Scientific advances in recent years have allowed researchers to retrieve and
analyse genomes from ancient
burials. The genome is the genetic blueprint for a human, contained within the
nucleus of every cell.
This deluge of data has transformed our understanding of the modern human
genetic landscape. It has
also shown that present-day genetic patterns are poor guides to ancient ones.
The first layer of European ancestry, the indigenous hunter-gatherers,
entered Europe before the
Ice Age 40,000 years ago. But 7,000 years ago, they were swept up in a migration
of people from the Middle East,
who introduced farming to Europe.
About 5,000 years ago, herders called the Yamnaya entered Europe from the
eastern Steppe region -
in present day Ukraine and Russia.(Ямная культура*//geo-logaritmica)
These horse riding metal workers may have brought Indo-European languages with
them; today this language
family comprises most of the tongues spoken in Europe. The discovery of plague DNA
in Yamnaya burials and a
population decline in Europe around the same time has led some researchers to wonder
if their passage
west was facilitated
by the spread of disease.
But the Yamnaya were themselves a mixed population. Around half of their
ancestry came from a
sister group to the hunter-gatherers who inhabited Europe before farming,
while the other half
appears to be from a population related to - but noticeably different from
- the Middle Eastern
migrants who introduced farming.
Researchers have now analysed genomes from two hunter-gatherers from
Georgia that are 13,300 and
9,700 years old. The results show that these Caucasus hunters were probably
the source of the
farmer-like DNA in the Yamnaya.
Isolation by ice
The Caucasus hunter-gatherer genomes show a continued mixture with their Middle Eastern
cousins to the south, who would go on to invent farming 10,000 years ago. However, this
mixing ended about 25,000 years ago - just before the time of the last glacial maximum,
or peak of the Ice Age.
The Yamnaya people had an important impact on the genetics of
northern and central Europe
At this point, populations shrank - as shown by their genes homogenising,
a sign of breeding between those with increasingly similar DNA.
Once the ice retreated, the Caucasus groups came into contact with a
different group of
hunter-gatherers living on the Steppe and mixed with them, laying the
genetic foundations of the Yamnaya people.
A view from the Satsurblia cave in Western Georgia, where a human
bone dating from over 13,000
years ago was discovered.
The question of where the Yamnaya come from has been something
of a mystery up to now, said co-author
Dr Andrea Manica, from the University of Cambridge.
We can now answer that as we've found that their genetic make-up
is a mix of Eastern
European hunter-gatherers and a population from this pocket of Caucasus
weathered much of the last Ice Age in apparent isolation..
The researchers also suggest that the Caucasus hunter-gatherers
further east, particularly in South Asia.
They suggest that this strand of ancestry may also have been
associated with the spread
of Indo-European languages to the region.