Journal of Archaeological Science 42 (2014) 273e294
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Journal of Archaeological Science
journal homepage: http://www.elsevier.com/locate/jas
More questions than answers: the Southeast Asian Lead Isotope
Project 2009e2012
Thomas Oliver Pryce a, *, Sandrine Baron a, Bérénice H.M. Bellina a, Peter S. Bellwood b,
Nigel Chang c, Pranab Chattopadhyay d, Eusebio Dizon e, Ian C. Glover f,
Elizabeth Hamilton g, Charles F.W. Higham h, Aung Aung Kyaw i, Vin Laychour j,
Surapol Natapintu k, Viet Nguyen l, Jean-Pierre Pautreau a, Ernst Pernicka m,
Vincent C. Pigott g, Mark Pollard n, Christophe Pottier o, Andreas Reinecke p,
Thongsa Sayavongkhamdy q, Viengkeo Souksavatdy q, Joyce White g
a
Centre National de la Recherche Scientifique, France
b
Australian National University, Australia
c
James Cook University, Australia
d
Centre for Archaeological Studies and Training, Kolkata, India
e
Archaeology Division, National Museum of the Philippines, Manila, Philippines
f
University College London, UK
g
University of Pennsylvania Museum, United States
h
University of Otago, New Zealand
i
Mandalay Department of Archaeology, Myanmar
j
Ministry of Culture and Fine Arts, Cambodia
k
Silpakorn University, Thailand
l
Centre for Southeast Asian Prehistory, Viet Nam
m
Curt Engelhorn Centre for Archaeometry, Germany
n
Oxford University, UK
o
Ecole française d’Extrême-Orient, France
p
Deutsches Archäologisches Institut, Germany
q
Ministry of Information and Culture, Lao Democratic People’s Republic
a r t i c l e i n f o a b s t r a c t
Article history: As in most parts of the world, ancient Southeast Asian metal production and exchange has been accorded
Received 11 February 2013 great importance as a cultural and technological development with far-reaching economic and political
Received in revised form impacts. Here we present the results of the Southeast Asian Lead Isotope Project’s 2009e2012 research
26 August 2013
campaign, a systematic effort to empirically reconstruct regional metal exchange networks and their
Accepted 31 August 2013
attendant social interactions c. 1000 BCec. 500 AD. The study’s morpho-stylistic, technological,
elemental and isotopic datasets cover early metal production (minerals and slag) and consumption (Cu,
Keywords:
CueSn, CuePb, CueSnePb alloys) assemblages from thirty sites in eight countries. These data have either
Southeast Asia
Copper-base metal exchange
identified or substantiated long-range maritime and terrestrial exchange networks connecting Han China
Lead isotope and Mauryan India with most of continental Southeast Asia. The variety and intensity of the attested
Eurasian technology transmission metal exchange behaviours hints at a dynamic and innovative 1st millennium BC regional economy and
the vibrant exchange of cultural practices amongst populations separated by thousands of kilometres.
Important too is the provision of indirect evidence for intra-regional economic integration between the
Southeast Asia’s metal-consuming lowland majorities and metal-producing upland minorities. Southeast
Asia has a comparable surface area and present day population to Europe, and thus our efforts represent
only the beginning for diachronic and multi-scalar metal exchange research. However, archae-
ometallurgical methodologies have the potential to greatly improve our understanding of Southeast
Asia’s vast cultural diversity and interconnectedness. With this paper we lay the framework for such an
endeavour and, we hope, define the major questions for its next phase.
Ó 2013 Elsevier Ltd. All rights reserved.
* Corresponding author.
E-mail address: opryce@gmail.com (T.O. Pryce).
