DNA Research Shows a Mystery Population Invented Agriculture
Credit: Peter the Great Museum
A ground-breaking study on DNA recovered from the Kostenki skull
a man who lived 36,000 years ago in Kostenki, western Russia shows
that the earliest European humans' genetic ancestry survived
the Last Glacial Maximum: the peak point of the last ice age.
- Our earliest European genomes or DNA profiles, weathered the Ice Age.
- The date when our ancestors interbred with Neandertals.
- That a mystery population that disappeared for around 30,000 years are the people who gave us agriculture about 8,000 years ago.
"That there is continuity from the earliest Upper Palaeolithic (Late Stone Age) to the Mesolithic, (a cultural period between the Palaeolithic and the Neolithic or New Stone Age), across a major glaciation, is a great insight into the evolutionary processes underlying human success."
Dr Marta Mirazón Lahr, Cambridge's Leverhulme Centre for
Human Evolutionary Studies (LCHES). and co-author of this study
Work by other geneticists, archeologists and anthropologists focus on the Nile Delta to the Fertile Crescent as the home of modern humans before we wandered off to establish ourselves as the dominant species from the Arctic to Australia. Geneticists have even identified a genetic Adam, based on analysis of our common Y chromosome, and a genetic Eve, based on our mitochondrial DNA. While genetic Eve predates Adam by some thousands of years, our functional Adam and Eve lived in wetlands between the Nile River and the swamps north of the Red Sea, site of today's Suez Canal, about 10,000 years ago.
36,000 years ago we were still hunters and gatherers of the Stone Age, all with black skin but some of us having blue eyes, taking our food and creating tools as we could find them before we figured out that we could cultivate plants and even corral the beasts of the wild for a more stable, predictable source of food. This innovation happened about 8,000 years ago. Agriculture gave us a surplus, which allowed for a stable, settled life which promoted the development of government, architecture, the arts and eventually writing leading directly to Homer, Confucius, Shakespeare, The Simpsons and the rest of today's culture.
Living near us during much of our journey, was another, not necessarily primitive species, the Neandertal, trapped to its doom in hunting and gathering bands struggling against a changing climate and the competition of our ancestors.
Our Interbreeding with Neandertal
So when did interbreeding occur? The Kostenki genome contains, as with all people of Eurasia today, a small percentage of Neandertal genes, confirming there was a brief period of interbreeding. This study shows that interbreeding took place around 54,000 years ago, before today's Eurasian population began to separate from our older, African stock. This means that today anyone with a Eurasian ancestry -- from Chinese to Scandinavian and North American -- has a small element of Neandertal DNA.
However, despite going on to share the European landmass with Neandertals for another 10,000 years, no additional evidence of interbreeding has been found. This leads Professor Robert Foley, from LCHES, and a co-author of this study, to ask,
- "Were Neanderthal populations dwindling very fast?
- Did modern humans still encounter them?
- We were originally surprised to discover there had been interbreeding. Now the question is, why so little? It's an extraordinary finding that we don't understand yet."
These scientists have developed evidence that supports the idea that our ancestors separated into at least three populations earlier than 36,000 years ago: Western Eurasians, East Asians and a mystery third lineage, all of whose descendants would develop the unique features of most non-African peoples such as a lighter skin color about 10,000 years ago just as our branch of the human family moved out of Africa. They also gave us agriculture.
"For 30,000 years ice sheets came and went, at one point covering two-thirds of Europe. Old cultures died and new ones emerged -- such as the Aurignacian and the Grevettian -- over thousands of years, and the hunter-gatherer populations ebbed and flowed. But we now know that no new sets of genes are coming in: these changes in survival and cultural kit are overlaid on the same biological background," Mirazón Lahr said. "It is only when famers from the Near East arrived about 8,000 years ago that the structure of the European population changed significantly."
Unique to the Kostenki genome is a small element it shares with people who live in parts of the Middle East now, and who were also the population of farmers that arrived in Europe about 8,000 years ago and assimilated with existing populations of hunter-gatherers. This early contact is surprising, and provides the first clues to a hereto unknown lineage that could be as old as -- or older than -- the other major Eurasian genetic lines. These two populations must have interacted briefly before 36,000 years ago, and then remained isolated from each other for tens of thousands of years.
Marta Mirazón Lahr of Cambridge University and co-author of this study points out that, while Western Eurasia was busy mixing as a 'meta-population', there was no interbreeding with these mystery populations for some 30,000 years -- meaning there must have been some kind of geographic barrier, despite the fact that Europe and the Middle East seem, for us at least, to be so close geographically. But the Kostenki genome not only shows the existence of these unmapped populations, but that there was at least one window of time when whatever barrier existed came down.
"This mystery population may have remained small for a very long time, surviving as refugees in areas such as the Zagros Mountains of Iran and Iraq, for example," said Mirazón Lahr. "We have no idea at the moment where they were for those first 30,000 years, only that they were in the Middle East by the end of the ice age, when they invented agriculture." From there, work by other researchers shows that agriculture spread through the Middle East and Europe in a leap-frogging movement by early farmers traveling by boat along the coasts of the continents. See related story below.
Lead author and Lundbeck Foundation Professor Eske Willerslev added: "This work reveals the complex web of population relationships in the past, generating for the first time a firm framework with which to explore how humans responded to climate change, encounters with other populations, and the dynamic landscapes of the ice age."To me, this is the most fascinating part of this research: that a small band of our ancestors disappeared from history, but developed agriculture, which completely changed our history. This implies that they were living in isolation perhaps caused by geography or competition from surrounding bands and to survive they had by necessity to domesticate plants. If necessity is the mother of invention, they created something amazing. The story potential of this isolation is a story that both researchers and writers of fiction need to explore.
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* * * * *Story Source: Materials provided by the University of Cambridge, original story licensed under a Creative Commons License. "Ancient DNA shows earliest European genomes weathered the Ice Age: Neanderthal interbreeding clues and a mystery human lineage." ScienceDaily, 6 November 2014.