“Out of Africa” –Which Way Did Humans Migrate?


It is a widely held and scientifically viable belief that humans originated in sub-Saharan Africa some 150 to 200 thousand years ago. However our migration away from there, to populate immediate areas and, later, the planet, is currently conjecture.

Archaeological evidence has thrown up question marks for previous explanations. Tracking mitochondrial DNA has shown travel patterns across the entire planet. But no one migration explanation has been able to properly explain all the evidence.

Looking at a map of Africa, sub-Saharan Africa is everything that is not the Sahara Desert. A massive expanse, the Sahara is the planet’s largest hot desert (second largest desert after Antarctica). To travel across it to where humans ended up is a massive challenge today.

But the team from Bristol University has suggested that wetter conditions existed much further north than previously believed. As a result, a wet corridor through Libya might have existed, allowing for early human migrations to avoid what we know as today’s Sahara.

"Space-born radar images showed fossil river channels crossing the Sahara in Libya, flowing north from the central Saharan watershed all the way to the Mediterranean,” said Anne Osborne, lead author on the study. “Using geochemical analyses, we demonstrate that these channels were active during the last interglacial period. This provides an important water course across this otherwise arid region."

The researchers traced the isotopic composition of snail shells taken from two sites in the fossil river channels and from shells of planktonic microfossils in the Mediterranean. Despite being hundreds of kilometers from the volcanic rocks in the mountains of the Saharan watershed, previously believed to the limit of the wet region in our early ancestors time, these shells had a distinctly volcanic signature that could only be explained by water flowing from the volcanic mountains.

Dr Derek Vance, senior author on the paper, added: "The study shows, for the first time, that monsoon rains fed rivers that extended from the Saharan watershed, across the northern Sahara, to the Mediterranean Sea. These corridors rivalled the Nile Valley as potential routes for early modern human migrations to the Mediterranean shores."

The Daily Galaxy via http://www.eurekalert.org

Get 'The Daily Galaxy' in Your Facebook News Feed!

Images: A map showing the sample locations mentioned here, plus other images of the Sahara,  https://www.bris.ac.uk/fluff/u/inclel/hLpdnnvzzmnVVGYNlnETAAy1/


"The Galaxy" in Your Inbox, Free, Daily