Fungal spores located in 18th century human dental calculi in the

Journal of Archaeological Science: Reports 2 (2015) 106–113
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Journal of Archaeological Science: Reports
journal homepage: http://ees.elsevier.com/jasrep
Fungal spores located in 18th century human dental calculi in the church
“La Concepción” (Tenerife, Canary Islands)
José Afonso-Vargas a, Irene La Serna-Ramos b, Matilde Arnay-de-la-Rosa a,⁎
a
b
Dpto. de Geografía e Historia, Universidad de La Laguna, 38071 La Laguna, Tenerife, Canary Islands, Spain
Dpto. de Biología Vegetal (Botánica), Universidad de La Laguna, 38071 La Laguna, Tenerife, Canary Islands, Spain
a r t i c l e
i n f o
Article history:
Received 31 July 2014
Received in revised form 4 January 2015
Accepted 4 January 2015
Available online xxxx
Keywords:
Spores
Ustilago maydis
Corn
Dental calculus
Phytoliths
Palynomorphs
Canary Islands
a b s t r a c t
We present the results of our study of fungal spores found in two samples of mineralized dental calculi or “tartar”
identified during the analysis of plant microfossils (phytoliths and starch granules), taken from individuals from
the late 18th century, buried in graves in the church “La Concepción” (Santa Cruz de Tenerife). The identification
of palynomorphs motivated the application of a specific methodology to investigate the nature of their presence
in the dental tartar, seeking to discover whether this was the result of archaeological sediment contamination or
of particles trapped within it. Comparative analysis of the palynomorphs found in the calculi, using reference
material from the Palynotheque in the Department of Plant Biology, University of La Laguna, and analysis of
the archaeological sediment, allowed us to confirm that the fungal spores were exclusively located inside the matrix of the calculi and did not originate from a contaminant source. Morphometric study of the spores, reference
material and bibliographic descriptions allow us to propose that these are spores of Ustilago maydis (D.C) Corda, a
parasitic corn (Zea mays L.) fungus. These results confirm, on the one hand, the historical consumption of corn as
opposed to cereals produced locally until that time, such as barley and wheat, and, on the other hand, consumption of some shipments of maize contaminated by the so-called “corn smut” (U. maydis).
© 2015 Elsevier Ltd. All rights reserved.
1. Introduction
The study of microfossils contained in partially mineralized human
dental tartar or dental calculi is one of the sources of direct information
about palaeodietary aspects (Lalueza Fox and Pérez-Pérez, 1994). From
an archaeological perspective, the study of plant microfossils in dental
calculus yields information on the diet of prehistoric ungulates
(Armitage, 1975), historic ungulates (Middleton, 1990) and primates
linked to the evolutionary chain (Ciochon et al., 1990), finally being
applied to human populations in different contexts and periods of
time (Scott-Cummings and Magenis, 1997; Juan-Tresserras, 1997).
The first microfossils detected in these studies were silicophytoliths
and starch granules, which also cause tooth enamel striation (Lalueza
Fox and Pérez-Pérez, 1994; Lalueza et al., 1996) and both indicate the
consumption of plants or plant products. As for palynomorphs as part
of the microfossil record, distinguishing them from those found in
non-human calculi (Middleton and Rovner, 1994), the first reference
seems to be that of Torok et al. (1999), in this case in corpses from the
18th and 19th centuries. Fungal basidiospores were detected among
microfossils such as oxalates and phytoliths, but without referring to
specific taxa. More recently, Blatt et al. (2010) have also identified
cotton fibre microfossils and other plant microfossils in historic
⁎ Corresponding author.
E-mail address: [email protected] (M. Arnay-de-la-Rosa).
http://dx.doi.org/10.1016/j.jasrep.2015.01.003
2352-409X/© 2015 Elsevier Ltd. All rights reserved.
human dental calculi from Ohio (USA). The history of oral hygiene
shows the attention given in the past to the removal of dental tartar,
with the use of a wide variety of specific instruments that varied in morphology and sophistication throughout history (González et al., 2003).
