Diet-Related Buccal Dental Microwear Patterns in Central African Pygmy Foragers and Bantu-Speaking Farmer and Pastoralist Populations
Prez-Prez A (2013) Diet-Related Buccal Dental Microwear Patterns in Central African Pygmy
Foragers and Bantu-Speaking Farmer and Pastoralist Populations. PLoS ONE 8(12): e84804. doi:10.1371/journal.pone.0084804
Diet-Related Buccal Dental Microwear Patterns in Central African Pygmy Foragers and Bantu-Speaking Farmer and Pastoralist Populations
Alejandro Romero 0
Fernando V. Ramrez-Rozzi 0
Joaqun De Juan 0
Alejandro Prez-Prez 0
Michael D. Petraglia, University of Oxford, United Kingdom
0 1 Universidad de Alicante, Departamento de Biotecnologia , Alicante , Spain , 2 Centre National de la Recherche Scientifique, Unite Propre de Recherche Dynamique de l'Evolution Humaine, Paris, France, 3 Universitat de Barcelona, Departament de Biologia Animal , Barcelona , Spain
Pygmy hunter-gatherers from Central Africa have shared a network of socioeconomic interactions with non-Pygmy Bantu speakers since agropastoral lifestyle spread across sub-Saharan Africa. Ethnographic studies have reported that their diets differ in consumption of both animal proteins and starch grains. Hunted meat and gathered plant foods, especially underground storage organs (USOs), are dietary staples for pygmies. However, scarce information exists about forager-farmer interaction and the agricultural products used by pygmies. Since the effects of dietary preferences on teeth in modern and past pygmies remain unknown, we explored dietary history through quantitative analysis of buccal microwear on cheek teeth in well-documented Baka pygmies. We then determined if microwear patterns differ among other Pygmy groups (Aka, Mbuti, and Babongo) and between Bantu-speaking farmer and pastoralist populations from past centuries. The buccal dental microwear patterns of Pygmy hunter-gatherers and non-Pygmy Bantu pastoralists show lower scratch densities, indicative of diets more intensively based on nonabrasive foodstuffs, compared with Bantu farmers, who consume larger amounts of grit from stoneground foods. The Baka pygmies showed microwear patterns similar to those of ancient Aka and Mbuti, suggesting that the mechanical properties of their preferred diets have not significantly changed through time. In contrast, Babongo pygmies showed scratch densities and lengths similar to those of the farmers, consistent with sociocultural contacts and genetic factors. Our findings support that buccal microwear patterns predict dietary habits independent of ecological conditions and reflect the abrasive properties of preferred or fallback foods such as USOs, which may have contributed to the dietary specializations of ancient human populations.
Funding: This work was funded by Spanish Conselleria dEducaci de la Generalitat Valenciana (BEST/2009/258), Ministerio de Educacin y Ciencia
(CGL2010-15340 and CGL2011-22999), Universidad de Alicante (UAUSTI10-02), grants from National Geographic Society (8863-10), The French
National Research Agency, ANR Blanc Program (ANR-11-BSV7-0011), and the Wenner-Gren Foundation (7819). The funders had no role in study design,
data collection and analysis, decision to publish, or preparation of the manuscript.
Competing interests: The authors have declared that no competing interests exist.
Both present-day African Pygmy hunter-gatherers (PHGs),
characterized by a reduced adult stature (<160 cm) , and
their non-Pygmy Bantu-speaking neighbors live in the tropical
rainforests throughout the Congo Basin in a complex network
of economic and social contacts with different subsistence
strategies [2,4,5]. In contrast to PHGs, whose lifestyle and
culture are forest based, non-Pygmy Bantu speakers have an
agro-pastoralist, sedentary lifestyle [1,57]. Genetic analyses
suggest that gene flow between the two populations is limited
and asymmetrical due to sociocultural and demographic
constraints . Linguistic differences have also been
demonstrated [2,12], and phenotypic peculiarities in PHGs are
not limited to adult height . Central African rainforest
environments show great plant and animal biodiversity ,
including aboveground edible plants and starch-rich plant
underground storage organs (USOs), as well as
accessible prey animals. Ethnographic evidence has shown
that foraging activities, mainly providing wild yam tubers
(Dioscorea spp.), supply the bulk of the diet among PHGs, who
rarely spend time cultivating plant foods . Agricultural
resources are obtained mainly by exchange for forest products
(meat and honey for iron tools and starchy foods) with
Bantuspeaking farmers (BSFs) . Reports on dental health 
with stable isotopes  corroborate
ethnographic data that indicate significant dietary differences in
animal protein and starch-grain consumption between PHGs
and agro-pastoralist Bantu speakers.