0305-4403/$ e see front matter Ó 2013 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.jas.2013.08.024
,274 T.O. Pryce et al. / Journal of Archaeological Science 42 (2014) 273e294
1. Introduction a rudimentary and probably experimental mode of production to
one standardised and intensive, with the 4th/3rd c. BC as the likely
As in many parts of the world, the origin/s of Southeast Asian switching point. Similar analysis of the Phu Lon industrial assem-
metal technologies have been accorded great significance by some blage also indicates the crucible-based reduction of local copper
regional archaeologists because of traditionally assumed correla- minerals, plus the processing of necessarily imported tin minerals
tions between early copper-base metallurgy and the increasing or metal (Pryce et al., 2011b; Vernon, 1996e1997). As descriptions
economic, political, and social complexity that can signal or of fieldwork at Phu Lon and Khao Wong Prachan are available
accompany state formation (e.g. Childe, 1936; Thornton and elsewhere it suffices to say here that the sites are unusually large
Roberts, 2009). Global interest in Southeast Asian metallurgy was (multi-hectare) and the quantity of industrial waste certainly rep-
heavily stimulated in the 1960s and 1970s with claims for 4th/3rd resents a considerable output of raw copper during their extended
millennium BC metal-bearing contexts at sites in northeast period of activity.
Thailand (Bayard, 1972; Gorman and Charoenwongsa, 1976; Until very recently all that Southeast Asian archaeologists knew
Solheim, 1968). As these dates were, at the time, earlier than of regional copper mining and smelting came from the in-
those in Eastern Asia and comparable to those of Western Asia, vestigations of the Thailand Archaeometallurgy Project at Phu Lon
suggestions naturally followed of an indigenous Southeast Asian and Khao Wong Prachan. Although prehistoric primary copper
invention of copper-base metallurgy (reviewed in White, 2008). production has long been suspected in northern Vietnam it con-
This very early chronology was doubted by some (Higham, 1975; tinues to be undemonstrated, and thus the known Thai sites came
Muhly, 1981), and subsequently overturned during the 1980s and to be regarded as the Southeast Asian copper sources in regional
1990s (Spriggs, 1996e1997, White, 1986), and no regional scholars archaeology textbooks (Higham, 1989, 1996, 2002) e an unlikely
now support Thailand being an independent centre of metallur- scenario given the region’s mineral wealth (e.g. Smith, 2012).
gical invention. Therefore, in 2009 the lead author founded the Southeast Asian
With early Southeast Asian metallurgy now fitting broadly into Lead Isotope Project (SEALIP) with the objective of investigating
the 2nd millennium BC (see Section 4.7), within a perceived West to diachronic and multi-scalar relationships amongst culturally and
East chronometric gradient across Eurasia (Roberts et al., 2009), it is ecologically diverse prehistoric populations, including those in
most probable that regional metal technologies have a foreign neighbouring East and South Asia, using copper-base and lead
origin. The possibility of cultural interaction with South Asian metal exchange networks as social interaction proxies. SEALIP had
metal-using societies to the west remains difficult to investigate the benefit of decades of comparable research on highly complex
due to the extreme dearth of material culture data linking the two metal exchange systems in other parts of the world (e.g. Gale, 2001;
areas prior to the mid-1st millennium BC. However, the over- Pollard, 2009), and therefore the programme commenced with the
whelming amount of evidence linking 2nd millennium BC South- null hypothesis that all the copper/bronze consumed in Southeast
east Asia to the north suggests a technology source in or via the Asia was produced at Phu Lon and the Khao Wong Prachan. An
communities of the present-day Peoples’ Republic of China alternative hypothesis was that there would be numerous primary
(Higham, 1996; White, 1988). The debate on the origins of South- productions systems with complex exchange and recycling pools.