Dental calculus is mineralized bacterial plaque adhered to the
surface of the tooth. Diet affects the formation of tartar, but it is not
easy to establish the processes because of the numerous ways tartar
can be formed. Some authors relate its formation almost exclusively to
a protein-rich diet, for example, a diet based on meat products (Lillie,
1996; Malgosa and Subirá, 1996), while others link it to starch-rich
diets, such as those based on cereals (Hanikara et al., 1994; Eshed
et al., 2006; Afonso, 2007).
In terms of its composition, organic and inorganic components can be
distinguished. Among the former there are remains of cells, food, bacteria
and protein components from saliva, while the latter comprise calcium
salts deposited on this matrix (Jin and Ying, 2002; Pérez et al., 2004).
The components trapped in the tartar are an important source of information about the food consumed, because the presence of saliva is necessary
for this process to take place. Therefore, many researchers suggest that
this rules out the possibility that many of the components of the calculi
were acquired after death and they defend its validity as a source of direct
information about the products consumed (Afonso, 2007).
The extraction and study of this type of material has required numerous methodological reviews (Boyadjian et al., 2007; Afonso, 2007)
focussing on the above-mentioned aspects. Unlike other archaeological
J. Afonso-Vargas et al. / Journal of Archaeological Science: Reports 2 (2015) 106–113
materials, the samples involved must be destroyed to be analysed, in
order to recover as much information as possible. In this case, the
information takes the form of microfossils such as starch granules and
silica phytoliths, which are not affected by the chemical treatments
used, as opposed to calcium oxalates (Juan-Tresserras, 1997) which
are completely dissolved. In this regard, we have evidenced the partial
alteration of reference spores after chemical treatment, which supposedly also occurred in spores found within the dental calculi of the
present study, but to our knowledge the literature contains no information on this.
From a historical research perspective, the information provided by
plant microfossils contained in dental calculi allows a direct approximation of the diet at different periods of time and historical processes
(González et al., 2003; Flandrin and Montanari, 2004; Juan-Tresserras,
1997).
In the case of the calculi from the church “La Concepción”, the study
provides insight into dietary patterns of the inhabitants of the Canary
Islands and of Tenerife in particular, during the 18th century, a boom
time for the city of Santa Cruz de Tenerife as a port and commercial centre, connected to the rest of the Canary Islands' capital cities, the Spanish
mainland and the Spanish colonies in America. In terms of food, it also
meant the expansion of habits that gradually changed the diet of the Canary population, probably starting with the upper classes, as suggested
by the differential content of strontium/barium (Arnay et al., 2009)
among individuals buried near the altar or far from the altar. As previously reported, tombs near the Altar were destined to individuals
belonging to the high social class (Cioranescu, 1998). Among dietary
change, it is important to highlight the increased consumption of corn
or maize (Zea mays) compared to other common grains such as wheat
or barley. The gradual production of the former from the late 16th century in islands such as Gran Canaria, resulted in exportation to the rest of
the archipelago (Alzola, 1984). The 18th century was a period of great
social crises and famines that led not only to the importation of cereals
such as corn (or “millo” in the Canary Islands) but also to the proliferation of domestic cultivation and consumption.
The numerous human remains found in the subsoil of the church “La
Concepción” have provided a considerable number of teeth that have
been subjected to various palaeopathological and anthropological
analyses, including the study of tartar as a variable of great interest in revealing the diet and oral health conditions of the population of the 18th
century (Afonso, 2007; Gámez Mendoza, 2004; Arnay et al., 2009).
Early studies of microfossils in these samples confirmed the presence of silicophytoliths and starch granules, as well as palynomorphs
in two of them, which were provisionally classified as spores (Afonso,
2007). A detailed study revealed that they could be identified taxonomically using morphometric and statistical analyses, including that of
reference materials and sediments surrounding the human remains
from which the dental calculi came.
