tongues untied
WHY DO PEOPLE SPEAK SO MANY LANGUAGES?
by
MICHAEL GAVIN
______________________________________________________________
Michael Gavin is a research assistant (Deparment
of Linguistic and Cultural Evolution) at the Max
Planck Institute for the Science of Human History.
The thatched
roof held back the sun’s rays, but it could not keep the
tropical heat at bay. As everyone at the research workshop headed
outside for a break, small groups splintered off to gather in
the shade of coconut trees and enjoy a breeze. I wandered from
group to group, joining in the discussions. Each time, I noticed
that the language of the conversation would change from an indigenous
language to something they knew I could understand, Bislama or
English. I was amazed by the ease with which the meeting’s
participants switched between languages, but I was even more astonished
by the number of different indigenous languages.
Thirty
people had gathered for the workshop on this island in the South
Pacific, and all except for me came from the island, called Makelua,
in the nation of Vanuatu. They lived in 16 different communities
and spoke 16 distinct languages.
In many
cases, you could stand at the edge of one village and see the
outskirts of the next community. Yet the residents of each village
spoke completely different languages. According to recent work
by my colleagues at the Max Planck Institute for the Science of
Human History, this island, just 100 kilometers long and 20 kilometers
wide, is home to speakers of perhaps 40 different indigenous languages.
Why so many?
We could
ask this same question of the entire globe. People don’t
speak one universal language, or even a handful. Instead, today
our species collectively speaks over 7,000 distinct languages.
And these
languages are not spread randomly across the planet. For example,
far more languages are found in tropical regions than in the temperate
zones. The tropical island of New Guinea is home to over 900 languages.
Russia, 20 times larger, has 105 indigenous languages. Even within
the tropics, language diversity varies widely. For example, the
250,000 people who live on Vanuatu’s 80 islands speak 110
different languages, but in Bangladesh, a population 600 times
greater speaks only 41 languages.
Why is
it that humans speak so many languages? And why are they so unevenly
spread across the planet? As it turns out, we have few clear answers
to these fundamental questions about how humanity communicates.
SOME
IDEAS BUT LITTLE EVIDENCE
Most
people can easily brainstorm possible answers to these intriguing
questions. They hypothesize that language diversity must be about
history, cultural differences, mountains or oceans dividing populations,
or old squabbles writ large – “we hated them, so we
don’t talk to them.”
The questions
also seem like they should be fundamental to many academic disciplines
– linguistics, anthropology, human geography. But, starting
in 2010, when our diverse team of researchers from six different
disciplines and eight different countries began to review what
was known, we were shocked that only a dozen previous studies
had been done, including one we ourselves completed on language
diversity in the Pacific.
These
prior efforts all examined the degree to which different environmental,
social and geographic variables correlated with the number of
languages found in a given location. The results varied a lot
from one study to another, and no clear patterns emerged. The
studies also ran up against many methodological challenges, the
biggest of which centered on the old statistical adage –
correlation does not equal causation.
We wanted
to know the exact steps that led to so many languages forming
in certain places and so few in others. But previous work provided
few robust theories on the specific processes involved, and the
methods used did not get us any closer to understanding the causes
of language diversity patterns.
For example,
previous studies pointed out that at lower latitudes languages
are often spoken across smaller areas than at higher latitudes.
You can fit more languages into a given area the closer you get
to the equator. But this result does not tell us much about the
processes that create language diversity. Just because a group
of people crosses an imaginary latitudinal line on the map doesn’t
mean they’ll automatically divide into two different populations
speaking two different languages. Latitude might be correlated
with language diversity, but it certainly did not create it.
CAN A
SIMPLE MODEL PREDICT REALITY?
A better
way to identify the causes of particular patterns is to simulate
the processes we think might be creating them. The closer the
model’s products are to the reality we know exists, the
greater the chances are that we understand the actual processes
at work.
Two members of our group, ecologists Thiago Rangel and Robert
Colwell, had developed this simulation modeling technique for
their studies of species diversity patterns. But no one had ever
used this approach to study the diversity of human populations.
We decided
to explore its potential by first building a simple model to test
the degree to which a few basic processes might explain language
diversity patterns in just one part of the globe, the continent
of Australia.
Our colleague
Claire Bowern, a linguist at Yale University, created a map that
shows the diversity of aboriginal languages – a total of
406 – found in Australia prior to contact with Europeans.
There were far more languages in the north and along the coasts,
with relatively few in the desert interior. We wanted to see how
closely a model, based on a simple set of processes, could match
this geographic pattern of language diversity.
Our simulation
model made only three basic assumptions. First, populations will
move to fill available spaces where no one else lives.
Second, rainfall will limit the number of people that can live
in a place; Our model assumed that people would live in higher
densities in areas where it rained more. Annual precipitation
varies widely in Australia, from over three meters in the north-eastern
rainforests to one-tenth of a meter in the Outback.
Third,
we assumed that human populations have a maximum size. Ideal group
size is a trade-off between benefits of a larger group (wider
selection of potential mates) and costs (keeping track of unrelated
individuals). In our model, when a population grew larger than
a maximum threshold – set randomly based on a global distribution
of hunter-gatherer population sizes – it divided into two
populations, each speaking a distinct language.
We used
this model to simulate language diversity maps for Australia.
In each iteration, an initial population sprung up randomly somewhere
on the map and began to grow and spread in a random direction.
An underlying rainfall map determined the population density,
and when the population size hit the predetermined maximum, the
group divided. In this way, the simulated human populations grew
and divided as they spread to fill up the entire Australian continent.
Our simple
model didn’t include any impact from contact among groups,
changes in subsistence strategies, the effects of the borrowing
of cultural ideas or components of language from nearby groups,
or many other potential processes. So, we expected it would fail
miserably.
Incredibly, the model produced 407 languages, just one off from
the actual number.
The simulated
language maps also show more languages in the north and along
the coasts, and less in the dry regions of central Australia,
mirroring the geographic patterns in observed language diversity.
And so
for the continent of Australia it appears that a small number
of factors – limitations rainfall places on population density
and limits on group size – might explain both the number
of languages and much of the variation in how many languages are
spoken in different locations.
APPLYING
THE MODEL ELSEWHERE
But we
suspect that the patterns of language diversity in other places
may be shaped by different factors and processes. In other locations,
such as Vanuatu, rainfall levels do not vary as widely as in Australia,
and population densities may be shaped by other environmental
conditions.
In other
instances, contact among human groups probably reshaped the landscape
of language diversity. For example, the spread of agricultural
groups speaking Indo-European or Bantu languages may have changed
the structure of populations and the languages spoken across huge
areas of Europe and Africa, respectively.
Undoubtedly,
a wide variety of social and environmental factors and processes
have contributed to the patterns in language diversity we see
across the globe. In some places topography, climate or the density
of key natural resources may be more critical; in others the history
of warfare, political organization or the subsistence strategies
of different groups may play a bigger role in shaping group boundaries
and language diversity patterns. What we have established for
now is a template for a method that can be used to uncover the
different processes at work in each location.
Language
diversity has played a key role in shaping the interactions of
human groups and the history of our species, and yet we know surprisingly
little about the factors shaping this diversity. We hope other
scientists will become as fascinated by the geography of language
diversity as our research group is and join us in the search for
understanding why humans speak so many languages.