Buccal dental microwear, the pattern of microscopic
usewear on nonworking enamel surfaces of premolar and molar
teeth, has been shown to reflect the physical properties of
chewed foodstuffs and long-term trends in dietary preferences
. During food chewing, scratches of different length and
orientations are formed across buccal enamel surfaces by the
indentation effect of micrometer-scale (106 m) particles that
are harder than enamel, such as plant phytoliths, grit, or quartz
dust . Thus, the type and amount of chewed abrasives
are critical in the formation of tooth wear and microscopic
scratch patterns [27,28,3133]. Distinct buccal microwear
patterns have been shown to distinguish nonhuman primates
and fossil hominins [34,35], as well as foraging and horticultural
populations with distinct dietary habits and food processing
methods . However, reliable buccal microwear patterns
of modern human populations with known diets are still lacking,
so the effect of preferred diets and the physical properties of
ingested foodstuffs on dental microwear patterns need to be
better understood [25,40]. Here we present analyses of buccal
microwear patterns of both PHGs and non-Pygmy
Bantuspeaking populations from Central Africa with distinct and
wellcharacterized diets, including BSFs, inhabiting the same forest
environment as PHGs, and Bantu-speaking pastoralists (BSPs)
Maasai populations from savanna habitats [7,14]. We first
assessed if the populations distinct reported diets (foraging,
farmer, and pastoralist subsistence economies) are reflected in
buccal microwear patterns. We then analyzed if the differential
access to cultivated products among the PHGs was apparent
in their buccal microwear patterns, which might provide new
insights on the abrasive effect of the consumption of USOs and
silica-based aboveground plant foods [34,35,41,42] for the
characterization of hominin dietary preferences and
Materials and Methods
All participants provided verbal informed consent for this
study funded by The French National Research Agency
(ANR-11-BSV7-0011). Written consent was not obtained
because the Baka people included in the study cannot read or
write, and the data were analyzed anonymously. However, the
information and acceptance process of all participants was
video recorded. A native who spoke French and Baka
explained the standard statement to each volunteer. The Ethics
Committee of the Centre National de la Recherche Scientifique
approves this procedure for illiterate traditional populations.
The protocol was in accordance with the Declaration of Helsinki
and was approved by the Ethics Commission of the Centre
National de la Recherche Scientifique (CNRS-UPR2147) and
the Institut National de la Sant et de la Recherche Mdicale
A total of 143 first mandibular molars (M1), preferably left
side, were analyzed. Teeth from PHGs (n = 51) correspond to
four different ethnographic groups: extant Baka from Cameroon
(n = 36) and Aka from Central African Republic (CAR; n = 4),
Babongo from Gabon (n = 6), and Mbuti from the Democratic
Republic of Congo (DRC; n = 5). The BSFs (n = 80) included
individuals of different ethnic affiliations from CAR, Congo,
DRC, Gabon, and Rwanda, and BSPs (n = 12) included a
Maasai sample used as a control group. Anthropological and
ethnographical data from museum records and available
literature were used to assign geographical provenance and
dietary habits since no quantitative diet data exist in
association with the museum samples we surveyed (see Table
S1 in File S1 for sample details).
