Giant moles were on the menu, and there was plenty of fresh water and a nearby obsidian source for crafting tools, making a high elevation settlement for ancient humans in Ethiopia a livable space.
High elevation archaeological research has steadily expanded the knowledge about ancient people using mountainous terrain, everywhere from the Beartooth Plateau in Montana to Wyoming's Wind River Range and the highlands of Peru in South America.
New research has confirmed such use in an area of Ethiopia that's above 11,000 feet. What's more, the data points to human use dating back 45,000 years, much later than New World high elevation sites.
"Whenever and wherever inquisitive and creative people are concerned, there's never a shortage of meaningful research questions," said Craig Lee, of the Institute of Arctic and Alpine Research at the University of Colorado at Boulder. "The application of archaeological science to understanding human adaptation in Ethiopia during the Middle Stone Age provides yet another point of reference for fostering learning about high elevation human adaptations the world over, including in the Rocky Mountains."
People inhabited Ethiopia's Bale Mountains for several reasons, according to an international team of researchers led by Martin Luther University Halle-Wittenberg in cooperation with the Universities of Cologne, Bern, Marburg, Addis Ababa and Rostock. The area had fresh water, a nearby source of obsidian for tools and plentiful giant rodents to eat.
Research into the Palaeolithic period site is detailed in the current issue of "Science."
At around 4,000 metres above sea level, the Bale Mountains in southern Ethiopia are a rather inhospitable region. There is a low level of oxygen in the air, temperatures fluctuate sharply, and it rains a lot.
"Because of these adverse living conditions, it was previously assumed that humans settled in the Afro-Alpine region only very lately and for short periods of time," said professor Bruno Glaser, an expert in soil biogeochemistry at MLU, in a press release.
Together with an international team of archaeologists, soil scientists, palaeoecologists, and biologists, Glaser has been able to show that people had been living for long periods of time on the ice-free plateaus of the Bale Mountains at a time when the lower valleys were too dry for survival.
For several years, the research team investigated a rocky outcrop near the settlement of Fincha Habera in southern Ethiopia. During their field campaigns, the scientists found a number of stone artifacts, clay fragments and a glass bead.
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"We also extracted information from the soil as part of our subproject," Glaser said.
Based on the sediment deposits in the soil, the researchers from Halle were able to carry out extensive biomarker and nutrient analyses as well as radiocarbon dating and thus draw conclusions as to how many people lived in the region and when they lived there.
For this work, the scientists also developed a new type of palaeothermometer which could be used to roughly track the weather in the region — including temperature, humidity and precipitation. Such analyses can only be done in natural areas with little contamination, otherwise the soil profile will have changed too much by more recent influences. The inhospitable conditions of the Bale Mountains present ideal conditions for such research since the soil has only changed on the surface during the last millennia, according to the university.
Using such data, the researchers were not only able to show that people have been there for a longer period of time but also may have uncovered the reason why: during the last ice age the settlement of Fincha Habera was located beyond the edge of the glaciers. According to Glaser, there was a sufficient amount of water available since the glaciers melted in phases.
The researchers are even able to say what people ate: giant mole rats, endemic rodents in the region. These were easy to hunt and provided enough meat, thereby providing the energy required to survive in the rough terrain.
Humans probably also settled in the area because there was deposit of volcanic obsidian rock nearby from which they could mine obsidian and make tools out of it.
"The settlement was therefore not only comparatively habitable, but also practical," Glaser said.
The soil samples also reveal a further detail about the history of the settlement. Starting around 10,000 years before the Common Era, the location was populated by humans for a second time. At this time, the site was increasingly used as a hearth.
"For the first time, the soil layer dating from this period also contains the excrement of grazing animals," Glaser said.
According to the research team, the new study in "Science" not only provides new insights into the history of human settlement in Africa, it also imparts important information about the human potential to adapt physically, genetically and culturally to changing environmental conditions. For example, some groups of people living in the Ethiopian mountains today can easily contend with low levels of oxygen in the air.