Field Museum of Natural History
From the SelectedWorks of Gary M. Feinman
2012
Complexities of collapse: the evidence of Maya
obsidian as revealed by social network graphical
analysis
Gary M. Feinman, Field Museum of Natural History
Mark Golitko
James Meierhoff
Patrick Ryan Williams
Available at: http://works.bepress.com/gary_feinman/2/
Complexities of collapse: the evidence of
Maya obsidian as revealed by social
network graphical analysis
The authors use a social network analysis
to map the changing patterns of obsidian
supply among the Maya during the period of
Classic to Postclassic transition. The quantity
of obsidian received from different sources
was calculated for 121 sites and the network
analysis showed how the relative abundance
of material from different sources shifted
over time. A shift from inland to coastal
supply routes appears to have contributed
to the collapse of inland Maya urban
centres. The methods employed clearly have
a high potential to reveal changing economic
networks in cases of major societal transitions
elsewhere in the world.
Mexico
Guatemala
Honduras
El Salvador
Nicaragua
Keywords: Mesoamerica, Maya, Classic, Postclassic, third–fifteenth century AD, obsidian,
social network graphical analysis, urbanism, systems collapse
Supplementary material can be found online at: http://www.antiquity.ac.uk/projgall/
golitko332/.
Introduction
Explanations for the florescence and subsequent decline of large urban societies have
generated persistent archaeological interest worldwide, for instance the collapse of Minoan
urban centres on Crete during the Bronze Age, the decline of urbanism and political
integration in the post-Roman period in Europe, and the rise and fall of major urban
centres such as Teotihuacan in central Mexico. The decline of urban centres and the
depopulation of particular regions in eastern Mesoamerica beginning around AD 800,
sometimes termed the Classic Maya ‘collapse’, has served as an important case for more
1
2
Department of Anthropology, Field Museum of Natural History, 1400 South Lakeshore Drive, Chicago,
IL 60605, USA (Author for correspondence, email: [email protected])
Department of Anthropology, University of Illinois at Chicago, 1007 West Harrison Street, Chicago, IL 60607,
USA
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Complexities of collapse
general models of the rise and decline of urbanism and political integration in the past
(e.g. Tainter 1988) and continues to generate new debate (e.g. Webster 2002; Aimers
2007). Models of Maya political reorganisation, as for other global regions, propose causes
both environmental (drought, catastrophic volcanic eruptions, hurricanes, anthropogenic
environmental degradation) and socio-economic (warfare and invasion, peasant revolt,
overpopulation, changing exchange routes) (Webster 2002; Demarest 2004; Chase & Chase
2006; Aimers 2007).
The role of changing trade networks has also been recognised by Maya scholars as a factor
that contributed to the transition that characterised the Terminal Classic. Rathje (1973)
argued that sites in the Classic ‘core’ (southern lowlands) were out-competed by settlements
on the periphery (for example in the northern Yucatán and eastern Maya area), leading
to inland collapse. Webb (1973), in contrast, argued that Maya polities were secondary
states that arose in response to an influx of Mexican goods (including obsidian), and that
emergence of commercial trade at the end of the Classic period caused a rapid loss of
economic viability at inland centres.
Here we examine pan-regional exchange networks by applying graphical techniques from
social network analysis (SNA) to chronicle variations in the supply of obsidian to inland and
coastal centres. The resulting trends allow us to argue that increasing reliance on coastal trade
networks played a key role in the decline of Maya settlements in the western lowlands and
contributed to the fluorescence of coastal centres during the Terminal and Postclassic periods.
Maya obsidian exchange
Obsidian is an ideal material to use in reconstructing ancient trade relations. The chemical
composition of obsidian recovered in archaeological contexts allows for the original source to
be determined with high confidence, provided the regional sources are well understood. This
is particularly the case in Mesoamerica, where over four decades of research have resulted
in a comprehensive knowledge of the distinctive chemical signatures. In the Maya area of
Mexico, Belize, Guatemala, Honduras and El Salvador, obsidian was primarily obtained
from three sources located in the highlands of Guatemala, San Martı́n Jilotepeque (also
referred to as Rı́o Pixcaya), El Chayal and Ixtepeque (Figure 1).