In vivo epoxy casts of Baka Pygmy samples were collected
under informed consent in June 2008 at the village
Moang-LeBosquet in the Dja Biosphere Reserve (Lomi district,
southeastern Cameroon) . The other Pygmy and non-Pygmy
samples studied were from skeletal collections at the American
Museum of Natural History (New York), the Institut Royal des
Sciences Naturelles de Belgique (Brussels), the Muse de
lHomme (Paris), and the University of Geneva (Geneva,
Individual teeth were classified as PHG and non-Pygmy BSF
and BSP using population-based physical [1,3,13], cultural
[1,2,12], and genetic criteria . All non-Pygmy BSF
populations studied were pooled based on similar dietary
habits and low levels of phenotypic [3,13] and genetic variation
 within groups compared to PHGs.
Both PHGs and BSFs inhabited Central African tropical rain
forests, whereas the BSP Maasai populations lived in
savannah environments . The ecosystem in the Congo
Basin is characterized by a closed evergreen forest with
vegetation consisting mainly of the evergreen rain forest,
semideciduous forest, and mixed forest [14,43,44]. The Central
and West African forests extend discontinuously from Senegal
in West Africa to extreme western Kenya and northern Angola.
The maximum annual rainfall is 1500 mm, and temperatures
range from 23.1C to 25C. The closed evergreen forest does
not show any noticeable seasonal behavior with two rainy
seasons (MarchJune and SeptemberNovember) and two dry
seasons (DecemberFebruary and JulyAugust) in a year, and
faunal and floral species often share similar patterns of
For the current study no attempt was made to determine
individuals sex, and only juvenile or adult individuals were
selected. Subadult individuals were not considered. Early
reports have shown that neither age-related (juvenile and adult
age groups) nor sex-related differences in buccal microwear
are detectable within farming [36,39] or hunter-gatherer 
populations. All sample were aged using dental development
sequences , including Baka individuals, since no accurate
age data were available due to the lack of birth records .
Individuals presenting fully erupted third lower molar (M3) were
considered adults. Otherwise, juveniles were limited to
individuals with the presence of a fully erupted second lower
molar (M2) (>15 years 36 months). Individuals with no
erupted M2 were excluded. Marquer  provided a detail
description of sex and age for the Pygmy sample. When
available, the age of non-Pygmy individuals was compared with
information provided in the collection data sets. Pygmy and
non-Pygmy samples from museums were collected between
the middle of 19th century and the first half of the 20th century.
Specifically, Pygmy samples used in this study are
representative of all Pygmy skulls present in collections, which
were deposited between 1879 and 1953 (see Ramrez-Rozzi
and Sardi  and Marquer ). Final Pygmy and non-Pygmy
sample sizes correspond to individual skulls with a complete
jaw and in situ M1 teeth suitable for microwear analysis.
Southeastern Cameroon Baka pygmies, one of the largest
groups of seminomadic hunter-gatherers in Central Africa,
show the lowest genetic admixture rates with BSF neighbors
[9,47]. Since they lack both plantations and domestic animals,
the Baka pygmies subsistence economy heavily depends on
forest products [2,19,48]. Over 90% of their daily energy intake
on a weight basis is obtained from yam (Dioscorea spp.) tuber
(60%), game meat from small mammals (15%20%), and nuts
(10%), with few seasonal differences . Other food types
(fish, honey, or insects) play a complementary role [19,49]. The
Aka pygmies live in the southern forest regions of CAR and
northern Congo-Brazaville. Their subsistence is based on
gathered foods, mainly yam, and game from hunting. The Aka
spend little or no time cultivating plant foods [2,16,22], and
consumption of agricultural foods remains very limited
[22,50,51]. This pattern of resource accessibility resembles that
of the Baka pygmies [2,19,49].
The Mbuti pygmies inhabit the southern part of the Ituri
Forest in the DRC. Ethnographic descriptions show that they
do not practice agriculture, and hunting activities have been
more important than gathering wild vegetables in their
subsistence strategies for centuries, with fish representing only
a small portion of their diet [4,15]. The Mbuti largely rely on
forest products, although they also obtain farm products
(cassava, plantain, and agricultural crops) from Bantu villagers
[23,24], which does not affect their foraging lifestyle [4,23,52].
