For decades, paleoanthropologists working in east Africa have concentrated on lower-altitude locations. Archaeologists have assumed that towering mountains and plateaus were among the last places to be populated by ancient humans, but artefacts including stone tools, clay fragments, burnt animal bones, and a glass bead found more than 3,400 metres above sea level in Ethiopia's Bale Mountains indicate that people lived there as early as 47,000 years ago - the earliest evidence of prehistoric high-altitude human occupation.
     To reach the site of Fincha Habera - one of more than 300 elevated rock shelters investigated - researchers and pack horses had to trek more than 400 kilometres. They quickly found signs of ancient human occupation, including the remnants of hearths dated to between 47,000 and 31,000 years ago.
     The new findings are not the first proof that our ancestors ventured to high altitudes earlier than previously thought. Scientists recently reported discovering the jawbone of a Denisovan - an extinct hominin species - in a cave in China about 3,300 metres above sea level. That specimen was dated to around 160,000 years ago. Stone tools have also been found high on the Tibetan Plateau along with relics dating between 30,000 and 40,000 years ago.
     The Fincha Habera finds provide robust evidence of humans actually living at high altitudes. Although the settlement was probably not permanent, evidence suggests that prehistoric people spent considerable time there during the Last Glacial Maximum; the site was a refuge when much of the Bale Mountains were covered with ice. Melting glaciers would have offered an ample supply of water. An abundance of burnt bones - mostly of giant mole-rats - suggest the inhabitants were roasting rodents for food. They also seem to have exploited nearby obsidian outcrops for materials to make tools.
     The researchers plan to return. They would like to find the bones of the humans who lived there - bones with extractable DNA. Such a find could help us learn more about high altitude adaptations inherited by mountain-dwelling peoples of the present.

Edited from Smithsonian Magazine (9 August 2019)