Archaeologists have uncovered the earliest evidence of high-altitude prehistoric living at a newly discovered site nestled high in the Bale Mountains of Ethiopia. More than 30,000 years ago, the Fincha Habera rock shelter at more than 11,000 feet above sea level was home to Middle Stone Age foragers, who made use of nearby resources in the cold, glaciated environment while feasting on the region's plentiful giant-mole rats.
The findings, published in the August 9 issue of Science, challenge the long-held belief that the high mountains of western Africa were too harsh and unforgiving for extended human occupation. Instead, the authors suggest that the ecological stability of the humid highlands may have served as ice-age refugia offering unique collections of resources unavailable elsewhere during the Last Glacial Maximum more than 25,000 years ago, when lowland climates were far more arid.
Life at high altitude imposes a number of challenges and stresses on daily life and the human body. Important resources, such as edible plants and animals, water and even shelter are scattered across relatively barren landscapes characterized by frigid temperatures and highly unstable weather conditions. The most important and limiting environmental factor for humans is the general lack of oxygen at such great heights. High-altitude hypoxia impacts nearly every aspect of human life, from health and nutrition to the overall ability to perform work related tasks, such as gathering food.
Because of these factors, it's long been assumed that high-elevation mountains and plateaus — those more than 8,200 feet above sea level — were among the last places permanently settled by humans and are only a recent occurrence in antiquity.
However, a growing number of archaeological discoveries from high places across the globe have begun to show otherwise. From the Andean Altiplano of South America to Asia's Tibetan Plateau, newly discovered prehistoric sites — including Fincha Habera — help build a compelling case that people have occupied Earth's high-elevation landscapes since at least the last ice age.
Still, these sites are rare and much remains to be discovered about the nature of human high-altitude settlements as well as how humans adapted to the unique environments.
"What we today perceive as marginal or uneconomic, resource-poor landscapes certainly does not reflect the prehistoric mindset," said Götz Ossendorf, the study's lead author and archaeologist at the University of Cologne, Germany. According to Ossendorf, the factors attracting early humans to high-altitude areas have been largely overlooked in the past.
In the sediments underlying a dusty rock overhang nestled high in a remote section of the Ethiopian highlands, Ossendorf and a team of researchers discovered the Fincha Habera site after several years of extensive surveys by foot and pack horse to investigate rock shelters in the present-day Bale Mountain National Park.
"Many of these [rock shelters], especially the larger ones, are well known to the local Oromo pastoralists," who continue to use the natural features as temporary livestock enclosures as they have for generations, said Ossendorf. The Fincha Habara shelter, however, was unique in largely lacking modern pastoral activities and containing relatively undisturbed sediments protected from the elements.
Excavations at the site revealed thousands of Middle Stone Age artifacts in the shallow sediment, including locally collected stones, burnt animal bones and the hearths of former fires. Radiocarbon dates from the site's earliest levels suggest that the occupation began during the Late Pleistocene, sometime between 47,000 and 31,000 years ago.
Tools indicative of Middle Stone Age cultures and made from obsidian — a highly sought-after stone prized for its razor-sharp cutting edge — and the byproducts of their manufacture were found in great quantities and almost exclusively made from material sourced to nearby obsidian outcrops six miles away and more than 2,000 feet higher in elevation.
The discovery of large amounts of burned rodent bones at the site provides evidence that the now-endangered Afroalpine giant mole-rat, likely roasted and eaten, provided prehistoric inhabitants of Fincha Habera with a reliable and sustainable source of locally available food.
However, not all artifacts were of local provenance. "One fact that can be quickly overlooked is that we also found a fragment of an ostrich eggshell," said Ossendorf. Since ostriches have never lived remotely close to the 11,381 feet above sea level elevation of the rock shelter, the shell was likely brought there by people from the lowlands, indicating that Fincha Habera residents were connected with other groups or environments.
"They were not stranded, isolated, fragmented groups, but had a network and regular contacts with other mobile hunter-gatherers," said Ossendorf.
According to Ossendorf, performing field research in such remote areas, and particularly in an African country is not easy. Permitting and regulations from Ethiopian authorities, political unrest as well as several dangerous situations involving team members complicated the research. In addition, work in remote regions such as the Bale Mountains is logistically challenging, and all necessary equipment required for at least four weeks — including excavation tools, tents, food and kitchen supplies — must be packed into the site by "very resilient horses," or on the backs of the researchers for temporary field camps, said Ossendorf.
While the study demonstrates that prehistoric humans were capable of adapting to and living in Africa's cold and glaciated Late Pleistocene environments far earlier than previously thought, a great deal concerning the nature of high-altitude occupations around the world remains a mystery.
"Right now, we know when people were there, we know a bit about the activities they performed and what they ate, but we have an incomplete understanding of how the site may have fit into a regional scale settlement system," said Mark Aldenderfer, a University of California, Merced archaeologist, who was not involved with the study.
The study of Fincha Habera and similar high-elevation sites plays an important role in understanding the evolutionary story of our species, said Aldenderfer.
Modern humans began their evolutionary journey as lowlanders. However, at some point along that journey, some lowlanders — perhaps those roasting rats in Fincha Habera — became highlanders and acquired specific genetic adaptations to ameliorate hypoxia that are known in modern peoples living at high elevation today.
"So really, the question is not so much when did people start using high altitude places but when did they begin to live there permanently," said Aldenderfer.
[Credit for associated photo: H. Veit]