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Brief communication Diachronic investigation of linear enamel hypoplasia in prehistoric skeletal samples from Trentino Italy.

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AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 119:283–287 (2002)
Brief Communication: Diachronic Investigation of Linear
Enamel Hypoplasia in Prehistoric Skeletal Samples From
Trentino, Italy
Andrea Cucina*
Department of Anthropology, University of Missouri-Columbia, Columbia, Missouri 65211, and Department of
Human and Animal Biology, University of Rome “La Sapienza,” 00185 Rome, Italy
KEY WORDS
environment
enamel hypoplasia; Neolithic; Copper Age; Early Bronze Age; stress; Alpine
ABSTRACT
Linear enamel hypoplasia was scored on
Neolithic, Copper Age, and Early Bronze Age samples
from the Trentino region, Italy, in order to compare the
extent of growth disruption in different biocultural subsistence systems (foragers with little agriculture, to agriculturists and agropastoralists). The Early Bronze Age
sample shows a higher frequency of enamel defects and an
earlier chronological onset than the early Neolithic sample. The higher frequency of defects in the Bronze Age
sample could be linked to less diversified nutrition and,
because of increased sedentism, a higher risk of disease.
Am J Phys Anthropol 119:283–287, 2002.
Skeletal markers of physiological disruption are
biological markers that help us understand stressful
processes. Linear enamel hypoplasia (LEH), a frequently used parameter in anthropological investigations, appears as macroscopic transverse areas of
depression in the enamel as a consequence of the
ameloblasts’ nonspecific response to physiological
stress (Sarnat and Schour, 1941; Goodman and
Rose, 1990). Unlike bony tissue, tooth enamel does
not undergo remodeling after being laid down; thus,
any event that is strong enough to slow down the
ameloblasts’ activity and reduce the amount of
enamel matrix during crown formation is permanently recorded (Kreshover, 1960; Goodman and
Rose, 1990). The severity of stressful events varies
according to several biological and cultural factors.
Among them, technological innovations and change
in subsistence patterns affect responses to environmental pressure (Goodman et al., 1980; Goodman
and Rose, 1991).
In Trentino, one of Italy’s northeastern Alpine
regions, differential exploitation of the environment
and changes in subsistence strategies to suit the
needs of past populations are evident. The Alpine
ecosystem has been utilized in a variety of ways
through time in order to accommodate the prevailing lifestyle and economy (Bagolini et al., 1973;
Riedel, 1994).
Archaeological excavations in Trentino have unearthed human skeletal remains from several chronological periods, encompassing the Late Neolithic
(ca. 3000 –2500 BC), the Copper Age (2500 –1800
BC), and the Early Bronze Age (1800 –1550 BC)
(Barfield, 1971). Despite their small sizes, the samples provide insight into the different strategies of
environmental exploitation and subsistence patterns in the region through time. Neolithic cultures
based their subsistence on hunting and husbandry
(Uerpmann, 1976; Pedrotti and Demetz, 1997). Agriculture, though present, does not appear as a primary source of nutrients. Hunting decreased over
time, and during the Copper Age animal exploitation leaned toward pastoralism and use of animals’
secondary products (Riedel, 1994). With the invention of the animal-towed plow, agriculture and pastoralism became the major source of food (Bagolini
et al., 1988).
The present study focuses on hypoplastic enamel
defects and their age of occurrence in skeletal samples from Trentino, Italy. It represents one further
step in an ongoing investigation into lifestyle and
living conditions of prehistoric populations in the
area (Cucina et al., 1999). This paper describes the
©
2002 WILEY-LISS, INC.
©
2002 Wiley-Liss, Inc.
Grant sponsor: Museo Tridentino di Scienze Naturali; Grant sponsor: C.N.R. Progetto Finalizzato Beni Culturali; Grant numbers:
96.01106.36, 97.00623.PF36; Grant sponsor: COFIN 97.
*Correspondence to: Dr. Andrea Cucina, Department of Anthropology, University of Missouri-Columbia, 107 Swallow Hall, Columbia,
MO 65211. E-mail: acucina@yahoo.com
Received 7 August 2001; accepted 14 May 2002.
DOI 10.1002/ajpa.10135
Published online in Wiley InterScience (www.interscience.wiley.
com).