107
Our study, based on the location of concentrations of fungal spores in
the two aforementioned samples, expands the possibilities of obtaining
historical information related to diet in the Canary Islands. In this case,
we applied an interdisciplinary approach which allowed us to identify
of the fungus Ustilago maydis and therefore confirms the consumption
of corn (Z. mays) among part of the population of Santa Cruz de Tenerife
in the late 18th century.
2. Materials and methods
2.1. Materials
The study material comes from the church “Nuestra Señora de La
Concepción” in Santa Cruz de Tenerife. This was recovered during
excavations carried out in two separate campaigns in 1993 and 1995,
which brought to light an important part of the last burials in the subsoil
of the inside of the church. Two hundred and seven burial pits were
excavated and human remains belonging to at least 776 individuals
were recovered. The available documentation allows us to chronologically place these burials in the period dating from the expansion of the
church, in the early 18th century, when the fourth and fifth naves
were built, until 1829, the year in which new floor paving was laid in
the temple, which meant that it would be impossible to continue
using it as a burial site (Arnay, 2009).
2.1.1. Specimens
Of the 537 specimens, belonging to 62 mandibles, analysed during
dental pathology studies, we selected those that contained tartar,
graded into different categories: Grade 1 slight: very thin continuous
or discontinuous deposits, Grade 2 substantial: thick deposit covering
almost all of a dental surface, and Grade 3 abundant: a very thick deposit
covering the entire dental surface, following criteria established by
Brothwell (1981), Delgado Darias (2009) and Chimenos (2003).
We finally analysed the 14 specimens that showed the greatest
proportion of calculi, labelled with the initials of the archaeological
site followed by the serial number (LC-24, LC-25, LC-39, LC-44, LC-45,
LC-64, LC-112, LC-137, LC-608, LC-1192, LC-3369, LC-2173, LC-1962,
LC-3382).
2.1.2. Contextual sediments
To test whether the spores or palynomorphs found really came from
the calculi or whether they were also present in the archaeological
sediment, samples were taken from the area surrounding the human
remains from which they came, corresponding to burial pits 185 and
321, labelled LC-185 and LC-321 respectively.
Fig. 1. Relationship between the weight (in grams) of the dental calculi before and after treatment. Grey bars represent the initial weights and white stippled bars the final weights of the
samples after treatment. In the x axis we show the sample signature (The prefix LC [La Concepción] has been deleted due to space problems).
108
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Table 1
Silica phytoliths, starches and spores found in the dental calculi.
Sample
LC-25
LC-44
LC-45
LC-64
LC-39
LC-137
LC-24
LC-112
LC-2173
LC-608
LC-1962
LC-1192
LC-3382
LC-3369
Number
Silica phytoliths
Starches
Spores
12
3
4
4
2
5
24
2
1
4
2
1
1
1
2
1
3
4
0
1
5
1
1
8
–
1
1
4
–
–
–
–
–
–
–
–
–
162
–
–
–
335
2.1.3. Reference spores
In order to identify the spores in the calculi, descriptions from von
Arx (1974) and La Serna and Domínguez (2003) were consulted
and compared to spores of two species of Ustilago [U. maydis L. and
Ustilago segetum (Bull.) Roussel] using material from the Herbarium in
the Department of Plant Biology, University of La Laguna (TFC),
specifically from the TFC 27104 and TFC 37894 respectively, as indicated
in Section 2.2.3 (reference spores).
2.2. Methods
2.2.1. Dental calculi
The calculi were treated according to the method described by ScottCummings and Magenis (1997) and carrying out the steps described by
Afonso (2007).
Fig. 2. A–B, dental calculi. A (LC-608): echinulate long cell silicophytoliths and fungal spores, B (LC-608): polyhedral starch. C–D, contextual sediment. C (LC-185): dendriform
silicophytoliths, D (LC-321): bilobed silicophytoliths. E–F, Ustilago maydis reference spores. E (P-TFC 1143): untreated echinulate spores, F: echinulate spores after chemical treatment.