Our regional analysis draws on earlier compilations, particularly Braswell’s (2003)
synthesis of Terminal (∼AD 800–1050), Early Postclassic (∼AD 1050–1300) and Late
Postclassic (∼AD 1300–1520) obsidian for the broader Mesoamerican region. For the
Classic period (∼AD 250/300–800), data were drawn from earlier summaries as well
as primary sources (see supplemental digital material for a complete listing). We have also
included new sourcing data (see online supplement) for 70 pieces of obsidian from the Classic
and Terminal Classic settlement of San José, Belize, excavated by Field Museum curator
J. Eric Thompson during the early 1930s. San José is geographically situated between
settlements in the Petén Lakes region to the west and Chetumal Bay to the north-east,
both important nodes on routes of transport for obsidian and other goods at contact (e.g.
Hammond 1972). Although most of the data included in our analysis were collected by
chemical analysis (by XRF, INAA or ICP-MS), we have included visually sourced materials
published by other scholars (see Braswell et al. 2000).
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Figure 1. Map of eastern Mesoamerica with study sites indicated and location in Mesoamerica coded by zone. Inset: obsidian
sources in Mesoamerica displayed as black dots. The sites are listed by number in the online supplement.
In total, obsidian assemblages from 121 archaeological sites were analysed, including 50
that have components dating to the Classic period, 47 to the Terminal Classic, 19 to the
Early Postclassic, and 44 to the Late Postclassic. Braswell combined all non-major sources
from Guatemala and Honduras into an ‘other’ category; we have recoded all data in the
same way and, for ease of viewing and analysis, pooled all central Mexican sources into a
single category. The chances of identifying minority obsidian types in an assemblage decline
with decreasing sample size (McKillop 1996), and as such we removed from analysis all
sites with less than ten analysed pieces. For the Classic period, we included those assemblages
with eight or more analysed pieces so as to include the San José assemblage. For visual display
purposes and to assist in the geographical positioning of sites, all data points have been coded
by regional ‘zone’ after Adams and Culbert (1977) (see Figure 1).
Social network analysis
SNA was developed in the social sciences to examine the functioning of active social
networks (e.g. friendship networks, corporations, government or scientific collaboration
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networks) in which all network ties can be quantified (Hage & Harary 1991; Newman
2001; Hanneman & Riddle 2005; Borgatti et al. 2009). In archaeology it has proved useful
as a means of ordering data, even where all network actors and connections between them
cannot be comprehensively quantified. SNA techniques have, for instance, been utilised to
study regional patterning in ceramic style (Cochrane & Lipo 2010), relationships between
geography and the patterning of genes, language and material culture (Terrell 2010a, 2010b),
the development of ancient centres and states (Knappett et al. 2008; Mizoguchi 2009) and
obsidian exchange networks (Phillips 2011). SNA has been previously applied to Maya
Classic and Terminal Classic period political organisation by Munson and Macri (2009), who
used measures of centrality derived from glyphic evidence to examine the degree to which
Maya political networks were centralised during the Classic and Terminal Classic periods.
SNA is performed on sets of relational data consisting of ‘nodes’ (sites, individuals, objects,
etc. . .) connected by ties or ‘edges’ (friendship ties, trade connections, etc. . .) (Hanneman
& Riddle 2005; Mizoguchi 2009; Terrell 2010a). Although edges typically represent the
presence or absence of documented connections between nodes, as in the approach to
Maya glyphic evidence used by Munson and Macri, measures of similarity between node
characteristics (e.g. archaeological assemblage data such as frequency of ceramic attributes,
presence or absence of classes of material or frequency of raw material source types) also
may be used to determine the strength of connection.