284
A. CUCINA
TABLE 1. List of sites and number of individuals forming the
three groups
Site
Neolithic
(3000–2500 BC)
Copper Age
(2500–1800 BC)
Early Bronze Age
(1800–1550 BC)
1
Solteri A
Dos Trento
La Vela
Appiano
Paludei di Volano
Nogarole II
Madonna Bianca
Moletta Patone
Romagnano
Nogarole III
Solteri
Vezzano
Number of
individuals
1
2
9
3
1
1
6
MNI1 10 adults and
8 subadults
14
2
10
3
MNI, minimum number of individuals.
occurrence of LEH in the Trentino area in terms of
changing biocultural dynamics, and will contribute
an ecological perspective to future investigations of
skeletal pathological conditions.
MATERIALS AND METHODS
The Neolithic (NEO), Copper Age (CA), and Early
Bronze Age (EBA) samples analyzed are listed in
Table 1. Coeval specimens, coming from several
small sites, were pooled in order to maximize sample
sizes. The NEO sample consists of 12 individuals.
The CA sample is represented by 11 individuals,
plus loose teeth from the site of Moletta Patone that
represent a minimum number of 10 adults and 8
subadults. A total of 29 individuals constitutes the
EBA group.
The presence or absence of linear enamel hypoplasia was scored on all available permanent teeth that
had at least half of the crown present. Each tooth
was examined under a tangential light spot, both by
visual inspection and with the help of a ⫻4 magnifier. Then, number of defects per tooth and their
position on the crown were recorded on anterior
teeth only in light of their higher susceptibility to
stress (Cutress and Suckling, 1982; Goodman and
Armelagos, 1985; Goodman et al., 1987). For this
undertaking, only teeth with at least two thirds of
their crown were considered. Nonetheless, a few
teeth were further excluded due to occlusal wear,
which was not a major problem in these populations.
To avoid double counting, the tooth showing more
defects was used when both antimeres were present.
Although two different categories of defects (slight
and severe) were initially recognized following Corruccini et al. (1985) and Blakey et al. (1994), due to
small sample size, all defects were considered regardless of their severity.
The position of enamel hypoplasia on the crown
surface was located by measuring the distances between the cemento-enamel junction (CEJ) and the
upper and lower limits of each groove, using a thinpoint digital Mitutoyo sliding caliper. Chronological
age at occurrence was determined based on the
Trentino population-specific mean height of the
crown (Hodges and Wilkinson, 1990; Cucina and
Iscan, 1997) and the development chart in Reid and
Dean (2000). The chronological age distribution of
defects was assigned after analyzing all the anterior
teeth of each individual. In order to avoid double
counting, any age interval overlapping between different teeth from the same individual was included
only once. The resulting age distribution must be
considered just an estimate, for it cannot account for
the actual age of formation of each tooth crown, the
within-group variability, and the original crown
height in the cases of even slight occlusal wear
(Goodman and Song, 1999). The choice to use the
developmental chart of Reid and Dean (2000) for
crown development was driven by the need to use a
more updated, precise, and accurate standard than
those previously used, and the need to use one developed on a population geographically close to our
Italian sample. Currently, no such accurate standards are available for Italian populations. Histological techniques such as counting the cross striations
within the enamel (Fitzgerald and Rose, 2000) could
not be applied because they require invasive sectioning of the teeth that was not allowed. Also, the
sample-specific count of perikymatas (Fitzgerald
and Rose, 2000) was not performed because of the
partly worn teeth and the unknown hidden enamel
formation time that still would have required application of the chart by Reid and Dean (2000).
RESULTS
Number and frequencies of enamel defects per
type of tooth in the three samples are listed in Table
2. Lower frequencies occur in the earlier sample,
while the EBA group shows higher values with minor differences from CA. Fisher’s exact test was
performed for each tooth type between NEO-CA and
NEO-EBA, and showed that differences were not
statistically significant. When all of the tooth types
are gathered into anterior (incisors and canine) and
posterior (premolar and molars) groups separately
for the upper and lower dentition, Fisher’s test and
the chi-square test provide more significant results
(Table 3). The increased occurrence of enamel hypoplasia in CA and EBA is also emphasized when the
mean number of defects calculated on the two most
representative teeth for LEH (i.e., the upper central
incisor and lower canine) is considered (Goodman
and Armelagos, 1985). In the incisors, mean values
range between 1.3 defects in NEO to 2.2 in CA, with
EBA evidencing 2.0 defects, while in the canines
they range between 1.2 defects in NEO to 3.4 in
EBA, with CA showing 2.6 defects. Differences are
noteworthy, although a t-test did not provide statistically significant results.
