Living at high altitude isn't easy. The thinner air above 4,000 meters makes for colder temperatures, less oxygen, and less protection from the sun's harmful ultraviolet rays. Yet humans occupied sites that high and higher in the Peruvian Andes as early as 12,800 years ago, according to a new study. The result could change how archaeologists think about the earliest human inhabitants in South America and how they managed to adapt to extreme environments.
Traveling to 4,000 meters and higher isn't such a big deal as it once was. Mountaineers regularly climb 4,392-meter high Mount Rainier and miners work just outside of the highest city in the world, La Rinconada, Peru, which stands at 5,100 meters. India and Pakistan have even fought battles at 6,100 meters on the disputed Siachen glacier.
Traveling to 4,000 meters and higher isn't such a big deal as it once was. Mountaineers regularly climb 4,392-meter high Mount Rainier and miners work just outside of the highest city in the world, La Rinconada, Peru.
But how and how early people actually lived in such extraordinary places is less clear. For some, human occupation in the Andes didn't make any sense. Even if settlers could survive freezing temperatures and limited oxygen, altitude increases metabolism, meaning they'd need to eat more in a place where travel was difficult and food was scarce.
Regardless, Kurt Rademaker and colleagues report they've found evidence of two high-altitude settlements at sites in southern Peru. Members of the team had been on the trail of obsidian that turned up in the earliest coastal villages in the region, which were dated to between 12,000 and 13,500 years ago. But the obsidian didn't originate there. Archaeologists have known for some time that it came from Alca in the Peruvian highlands, strongly suggesting contemporary outposts or base camps in the Andes.
Eventually, a combination of obsidian surveys, mapping of likely settlement locations, and reconnaissance led the team to 4,355-meter-high Pucuncho and 4,445-meter-high Cuncaicha. There, researchers found tools, animal and plant remains, and other signs of habitation. Using a carbon-dating variant called accelerator mass spectrometry, the team dated Pucuncho to between 12,800 and 11,500 years ago and Cuncaicha to between 12,400 and 11,800 years ago, roughly a millennium earlier than previously discovered settlements at similar altitudes.
The results may help scientists understand the genetic adaptations particular to high-altitude dwellers, especially with regard to how quickly humans were able to adjust biologically to harsh environments. "Our data do not support previous hypotheses, which suggested that climatic amelioration and a lengthy period of human adaptation were necessary for successful human colonization of the high Andes," the team writes in Science. "As new studies identify potential genetic signatures of high-altitude adaptation in modern Andean populations, comparative genomic, physiologic, and archaeological research will be needed to understand when and how these adaptations evolved."
"This research assists in finally explaining some of the key archaeological questions regarding early South American occupation," Washington State University archaeologist Louis Fortin, who has worked with Rademaker in the past but was not involved in the present research, writes in an email. The work, he says, "has brought to light a significant discovery for South American archaeology and specifically high-altitude adaptation and the peopling of South America."