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17 September 2014 Last updated at 13:46 ET
Europeans drawn from three ancient 'tribes'
By Paul Rincon Science editor, BBC News website
The modern European gene pool was formed when three ancient
populations mixed within the last 7,000 years, Nature journal reports.
Blue-eyed, swarthy hunters mingled with brown-eyed, pale skinned
farmers as the latter swept into Europe from the Near East.
But another, mysterious population with Siberian affinities also
contributed to the genetic landscape of the continent.
The findings are based on analysis of genomes from nine ancient
Europeans.
Agriculture originated in the Near East - in modern Syria, Iraq and
Israel - before expanding into Europe around 7,500 years ago.
It really does look like the indigenous West European hunter gatherers
had this striking combination of dark skin and blue eyes that doesn't
exist any more"
Prof David Reich Harvard Medical School Multiple lines of evidence
suggested this new way of life was spread by a wave of migrants, who
interbred with the indigenous European hunter-gatherers they
encountered on the way.
But assumptions about European origins were based largely on the
genetic patterns of living people. The science of analysing genomic
DNA from ancient bones has put some of the prevailing theories to the
test, throwing up a few surprises.
Genomic DNA contains the biochemical instructions for building a
human, and resides within the nuclei of our cells.
In the new paper, Prof David Reich from the Harvard Medical School and
colleagues studied the genomes of seven hunter-gatherers from
Scandinavia, one hunter whose remains were found in a cave in
Luxembourg and an early farmer from Stuttgart, Germany.
The hunters arrived in Europe thousands of years before the advent of
agriculture, hunkered down in southern refuges during the Ice Age and
then expanded during a period called the Mesolithic, after the ice
sheets had retreated from central and northern Europe.
Their genetic profile is not a good match for any modern group of
people, suggesting they were caught up in the farming wave of advance.
If you look at all the reconstructions of Mesolithic people on the
internet, they are always depicted as fair skinned... This shows the
opposite"
Prof Carles Lalueza-Fox Institute of Evolutionary Biology (CSIC - UPF)
However, their genes live on in modern Europeans, to a greater extent
in the north-east than in the south.
The early farmer genome showed a completely different pattern,
however. Her genetic profile was a good match for modern people in
Sardinia, and was rather different from the indigenous hunters.
But, puzzlingly, while the early farmers share genetic similarities
with Near Eastern people at a global level, they are significantly
different in other ways. Prof Reich suggests that more recent
migrations in the farmers' "homeland" may have diluted their genetic
signal in that region today.
Prof Reich explained: "The only way we'll be able to prove this is by
getting ancient DNA samples along the potential trail from the Near
East to Europe... and seeing if they genetically match these
predictions or if they're different.
"Maybe they're different - that would be extremely interesting."
The agricultural transition was a period of momentous cultural and
demographic change Pigmentation genes carried by the hunters and
farmers showed that, while the dark hair, brown eyes and pale skin of
the early farmer would look familiar to us, the hunter-gatherers would
stand out if we saw them on a street today.
"It really does look like the indigenous West European hunter
gatherers had this striking combination of dark skin and blue eyes
that doesn't exist any more," Prof Reich told BBC News.
Dr Carles Lalueza-Fox, from the Institute of Evolutionary Biology
(CSIC - UPF) in Barcelona, Spain, who was not involved with the
research, told BBC News: "If you look at all the reconstructions of
Mesolithic people on the internet, they are always depicted as fair
skinned. And the farmers are sometimes depicted as dark-skinned
newcomers to Europe. This shows the opposite."
So where did fair pigmentation in present-day Europeans come from? The
farmer seems to be on her way there, carrying a gene variant for light
skin that's still around today.
"There's an evolutionary argument about this - that light skin in
Europe is biologically advantageous for people who farm, because you
need to make vitamin D," said David Reich.
"Hunters and gatherers get vitamin D through their food - because
animals have a lot of it. But once you're farming, you don't get a lot
of it, and once you switch to agriculture, there's strong natural
selection to lighten your skin so that when it's hit by sunlight you
can synthesise vitamin D."
This reconstruction shows the dark skin and blue eyes of a
7,000-year-old hunter from northern Spain When the researchers looked
at DNA from 2,345 present day people, they found that a third
population was needed to capture the genetic complexity of modern
Europeans.
This additional "tribe" is the most enigmatic and, surprisingly, is
related to Native Americans.
Hints of this group surfaced in an analysis of European genomes two
years ago. Dubbed Ancient North Eurasians, this group remained a
"ghost population" until 2013, when scientists published the genome of
a 24,000-year-old boy buried near Lake Baikal in Siberia.
This individual had genetic similarities to both Europeans and
indigenous Americans, suggesting he was part of a population that
contributed to movements into the New World 15,000 years ago and
Europe at a later date.
The ancient hunter from Luxembourg and the farmer from Germany show no
signs of mixture from this population, implying this third ancestor
was added to the continental mix after farming was already established
in Europe.
The study also revealed that the early farmers and their European
descendents can trace a large part of their ancestry to a previously
unknown, even older lineage called Basal Eurasians. This group
represents the earliest known population divergence among the humans
who left Africa 60,000 years ago.
