Nicholas Wade
Biologists using tools developed for
drawing evolutionary family trees say that they have solved
a long-standing problem in archaeology: the origin of the
Indo-European family of languages.
The family includes English and most other European
languages, as well as Persian, Hindi and many others. Despite the
importance of the languages, specialists have long disagreed about
their origin.
Linguists believe that the first
speakers of the mother tongue, known as proto-Indo-European,
were chariot-driving pastoralists who burst out of their
homeland on the steppes above the Black Sea some 4,000 years
ago and conquered Europe and Asia. A rival theory holds that,
to the contrary, the first Indo-European speakers were
peaceable farmers in Anatolia, now Turkey, some 9,000 years
ago, who disseminated their language by the hoe, not the
sword.
The result, they
announced in Thursday’s [August 23, 2012] issue of the journal Science, is
that “we found decisive support for an Anatolian origin over a
steppe origin.” Both the timing and the root of the tree of
Indo-European languages “fit with an agricultural expansion
from Anatolia beginning 8,000 to 9,500 years ago,” they
report.
But despite its advanced statistical
methods, their study may not convince everyone.
The researchers started with a menu of
vocabulary items that are known to be resistant to linguistic
change, like pronouns, parts of the body and family relations,
and compared them with the inferred ancestral word in
proto-Indo-European. Words that have a clear line of descent
from the same ancestral word are known as cognates. Thus
“mother,” “mutter” (German), “mat’ ” (Russian), “madar”
(Persian), “matka” (Polish) and “mater” (Latin) are all
cognates derived from the proto-Indo-European word “*mehter.”
Dr. Atkinson and his colleagues then
scored each set of words on the vocabulary menu for the 103
languages. In languages where the word was a cognate, the
researchers assigned it a score of 1; in those where the
cognate had been replaced with an unrelated word, it was
scored 0. Each language could thus be represented by a string
of 1’s and 0’s, and the researchers could compute the most
likely family tree showing the relationships among the 103
languages.
A computer was then supplied with
known dates of language splits. Romanian and other Romance
languages, for instance, started to diverge from Latin after
A.D. 270, when Roman troops pulled back from Dacia. Applying
those dates to a few branches in its tree, the computer was
able to estimate dates for all the rest.
The computer was also given
geographical information about the present range of each
language and told to work out the likeliest pathways of
distribution from an origin, given the probable family tree of
descent. The calculation pointed to Anatolia, particularly a
lozenge-shaped area in what is now southern Turkey, as the
most plausible origin — a region that had also been proposed
as the origin of Indo-European by the archaeologist Colin
Renfrew, in 1987, because it was the source from which
agriculture spread to Europe.
Dr. Atkinson’s work has integrated a
large amount of information with a computational method that
has proved successful in evolutionary studies. But his results
may not sway supporters of the rival theory, who believe the
Indo-European languages were spread some 5,000 years later by
warlike pastoralists who conquered Europe and India from the
Black Sea steppe.
A key piece of their evidence is that
proto-Indo-European had a vocabulary for chariots and wagons
that included words for “wheel,” “axle,” “harness-pole” and
“to go or convey in a vehicle.” These words have numerous
descendants in the Indo-European daughter languages. So
Indo-European itself cannot have fragmented into those
daughter languages, historical linguists argue, before the
invention of chariots and wagons, the earliest known examples
of which date to 3500 B.C. This would rule out any connection
between Indo-European and the spread of agriculture from
Anatolia, which occurred much earlier.
“I see the wheeled-vehicle evidence as
a trump card over any evolutionary tree,” said David Anthony,
an archaeologist at Hartwick College who studies Indo-European
origins.
Historical linguists see other
evidence in that the first Indo-European speakers had words
for “horse” and “bee,” and lent many basic words to
proto-Uralic, the mother tongue of Finnish and Hungarian. The
best place to have found wild horses and bees and be close to
speakers of proto-Uralic is the steppe region above the Black
Sea and the Caspian. The Kurgan people who occupied this area
from around 5000 to 3000 B.C. have long been candidates for
the first Indo-European speakers.
In a recent book, “The Horse, the
Wheel and Language,” Dr. Anthony describes how the steppe
people developed a mobile society and social system that
enabled them to push out of their homeland in several
directions and spread their language east, west and south.
Dr. Anthony said he found Dr.
Atkinson’s language tree of Indo-European implausible in
several details. Tocharian, for instance, is a group of
Indo-European languages spoken in northwest China. It is hard
to see how Tocharians could have migrated there from southern
Turkey, he said, whereas there is a well-known migration from
the Kurgan region to the Altai Mountains of eastern Central
Asia, which could be the precursor of the Tocharian-speakers
who lived along the Silk Road.
Dr. Atkinson said that this was a
“hand-wavy argument” and that such conjectures should be
judged in a quantitative way.
Dr. Anthony, noting that neither he
nor Dr. Atkinson is a linguist, said that cognates were only
one ingredient for reconstructing language trees, and that
grammar and sound changes should also be used. Dr. Atkinson’s
reconstruction is “a one-legged stool, so it’s not surprising
that the tree it produces contains language groupings that
would not survive if you included morphology and sound
changes,” Dr. Anthony said.
Dr. Atkinson responded that he did
indeed run his computer simulation on a grammar-based tree
constructed by Don Ringe, an expert on Indo-European at the
University of Pennsylvania, but that the resulting origin was,
again, Anatolia, not the Pontic steppe.
"The New York Times," August 23, 2012
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