WASHINGTON, Aug. 9 (Xinhua) -- A study published on Thursday in the journal Science revealed that prehistoric humans lived in Ethiopia's Bale Mountains at around 4,000 meters above sea level.
It is the oldest evidence of human settlement at extreme altitudes so far, the study said.
It was previously assumed that humans inhabited the Afro-Alpine region only very lately and for short periods of time because of the low oxygen and sharply fluctuating temperatures there.
The new study showed that ancient humans settled in the ice-free plateaus of the Bale Mountains in southern Ethiopia 45,000 years ago during the Middle Pleistocene Epoch when the lower valleys were too dry for survival.
Scientists investigated a rocky outcrop near a settlement in the Bale Mountains and found a number of stone artefacts, clay fragments and a glass bead.
On mountains, prehistoric people had enough water as the glaciers melted, and they built tools out of obsidian and relied mainly on giant mole rats for nourishment, according to the study.
The lead author of the new study is Gotz Ossendorf, an archaeologist at the University of Cologne in Germany.