G–H, Ustilago segetum reference spores (P-TFC 1145). G: untreated psilate spores, H: psilate spores after chemical treatment.
J. Afonso-Vargas et al. / Journal of Archaeological Science: Reports 2 (2015) 106–113
microscopic preparations, the method described by Bárcena and Flores
(1990) was followed.
Table 2
Frequency of spores found in dental calculi according to their ornamentation.
Sample
LC-608
LC-3369
109
Spores
Total number
Psilates (%)
Echinulates (%)
162
335
25
40
75
60
2.2.2. Archaeological sediments
To detect all of the plant microfossils present in this material, we removed carbonates and organic matter, following the method proposed
by Piperno (2006) and, in the case of clays,that of Lefter and Boyd
(1999) with slight modifications (Afonso, 2014). In order to isolate the
fraction containing the microfossils, we applied the protocol described
by Bárcena and Flores (1990) for the study of microalgae, based on
the Random Settling Method (Moore, 1973). This allows a qualitative
and quantitative study of all of the microfossils present in a sediment
sample and can be applied to phytoliths and other plant microfossils
in archaeological contexts (Afonso, 2014). Its application in this
case sought to confirm the presence of palynomorphs, as does the
densimetric method described by Uitdehaag and Kuiper (2007) for
forensic practice. Application of the random settling method was an acceptable alternative which allowed identification of all the microfossils
present in the sediment.
After drying the samples at 60 °C, 1 g of each was taken and subjected to oxidation with hydrogen peroxide (H2O2, 30%) and then to a
mixture of hydrochloric acid (HCl) and nitric acid (NHO3) at 10%, ratio
1:1. After repeated washing with distilled H2O, we eliminated the clay
fraction, for which the samples were placed in 50 ml tubes with 15 ml
of sodium hexametaphosphate (NaPO3)6 comprising 35.7 g of sodium
polyphosphate and 2.94 g of anhydrous sodium carbonate, subsequently subjected to ultrasound for 2 min. The samples were then diluted
(to 40 ml) with distilled H2O, and shaken vigorously, letting them
stand at room temperature as specified in the tables created according to Stokes' Law, based on the time particles taken to drop in a
liquid medium in relation to their size. Once this time has elapsed (an
average of 4 h for a 5 cm water column), the supernatant is removed
with the aid of a manual siphon. The cycle of dispersion, filling, shaking,
standing and decantation is repeated until the supernatant is observed
to be clear.
Finally, after shaking the container made up to 40 ml, a 1000 μl
aliquot is removed using an automatic pipette. For the assembly of
2.2.3. Reference spores
On the one hand, the spores without any type of treatment were
mounted directly on Kaiser's glycerol-gelatin and sealed with paraffin.
And, on the other hand, in order to test whether they had suffered any
kind of transformation due to the treatments applied to the calculi,
they were also treated using the same protocol.
In both cases, the sporal preparations were stored in the
Palynotheque in the Department of Plant Biology, University of La
Laguna, and labelled as P-TFC.
List of the material:
– U. maydis. Tenerife: La Guancha (corn fields), 15.08.1971, W.
Wildpret de la Torre and E. Beltrán Tejera (TFC 27104; P-TFC 1143:
untreated spores; P-TFC 1146: treated spores).
– U. segetum. Tenerife: Los Rodeos (oat fields), 08.05.1995, W.
Wildpret de la Torre (TFC 37894; P-TFC 1145: untreated spores;
P-TFC 1146: treated spores).
The nomenclature adopted for fungi has been proposed by Beltrán
Tejera (2010) and for spermatophytes, that of Acebes Ginovés
et al. (2010).
2.2.4. Microscopic observations, quantification and statistical analysis
In the spores that appeared in the calculi and in the reference spores,
the parameters observed were: length of the minor axis (D1) and the
major axis (D2) of the ellipsoidal grains in optical section (axes are
the same size in spheroidal ones); colour and ornamentation. The
D1/D2 quotient is also incorporated.