Babongo pygmies inhabit forested areas of the central and
southern Gabon . Compared with the Aka and Baka, the
Babongo people lead a highly sedentary lifestyle , having
adopted agriculture earlier than other forest peoples but not to
an extent sufficient to satisfy all their nutritional requirements
[20,54]. At present, meat from the forest occupies an important
position in their diet (25%), but starchy foods (cassava, maize,
plantains, and peanuts) from farming constitute their major
subsistence strategy (46%), which is complemented by plant
gathering (13%) and fish (8%) being mainly consumed as a
Non-Pygmy BSFs include groups from CAR (Banda, Banziri,
Baya, Bayanda, Bopan, Boupara, Mandjia, and Yakoma),
Congo (Batk-Balali and Bondjo), DRC (Azande, Bassoko,
Luba, Mamvu, Mayanga, Mongo, and Yomb), Gabon
(Adouma, Ashango, Bakalai, Bayaka, Boulou, Bwiti, Galoa,
Mpongue, NKomi, and Pahouin), and Rwanda (Bahutu). All
Bantu speakers in this study inhabit the rainforest near or in
close contact with pygmies . Ethnographic reports (see
references in Table S1 in File S1) show that BSFs tend to
cluster in small villages with subsistence strategies mainly
dependent on crop plants from small-scale riverine plantations,
based upon slash-and-burn techniques [14,15,20,25]. Farmed
products include manioc, plantains, maize, rice, and peanuts.
Animal farming consists of poultry and some goats, either with
or without raising cattle. Despite BSFs occasionally hunting,
hunted meat resources are primary obtained from trade with
Pygmy groups [2,5,23,25,54]. In contrast to PHGs and BSFs,
the BSP Maasai from Kenya and Tanzania have a highly
specialized pastoralist diet, mainly based on milk, meat, and
blood, with little foraging and no agricultural practices .
Buccal microwear analysis
Tooth crowns were molded with polyvinylsiloxane dental
impression material (PresidentJet regular body, Coltne
Corp.) and the resultant high-resolution epoxy casts (Araldite
2020, Vantico Ltd.) were produced from molds following
standard procedures [27,55]. For the in vivo Baka sample, prior
to silicone-based molds being made, volunteers teeth were
brushed and dried with an air compressor . Original teeth
selected from skeletal collections were cleaned using a cotton
swab soaked in pure ethanol, air-dried, and then molded using
the dental impression material . All replicas were examined
under light microscopy to determine suitability for buccal
enamel-surface microwear analysis. Based on standard
assessments [33,35,39], casts exhibiting postmortem chipping,
cracking, or surface erosion on buccal enamel surfaces were
discarded. The final sample included only casts that showed
buccal enamel surfaces with preserved antemortem microwear
features [33,35]. The replicas suitable for buccal microwear
analysis were coated with a ~15-nm layer of gold-palladium
and analyzed using scanning electron microscopy.
Micrographs (1280 960 pixels) were taken at 100
magnification in the middle third of the buccal surface of dental
crowns, preferably under the protoconid cusp tip, purposely
avoiding microwear features caused by intertooth contact on
occlusal facets . The digital micrographs were cropped with
Adobe PhotoshopTM 6.0 to cover exactly 0.56 mm2 of the
buccal enamel surface and enhanced with a high-pass filter (50
pixel) and automatic level adjustment [35,56]. A total of 10
microwear variables were considered , including the
scratch density (N) and average length (X) (in micrometers) of
all observed lineal scratches 10 m (NT and XT, respectively),
which were recorded and measured with Sigma Scan ProV
SPSSTM [35,36,56], and eight independent microwear density
and length variables, which were classified by 45 orientation
intervals (from 0 to 180) for lower M1 teeth, with regard to the
cemento-enamel junction of the tooth, as follows: mesio-distal
(NMD, XMD), vertical (NV, XV), horizontal (NH, XH), and
distomesial (NDM, XDM) [see Prez-Prez et al.  for detailed
Microwear variables were rank-transformed before running
statistical analyses to mitigate effects of noncollinearity of
variables distribution and heteroscedasticity [57,58]. Further,
ranked data can be used for parametric and multivariate
analyses even with small sample sizes . All the variables
studied passed Kolmogorov-Smirnov normality tests.
