Lactose tolerance and language

Wish there were more details, but here's a news story from the Nov.
19 issue of Science:
Ural Farmers Got Milk Gene First?
Jocelyn Kaiser

TORONTO, CANADA--More than 5000 experts met here from 26 to 30
October for the annual meeting of the American Society of Human
Genetics. Longevity, milk digestion, and cancer were among the
topics.
By some estimates, less than half of all adults can easily digest
milk, a trait believed to have first appeared in people who kept
dairy animals. Now scientists have traced the genetic roots of milk
tolerance to the Ural mountains of western Russia, well north of
where pastoralism is thought to have begun. The surprising result
may support a theory that nomads from the Urals were one of two
major farmer groups that spread into Europe, bringing the Indo-
European languages that eventually diverged into the world's largest
family of modern languages.
Almost all mammalian babies produce lactase, the enzyme that digests
the milk sugar lactose. But in most animals and many people, the
lactase gene is gradually turned off after infancy, leaving them
unable to tolerate milk as adults. Two years ago, a team led by
Leena Peltonen of the University of Helsinki, Finland, and the
University of California, Los Angeles, identified mutations near the
lactase gene that are associated with adult lactose tolerance and
likely play a role in regulating the lactase gene. Now, Peltonen's
team has tried to trace the origins of lactose tolerance by looking
at 1611 DNA samples from 37 populations on four continents.


Milk route. A new study suggests that tribes from the Asian steppes
(blue circle) migrated to the Ural mountains, where they mixed with
locals (red circle), generating a gene variant endowing lactose
tolerance that Ural farmers later spread.
SOURCE: N. ENATTAH (blue circle in southern Mongolia; red circle
near lower Volga -- djm)


The populations having the greatest DNA sequence diversity around
the lactase gene mutations--suggesting that lactose tolerance first
appeared in them--include the Udmurts, Mokshas, Ezras, and other
groups that originally lived between the Ural mountains and the
Volga River. The trait most likely developed 4800 to 6600 years ago,
Peltonen says. Her team linked the lactase gene changes to an
ancestral variant that these groups apparently got from intermixing
with tribes migrating from the Asian steppes.
After the Ural peoples gained this earlier form of the lactase gene,
the lactose tolerance mutation "probably emerged by chance," says
Peltonen, and then remained because it was beneficial for milk
consumption. The Ural groups then likely later spread the variant to
Europe--especially northern Europe, which has the highest lactose
tolerance today--and the Middle East. The findings support the
somewhat controversial theory that nomadic herders known as Kurgans
expanded into Europe from the southern Urals 4500 to 3500 years ago,
bringing Indo-European languages with them, according to Peltonen.

"I find [the new study] very interesting," says population
geneticist Luigi Luca Cavalli-Sforza of Stanford University. He
notes that a competing idea for explaining the origin of the Proto-
Indo-Europeans is that they were crop-growing farmers from the
Anatolia region in modern Turkey (Science, 27 February, p. 1323).
But the milk study reinforces Cavalli-Sforza's view that both
theories are correct: Indo-Europeans migrated to Europe in two
waves, first from Turkey and later from the Urals.

Other geneticists caution that trying to pin down where a gene
variant originated is tricky because the people in whom it's most
common today may have migrated from somewhere else, or the original
population could now be extinct. But if the milk gene's origin holds
up, linguists and archaeologists will have new food for thought.