Fifty spores in each of the calculi and 30 in the references spores
were measured. The interval range (m–M) and mean (X) were
established in all cases together with their 95% confidence intervals
(CI).
The data were processed statistically, applying the Simpson and Roe
graphical test (Van der Pluym and Hideux, 1977).
Qualitative characteristics were observed at 1500× and quantitative
characteristics at 600× using a LEICA CME optical microscope. The microphotographs were taken with a NIKON COOLPIX camera, adapted
to the same microscope.
Table 3
Biometry of fungal spores of the different samples.
Sample
N°
Values
D1 (μm)
D2 (μm)
D1/D2
Psilates
10
Echinulates
40
Total
50
Psilates
23
Echinulates
27
Total
50
P-TFC 1143
Total
30
P-TFC 1144
Total
30
P-TFC 1145
Total
30
P-TFC 1146
Total
30
m–M
X ± IC95
m–M
X ± IC95
m–M
X ± IC95
m–M
X ± IC95
m–M
X ± IC95
m–M
X ± IC95
m–M
X ± IC95
m–M
X ± IC95
m–M
X ± IC95
m–M
X ± IC95
8.10–12.15
10.52 ± 0.66
8.10–13.50
11.17 ± 0.41
8.10–13.50
11.04 ± 0.36
8.10–12.15
9.68 ± 0.49
9.45–13.50
11.55 ± 0.50
8.10–13.50
10.64 ± 0.44
8.10–10.80
9.43 ± 0.34
5.40–10.80
7.79 ± 0.27
5.40–5.94
6.16 ± 0.16
3.78–5.94
4.73 ± 0.20
9.45–13.50
11.21 ± 0.69
9.45–14.85
11.78 ± 0.40
9.45–14.85
11.66 ± 0.35
8.10–13.50
10.74 ± 0.54
9.45–11.85
12.30 ± 0.53
8.10–14.85
11.50 ± 0.45
8.10–12.15
9.99 ± 0.35
6.75–10.80
8.34 ± 0.26
5.94–8.64
7.07 ± 0.20
4.32–6.48
5.47 ± 0.12
0.86–1.00
0.93 ± 0.04
0.86–1.00
0.95 ± 0.02
0.86–1.00
0.95 ± 0.02
0.60–1.00
0.90 ± 0.04
0.88–1.00
0.94 ± 0.02
0.60–1.00
0.93 ± 0.02
0.75–1.00
0.95 ± 0.03
0.67–1.00
0.94 ± 0.03
0.67–1.00
0.87 ± 0.03
0.67–1.00
0.87 ± 0.04
LC-608
LC-3369
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Fig. 3. Simpson & Roe test for major axis length (D1). LC-608(E): psilate spores; LC-608(E): echinulate spores; LC-608(T): total spores (psilate + echinulate); LC-3369(E): psilate spores;
LC-3369(E): echinulate spores; LC-3369(T): total spores (psilate + echinulate); P-TFC 1143 and P-TFC 1144: echinulate spores; P-TFC 1145 and P-TFC 1146: psilate spores.
3. Results
but which may also coincide with those present in Triticeae (Aceituno
and López, 2012).
3.1. Dental calculi
3.2. Contextual sediment
The majority of the dental calculi were greater than 2 mm in size and
initial weight (Fig. 1) ranged from 0.0123 g to 0.0615 g. We found that
when initial weight was less than 0.01 g there was little possibility of
locating the resulting residue after the treatments, since the action of
the reactants destroyed all of the calculi, hindering microfossil detection. The estimated weight loss and observation of the resulting residue
indicated that treatment destroyed 70%–100% of the sample, which
finally acquired the form of practically translucent fine films, a state
controlled by the duration of acid reactants used.
The quantification and types of microfossils detected are listed in
Table 1. Fungal spores only appeared in the LC-608 and LC-3369
(Fig. 2A) samples.