Here, we employ SNA on matrices of pair-wise Brainerd-Robinson coefficients of
similarity between frequencies of source types for Maya obsidian assemblages spanning
the Classic to Late Postclassic periods (Cowgill 1990). All analysis was performed using the
network software packages Ucinet 6.289 and Netdraw 2.097 (Borgatti 2002; Borgatti et al.
2002). We utilise a method known as ‘spring embedding’ to position nodes—as DeJordy et
al. (2007: 247) explain,
the (spring-embedding) algorithm works by modeling a network of social ties as a
system of springs stretched between posts. If a pair of posts with a spring between
them is placed too closely together, the spring is compressed and tries to push the
posts apart (a property called node repulsion). If the posts are too far apart, the spring
is stretched and tries to pull the posts together (a property called node-attraction).
The density of linkages utilised is generated by what is known as a ‘mini-max’ graph
(Cochrane & Lipo 2010), one in which nodes are connected by the minimum number of
edges necessary to connect the maximum number of nodes (typically all nodes, although
some may be excluded if data quality or sample size is inadequate) into a single network.
Whereas techniques such as multidimensional scaling, principal components analysis and
contour plots display major trends in data at the expense of more ‘local’ variability, springembedded network graphs maintain an accurate representation of all nodal relationships
across different scales of similarity (DeJordy et al. 2007).
Additionally, we utilise the ‘factions’ method (Hanneman & Riddle 2005: 189–92) to
further explore ‘neighbourhood’ structure in Maya obsidian networks—clusters of nodes
that are substantially more connected to each other than they are to other network nodes. The
goodness of fit for different numbers of factions can be numerically assessed to find the most
natural partitioning of nodes. Factions or groupings in this case do not imply an underlying
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assumption of political connectedness or acquisition of obsidian through identical and
exclusive network connections; SNA network graphs instead represent a flexible means
of examining assemblage similarity against which varying hypotheses can be compared to
explain aspects of network structure.
Networks were constructed for four periods: the Classic (Figures 2 & 3), the Terminal
Classic (Figures 4 & 5), the Early Postclassic (Figures 7 & 8) and the Late Postclassic (Figures
9 & 10). On these figures, the geographical affinities of sites are shown by a symbol (as in
Figure 1) and the groups having a similar pattern of supply (factions) by a colour. The data
used in the analysis will be found in the online supplement.
Results by period
Classic period obsidian assemblages are generally dominated by El Chayal obsidian (Figure 2), which in many parts of the lowlands replaced San Martı́n Jilotepeque obsidian,
the dominant source during the preceding Preclassic period and earlier (Nelson 1985). San
Martı́n obsidian remained in circulation, but is frequent only at sites in Soconusco and is
present in small amounts near Palenque and in northern Guatemala. Ixtepeque obsidian is
present in very high frequencies at Copán and other sites near its source but also at sites
in the vicinity of Chetumal Bay, a point of entry for goods transported along the coast
into inland waterways. Mexican obsidian, while generally infrequent during the Classic, is
present at frequencies of greater than 1 per cent only in Soconusco, Yoxiha, and several sites
in northern Guatemala. Mexican obsidian is also present at frequencies of less than 1 per
cent in western Belize and at Copán. This distribution is in accord with a reliance on inland
routes of transport in the Maya area.
The spring-embedded network mapping (Figure 3) divides the sites into three groups,
with the Soconusco sites constituting one such faction, Copán and a handful of sites along
the east coast a second, and the remaining sites making up a third faction in which El Chayal
is the predominant obsidian variety present. The Copán group, characterised in particular
by a dominance of Ixtepeque obsidian, also includes Quirigua, likewise positioned near the
Ixtepeque source, but also Ek Luum, a coastal settlement at the entrance to Chetumal Bay.
San José is more closely linked to inland sites such as Trinidad de Nosotros and Uxbenka
than to those near Chetumal Bay.
