www.sciencemag.org SCIENCE VOL 343 28 FEBRUARY 2014 979
Out of Beringia?
John F. Hoffecker,1 Scott A. Elias,2 Dennis H. O’Rourke3
A shrub tundra refugium on the Bering land bridge may have played a pivotal role in the peopling
of the Americas.
Based on the distribution of tundra plantsaroundthe Bering Straitregion, Eric Hultén proposed in the 1930s
that the now-submerged plain between Chukotka and Alaska—the Bering land bridge—
became a refugium for shrub tundra vegetation during cold periods (1), which include
the last glacial maximum (LGM) between
~28,000 and 18,000 cal BP (calibrated radiocarbon years before the present). Adjoining
areas to the west and east supported drier
plant communities with a higher percentage
of grasses during glacial periods. According
to Hultén, when warmer and wetter conditions returned to these areas, the land bridge,
which he named Beringia, became a center
of dispersal for tundra plants. Now it appears
that it also may have been a glacial refugium
and postglacial center of dispersal for the people who first settled the Americas.
Since 1960, much evidence has accumu-
lated to support the shrub tundra refugium
thesis, including data collected from the for-
mer surface of the Bering land bridge. Pollen,
plant macrofossils, and insect remains from
dated sediments extracted from the floor of
the Bering Sea indicate a mesic tundra habitat
during the LGM (2, 3). Although pollen data
from islands in the Bering Sea suggest more
steppic vegetation (or “steppe-tundra”), these
islands represent former upland areas on the
now-submerged land bridge (see the figure).
Several tree species, including spruce, birch,
and alder, also probably survived locally dur-
ing the LGM (3, 4). Fossil insect remains from
both sides of the Bering Strait suggest sur-
prisingly mild temperatures during the cold-
est phases of the LGM, despite the high lati-
tude. All of these data presumably reflect the
impact of the North Pacific circulation, which
brought comparatively moist and warm air
to southern Beringia during the LGM (4). In
fact, the latest study of Beringian vegetation
indicates that grasses were less dominant in
areas outside the land bridge than previously
The shrub tundra refugium in Beringia
may also have played a pivotal role in the
peopling of the Americas. Genetic evidence
suggests that most Native Americans are
descended from a population that was isolated somewhere between northeast Asia and
Alaska during the LGM (6). According to the
Beringian standstill hypothesis, this popula-
1Institute of Arctic and Alpine Research, University of
Colorado, Boulder, CO 80309, USA. 2Department of Geography, Royal Holloway University of London, Egham TW20
0EX, UK. 3Department of Anthropology, University of Utah,
Salt Lake City, UT 84112, USA. E-mail: john.hoffecker@
in a multitude of contexts nonetheless activate
the same brain regions. Moreover, invariance
seems to be governed by articulatory distinctive features, thereby supporting the 80-year-
old theory of Jakobson and Trubetzkoy. Interestingly, features do not have equal neural
representation, and those that induce strong
neural invariance have strong acoustic correlates. Speech representation in the auditory
cortex, in other words, is governed by acoustic features, but not by just any acoustic feature—the features that dominate speech representation are precisely those that are associated with abstract, linguistically defined
distinctive features. Mesgarani et al., who
base their investigation on linguistic distinctions (6), further demonstrate that features are
distinguishable by the degree of the neural
invariance they evoke, forming an order that
is remarkably in keeping with old linguistic
observations: Manner of articulation (
manifesting early in developing children) produces a neural invariance that is more prominent than that related to place of articulation
(manifesting late in children). A hierarchy
noted in 1941 for language acquisition is now
resurfacing as part of the neural sensitivity to
speech sounds (7).
But linguistic communication is based on
larger pieces than the basic building blocks of
speech. It also requires rules that create complex combinations from basic units. Linguistic combinatorics is therefore an essential part
of verbal communication, allowing it to be
flexible and efficient. Here, too, Mesgarani et
al. offer some clues. They show that sequencing processes, particularly those that determine voice onset time, tend to be more distributed in neural tissue than the rather localized distinctive features (8, 9). This suggests
that combinatorial rules that concatenate
basic elements into bigger units might depend
on larger, perhaps somewhat more widely distributed, neural chunks, than the stored representations of basic building blocks. How
distributed (and speech-specific) such processes are is not revealed by the Mesgarani et
al. study, but evidence about the neural specificity of language combinatorics at other levels of analysis does exist: Operations involved
in building complex expressions—sentences
with rich syntax and semantics—are relatively localized in parts of the left cerebral
hemisphere (and distinct from other combinatorial processes such as arithmetic), even if
the neural chunks that support them may be
as large as several cubic centimeters (10, 11).
Although the study of Mesgarani et al.
was carried out in English, the findings have
universal implications. Cross-linguistic evi-
dence for universal neural representation of
higher aspects of linguistic communication
also exists, at least to some extent (12, 13).
These results may suggest a shift in view on
brain-language relations: from earlier modal-
ity-based models (14), we moved to attempts
to identify the neural code for specific linguis-
tic units and concatenating operations. This
move carries the hope that someday, the com-
plete neural code for language will be identi-
fied, thereby making good on the promise that
linguistics be “part of psychology, ultimately
References and Notes
1. N. Mesgarani et al., Science 343, 1006 (2014);
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Studdert-Kennedy, Psychol. Rev. 74, 431 (1967).
3. N. Trubetzkoy, Principles of Phonology (Univ. of California Press, Berkeley, 1969).
4. A. M. Liberman, I. G. Mattingly, Cognition 21, 1 (1985).
5. L. Fadiga et al., in Broca’s Region, Y. Grodzinsky,
K. Amunts, Eds. (Oxford Univ. Press, New York, 2006).
6. N. Chomsky, M. Halle, The Sound Pattern of English
(Harper & Row, New York, 1969).
7. R. Jakobson, Kindersprache, Aphasie und allgemeine
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11. S. Heim et al., Front. Evol. Neurosci. 4, 4 (2012).
12. M. Makuuchi et al., Cereb. Cortex 23, 694 (2013).
13. A. D. Friederici et al., Cereb. Cortex 16, 1709 (2006).
14. N. Geschwind, Science 170, 940 (1970).
15. N. Chomsky, Knowledge of Language, Its Nature, Origin,
and Use (Praeger, New York, 1986).
Acknowledgments: Support by an Insight grant from the
Canada Social Sciences and Humanities Council (Y.G.) and by the
Canada Research Chairs (Y.G.) and by the Israel Science Foundation (I.N.).