The silicophytoliths identified correspond to fragments of long
echinate cells (Fig. 2A), as cited by Afonso (2007), and short,
trapezoidal-type cells; both being similar to those in Triticeae cereal inflorescences. With regard to the starch granules, not only common lenticular forms were detected, but also polyhedral types with straight
edges (Fig. 2B) and in no case spherical ones. Maximum and minimum
size ranged from 18.9–13.5 μm in LC-608 to 17.55–8.5 μm in LC-3369,
with morphologies and sizes that fit the descriptions given by Wallis
(1968) and Flint (1996) for some of the starches developed by Z. mays
The sediment matrix, which enveloped the bio-anthropological samples in which the fungal spores were detected, presented a loose, dusty
appearance and a yellowish/light ochre colour (Munsell 10YR/7-8).
Weight loss associated with organic matter content and carbonates
was between 14% and 4%. On a granulometric level, the clay content
was estimated to be close to 50%.
Microscopic analysis revealed the absence of palynomorphs in sand,
silt and clay fractions. It also showed the presence of the following
microfossils:
– Siliceous microfossils from the phytolith group with long echinate/
dendriform cell morphotypes (Fig. 2C) and bilobed short stem
cells, with well-defined lobes and concave ends (Fig. 2D), both
being characteristics of Poaceae (Twiss et al., 1969).
– Microalgae of the chrysophycean cyst type with an ornamented
surface morphology, globular shape and possible simple neck, are
consistent with some types described by Pla (2001) and with both
centric diatoms (Aulacoseira sp.) and pennate diatoms in different
states of preservation, which we propose as belonging to the genus
Navicula sp., based on the descriptions of Round et al. (1990).
Fig. 4. Simpson & Roe test for major axis length (D2). LC-608(E): psilate spores; LC-608(E): echinulate spores; LC-608(T): total spores (psilate + echinulate); LC-3369(E): psilate spores;
LC-3369(E): echinulate spores; LC-3369(T): total spores (psilate + echinulate); P-TFC 1143 and P-TFC 1144: echinulate spores; P-TFC 1145 and P-TFC 1146: psilate spores.
J. Afonso-Vargas et al. / Journal of Archaeological Science: Reports 2 (2015) 106–113
111
Fig. 5. Simpson & Roe test for the quotient D1/D2. LC-608(E): psilate spores; LC-608(E): echinulate spores; LC-608(T): total spores (psilate + echinulate); LC-3369(E): psilate spores;
LC-3369(E): echinulate spores; LC-3369(T): total spores (psilate + echinulate); P-TFC 1143 and P-TFC 1144: echinulate spores; P-TFC 1145 and P-TFC 1146: psilate spores.
While Aulacoseira sp. was only detected in sediments, there was
some example of Navicula sp. in the dental calculus LC-608.
– Numerous microcarbon fragments, which do not provide information beyond their obvious relation to plant matter combustion
processes.
3.3. Fungal spores
3.3.1. Spores in dental calculi
In the two calculi harbouring spores, these were brown in colour
(Fig. 2A), with a size ranging from 8.10–13.50 μm on the minor
axis (D1) and 8.10–14.85 μm on the major axis (D2), spheroidal or
ellipsoidal (D1/D2 = 0.60–1.00), with an echinulate or psilate wall,
predominantly the former (Table 2).
3.3.2. Reference spores
The U. maydis spores are brown in colour, with D1 = 8.10–10.80 μm
and D2 = 8.10–12.15 μm in the untreated ones, D1 = 5.40–10.80 μm
and D2 = 6.75–10.80 μm in the treated ones. They are spheroidal or
ellipsoidal (D1/D2 = 0.75–1.00 in untreated ones, D1/D2 = 0.67–1.00
in the treated ones) and consistently present an echinulate wall
(Fig. 2E, F; Table 3).