The chronological distribution of defects according
to age class is shown in Figure 1. Each group tends
to show major increases in the classes around the
center of the age range (approximately between 2.5–
4.5 years). Notable differences occur in the earlier
285
ENAMEL HYPOPLASIA IN PREHISTORIC TRENTINO
TABLE 2. Number of teeth affected by linear enamel hypoplasia, number of teeth present, and frequency of LEH, per type of tooth
Neolithic
Maxilla
I1
I2
C
P3
P4
M1
M2
M3
Mandible
I1
I2
C
P3
P4
M1
M2
M3
Copper Age
Early Bronze Age
Teeth affected
Teeth present
%
Teeth affected
Teeth present
%
Teeth affected
Teeth present
%
4
6
4
4
2
0
2
1
6
7
6
6
6
7
5
4
66.7
85.7
66.7
66.7
33.3
0.0
40.0
25.0
8
9
18
7
5
4
3
2
10
11
21
10
13
8
8
5
80.0
81.8
85.7
70.0
38.5
50.0
37.5
40.0
9
8
8
7
4
6
3
4
10
11
9
9
10
12
6
8
90.0
72.7
88.9
77.8
40.0
50.0
50.0
50.0
3
4
4
3
4
5
2
0
6
6
6
7
7
9
7
1
50.0
66.7
66.7
42.9
57.1
55.6
28.6
0.0
9
16
13
5
11
4
4
1
14
18
14
15
17
9
10
3
64.3
88.9
92.9
33.3
64.7
44.4
40.0
33.3
5
7
11
12
5
7
2
3
6
10
13
15
6
13
4
4
83.3
70.0
84.6
80.0
83.3
53.8
50.0
75.0
TABLE 3. P values from Fisher’s exact test and from
chi-square test between Neolithic, Copper Age,
and Early Bronze Age samples1
Fisher’s exact test
Anterior-maxilla
Posterior-maxilla
Anterior-mandible
Posterior-mandible
NEO-CA
NEO-EBA
CA-EBA
Chisquare2
0.49
0.22
0.10
1.00
0.06
0.09
0.19
0.053
1.00
0.67
0.76
0.033
0.07
0.20
0.17
0.043
1
Teeth were gathered into anterior (incisors and canines) and
posterior (premolars and molars) groups, respectively, for maxilla
and mandible.
2
Chi-square test was run on the three samples together (df ⫽ 2).
3
Difference significant a 95% level, P ⬍ 0.05.
classes from 1.0 to 2.5–3.0 years, where the NEO
population, relative to the others, is minimally represented or not represented at all. In particular, the
Bronze Age group stands out for its early onset of
lesions.
DISCUSSION
The results of the investigation of hypoplastic defects in the three prehistoric groups from the Alpine
region of Trentino, Italy, show an increased frequency of enamel disruption from the earlier (NEO)
to the later (EBA) population. Although the differences are not always significant, the trend of increase is consistent. However, because of the relatively small sample sizes, the results only suggest
trends and must be treated with caution.
Based on evidence that the groups do not differ
between one another in terms of dental metric and
nonmetric traits (Cucina et al., 1999), which indicates a biological continuity of the settlers, the differences encountered here should be interpreted
mainly as consequences of environmental factors.
The picture that emerges could result from a differential exploitation of environmental habitats, and
could be the expression of cultural changes. The
Neolithic groups appear to have settled open spaces
at the bottoms of valleys, where archaeologists have
encountered small camp sites. The associated faunal
remains were mainly of wild game species, as in the
group of La Vela, where deer-hunting was dominant
(Pedrotti and Demetz, 1997). Although agriculture
was known in this period, it did not represent an
important contribution to subsistence. This interpretation is supported by the material record and by
the low frequency of cavities (4.1%) reported in a
previous study (Cucina et al., 1999). It seems that
the Alpine valleys did not represent an ideal environment for this kind of subsistence activity (Bagolini et al., 1973).