Descriptive statistics and tests at the = 0.05 significance
level were conducted using AddinsoftTM XLSTAT-3.02. A
multivariate analysis of variance (MANOVA), followed by
oneway analyses of variance (ANOVA) and post hoc paired
comparisons using Tukeys Honest Significant Difference test
(Tukeys HSD) were used as needed to check interpopulation
differences in microwear patterns. Finally, a Principal
Components Analysis (PCA) was done with density-derived
(NMD, NV, NH, NDM) and length-derived (XMD, XV, XH, XDM)
variables, removing NT and XT variables because their high
collinearity levels (r Pearson = 0.4 to 0.8; p < 0.01) with other
variables , to show the major trends in buccal microwear
among the analyzed groups, as applied previously , and to
identify the influence of the consumption of abrasive foods on
microwear patterns .
Overall differences in total scratch densities and average
length (in micrometers) were observed between PHGs and
Bantu speakers (Figure 1 and Table 1). The PHGs showed the
smallest scratch density (NT = 64.47 27.31 mean SD-, n =
51), followed by the BSPs (NT = 77.00 9.12, n = 12), with the
BSFs having the highest scratch density value (NT = 151.25
30.62, n = 80). Moreover, the PHGs showed the largest scratch
length (XT = 146.37 28.06 m) (Figure 2A). Within the PHG
groups, the Babongo showed the highest density values (NT =
121.83 31.44) and the Mbuti had the lowest XT value (97.37
17.80 m), close to that of the BSFs (87.11 18.50 m)
(Figure 2B). In an analysis of scratch density and length
variables by orientation (see Methods and Table 1), we found
that BSFs had higher densities of shorter scratches than the
PHGs. Otherwise, the BSPs presented the lowest
betweengroup length values. Among PHGs, the Babongo had the
largest scratch densities by orientation, whereas the Mbuti
showed the shortest. Significant differences in overall scratch
density (NT) and length (XT) were observed among the three
main socioeconomic groups: PHGs, BSFs, and BSPs (F =
23.44, p < 0.001; Wilks = 0.129, partial 2 = 0.641, MANOVA;
Table 2). The univariate ANOVAs showed that among-group
differences were significant for all 10 microwear variables (p <
0.001). Pairwise comparisons (Tukeys HSD post hoc test)
showed (Table 3) that PHGs had significantly (p < 0.05) lower
scratch densities and larger lengths than the BSFs for all
orientations, while the PHGs and BSPs significantly differed for
NV and all the length variables, while the BSFs and BSPs
differed for all the density variables, except NV, and for XMD
and XH (Table 2). The forager group (PHGs), including the
Aka, Baka, Babongo, and Mbuti, was characterized by low
scratch densities and high scratch lengths, a microwear pattern
that was clearly opposite that of the farmer group (BSFs).
Although the PHGs showed a more homogenous microwear
pattern compared with the Bantu speakers, significant
differences were observed among populations when the Baka,
Aka, Babongo, and Mbuti were considered separately (Table
S2 in File S1). All microwear variables showed significant
among-group differences (p < 0.001, ANOVA). However, in a
comparison of the Aka and Baka (Tukeys HSD; p < 0.05), no
significant differences in any microwear variables were found.