Follow Paul on Twitter.
http://m.bbc.com/news/science-environment-29213892
Europeans drawn from three ancient 'tribes'
By Paul Rincon Science editor, BBC News website
The modern European gene pool was formed when three ancient
populations mixed within the last 7,000 years, Nature journal reports.
Blue-eyed, swarthy hunters mingled with brown-eyed, pale skinned
farmers as the latter swept into Europe from the Near East.
But another, mysterious population with Siberian affinities also
contributed to the genetic landscape of the continent.
The findings are based on analysis of genomes from nine ancient
Europeans.
Agriculture originated in the Near East - in modern Syria, Iraq and
Israel - before expanding into Europe around 7,500 years ago.
It really does look like the indigenous West European hunter gatherers
had this striking combination of dark skin and blue eyes that doesn't
exist any more"
Prof David Reich Harvard Medical School Multiple lines of evidence
suggested this new way of life was spread by a wave of migrants, who
interbred with the indigenous European hunter-gatherers they
encountered on the way.
But assumptions about European origins were based largely on the
genetic patterns of living people. The science of analysing genomic
DNA from ancient bones has put some of the prevailing theories to the
test, throwing up a few surprises.
Genomic DNA contains the biochemical instructions for building a
human, and resides within the nuclei of our cells.
In the new paper, Prof David Reich from the Harvard Medical School and
colleagues studied the genomes of seven hunter-gatherers from
Scandinavia, one hunter whose remains were found in a cave in
Luxembourg and an early farmer from Stuttgart, Germany.
The hunters arrived in Europe thousands of years before the advent of
agriculture, hunkered down in southern refuges during the Ice Age and
then expanded during a period called the Mesolithic, after the ice
sheets had retreated from central and northern Europe.
Their genetic profile is not a good match for any modern group of
people, suggesting they were caught up in the farming wave of advance.
If you look at all the reconstructions of Mesolithic people on the
internet, they are always depicted as fair skinned... This shows the
opposite"
Prof Carles Lalueza-Fox Institute of Evolutionary Biology (CSIC - UPF)
However, their genes live on in modern Europeans, to a greater extent
in the north-east than in the south.
The early farmer genome showed a completely different pattern,
however. Her genetic profile was a good match for modern people in
Sardinia, and was rather different from the indigenous hunters.
But, puzzlingly, while the early farmers share genetic similarities
with Near Eastern people at a global level, they are significantly
different in other ways. Prof Reich suggests that more recent
migrations in the farmers' "homeland" may have diluted their genetic
signal in that region today.
Prof Reich explained: "The only way we'll be able to prove this is by
getting ancient DNA samples along the potential trail from the Near
East to Europe... and seeing if they genetically match these
predictions or if they're different.
"Maybe they're different - that would be extremely interesting."
The agricultural transition was a period of momentous cultural and
demographic change Pigmentation genes carried by the hunters and
farmers showed that, while the dark hair, brown eyes and pale skin of
the early farmer would look familiar to us, the hunter-gatherers would
stand out if we saw them on a street today.
"It really does look like the indigenous West European hunter
gatherers had this striking combination of dark skin and blue eyes
that doesn't exist any more," Prof Reich told BBC News.
Dr Carles Lalueza-Fox, from the Institute of Evolutionary Biology
(CSIC - UPF) in Barcelona, Spain, who was not involved with the
research, told BBC News: "If you look at all the reconstructions of
Mesolithic people on the internet, they are always depicted as fair
skinned. And the farmers are sometimes depicted as dark-skinned
newcomers to Europe. This shows the opposite."
So where did fair pigmentation in present-day Europeans come from? The
farmer seems to be on her way there, carrying a gene variant for light
skin that's still around today.
"There's an evolutionary argument about this - that light skin in
Europe is biologically advantageous for people who farm, because you
need to make vitamin D," said David Reich.
"Hunters and gatherers get vitamin D through their food - because
animals have a lot of it. But once you're farming, you don't get a lot
of it, and once you switch to agriculture, there's strong natural
selection to lighten your skin so that when it's hit by sunlight you
can synthesise vitamin D."
This reconstruction shows the dark skin and blue eyes of a
7,000-year-old hunter from northern Spain When the researchers looked
at DNA from 2,345 present day people, they found that a third
population was needed to capture the genetic complexity of modern
Europeans.
This additional "tribe" is the most enigmatic and, surprisingly, is
related to Native Americans.
Hints of this group surfaced in an analysis of European genomes two
years ago. Dubbed Ancient North Eurasians, this group remained a
"ghost population" until 2013, when scientists published the genome of
a 24,000-year-old boy buried near Lake Baikal in Siberia.
This individual had genetic similarities to both Europeans and
indigenous Americans, suggesting he was part of a population that
contributed to movements into the New World 15,000 years ago and
Europe at a later date.
The ancient hunter from Luxembourg and the farmer from Germany show no
signs of mixture from this population, implying this third ancestor
was added to the continental mix after farming was already established
in Europe.
The study also revealed that the early farmers and their European
descendents can trace a large part of their ancestry to a previously
unknown, even older lineage called Basal Eurasians. This group
represents the earliest known population divergence among the humans
who left Africa 60,000 years ago.
Follow Paul on Twitter.
http://m.bbc.com/news/science-environment-29213892