The U. segetum spores are somewhat darker brown in colour than
those of U. maydis, but smaller in size (D1 = 5.40–5.94 μm, D2 =
5.94–8.64 μm in the untreated ones; D1 = 3.78–5.94 μm, D2 = 4.32–
6.48 μm in the treated ones). They are spheroidal or ellipsoidal
(D1/D2 = 0.67–1.00 in both the untreated ones and those undergoing
treatment), and consistently present a psilate wall (Fig. 2G, H;
Table 3). These results are graphically shown in Figs. 3–5 (applying
the graphic test of Simpson and Roe (Van der Pluym and Hideux,
1977)). The frequency of spores in all the samples according to their
morphology is depicted in Fig. 6.
4. Discussion
The application of the simplified graphical test of Simpson & Roe
(Van der Pluym and Hideux, 1977) for D1, D2 and D1/D2 enabled us
to make the following observations:
– The non-overlapping rectangles in the reference spores, both those
treated and untreated, indicated a clear difference in size (Figs. 3
and 4) between the U. segetum and the U. maydis spores. While
spores with psilate walls appeared in the calculi, their larger size
allowed us to rule out the idea that they corresponded with
U. segetum or other species, which are also psilate, such as Ustilago
Fig. 6. Frequency of spores in all samples according to their morphology. LC-608(E): psilate spores; LC-608(E): echinulate spores; LC-608(T): total spores (psilate + echinulate);
LC-3369(E): psilate spores; LC-3369(E): echinulate spores; LC-3369(T): total spores (psilate + echinulate); P-TFC 1143 and P-TFC 1144: echinulate spores; P-TFC 1145 and P-TFC
1146: psilate spores.
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hordei (a parasite found in barley and other grasses) and according
to von Arx (1987) measure 5–8 μm.
– Comparing the spores from the calculi with those of U. maydis, we
can say that, although the rectangles are not completely overlapping,
the variations in size (Figs. 3 and 4), are minor and therefore both
the echinulate (ornamentation typical of U. maydis) and the psilate
spores coincide in size with those of “corn smut”.
– While there were no significant differences in the D1/D2 quotient
(Fig. 5) between the calculus spores and the U. maydis and
U. segetum ones, in this case, shape was not a determinant in identifying these spores. This was also clearly evident in Fig. 6, where, in
one of the calculi (LC-608), the spherical spores predominated,
whether echinulate or psiladas, as opposed to those of the calculus
LC-3369, where they appeared in smaller proportions.
The absence of fungal spores in the contextual sediment and the
presence of microfossils that were not detected in the calculi, rule out
the possibility of contamination.
Furthermore, these microfossils allowed us to confirm that the burial
pits were filled with soil obtained from outside the church. The presence
of diatoms and chrysophyte cysts, indicators of wet conditions like
those of the nearby gully bed “Barranco de Santos” (Afonso, 2004) confirms that the burial pits were filled with soil from outside the church.
These data could also indicate the origin of some of the phytoliths
found, as in the case of short bilobed cells. Until we have more accurate
morphometric studies, we will consider two interpretative approaches,
one linked to grasses of the Arundinoideae subfamily, typical in wet environments, such as the edges of the gully bed mentioned above; the
other could refer to a Panicoideae grass adapted to drier environments,
such as Hyparrhenia hirta or “cerrillo”, a very common species in coastal
and mid-mountain regions of the Canary Islands (Afonso, 2014).
The presence of echinate long cell phytoliths, common in the inflorescences of cultivated grasses (Poaceae of the Triticeae tribe), indicated the
existence of an agricultural sedimentary context, either near the church or
located at higher altitudes and arriving there by seasonal rainfall runoff.
The presence of microcarbons in the sediment may be related to
activities carried out in the vicinity of the church, such as an “aseptic
burning” of waste materials, or it could be evidence of previous fires,
both nearby and inside the church premises.
Morphometric analysis of the echinulate spores and comparison
with the reference preparations (P-TFC 1143 and P-TFC 1144) allowed
us to determine that they were associated with corn smut (U. maydis).
