial has . . . two children between four and six years old, and at least one man over 50 years old. We have men and women,” said Haas. “So this was another line of evidence that seemed to suggest they were living up here long term.”

The chemical makeup of the bones has a story to tell too. Haas got help from some graduate students, who tested the isotopes in the bones. Signature ratios of carbon, nitrogen and oxygen revealed the water and food these folks consumed was sourced exclusively at high altitudes.  

“It was really amazing to see that they fell into the high-altitude precipitation values for oxygen, and I was like ‘these people lived there,” said Ioana Stefanescu, is a geology graduate students who tested the isotopes.

She was the first person to see the results. “I remember I put my laptop in my purse. I was like running. I couldn’t wait to tell him.”

This groundbreaking discovery earned Haas and his team a place in the July issue of Royal Society Open Science a journal that requires an arduous scientific review of an article before it's published. It's a sign that scholars are coming around to Haas’s hypothesis that hunter-gatherers did indeed occupy the highlands full time even before the advent of agriculture.

Haas’s next big question is: How did they do it?

He said there is already an important clue. All the bodies he found exhibited evidence of cranial modification -- or head shaping. Haas said this physical expression of connection tells us, “something more about the importance of community in surviving, and not only surviving, but thriving in adverse conditions.”

Haas will join the archaeology department at the University of California Davis this fall where he plans to continue his research on hunter-gatherers.