"Using genetic fragments extracted from ancient remains spanning almost 30,000 years, scientists reconstructed the DNA of people who lived in Europe between 35,000 years and 7,000 years ago.
Focusing on mitochondrial DNA they were able to trace their maternal lines, and found that specific genetic markers present in the population suddenly disappeared at the end of the ice age.
This type of DNA is the genetic material from mitochondria which are ‘power units’ of cells that generate their energy.
In particular, fragments of DNA were used to rebuild the mitochondrial DNA of individuals from Italy, Germany, Belgium, France, the Czech Republic, and Romania during the period.
Three of the earliest individuals, who lived in France and Belgium during the last Ice Age, were found to have a unique set of identifiable genetic markers, or haplotype.
But by the time the ice sheets had melted, these markers had disappeared from the European population.
Analysis of DNA from the Europeans who lived after the Ice Age show they lacked the haplotype seen in the older Europeans.
Today, this unique set of markers, called the M-haplotype, is commonly found in modern Asian, Australasian and Native American people, leading to theories that non-African people in Europe spread out in multiple waves to Asia and Australasia.
The new findings suggest that all non-African people moved out in a single event, some 50,000 years ago.
Further evidence showed that the M-haplotype was gone completely from Europe by 14,500 years ago.
But the DNA analysis unveiled another secret.
One of the biggest changes to the European population, the researchers said, was the takeover of the population at the same time. This coincided with the warming climate.
‘We uncovered a completely unknown chapter of human history: a major population turnover in Europe at the end of the last Ice Age,’ explained lead author Professor Johannes Krause.
‘There has been a real lack of genetic data from this time period, so consequently we knew very little about the population structure or dynamics of the first modern humans in Europe,’ said Krause.
‘Our model suggests that during this period of climatic upheaval, the descendants of the hunter-gatherers who survived through the Last Glacial Maximum were largely replaced by a population from another source," explained Adam Powell, another senior author.
Lead author of the study, Professor Cosimo Posth of the University of Tübingen, suggests that European hunter-gatherer populations would have headed south to find refuge from the harsh environmental conditions.
The team wrote: ‘Our demographic modelling reveals a dynamic history of hunter-gatherers, including a previously unknown major population shift during the Late Glacial period.’
The researchers believe that the small, initial population of Europe grew slowly until 25,000 years ago, and survived the Late Glacial Maximum (LGM).
But they then fled south when the ice sheet started to retract.
This created a ‘genetic bottleneck’ of hunter-gatherers and the loss of hunter-gatherer mitochondrial DNA after the LGM.
The subsequent Late Glacial period was characterised by drastic climatic fluctuations, beginning with an abrupt warming during what’s known as the Bølling-Allerød interstadial, followed by drastic period of cooling during the Younger Dryas.
Globally, the early warming phases of the Late Glacial are strongly associated with substantial demographic changes, including extinctions of several megafaunal species and the first expansion of modern humans into the Americas.
The researchers add: ‘In European hunter-gatherers, our model explains this period of upheaval as a replacement of the population by another source.
‘Although the exact origin for this later population is unknown, the inferred demographic history suggests that it descended from another, separate [isolated population.]
This is also known as a refugium, or a location where an isolated population from a once more widespread group seeks’ refuge’ in a new location.
The group said the next step will be to build up the picture with more DNA analyses, giving a complete view of the genomes of ancient Europeans . . ."