These valleys had been well-populated since Neolithic times and experienced a rapid population
growth from the end of the Copper Age and the start
of the Bronze Age (Barfield, 1971). Population expansion coincided with a shift in subsistence economy that emphasized intensive agropastoralism
(Nicolis and Dal Ri, 1997), as supported by the
higher rate of cavities in the Bronze Age group
(16.1%; Cucina et al., 1999). The intensification of
agriculture, along with population growth, might
have led to two possible adaptive responses: population crowding in the valleys with epidemiological
consequences (i.e., the spread of diseases), or incentive for some groups to move toward less hospitable
highlands in search of new land to cultivate. Demand for land for pastoralism and decreased reliance on hunting increased this need (Riedel and
Tacchiati, 1997).
The chronological distribution of LEH also supports this evidence. The common occurrence of
peaks after age 3 years can be explained by higher
child mobility inside the settlement around that age,
which increases the exposure to disease, and by the
lack of maternal antibodies after weaning (Clarke,
1980; Katzenberg et al., 1996). In addition, the geometric structure of the enamel reduces the macroscopic manifestation of defects in the occlusal third
of the crown (Hillson and Bond, 1997), whose forma-
286
A. CUCINA
Fig. 1.
Chronological distribution of defects per individual, calculated from anterior teeth.
tion in anterior teeth lasts to around 2.5 years of age
(Reid and Dean, 2000). The macroscopic presence of
defects in this age range in EBA and CA and, in
turn, their absence in NEO indicate that stress in
the former groups was severe enough to overcome
physiological and histological thresholds. Variability between groups in the initial appearance of defects seems to be due to actual differences between
populations and not to attrition that reduced the
occlusal portion of the crowns. The CA group is
formed by a larger number of subadults than the
other groups. This could explain the onset of defects
in the CA population, but not the earlier onset in the
EBA group. The conservative approach used here
excluded all teeth that could have biased the results.
The results could be interpreted in two ways. Either the CA and EBA groups faced more difficult
environmental conditions than did the NEO group,
or the NEO group faced such harsh conditions that
individuals died before the onset of LEH. If the
second alternative were the case, according to the
osteological paradox of Wood et al. (1992), then one
would expect to find other supportive evidence in the
NEO group. While the small sample size precludes
the use of demographic profiles as a reliable means
to answer these questions, a previous study (Cucina
et al., 1999) did not detect any substantive evidence.
Dental metric traits should have been affected, resulting in smaller crowns in those Neolithic individuals who were capable of surviving the period of
growth (Larsen, 1997). Instead, no statistical difference was noted (Cucina et al., 1999). For the time
being, tying the frequency of hypoplastic defects to
environmental conditions and cultural habits seems
to provide a more parsimonious explanation, given
the evidence at hand.
In conclusion, this investigation points toward an
increasing frequency of enamel disruption from the
Neolithic to the Early Bronze Ages. The factors accounting for this trend may relate to nutritional
changes (from a varied, animal-protein-based diet to
a less varied, more carbohydrate-dependent one)
and changing cultural habits. Although the small
sample size limits generalization, the results are
consistent with previous epidemiological findings
(Cohen and Armelagos, 1984). Future studies are
planned on skeletal pathologies. This paper and that
of Cucina et al. (1999) will form the background for
an epidemiological interpretation, which will provide a clearer insight into the living conditions in
prehistoric Alpine populations.
ACKNOWLEDGMENTS
The present analysis is part of a wider project
between the Museo Tridentino di Scienze Maturali,
Trento, and the Department of Animal and Human
Biology, University of Rome “La Sapienza.” the author thanks M. Lazinger and G. Dalmeri (Museo
Tridentino di Scienze Naturali of Trento) and F.
Nicolis (Archaeological Superintendency of Trentino)
for permission to study the materials. I am grateful
to A. Pedrotti (University of Trento) for valuable
information. Special thanks go to V. Tiesler (Universidad Autonoma de Yucatan, Hérida) for her comments, R. Benfer (University of Missouri, Columbia)
for statistical advice, and D.L. Cunningham for editing the manuscript. I am extremely grateful to the
editor of the journal and three anonymous reviewers
for their patience and precious comments that allowed me to improve this paper.
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