Prehistoric Africa is the home of all humans. Find out how the discovery of DNA evidence in a rock shelter in Cameroon is shedding new light on our common ancestors.
I’m part Neanderthal. I sent away one of those do-it-yourself DNA kits and that’s one of the things I found out.
It turns out that I have 257 genetic variants that came from Neanderthals. Mind you, that’s less than 4% of my overall DNA makeup.
The rest of me is 73% British and Irish, 12% French and 3% Scandinavian. It was kind of a letdown because I already knew that my ancestors were Scots with a possible Norman heritage. I’ve always been highly predictable.
DNA TESTING REVEALS THE HISTORY OF HUMAN EVOLUTION
DNA testing is revealing the history of many aspects of human evolution around the world. In a previous story, we discussed how DNA research in Botswana led to a theory that the Kalahari in prehistoric Africa was the birthplace of us all.
Most scientists who study human populations agree with the Recent African Origins Model. It says that we’re all descendants of a group of modern humans who arose between 200,000 and 300,000 years ago in North Africa.
That means that racism a very foolish idea. We’re all Africans at our core and we are all far more closely related than Chimpanzees, for example, even though there are far more humans than chimps.
THEY THOUGHT DNA COULDN’T SURVIVE IN CENTRAL AFRICA
Geneticist David Reich of Harvard explains how ancient DNA has transformed our understanding of human origins in his book Who We Are And How We Got Here: Ancient DNA And The New Science Of The Human Past. He and his team announced that they had located ancient DNA samples from Central Africa. Scientists used to think that DNA couldn’t survive for long there because of the heat and humidity.
Reich’s team surprised the world by announcing that they had found and analyzed prehistoric African DNA samples they had found in a rock shelter in Cameroon. It was a gravesite for four children at the famous African archaeological site at Shum Laka.
One of the best places to find DNA is in the bones of the inner ear. Using samples from there, they managed to sequence complete genomes for two of the children and partial genomes from the other two.
EAR BONES HELD 2 COMPLETE AND 2 PARTIAL GENOMES
The children were buried 3,000 and 8,000 years ago. By comparing their samples to those of some living Africans, the team can tell that they were all distant cousins.
Like mine, the children’s DNA comes from multiple sources. About one-third of their DNA ancestry comes from hunter-gatherers in western Central Africa.
They inherited the other two-thirds from what the team calls an “ancient basal source” in West Africa.
LONG LOST POPULATION SCIENTISTS DIDN’T KNOW ABOUT
The scientists were excited to find that part of that ancient basal DNA came from a long lost population in prehistoric Africa that scientists didn’t know about until now.
Those weren’t the only surprises from this discovery. Their find had a couple of other secrets to reveal.
First, they collected the samples in an area that is the present day, traditional homeland of indigenous people called Bantu speakers. Yet, the DNA samples are more like the hunter-gatherer people called the Baka and Aka, who we used to call pygmies.
DNA SAMPLES RESEMBLED PEOPLE LIVING 500 KM AWAY
The Baka and Aka live more than 500 kilometres away from where they found this ancient DNA. They live in the traditional rain forests of western Central Africa.
This confirms something that many scientists have long suspected. It seems that the Baka, Aka and others like them had a much larger range in prehistoric Africa before the Bantu speaking people came along and crowded them out.
The second important finding came when the team compared the ancient children’s DNA to other genetic information from Africa. They found that the Baka, Aka and others are part of one of the most ancient bloodlines of modern humans.
ROOTS IN PREHISTORIC AFRICA GO BACK 250,000 YEARS
Their roots in prehistoric Africa go back 250,000 years. That’s just about as far back as you can go with modern human ancestry.
What this all means is that prehistoric African populations were even more diverse than they are today. The Bantus had better technology than their neighbours, like pottery and forged iron.
As herders, their culture was more successful and they slowly took over the area. The Bantu gradually displaced the hunter-gatherers living next to them and they moved on.
HERDERS GRADUALLY DISPLACED HUNTER-GATHERERS
Based on comparing the ancient children’s DNA to other African samples, both living and dead, the scientists are proposing a bold new idea. They believe that the early human hunter-gatherer groups who predate the Bantus date back 200,000 to 250,000 years.
The group split off into the Khoisan hunter-gatherers of southern Africa, the East Africans and the mysterious new group that the team just discovered. They didn’t have much to do with each other, although there was some interbreeding at the edges of their territories.
After that, over a long period of time, many of the hunter-gatherer groups gradually migrated out of prehistoric Africa and into Eurasia. These migrations went in several waves and followed two main passages.
HUNTER GATHERERS GRADUALLY MIGRATED INTO EURASIA
These are called the Northern Route and the Southern Route. The Northern Route went through the Nile Valley and the Sinai Peninsula while the Southern Route passed through the Bab al Mandab Strait on the Arabian Peninsula.
In Eurasia, these homo sapiens occasionally interbred with archaic humans whose ancestors had come before them about a million years ago. That’s why I ended up with a trace of Neanderthal in my genes.
Not everyone agrees that this audacious new hypothesis is a proven, reliable model, at least not yet. One of the skeptics is Sarah Tishkoff of the University of Pennsylvania.
“NEEDS FURTHER TESTING WITH WHOLE-GENOME DATA”
She believes that, “It needs to be further tested with additional whole-genome data from both modern and, if possible, ancient DNA from more Africans.”
That’s why the scientists’ discovery that DNA actually can survive in the central African climate is so important. It leaves the door open for further research to either confirm or falsify this new hypothesis. That’s what science is all about.
We always have more to learn if we dare to know.
DNA from child burials reveals ‘profoundly different’ human landscape in ancient Africa
Ancient African genomes offer glimpse into early human history
Who We Are And How We Got Here: Ancient Dna And The New Science Of The Human Past
Is the Birthplace of All Humans in the Kalahari?
Rock Art Depicts Oldest Story Ever Told
Starchy Plants Cooked 170,000 Years Ago