An ancient European hunter-gatherer man had dark skin and blue eyes, a new genetic analysis has revealed.
The analysis of the man, who lived in modern-day Spain only about 7,000 years ago, shows
light-skin genes in Europeans evolved much more recently than previously thought.
The findings, which were detailed today (Jan. 26) in the journal
Nature, also hint that light skin evolved not to adjust to the
lower-light conditions in Europe compared with Africa, but instead to
the new diet that emerged after the
agricultural revolution, said study co-author Carles Lalueza-Fox, a paleogenomics researcher at Pompeu Fabra University in Spain.
Sunlight changes
Many scientists have believed that lighter skin gradually arose in
Europeans starting around 40,000 years ago, soon after people left
tropical Africa for Europe's higher latitudes. The hunter-gatherer's
dark skin pushes this date forward to only 7,000 years ago, suggesting
that at least some humans lived considerably longer than thought in
Europe before losing the dark pigmentation that evolved under Africa's
sun.
"It was assumed that the
lighter skin was something needed in high latitudes, to synthesize
vitamin D in places where UV light is lower than in the tropics,"
Lalueza-Fox told LiveScience.
Scientists had assumed this was true because people need
vitamin D
for healthy bones, and can synthesize it in the skin with energy from
the sun's UV rays, but darker skin, like that of the hunter-gatherer
man, prevents UV-ray absorption.
But the new discovery shows that
latitude alone didn't drive the evolution of Europeans' light skin. If
it had, light skin would have become widespread in Europeans millennia
earlier, Lalueza-Fox said.
Mysterious find
In 2006, hikers discovered two male skeletons buried in a labyrinthine
cave known as La Braña-Arintero, in the Cantabrian Mountains of Spain. [
Images of the Ancient Skeletons]
At first, officials thought the skeletons may have been recent murder
victims. But then, an analysis revealed the skeletons were about 7,000
years old, and had no signs of trauma. The bodies were covered with red
soil, characteristic of Paleolithic burial sites, Lalueza-Fox said.
At the time of the discovery, genetic techniques weren't advanced
enough to analyze the skeletons. Several years later, the team revisited
the skeletons and extracted DNA from a molar tooth in one skeleton.
(The other skeleton had been sitting in water for millennia, so his DNA
was more degraded, Lalueza-Fox said.)
Blue eyes, dark skin
The new analysis of that DNA now shows the man had the
gene mutation for blue eyes, but not the European mutations for lighter skin.
The DNA also shows that the man was more closely related to modern-day northern Europeans than to southern Europeans.
The discovery may explain why baby blues are more common in
Scandinavia. It's been thought that poor conditions in northern Europe
delayed the agricultural revolution there, so Scandinavians may have
more genetic traces of their hunter-gatherer past — including a random
blue-eye mutation that emerged in the small population of
ancient hunter-gatherers, Lalueza-Fox said.
The finding implies that for most of their evolutionary history,
Europeans were not what many people today would call 'Caucasian', said
Guido Barbujani, president of the Associazione Genetica Italiana in
Ferrara, Italy, who was not involved in the study.
Instead, "what
seems likely, then, is that the dietary changes accompanying the
so-called Neolithic revolution, or the transition from food collection
to food production, might have caused, or contributed to cause, this
change," Barbujani said.
In the food-production theory, the
cereal-rich diet of Neolithic farmers lacked vitamin D, so Europeans
rapidly lost their dark-skin pigmentation only once they switched to
agriculture, because it was only at that point that they had to
synthesize vitamin D from the sun more readily.
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