Instead, the Baka statistically differed from the Mbuti for XT (p
< 0.001) and XV (p = 0.003), and from the Babongo for NT (p <
0.001), NMD (p = 0.043), and NH (p < 0.001), whereas
significant differences between the Aka and Babongo were
found only for NT (p = 0.018). Finally, the Babongo differed
from the Mbuti only for NT (p = 0.015). The Babongo clearly
showed the most distinct microwear pattern among PHGs,
resembling the BSFs with regard to high scratch densities. The
other PHG groups showed similar scratch densities, but the
Mbuti had shorter average scratch lengths, which resulted in a
microwear pattern resembling that of the BSPs (Figure 2B)
The PCA of the eight independent microwear variables
(excluding NT and XT, see Methods) yielded two PCs with
Eigenvalues larger than 1 that explained 63.19% of the total
variance (Figure 3 and Table S3 in File S1). PC1 explained
44.37% of the total variance and was positively correlated with
the length variables (Pearson r ranging from 0.72 to 0.83) and
negatively correlated with the density ones (r values ranging
from 0.42 to 0.60). PC2 explained 18.82% of the total
variance and was mainly correlated with NH (r = 0.69), NMD (r
= 0.53), and NV (r = 0.52). Univariate ANOVAs for PC1 and
PC2 by dietary groups (PHGs, BSFs, and BSPs) showed
significant differences in both cases (p < 0.0001), which
indicates that PC1 distinguished PHGs for having longer and
less abundant scratches than BSFs and BSPs, and PC2
distinguished BSPs for having a lower scratch density than
Buccal microwear patterns reflect abrasive properties of
ingested foodstuffs , even in present-day living people
[33,39]. Meat is not hard enough to damage enamel surfaces
during chewing , whereas both plant phytoliths and
grittyquartz particles have been shown to cause enamel etching
[28,29,31]. However, the effect of specific abrasive agents on
enamel surfaces is difficult to characterize because differences
in the load-bearing capacity of teeth might be a function of
morphology (tooth size and geometry or enamel thickness)
rather than underlying mechanical properties [30,32,59,60].
Nonetheless, dental microwear formation seems to be strongly
influenced by the amount of abrasive particles ingested with
food and their intrinsic hardness compared to enamel [29,31].
Plant silica phytoliths and grit particles have been shown to be
involved in the formation and remodeling of microwear patterns
[27,29], with phytoliths being responsible for long-term
processes, mainly forming small microwear features, and
exogenous quartz particles (~2.5-fold harder than enamel)
causing significant biting stresses, even with modest loadings,
resulting in microwear features larger in size [27,31,32].
The variability of the buccal microwear pattern observed
between the BSF and PHG groups was clearly linked to the
inclusion of agricultural products in their diets, which likely had
a significantly higher content of abrasive particles than foraged
fruits and USOs. These microwear patterns are representative
of two distinct dietary habits, one mainly vegetarian and
including highly abrasive particles and the other having a
Figure 1. Buccal enamel surfaces showing different microwear patterns related to abrasive properties of chewed
foodstuffs. Baka Pygmy hunter-gatherer (left) and Pahouin (#9715, Muse de l'Homme, Paris) agriculturalist from Gabon (right).
Both individuals are adult females. Note highly abraded enamel surface in the Bantu-speaking farmer. Each micrograph represents
a buccal enamel area of 0.56 mm2 on mandibular first molars at 100. Scale bar: 100 m.
higher content of hunted meat and foraged plant foods.
Otherwise, the two Bantu-speaking groups (BSFs and BSPs)
resembled each other in having short scratches; however, the
pastoralist Maasai showed a distinct pattern, with both a low
density of scratches and short average lengths, likely due to
their soft and less abrasive diet . Both PHG and Maasai
populations have limited access to cultivated goods (a
significant source of phytoliths and dust grit) compared with
BSFs [2,4,7,1921]. Moreover, the PHGs overall showed lower
scratch densities and longer average lengths than the BSFs.