east Asian metallurgy has advanced significantly in recent years but While the 2009 conference presentation (Sayavongkhamdy
has always involved high stakes given the ramifications of varying et al., 2009) of a newly discovered prehistoric copper production
models of the ‘when, where, who, and why’ of long-range social complex at Xepon in central Laos showed that the null hypothesis
interactions for interpreting major cultural changes at the regional should be rejected (105.991 E, 16.958 N; Fig. 1: #23 & 28, Pryce
Neolithic to Bronze Age transition (Ciarla, 2007; Higham et al., et al., 2011b), the SEALIP data presented here allow us to demon-
2011a; Higham and Higham, 2009; Higham et al., 2011b; Pigott strate just how complicated early Southeast Asian metal exchange
and Ciarla, 2007; White, 2008; White and Hamilton, 2009). In and the attendant social relations must have been. SEALIP was
this paper we present data pertinent to the origins debate but are engaged with the firm understanding that firstly, as an additive
primarily united in our desire to move the discussion onto a technology, geochemical patterning in metal artefacts can be very
diachronic basis to understand the long-term impact and role of heavily influenced by mixing (multiple sources of the same metal,
copper-base metal production, exchange, and consumption in e.g. copper plus copper), alloying (multiple sources of different
Southeast Asian history. metals, e.g. copper plus lead), and recycling (repeated cycles of
In 1983, Vincent C. Pigott and Surapol Natapintu initiated the mixing and alloying); and secondly, that an artefact can never truly
Thailand Archaeometallurgy Project to investigate the local and be ‘provenanced’ and that a more neutral interpretation of an ar-
regional economic, political, and social factors surrounding the tefact’s lead isotope signature would be whether it was ‘consistent’
mining and smelting of copper at two industrial loci in northeast or not with any of the known sources; implying that other matches
and central Thailand (Pigott and Natapintu, 1988). The first of these, are in theory possible (Bray and Pollard, 2012; Gale, 2001; Pollard,
Phu Lon, consists of two adjacent ore bodies beside the River 2009; Pryce et al., 2011b).
Mekong (102.140 E, 18.204 N; Fig. 1: #19) with a complex of Detailed geological data pertaining to metallogenic deposits are
mining shafts and beneficiation/smelting areas radiocarbon dated difficult if not impossible to come by in Southeast Asia, due either to
to the 1st millennium BC and early 1st millennium AD (Pigott et al., their nonexistence or commercial sensitivity. Therefore, to fulfil the
1992). The second, Khao Wong Prachan, at the southwest extremity terms of the ‘Provenance Hypothesis’, “to establish that variation
of the Loei-Petchabun Volcanic Belt (100.711 E, 14.963 N; Fig. 1: between sources is greater than that within them” (Wilson and
#17 & 18), comprises mining, smelting, and settlement sites dating Pollard, 2001), SEALIP commenced by characterising the lead
from the terminal-2nd millennium BC to the mid-1st millennium isotope signatures of prehistoric copper smelting slag from the long
AD (Pigott et al., 1997). Technological analysis of excavated ceramic, known Thai production sites, Non Pa Wai, Nil Kham Haeng, and Phu
mineral, and slag assemblages from the Khao Wong Prachan Lon, as well as from the new Lao sites around Xepon, Puen Baolo
smelting sites of Non Pa Wai and Nil Kham Haeng reconstructed a (preliminary 14C date 2261 29 cal BP on charcoal in mining shaft/
crucible-based forced-blast smelting technique using copper car- pit, WK-33832) and Thong Na Nguak (preliminary 14C date
bonates and sulphides from nearby Khao Thab Khwai (Pryce et al., 2126 28 cal BP on charcoal in burial jar, WK-32284). These data
2010). Whilst this technological continuity is indicative of an un- demonstrate that we can clearly distinguish geographically discrete
interrupted local occupation, the smelting process did evolve from human mineral exploitation (Pryce et al., 2011b). To these primary
, T.O. Pryce et al. / Journal of Archaeological Science 42 (2014) 273e294 275
copper production datasets we here add slag analyses from Làng 2. Methodology
Nhón in Vietnam’s northern Yên Bái province (Fig. 1: #14). This area
has many bronze-bearing prehistoric sites but the Làng Nhón slags In attempting to establish a baseline for Southeast Asian metal
