Why humans in Africa fled to the mountains during the last ice age

New study in 'Science': Why humans in Africa fled to the mountains during the last ice age
The Fincha Habera rock shelter in the Ethiopian Bale Mountains served as a residence for prehistoric hunter-gatherers. Credit: Götz Ossendorf

People in Ethiopia did not live in low valleys during the last ice age. Instead they lived high up in the inhospitable Bale Mountains. There they had enough water, built tools out of obsidian and relied mainly on giant rodents for nourishment. This discovery was made by an international team of researchers led by Martin Luther University Halle-Wittenberg (MLU) in cooperation with the Universities of Cologne, Bern, Marburg, Addis Ababa and Rostock. In the current issue of Science, the researchers provide the first evidence that our African ancestors had already settled in the mountains during the Palaeolithic period, about 45,000 years ago.

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," says Professor Bruno Glaser, an expert in soil biogeochemistry at MLU. Together with an international team of archaeologists, soil scientists, palaeoecologists, and biologists, he has been able to show that this assumption is incorrect. People had already begun living for long periods of time on the ice-free plateaus of the Bale Mountains about 45,000 years ago during the Middle Pleistocene Epoch. By then the lower valleys were already too dry for survival.

For several years, the research team investigated a rocky outcrop near the settlement of Fincha Habera in the Bale Mountains in southern Ethiopia. During their field campaigns, the scientists found a number of stone artefacts, clay fragments and a glass bead. "We also extracted information from the soil as part of our subproject," says Glaser. 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 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 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.

Using this data, the researchers were not only able to show that people have been there for a longer period of time; the analyses may also have uncovered the reasons for this, too—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 the researchers investigated. 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," concludes Glaser.

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. And: "For the first time, the layer dating from this period also contains the excrement of grazing animals," says Glaser.

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.


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More information: Middle Stone Age foragers resided in high elevations of the glaciated Bale Mountains, Ethiopia, Science (2019). DOI: 10.1126/science.aaw8942
Journal information: Science

Provided by Martin-Luther-Universität Halle-Wittenberg
Citation: Why humans in Africa fled to the mountains during the last ice age (2019, August 8) retrieved 23 August 2019 from https://phys.org/news/2019-08-humans-africa-fled-mountains-ice.html
This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.
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Aug 08, 2019
R.U.S. burgers.
yum... :-)

Aug 08, 2019
"There is a low level of oxygen in the air" ??

"The percentage of oxygen is the same at sea level as it is at high altitudes, which is roughly 21 percent. However, because air molecules at high altitudes are more dispersed, each breath delivers less oxygen to the body."

"The percentage of oxygen stays the same regardless of where it is measured. An area of high pressure, for example, sea level during a cold front raising barometric pressure, or even a cylinder of compressed air will have 21% oxygen. An area of low pressure at a high elevation for example, will still contain 21% oxygen"

-But then

"Hig altitude less oxygen. Low altitue more percentage. Related to atmospehric pressure. Danton's Law of partial pressure"

Aug 08, 2019
We should test the DNA of the high altitude adapted people and compare it with other groups around the world who also have adaptations to high altitude. We know that the Tibetan people can thank Denisovans for their applicable genes, but this should give more mutations to look at.

Aug 09, 2019
@Jeffhans, you will probably find as many different adaptations as there are groups, or perhaps a few less.

Have you ever been to the top of a tall mountain? I took a tour up Mauna Kea and when I got back I was sick the day afterward. It's called "altitude sickness."

Aug 09, 2019
However, because air molecules at high altitudes are more dispersed, each breath delivers less oxygen to the body."
Mile high stadium, Denver, the visiting athletes notice the difference. Locals acclimate to it.

Aug 09, 2019
"The percentage of oxygen is the same at sea level as it is at high altitudes, which is roughly 21


You dope. The very definition of concentration is how much per unit volume.
Denver's oxygen level is only 17.3%


Aug 09, 2019
the visiting athletes notice the difference. Locals acclimate to it.


Yes, but the article is not discussing plasticity (in adults) or development adaptation (in adolescents). Some high altitude groups has evolved adaptations for it, such as famously the Himalayans that inherited those alleles from Denisovans:

"Previous work suggests that three high-dwelling populations – Andeans, Himalayans, and Ethiopians – have adapted unique ways to cope with these extreme environments. In a 2014 study, researchers trying to understand the basis for high-altitude adaptations analyzed the whole genomes of 13 native Ethiopian highlanders for genetic variation. Six of the participants live on the Bale Plateau, and the other seven individuals live on Chennek field in the Simien Mountains. This work highlighted certain genes linked to adaptations for hypoxia ..."

[ https://www.iflsc...ditions/ ]

Aug 09, 2019
"The percentage of oxygen is the same at sea level as it is at high altitudes, which is roughly 21


You dope. The very definition of concentration is how much per unit volume.
Denver's oxygen level is only 17.3%

You pinhead. That was a quote from a reputable source.
cont>

Aug 09, 2019
"Although the PERCENTAGE of oxygen in inspired air is CONSTANT at different altitudes, the fall in atmospheric pressure at higher altitude decreases the partial pressure of inspired oxygen and hence the driving pressure for gas exchange in the lungs. An ocean of air is present up to 9-10 000 m, where the troposphere ends and the stratosphere begins. The weight of air above us is responsible for the atmospheric pressure, which is normally about 100 kPa at sea level. This atmospheric pressure is the sum of the partial pressures of the constituent gases, oxygen and nitrogen, and also the partial pressure of water vapour (6.3 kPa at 37°C). As oxygen is 21% of dry air, the inspired oxygen pressure is 0.21×(100−6.3)=19.6 kPa at sea level."

-So the statement

"There is a low level of oxygen in the air"

-is wrong. And so are you.

Aug 12, 2019
well, i don't want to get involved in THAT argument!

the argument i will rudely intrude upon is what jeff speculated .
a modern version of the pseudo-science of eugenics

genes are not interchangeable as your socks
you just have to consider the recent wave of racehorse deaths
a direct result of idiots breeding by the Stud Book for conformity & illusory competitive advantage

domestic pets, producing hundreds of show "breeds" all sickly & beset with counter-survival traits

the current unfolding disaster resulting from thousands of years of reproducing food crops from cuttings(cloning)

jeff, how do you intend to convince people to exfiliation with strangers?
too what purpose would such inter-breeding serve?
what are the intended results?

might be helpful for the Andean's?
their adaptation is rift with high mortality rates due to heart problems
but instead you pass the deadly trait to others?

& finally the question of bio-ethics?
are you volunteering to be an experimental subject?

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