However, among PHGs the microwear pattern of the Babongo,
the most sedentary of the forager populations analyzed,
overlapping that of the BSFs, whose samples showed the
highest scratch densities and shorter striation lengths. The
buccal microwear variability of the Babongo (though
represented by a rather small sample) was much smaller than
that of the BSFs, showing similarities with the PHG microwear
pattern that might suggest they did not fully abandon a forager
As a whole, the feeding strategies of the PHGs clearly
translate into a distinct low-density pattern of buccal microwear
that depends on the amount of etching particles incorporated in
foodstuffs. Our microwear findings suggest that PHGs mainly
consume foraged plant foods with reduced abrasiveness
compared to harvested foods. Yam (including over 600
varieties, 95% of which are endemic to Africa), a monocot plant
that differs from sweet potatoes (a dicot called yams in some
parts of the world), is the most consumed starch-rich tuber,
either gathered or cultivated, by African populations [41,42],
including PHGs [18,19,24,40]. Yam tubers lack phytoliths,
useful for taxonomic classification , but show the highest
levels of fracture toughness (J m2) among 33 analyzed root
tubers . If cooked or roasted, their mechanical resistance
decreases, while the energetic gain increases, allowing for less
forceful mastication and easier digestion [42,61]. If abrasive
particles are not incorporated during processing prior to
ingestion, yam consumption in rainforest environments does
not cause enamel indentation [32,59]. In contrast, USOs from
savannah or desert habitats, including a wider range of edible
tubers, can be consumed raw  and frequently incorporate
grit-soil particles that cause higher tooth-wear rates in
savannah foragers, such as the Hadzabe in northern Tanzania,
than those seen in farmer populations . In PHG culture,
animal resources are frequently smoked [4,49,54,63] and
tubers, either wild or cultivated, are harvested with a digging
stick [18,50] and soaked in water for a few days before being
roasted or boiled for consumption [15,19,25,49]. Thereby, both
meat and tubers may incorporate abrasive particles from ashes
or dust that, despite usually being removed before ingestion,
may contribute to the formation of the buccal microwear
patterns observed in the PHGs. Otherwise, the highly abraded
microwear patterns shown by the Bantu farmers, who consume
gritty particles from stoneground foods [5,6], resemble those
observed in horticulturalist populations [38,39] and differ from
the groups that consume considerable quantities of meat .
The consistency of the association seen between food
abrasiveness and buccal microwear pattern supports the
hypothesis that PHG and BSP populations share an overall soft
diet, with significant consumption of meat and other
animalderived products. A diet including some exogenous, coarse,
and brittle particles, likely larger in diameter than those in
Maasai pastoralist diets, would explain the distinct microwear
pattern of the foragers compared with the pastoralist group.
The increasing reduction of natural areas and scarcity of big
game have greatly altered Pygmy economy [5,12,20,21,48].
Manioc cultivation by Baka pygmies was first described at the
beginning of the 20th century , but it is not yet clear if
dietary preferences have changed between ancient and
present-day pygmies [2,4,19]. No differences in buccal
microwear patterns were observed between the Aka (collected
at the beginning of the 20th century) and present-day Baka
(collected from living individuals), probably due to similarities in
their dietary regimens despite the temporal divergence , and
few differences were observed between the Baka and the
Mbuti (a 1950s collection). The buccal microwear pattern of the
Mbuti, and especially that of the Babongo, slightly resembles
that of the Bantu farmers, since they engage in food trade
contacts [8,9,23,54], whereas the Aka and Baka have less
access than the Babongo and Mbuti to cultivated products
[2,24,54]. When dietary preferences shift to include greater
amounts of abrasives, such as in agricultural goods, buccal
enamel microwear patterns have been shown to significantly
reflect the change [27,39]. The lack of information about the
studied ancient individuals prior to their deaths does not permit
seasonal buccal microwear inferences. Nonetheless, a relative
importance of wild yam gathering and hunting activities (up to
90%) among the Aka and Baka has been reported in both dry
and rainy seasons when no trade for Bantu resources occurs
[2,16,19] and supports the homogenous microwear patterns
found between these populations. By contrast, we have
insufficient data to extend our conclusions to any other PHGs
analyzed due to small sample sizes and the scarcity of similar
seasonal observational surveys [15,53,54]. Nonetheless, in
vivo experiments with humans have indicated that
buccalmicrowear might vary in populations with specific diets and
ecological conditions but at the same time, long-term
microwear patterns probably remain stable independent of
dietary habits [27,33].