Terminal Classic
Terminal Classic obsidian assemblages (Figure 4) are distinguished by much higher
frequencies of Mexican obsidian, the distribution of which indicates the opening of a
clear northern Yucatán route. This material falls off in frequency to the south, but even
at Copán 13 per cent of all sourced obsidian derives from Mexican sources. Ucareo and
Pachuca are relatively equally represented and constitute the majority of Mexican obsidian
in the Maya region at that time, but almost all important Mexican sources are present in
lower frequencies. Although Ixtepeque obsidian is more abundant at most sites than during
the preceding Classic period, sites in the northern Yucatán generally are dominated by El
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Figure 2. Classic period (∼AD 250/300–800) obsidian frequencies. Pie charts represent assemblages analysed from individual
sites, sized on a logarithmic scale based on analysed sample size. Lines link pie charts to real geographic locations in densely
sampled areas. x = minor sources in Guatemala and Honduras which were utilised in low frequencies in the pre-Hispanic
period.
Chayal obsidian. This is particularly the case at sites farther inland, and it would appear
that obsidian from El Chayal was still moving primarily through inland networks.
Terminal Classic network mapping (Figure 5) illustrates several trends—Soconusco sites
still form an outlying group, but several new factions appeared. First, San Gervasio on
Cozumel is linked into a network faction containing Copán and other Ixtepeque-dominated
assemblages, but also a larger number of Belizean coastal and near-coastal sites are now
divided into a nearby faction also characterised by high frequencies of Ixtepeque obsidian.
This group includes San José but also sites farther west such as Tipu. There is a distinct
faction that includes the emergent northern Yucatecan centre of Chichén Itzá, its affiliated
trade port of Isla Cerritos (Andrews et al. 1989), and several other northern Yucatán sites
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Figure 3. Spring-embedded network map calculated from Brainerd-Robinson coefficients for Classic period (∼AD 250/300–
800) obsidian assemblages, with assemblages with less than eight pieces omitted. Nodes were connected at a threshold similarity
of 120, the minimum value to connect all points into a single network, and are coded by zone (shape: see legend to Figure 1)
and faction (colour: best fit achieved with three factions).
characterised in particular by high frequencies of Mexican obsidian, particularly Ucareo
and Pachuca. Most other northern Yucatán sites are most closely linked to sites in the
central Petén and highlands, including Kaminaljuyú, the centre sometimes argued to have
controlled access to the El Chayal source (Braswell 2003). The exception to this pattern is
Uxmal, which is linked most closely to Chetumal Bay sites, particularly because of the high
frequencies of Ixtepeque found there.
San José is proximate to inland settlements and centres such as Xunantunich, yet the
linkage with sites farther north-east in Belize and along the eastern Yucatán coast (such as
Colha and Wild Cane Caye) is clearly revealed.
The frequency of Ixtepeque obsidian, as both the mapping and spring-embedded network
graph illustrate, falls off as a function of distance from the eastern coast of the Yucatán
Peninsula. This can be seen on a graph (Figure 6). Frequencies of Ixtepeque obsidian
increase significantly at sites that were occupied during both the Classic and Terminal
Classic. At San José, for instance, Ixtepeque frequency increased from 13 per cent to 27 per
cent, and at sites in the central Petén Lakes region (∼150m from the coast), frequencies
of Ixtepeque obsidian similarly doubled between the Classic and Terminal Classic. At San
Juan, McKillop (1995) notes a nearly eight-fold increase in the amount of obsidian recovered
in Terminal Classic deposits, strongly suggesting that the volume of material transported
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Figure 4. Terminal Classic period (∼AD 800–1500) obsidian frequencies. All symbology is otherwise the same as Figure 2.
through coastal routes, including Ixtepeque obsidian, increased substantially, and that the
relative gain in frequency of Ixtepeque was not simply the result of erosion of inland trade
volume. Conversely, evidence for intensive curation of obsidian at lowland sites (Braswell
2003) and the declining volume recovered in the Petén Lakes region (Rice 1987) suggests
that obsidian was increasingly hard to come by through inland routes.
