psychological adjustment or if they primarily motivate the superficial report of one’s positive qualities.
The questions raised by this research are important because of a growing interest in using
self-report measures of happiness to inform public policy (1, 6). Our research supports those
recommending caution about promoting any
particular ideology or policy as a road to happiness (32). Research investigating self-report–based
happiness differences between nonrandomized
groups (e.g., cultures, nations, and religious groups)
may inadvertently capture differences in self-reporting styles rather than actual differences
in emotional experience. Both behavioral measures and self-reports of subjective well-being
are valuable tools, but any comprehensive assessment of subjective well-being should involve
multiple methodological approaches (6, 8). Reliance on any single methodology is likely to lead
to an oversimplified account of not only who is
happier than whom but also what it means to be
happy at all.
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The authors received no financial support for the research,
authorship, and/or publication of this article and declared no
potential conflicts of interest. We thank J. Haidt and A. Stone for
their feedback on an earlier draft of the manuscript and
R. Idrogo-Lam and J. Larsen for their assistance in data collection.
The data used in this paper are available from Open ICPSR:
Materials and Methods
4 September 2014; accepted 5 February 2015
Direct evidence for human reliance
on rainforest resources in late
Pleistocene Sri Lanka
Patrick Roberts,1 Nimal Perera,2 Oshan Wedage,3 Siran Deraniyagala,3 Jude Perera,3
Saman Eregama,3 Andrew Gledhill,4 Michael D. Petraglia,1 Julia A. Lee-Thorp1
Human occupation of tropical rainforest habitats is thought to be a mainly Holocene
phenomenon. Although archaeological and paleoenvironmental data have hinted at
pre-Holocene rainforest foraging, earlier human reliance on rainforest resources has not
been shown directly. We applied stable carbon and oxygen isotope analysis to human and
faunal tooth enamel from four late Pleistocene–to–Holocene archaeological sites in Sri
Lanka. The results show that human foragers relied primarily on rainforest resources from
at least ~20,000 years ago, with a distinct preference for semi-open rainforest and rain
forest edges. Homo sapiens’ relationship with the tropical rainforests of South Asia
is therefore long-standing, a conclusion that indicates the time-depth of anthropogenic
reliance and influence on these habitats.
The expansion of Homo sapiens beyond Africa in the late Pleistocene [125 to 12 thousand years ago (ka)] required a capac- ity to adapt successfully to a diversity of environments (1, 2). One environment in
particular, tropical rainforest, has been widely
considered an unattractive prospect for long-
term foraging because it is difficult to navigate,
lacks abundant carbohydrate and protein re-
sources, and requires significant subsistence and
technological developments for occupation to be
feasible (3, 4). Ethnographic observations of ex-
isting and historical rainforest foragers, and
those foragers’ typical nutrient intake, however,
have called this view into question (5, 6).
Furthermore, discoveries and reappraisal of early
human archaeological sites in Africa (7), South-
east Asia (8), and Melanesia (9) have associated
environmental indications from pollen, archaeo-
botanical, and archaeozoological remains with
human material to demonstrate that human
rainforest resource use may have occurred as
early as ~46 ka. The association of stone tool
assemblages with offsite pollen records for forest
conditions of unknown catchment have been
more controversially argued to show human
forest foraging back to ~200 ka in Africa (7).
However, archaeological evidence against the con-
tention that prehistoric humans avoided rain-
forest environments as long-term ecologies for
1246 13 MARCH 2015 • VOL 347 ISSUE 6227 sciencemag.org SCIENCE
1School of Archaeology, Research Laboratory for Archaeology
and the History of Art, Dyson Perrins Building, University of
Oxford, South Parks Road, Oxford OX1 3QY, UK.
2Postgraduate Institute of Archaeology, 407 Bauddhaloka
Mawatha, Colombo 00700, Sri Lanka. 3Department of
Archaeology, Sir Marcus Fernando Mawatha, Colombo,
Sri Lanka. 4Division of Geographic, Archaeological and
Environmental Sciences, University of Bradford, Bradford
BD7 1DP, UK.
*Corresponding author. E-mail: firstname.lastname@example.org