tested were associated with nearby mine shafts that local tradition exchange research, a spatially and chronologically wide selection of
holds are only two hundred years old (Nguyễn2004). Nevertheless, artefacts was desirable to enable preliminary interpretations and
provided that minerals from the same geologically discrete deposit the formulation of new hypotheses. Cost and time were, as always,
were used the resulting lead isotope signature will be the same as factors, but as micro-destructive analysis of regional metal artefacts
that for any copper produced millennia ago, with only the ancient has been relatively infrequent, curatorial concerns and sampling
production sites themselves awaiting detection. permission were often an issue. Pragmatism thus played a large role
The new data (N ¼ 130þ) presented in this paper concern the in SEALIP’s sampling strategy. As the quality of Southeast Asian site
exchange and consumption of copper/bronze artefacts from 30 chronologies has improved greatly in recent years (Higham and
sites across Mainland and Island Southeast Asia (Fig. 1, Table 1). Higham, 2009; White, 2008), most of the assemblages sampled
About a dozen artefacts from the Thai sites, Ban Chiang, Ban Non were from fresh excavations. When museum access was possible
Wat, and Non Pa Wai are pertinent to the regional transition from reliable context was accorded priority. Given sufficient material, at
the Neolithic to Bronze Age. An artefact from Lou Island in the least ten samples would be taken from each site, and more for a
Admiralty Archipelago of Papua New Guinea and another from multi-period site. In each assemblage a range of artefact types e e.g.
Sabatang Island in the Batanes Archipelago of the Philippines offer ornaments, tools, and weapons e and typologies e e.g. axe mor-
insight on the possibility of production in Island Southeast Asia. phologies e would be selected where possible. Each artefact was
However, the remainder and majority (N ¼ 120þ) of the artefacts examined in hand specimen and photographed before cutting with
belong to the Mainland Iron Age period c. 500 BCec. 500 AD, which a 0.2 mm jeweller’s saw blade. Each sample was given an identi-
seems to have exhibited a vast increase in metal consumption for fication number including country and site codes. Also recorded
ornaments, tools, and weapons, recovered principally from burial were contextual details, and, as environmental contamination can
contexts (e.g. Higham and Higham, 2009). This period also sees the have an impact upon confidence in the resulting data, the visible
fluorescence of maritime exchange networks in exotic goods and degree of corrosion seen in the cut samples: shiny extant metal
commodities in the South China Sea and Bay of Bengal (e.g. ‘low’, black copper oxides ‘medium’, and green copper hydroxides
Dussubieux and Gratuze, 2010; Hung et al., 2007; Murillo-Barroso ‘high’ (Table 1). SEALIP is able to provide typological, micrographic,
et al., 2010), and ultimately extending from the Classical Mediter- elemental, and isotopic data for most of the artefacts, and, where
ranean to the Western Pacific (Bellina and Glover, 2004). Metal available, has attempted to make use of legacy elemental datasets.
typologies of particular interest include: wrought and incised high- This policy accounts for some of the methodological heterogeneity
tin bronze bowls thought to be from India; cast decorative copper- seen in Table 2 but we see no problem between e.g. XRF and EPMA
base drums thought to be from the northern Vietnamese Ðông Sơn for identifying alloy types at least. Most of the samples were ana-
culture; and cast leaded high-tin bronze mirrors and copper-base lysed at the Curt-Engelhorn Centre for Archaeometry (CEZA) in
bowls thought to be from Western Han China (Fig. 3, see e.g. Mannheim (Germany); using energy-dispersive X-ray fluorescence
Calò, 2009; Heger, 1902; Murillo-Barroso et al., 2010; Pryce et al., spectrometry for major elements, Laser Ablation Inductively-
2008; Rajpitak and Seeley, 1979; Yamagata et al., 2001). Coupled-Plasma Mass-Spectrometry for trace elements, and all
Fig. 1. Map of Southeast Asia and neighbouring regions, detailing the site assemblages sampled. White markers denote copper production sites Phu Lon, Khao Wong Prachan (Nil
Kham Haeng and Non Pa Wai) and Xepon (Puen Baolo and Thong Na Nguak).