Early Postclassic
Although San José, or at least its central sector, was apparently abandoned sometime before
the beginning of the Early Postclassic period (EPC), many parts of eastern Mesoamerica
remained densely settled during that time, actively participating in obsidian exchange.
Examination of EPC obsidian exchange networks is constrained by the relatively small
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Figure 5. Spring-embedded network graph calculated from Brainerd-Robinson coefficients for Terminal Classic period (∼AD
800–1500) obsidian assemblages, with assemblages with less than ten analysed pieces omitted. Nodes were connected at a
threshold distance of 124, the minimum value to connect all points into a single network, and are coded by zone (shape:
see legend to Figure 1) and faction (colour: coded by majority obsidian type, best fit achieved with five factions, with the
exception of the faction containing San José).
number of sites dating to this period from which obsidian has been sourced. Yet Ixtepeque
obsidian constitutes a large percentage of most assemblages dated to this period (Figure 7).
In the central Petén Lakes region, the frequency of Ixtepeque obsidian increased again from
∼20 per cent during the Terminal Classic to nearly 60 per cent of the EPC assemblages. A
few assemblages were dominated by Mexican obsidian (principally Pachuca), most of which
are small, so this apparent feature of EPC obsidian distribution may be an artefact of sample
size. Network mapping (Figure 8) results in a two-faction structure that principally divides
sites with high frequencies of Ixtepeque obsidian in their assemblages from those with either
very high frequencies of Mexican obsidian (Isla Cerritos) or those with very high frequencies
of San Martı́n obsidian (Chuisac and Izapa). There is, however, again a coastal/inland divide
in the Ixtepeque-dominated faction; near coastal settlements (San Gervasio, Colha, Xelha
and Wild Cane Caye) are more proximate to each other and to Chihuatun, a site near
the Ixtepeque source in the eastern highlands of Guatemala, than they are to sites such as
Chan and the Petén Lakes assemblages, which are positioned closer to Izapa in the network
mapping, which continues to show that assemblage structure was influenced by distance
from coastal exchange networks.
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Figure 6. Classic (∼AD 250/300–800) and Terminal classic (∼AD 800–1050) period frequencies of Ixtepeque obsidian
by distance from the eastern coast for sites north of 16◦ N at which ten or more samples were sourced.
Late Postclassic
A distributional mapping of Late Postclassic (LPC) obsidian frequencies (Figure 9) illustrates
that the increase in frequencies of Ixtepeque obsidian evident in the Terminal Classic
continued through the LPC, so that it became the predominant variety in all analysed
assemblages except in Soconusco and at sites in the immediate vicinity of the San Martı́n
Jilotepeque source. Network mapping of the LPC assemblages (Figure 10) yielded five
factions strongly structured by geographical location. Site assemblages from Belize and the
northern Yucatán are dominated by Ixtepeque obsidian, with lesser amounts of El Chayal
and only minor amounts of Mexican obsidian. The northern Yucatán sea route through
which Mexican obsidian was transported during the Terminal Classic (and possibly EPC)
appears to have been less active at that time, although Mexican sources do appear in some
assemblages around Chetumal Bay, and they form an extreme minority component of the
assemblage at Mayapán, the primary LPC political power in the northern Yucatán (Braswell
2003; Sabloff 2007). The proximal positioning and linkage between Sarteneja, San Gervasio
and Xelha shows a continued connection between Chetumal Bay and sites along the coast
of the northern Yucatán, a network structure that also may include Mayapán.
Sites near the San Martı́n obsidian source primarily utilised that raw material and
constitute a network faction, whereas three sites closest to the El Chayal source, Chitaqtzaq,
Finca El Pilar and Aldea Chimuch, are linked into a network faction characterised by
majority El Chayal acquisition. El Chayal obsidian is present in almost all assemblages
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Figure 7. Early Postclassic period (∼AD 1050–1300) obsidian frequencies. All symbology is otherwise the same as Figure 2.
during the LPC, however, and the fall of Kaminaljuyú apparently did not entirely sever
the networks through which this material moved. Media Cuesta, located roughly between
the El Chayal and Ixtepeque sources, forms an outlier faction reflecting the relatively high
frequency of ‘unspecified’ obsidian(s) there—possibly from Honduran sources.