Regarding the psilate spores, as we do not currently have the herbarium
material on other species of Ustilago (e.g.: Ustilago crameri, Ustilago
cynodontis, U. hordei, Ustilago longissima) and their much larger size
does not coincide with those described in the literature for these species
or the reference U. segetum studied, we cannot guarantee whether they
were of another Ustilago or U. maydis that had lost their ornamentation
through taphonomic processes.
On an archaeo-botanical level, several interpretations can be made:
– The phytoliths and starches found in the calculi confirm the consumption of cereals, both of the Triticeae family, to which wheat
and barley belong, and of the Panicoideae subfamily, to which corn
belongs. Although these phytoliths, characteristic of Triticeae inflorescences, are absent in Z. mays, the polyhedral starches are less numerous in cereals of the wheat group, which reinforces the existence
of corn smut spores.
– The fungal spores also provide direct information about the
consumption of cereals, particularly of corn (“millo”) by the two
individuals with spores. These individuals were buried in tombs located in different parts of the church, at different distances from
the altar. Therefore, from the location of the burial pits we cannot
infer that they belonged to the privileged social class. The corn
they consumed came from cobs infected with the U. maydis fungus,
which has no harmful effects for humans.
While it is believed that by the mid to late 16th century corn was
being cultivated in the Canary Islands, it was in the 18th century
when its cultivation and consumption as “"gofio” (toasted flour of one
or more grains) became generalized, surpassing that of wheat and
barley, which were already consumed in aboriginal times, Gran Canaria
being the main supplier (Alzola, 1984).
As already indicated, the type of diet is one of the main factors
involved in the formation of tartar. There are other factors besides diet
that can intervene in the presence and severity of tartar buildup, such
as oral hygiene, because if the bacterial plaque is removed, mineralization is avoided (Gámez Mendoza, 2010).
Plaque mineralization is intensified in an alkaline medium and,
therefore, in high protein diets, because these diets increase alkalinity
(Lieverse, 1999). However, in calculi formation, the oral microorganisms that inhabit dental plaque are also involved, which are favoured
by diets rich in carbohydrates. Among the carbohydrates, starch has
an important role on the mineralization of plaque. One can therefore
consider that populations with a diet rich in grains, and therefore in
starch, would therefore present a greater buildup of tartar (Littleton
and Frohlich, 1993; Lukacs, 1989; Delgado Darias, 2009).
Previous studies carried out on human remains from “La
Concepción” demonstrated the importance of the plant-based diet in
the population studied, despite the proximity to the sea and the possibility of consuming seafood. Thus, the average of the values obtained
by analysing tooth decay approaches that of societies with primarily agricultural economies. Chemical studies of the bone, to determine barium
and strontium content, have also shown the importance of plant
products in the diet. This diet, fundamentally rich in carbohydrates,
was found to be the same among children (Arnay et al., 2009; Gámez
Mendoza, 2010).
All of this is consistent with the historical documentation studied.
From the second half of the 18th century onwards, there was a significant increase in the consumption of plant products, especially cereals
such as corn and tubers such as potatoes (Gámez Mendoza, 2010).
5. Conclusions
The discovery of these phytopathogenic spores reveals a new line of
palynological research, at an archaeo-botanical level, in human dental
calculi, which seeks to extend the analysis of the teeth with low tartar
buildup from this very site and that of others from different sources
and time periods.
The absence of fungal spores in the contextual sediment and the
presence of microfossils that were not detected in the calculi rule out
possible contamination and allowed us to extract data related to the
diet from the 18th century population.
In the present study we detected U. maydis, a parasitic corn fungus,
using an interdisciplinary approach that supported the proposed
archaeo-botanical interpretation. The results of the present study are
consistent with the increased consumption of corn on the island of
Tenerife from the 18th century onwards, introducing dietary changes
which subsequently spread to all social classes.
Acknowledgements
This research was conducted as part of the project HAR2011-27413
supported by the Ministerio de Economía y Competitividad (Spain).
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