Based on overall observation, our results suggest that
dietary habits of Pygmy populations have not significantly
changed during the last century, as some ethnographic studies
have already indicated [4,19,21]. The economic associations
Figure 2. Buccal microwear pattern variability among the analyzed populations. (A) Box-plots showing scratch density (NT)
and their average length (XT, in micrometers) among dietary groups. Boxes enclose 25%75% percentile values, the mean and
median are indicated with a circle and horizontal bar, respectively, and whiskers denote minimummaximum values. (B) NT and XT
mean values plotted within PHGs (Aka, Baka, Babongo, and Mbuti) and Bantu farmer (BSFs) and pastoralist (BSPs) populations.
Error bars denote 2 standard error (SEM). The number of individuals (n) in each group is indicated.
between Bantu speakers and Pygmy seem to be limited to
specific time periods and vary according to the group, as
shown between the Mbuti and Bantu-speaking groups in the
Ituri forest [4,12,50,65], and do not significantly affect
microwear patterns of most of the forager groups analyzed
from Central Africa. Similar information from western Africa is
The implications of the buccal microwear variability of the
Pygmy and Bantu populations for the characterization of
hominin diets should not be dismissed. Meat and USOs may
have played a significant role in dietary adaptations of early
hominins [41,42] and morphological adaptations of dental traits
in the earliest members of the genus Homo (21.5 Ma) have
been related to the consumption of mechanically challenging,
tough high-energy foodstuffs, likely associated with brain
growth and cultural changes in stone-tool technology [66,67].
However, the USO-eating hypothesis [41,42] on tooth use and
microwear has not yet been tested in modern foragers [41:
494]. Our buccal microwear analysis of Pygmy populations
indicates that a diet mainly based on fire-processed meat and
USOs, similar to that hypothesized for early Homo [41,67],
should result in a low-density, not highly variable microwear
pattern. However, occlusal microwear texture complexity
analyses have shown highly variable microwear patterns for
this taxon, interpreted as dietary habits characterized by the
consumption of non-fracture-resistant foods and low
biomechanical demands on chewing , consistent with
cranio-dental evolutionary changes in early Homo . Buccal
microwear patterns of early Homo specimens, as well as of
other modern forager populations, contribute to this microwear
interpretation and to the characterization of the significance of
staple foods in ancient human diets.
Figure 3. Dispersion Principal Components (PC) 1 versus 2, derived from buccal microwear variables, by subsistence
economy. The proportion of the variance explained by the PCs is indicated in parentheses. The ellipses include 95% confidence
regions of the dietary groups considered. Pygmy hunter-gatherers (PHGs) have low density of longer scratches, whereas variation
in Bantu-speaking farmers (BSFs) and pastoralists (BSPs) are reflected in high (BSFs) and low (BSPs) density pattern of shorter
scratches. All individuals analyzed are plotted. See Materials and Methods sections for the details of methodology and sample
File S1. Table S1, African populations studied by
subsistence strategy. Includes provenance, sample sizes and
references. Table S2, Between groups statistical comparisons
(One-way ANOVA and Tukeys pots-hoc test) for all the buccal
microwear variables considered. Table S3, Results
(Eigenvalues, % of explained variance, and Pearson
correlations r) of the Principal Components (PCA) on buccal
dental microwear patterns for the populations considered.
We are grateful to all the Baka participants. We are also
indebted to A. Froment and P. Mennecier (Muse de L'Homme,
Paris), A. Sanchez-Mazas and G. Prreard (University of
Geneva), R. Orban and P. Semal (Institut Royal des Sciences
Naturelles de Belgique, Bruxelles), and Ian Tattersall
(American Museum of Natural History, New York) who
provided access to collections under their care. Thanks to Jordi
Galbany for helpful comments on earlier drafts of the
manuscript and to Frank L'Engle Williams and the reviewers for
valuable and detailed comments, which contributed to the
improvement of this paper.
Conceived and designed the experiments: AR FRR APP.
Performed the experiments: AR FRR APP. Analyzed the data:
AR JDJ. Contributed reagents/materials/analysis tools: AR
FRR JDJ APP. Wrote the manuscript: AR APP FRR. Obtained
permission for in vivo sampling: FRR. Provided funding: APP
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