As in prior time periods, Soconusco assemblages form a fourth distinct faction, but
during the LPC these assemblages are particularly distinguished by very high frequencies
of Mexican obsidian, primarily from the Pico de Orizaba and Pachuca sources. Soconusco
was under the political influence of the Aztec empire (Gasco & Voorhies 1989) and/or
its associated pochteca traders during the LPC (Blanton et al. 1993: 213), the patterns of
obsidian acquisition reflecting this new political arrangement.
Discussion
The shifting exchange networks, and particularly the growing role of coastally focused
trade, provide the basis for an explanatory model that corresponds spatially and temporally
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Figure 8. Spring-embedded network map calculated from Brainerd-Robinson coefficients for Early Postclassic period (∼AD
1050–1300) obsidian assemblages, with assemblages with less than ten pieces omitted and threshold distance set to 62, the
minimum value to connect all points into a single network. Nodes are coded by zone (shape: see legend to Figure 1) and
faction (colour: coded by majority obsidian type, best fit achieved with two factions).
to political reorganisation and shifts in the geographic balance of power. Inland Maya centres
that were important nodes in Preclassic and Classic period exchange networks have revealed
the earliest evidence for decline, whereas sites near the coast in Belize, and particularly those
around Chetumal Bay (Houston & Inomata 2009: 294–310), with easy access to coastal
trade routes, are in general those that experienced least disruption prior to the Spanish
incursion.
The increasing importance of coastal supply routes has been documented for other
commodities as well. Kepecs (2004), McKillop (1996, 2004) and others have persuasively
documented the importance of salt in coastal exchange, and other important coastal products
and exotic commodities likely travelled through similar routes, including ceramics, shells and
other goods of value to the Maya. For instance at San José, almost all Ixtepeque and Mexican
obsidian identified, including a superb monolithic axe (Figure 11), was recovered from two
caches also containing important marine products such as Spondylus shells, porcupine fish
spines, and pearl (Thompson 1939). If this interpretation is correct, then the distributional
data we have compiled indicate a significant increase in the importance of coastal trade
routes and decline of inland routes beginning already during the Classic period, a trend that
continued through the Terminal and Postclassic periods, when Ixtepeque dominated the
sourced obsidian from Maya sites.
Current network approaches stress the critical role that access, centrality and connectivity
play in determining the relative political and economic success of settlements, including
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Figure 9. Late Postclassic period (∼AD 1300–1520) obsidian frequencies. All symbology is otherwise the same as Figure 2.
the elites resident there (e.g. Knappett et al. 2008; Mizoguchi 2009). Kepecs and colleagues
(1994) for instance stress the role of access to trade routes in the rise of centres such
as Chichén Itzá during the Terminal Classic. Consequently, the growing importance of
Ixtepeque obsidian and the sea trade through which it was primarily acquired may signal a
shift in the balances of power and access routes to obsidian (and other exotic goods) that
occurred from inland to coastal sites. Although obsidian was a material available to and
utilised by all segments of Maya society, it was particularly associated with elite segments of
society during the Classic period (Rice 1987). The collapse of inland networks and network
connectivity may therefore have severely impacted elite segments of Maya society, who were
by the Late Classic period increasingly reliant on network power strategies (Blanton et al.
1996; Feinman 2001), whereby access to valuable exotics (e.g. Mexican obsidian, shell,
metals), many derived from coastal and marine sources, were essential for the maintenance
of socioeconomic power and status.
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Figure 10. Spring-embedded network map calculated from Brainerd-Robinson coefficients for Late Postclassic period (∼AD
1300–1520) obsidian assemblages, with assemblages with less than ten pieces omitted and threshold distance set to 114, the
minimum value to connect all points into a single network. Nodes are coded by zone (shape: see legend to Figure 1) and
faction (colour: coded by majority obsidian type, best fit achieved with five factions).
