Recently, archaeologists have found the highest-known leftovers of Ice Age human settlement in the Southern Peruvian Andes, which is believed to be roughly more than 12000 years old.

The study is published in the Science journal describing the two sites that sit higher than 4000 meters (more than 13,100 feet) above sea level and specify that humans might have acclimatized to the intense harsh climate far sooner than many researchers had predicted.

The author of the study wrote, “These sites widen the residence time of humans above 4,000 [meters above sea level] by nearly a millennium, entailing more moderate late-glacial Andean environments and greater physiological capabilities for Pleistocene humans than previously assumed.”

From around the same time period, the two sites in the Pucuncho Basin lies nearly 3,000 feet above other settlements. One site named as Pucuncho, is a workshop site filled with 260 formal tools such as stone scrapers and projectile points; it sits 14,288 feet above sea level and has been dated to 12,800 to 11,500 years ago. The second is Cuncaicha, which hosts a rock shelter lying 14,698 feet above sea level that dates back to 12,400 years and a workshop site 14,583 feet above sea level. The shelter is filled with soot-marked ceilings from campfires, rock art and sediments on the ground that include charred plant remains.

Cuncaicha also contains ceramics, chipped-stone tools, animal bones, bone beads and quartz crystals, as well as red ochre fragments. Most of the stone tools were made from the obsidian, andesite and jasper found nearby. The University of Maine, Orono researchers dated the Cuncaicha shelter using large mammal bones found near the human artifacts. The specimens were in good condition, for their age – cold, dry air might be difficult to live in, but it indeed protects dead organic matter well.

The high-altitude residents survived by hunting vicuña and guanaco (relatives of the alpaca) and taruka (an Andean deer). The bones were scattered around indicating that there were whole carcasses at the site, which means the animals were probably caught nearby. Cuncaicha appears to have been a base camp with all the signs of human occupation.

The researchers revealed that, “The Pucuncho Basin comprised of a high-altitude oasis that is perfect for a specialized hunting (and later, flocking) adaptation. But wet-season storms and the risk of hypothermia, along with the upholding of extended social networks and collection of edible plant resources, may have encouraged regular descents to lower elevations.”

The study authors wrote, “Tibet and the Andes, high-altitude living in places is a brutal and ceaseless test of survival. Above 13,100 feet, the thin air and treeless terrain provide little protection from the high solar radiation. There’s not much fuel to make fires, there’s much less oxygen available to breathe and it takes about twice the number of calories just to keep up the normal metabolic process.”

Certainly, these factors reveal authentic answer to the question why human settlements higher than about 13,100 feet and older than 11,500 years of age have evaded them. Probably, a long time for the genetic variations to arise in the population that would favor, among other traits, higher metabolic rates and more lung capacity traits found in certain high-altitude populations today.

Though, these high-altitude settlements were set up within about 2,000 years of humans’ first arrival in South America. Whether they had developed the ideal traits or not, clearly humans didn’t take that long to settle in (or, in this case, settle up).

The study authors believe that, “The glaciers in the region had to recede for humans to be able to reach the Pucuncho basin. However, it appears the forbidding walls of glacial ice might never have reached the area.”

The researchers further told that, “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 reason why these sites were not discovered before is not because early humans weren’t capable of living in such high altitudes, but that it’s difficult for scientists to find these hard-to-reach spots. Now that these two sites have been found, it hints that there could be many more tucked high in the Andes, study authors claimed.

“As the early settlement of high-altitude regions is understudied, other Terminal Pleistocene sites above 4,000 [meters above sea level] likely await discovery,” they wrote.

For the permanent settlements, we’ll go even higher: La Rinconanda, located near a Peruvian gold mine, which lies more than 16,700 feet (more than 3 miles) above sea level.