Content uploaded by Quentin D Atkinson
Author content
All content in this area was uploaded by Quentin D Atkinson
Content may be subject to copyright.
Languages Evolve in
Punctuational Bursts
Quentin D. Atkinson,
1
* Andrew Meade,
1
Chris Venditti,
1
Simon J. Greenhill,
2
Mark Pagel
1,3
†
A
merican English emerged abruptly
when Noah Webster introduced his
American Dictionary of the English
Language, insisting that “as an independent
nation, our honor requires us to have a system of
our own, in language as well as government” (1).
Punctuational or rapid bursts of change associated
with the emergence of new languages, or at later
language contact, have been proposed as an
important feature o f language evolution (2, 3),
echoing a long-standing parallel debate in biology
(4, 5). W ebster’s actions illustrate how the desire
for a distinct social identity may cause languages
to change rapidly (6, 7), but whether such punc-
tuational change is a regular feature of human
language evolution has never been demonstrated
(2). With use of three of the world’s major lan-
guage families comprising over one-third of all
the world’s languages, we found that punctua-
tional bursts of change at the time of language
splitting are an important and general process in
language evolution and account for 10 to 33% of
the total divergence among these languages in
their fundamental vocabularies.
We studied punctuational evolution in phylo-
genetic trees of language families inferred from
vocabula ry data (8). These trees describe the
separate paths of evolution leading from a com-
mon ancestral language to the set of observed
extant languages at the tips of the tree (Fig. 1A).
The lengths of the individual branches of the trees
record the amount of lexical divergence (replace-
ment of words) between an ancestral and a
descendant language. If lexical divergence is a
gradual process that is not affected by the
emergence of a new language, then the path length
or total distance from the root of the tree to the
languages at the tips should be independent of the
number of language-splitting events or nodes
found along that path. If language-splitting events
produce punctuational bursts of evolution, howev-
er , we expect to find more total lexical divergence
(longer path lengths) along paths through the tree
that record more language-splitting events (4, 8, 9).
In each language family , we found significantly
more lexical change along paths in which more
new languages have emerged, the signature of
punctuational evolution (Fig. 1B). These results
take into account the phylogenetic relationships
among languages, control for a well-known artifact
of phylogenetic reconstruction (10), and cannot be
attributed to borrowing of vocabulary (8). The
punctuational effects account for a surprising
amount of the total lexical divergence among the
languages (Fig. 1C): 31% of vocabulary differ-
ences among Bantu language speakers arose at or
around the time of language-splitting events, 21%
among Indo-European languages, and 9.5% in
Austronesian (8). In the settlement of the Pacific,
successive founder events (a small group coloniz-
ing a new location) by Polynesian language
speakers may have caused increased rates of
language change (11). Consistent with this, we
inferred a stronger punctuational effect in the
Polynesian subclade of the Austronesian tree,
contributing to about 33% of lexical differences
among these languages (Fig. 1C, purple bar).
These effects are comparable in size to punctua-
tional genetic changes observed among biological
species (~22%; Fig. 1C, yellow bar) (5).
Our results, representing thousan ds of years of
language evolution, identify a general tendency for
newly formed sister languages to diverge in their
fundamental vocabulary initially at a rapid pace,
followed by longer periods of slower and gradual
divergence . Punctuational bursts in phonology,
morphology , and syntax, or at later times of
language contact, may also occur. Linguistic
founder effects could cause these rapid changes if
newly formed languages emerge in small groups,
such as in Austronesian. Alternatively , as the
example of American English illus-
trates, speakers often use language not
just as a means of communication but
as a tool with social functions, includ-
ing promoting cohesion and group
identity (6, 7) . Punctuational language
change may thus reflect a human
capacity to rapidly adjust languages
at critical times of cultural evolution,
such as during the emergence of new
and rival groups.
References and Notes
1. N. Webster, Dissertations on the English
Language (Isaiah Thomas, Boston, 1789), p. 20.
2. R. D. Janda, B. D. Joseph, in The
Handbook of Historical Linguistics,B.D.
Joseph, R. D. Janda, Eds. (Blackwell,
Oxford, 2003), pp. 3–180.
3. R. M. W. Dixon, The Rise and Fall of
Languages (Cambridge Univ. Press,
Cambridge, 1997).
4. N.Eldredge,S.J.Gould,inModels in
Paleobiology,T.J.M.Schopf,Ed.(Freeman,
San Francisco, 1972), pp. 82–115.
5. M. Pagel, C. Venditti, A. Meade, Science 314, 119 (2006).
6. W. Labov, Principles of Linguistic Change: Internal
Factors (Blackwell, Oxford, 1994).
7. J. K. Chambers, Sociolinguistic Theory: Linguistic
Variation and Its Social Significance (Blackwell,
Cambridge, MA, 1995).
8. Materials and methods are available on Science Online.
9. A. J. Webster, R. J. Payne, M. Pagel, Science 301, 478
(2003).
10. C. Venditti, A. Meade, M. Pagel, Syst. Biol. 55, 637 (2006).
11. P. V. Kirch, R. C. Green, Curr. Anthropol. 28, 431 (1987).
12. Supported by a Leverhulme Trust grant to M.P.
Supporting Online Material
www.sciencemag.org/cgi/content/full/319/5863/588/DC1
Materials and Methods
Fig. S1
Tables S1 and S2
References
24 August 2007; accepted 21 November 2007
10.1126/science.1149683
BREVIA
1
School of Biological Sciences, University of Reading, Reading
RG6 6AS, UK.
2
Department of Psychology, University of
Auckland, Private Bag 92019, Auckland 1142, New Zealand.
3
Santa Fe Institute, 1399 Hyde Park Road, Santa Fe, NM
87501, USA.
*Present address: Institute of Cognitive and Evolutionary
Anthropology, University of Oxford, Oxford OX2 6QS, UK.
†To whom correspondence should be addressed. E-mail:
m.pagel@reading.ac.uk
AB C
Languages
Number of nodes
Language group
Total path length
Percentage of total evolution
0.4
0.2
0
40
30
20
10
0
0 10 20 30 40
B IE A P S
a b c d
Fig. 1. Inferring punctuational language evolution. (A) Tree of four languages. If language-splitting events (red nodes)
cause bursts of change, the paths from the root to a and b should be longest, followed by c then d (8); here, they are all
equal. (B) Root-to-tip path length plotted against number of nodes along each path for punctuational trees in Bantu
(orange), Indo-European (blue), Austronesian (green), and Polynesian (purple). Fitted lines show the relationship between
path length and nodes after controlling for phylogeny (8). A positive slope is indicative of punctuational evolution. Path
lengths for each data set were scaled to account for the number of characters examined. (C) Histogram showing the
percentage of lexical evolution attributable to punctuational bursts at language-splitting events (mean ± SD) for Bantu (B,
orange), Indo-European (IE, blue), Austronesian (A, green), and Polynesian (P, purple) (8). For comparison, the percentage
of molecular evolution attributable to punctuational effects in biological species is also shown (S, yellow) (4).
1 FEBRUARY 2008 VOL 319 SCIENCE www.sciencemag.org
588
on February 1, 2008 www.sciencemag.orgDownloaded from