Most archaeologists today eschew unicausal models of complex phenomena such as the
Maya collapse (e.g. Demarest et al. 2004: 565), and we do not suggest that changes in trade
routes caused political collapse. An explanation of the collapse of Maya centres resulting
solely by loss of trade route access would ignore other significant variables (Culbert 1988:
78). Our model is at present coarse-grained and addresses the collapse at the broadest level.
Intraregional differences in the relative success of particular Maya urban centres have been
noted (e.g. Pyburn 2008; Hutson et al. 2010; Braswell 2011) and Braswell (2010) argues that
political cycling in many cases occurred on a shorter time scale than fundamental changes
in economic structure. Environmental, demographic, subsistence economic, and internal
political factors certainly also played an important role in weakening the underpinnings and
legitimacy of Maya political hierarchy; warfare accompanied and in turn exacerbated the
decline (Demarest et al. 2004: 567–68). Nevertheless, our findings cast doubt on recent
arguments (e.g. Haug et al. 2003) that climatic changes alone were responsible for these
demographic declines.
Conclusion
Social network analysis graphical techniques, focused on sourced Maya obsidian
assemblages, have been utilised to examine changes in eastern Mesoamerican obsidian
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Figure 11. Monolithic axe from San José, Belize, made of Ixtepeque obsidian (photograph: John Weinstein, Field Museum,
A114855d 003).
exchange networks spanning the Classic through Late Postclassic periods (AD 200–1520),
including the site of San José, Belize. Our analysis indicates that San José initially was
connected into inland exchange networks through which El Chayal obsidian was primarily
moved. Later, during the Terminal Classic, the site inhabitants relied increasingly on
waterborne networks that followed the eastern coast of the Yucatán Peninsula, through
which Ixtepeque obsidian was principally transported. San José mirrors a broader
regional pattern that continued into the Late Postclassic, when regionalisation of obsidian
distribution and the primary presence of Ixtepeque obsidian at remaining sites in the
lowlands indicate that inland routes had largely collapsed.
Importantly, the growth of coastal trade at the expense of inland routes began prior to
the collapse of both urbanism and population in the Maya lowlands. Rather than being
the result of collapse and abandonment, the decline in the volume of inland trade may
have been an important contributing factor that led to a shift in the demographic and
political balance of power from the landlocked rainforest centres to the northern Yucatán
and eastern coastal regions. Over this period, access to critical resources and vestments
of elite authority were more readily obtained through these emerging coastal networks of
transport that moved not only obsidian but also formed the starting point and source of
important coastal goods such as salt and sea products. Although we have focused on only
one material type—obsidian—other materials that carry potential provenance information,
including jade, ceramics and chert, could also in principal be included in future SNA analysis
of Maya economic interaction to provide a multidimensional understanding of patterning
beyond that presented here. As Munson and Macri (2009) have similarly demonstrated, a
network approach provides useful methodological and theoretical tools for examining shifts
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in Maya political, social and economic structure over time, opening a new path of inquiry
into the factors that contributed to the relative success of different urban centres and political
formations over time in eastern Mesoamerica as well as other regions of the world.
Acknowledgements
We would like to thank Jeffrey Buechler, Linda Nicholas and John Edward Terrell for comments on earlier drafts
of this paper. Marilyn Masson provided access to unpublished data for which we are grateful. The equipment at
the Field Museum Elemental Analysis Facility utilised to analyse the obsidian from San José (project EAF004)
was acquired with grants from the National Science Foundation (BCS-0320903), The Museum’s Anthropology
Alliance and Grainger Foundation Fund for Scientific Research, and an anonymous donation. All remaining
errors are the sole responsibility of the authors.
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Received: 20 July 2011; Accepted: 7 October 2011; Revised: 24 October 2011
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