Alejandro Romero

Age-Related Tooth Wear Differs between Forest and Savanna Primates

Tooth wear in primates is caused by aging and ecological factors. However, comparative data that would allow us to delineate the contribution of each of these factors are lacking. Here, we contrast age-dependent molar tooth wear by scoring percent of dentine exposure (PDE) in two wild African primate populations from Gabonese forest and Kenyan savanna habitats. We found that forest-dwelling mandrills exhibited significantly higher PDE with age than savanna yellow baboons. Mandrills mainly feed on large tough food items, such as hard-shell fruits, and inhabit an ecosystem with a high presence of mineral quartz. By contrast, baboons consume large amounts of exogenous grit that adheres to underground storage organs but the proportion of quartz in the soils where baboons live is low. Our results support the hypothesis that not only age but also physical food properties and soil composition, particularly quartz richness, are factors that significantly impact tooth wear. We further propose that the accelerated dental wear in mandrills resulting in flatter molars with old age may represent an adaptation to process hard food items present in their environment.

Brief Communication: Short- and Long-Term In Vivo Human Buccal-Dental Microwear Turnover

Buccal-dental microwear depends on the abrasive content of chewed foodstuffs and can reveal long-term dietary trends in human populations. However, in vivo experimental analyses of buccal microwear formation processes are scarce. Here, we report the effects of an abrasive diet on microwear rates in two adult volunteers at intervals of 8 days over a period of 1 month and document long-term turnover over 5 consecutive years in the same subjects under an ad libitum Mediterranean diet. Buccal microwear was analyzed on mandibular first molars using high-resolution replicas and scanning electron microscopy. Microwear turnover was assessed by recording the scratches lost and gained at each time point. Our results indicate that scratch formation on enamel surfaces increased with a highly abrasive diet compared to both pre-test and post-test ad libitum dietary controls. In the long-term analysis, scratch turnover was higher than expected, but no significant long-term trends in microwear density or length were observed, because microwear formation was compensated by scratch disappearance. Our results confirm that buccal microwear patterns on mandibular molars show a dynamic formation process directly related to the chewing of abrasive particles along with ingested food. In addition, the observed long-term stability of buccal microwear patterns makes them a reliable indicator of overall dietary habits.

Diet-related buccal dental microwear patterns in Central African Pygmy foragers and Bantu-speaking farmer and pastoralist populations.

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.

Effectiveness of human spermatozoa biomarkers as indicators of structural damage during cryopreservation

Human spermatozoa cryopreservation techniques are used to maintain and protect male fertility in cases such as infertility and malignancy treatments. However, during cryopreservation, the spermatozoas metabolic rate is reduced and they undergo dramatic functional and structural changes owing to exposure to cryoprotectants and freezing-thawing procedures. While the effects of cryopreservation on cells are documented, to date the induced cryodamage on structural and/or functional sperm biomarkers is not well established at multivariate scale. To address this question, we performed basic sperm analysis, sperm DNA fragmentation assessment, spontaneous acrosome reaction measurement, and cytoskeleton evaluation after thawing samples from subjects with normal and low-quality semen. A cryodamage rate was used to determine the effects of the freeze-thaw process on spermatozoa. In addition, a Principal Component Analysis (PCA) was used for data reduction and to evaluate sperm-specific patterns during the cryopreservation process. We found that the vitality, progressive motility and sperm count from low-quality samples after cryopreservation show higher damage rates (≥40%) than in normal sperm samples. However, cytoskeleton, DNA, tail and mid-piece and acrosome display the highest cryodamage rates (∼50-99%) and are equally susceptible to cryopreservation-induced damage in both low- and normal-quality semen samples. Overall, the evaluation of these parameters provides meaningful information about different aspects of sperm functionality after cryopreservation.

The diet of the first Europeans from Atapuerca

Hominin dietary specialization is crucial to understanding the evolutionary changes of craniofacial biomechanics and the interaction of food processing methods’ effects on teeth. However, the diet-related dental wear processes of the earliest European hominins remain unknown because most of the academic attention has focused on Neandertals. Non-occlusal dental microwear provides direct evidence of the effect of chewed food particles on tooth enamel surfaces and reflects dietary signals over time. Here, we report for the first time the direct effect of dietary abrasiveness as evidenced by the buccal microwear patterns on the teeth of the Sima del Elefante-TE9 and Gran Dolina-TD6 Atapuerca hominins (1.2–0.8 million years ago − Myr) as compared with other Lower and Middle Pleistocene populations. A unique buccal microwear pattern that is found in Homo antecessor (0.96–0.8u2009Myr), a well-known cannibal species, indicates dietary practices that are consistent with the consumption of hard and brittle foods. Our findings confirm that the oldest European inhabitants ingested more mechanically-demanding diets than later populations because they were confronted with harsh, fluctuating environmental conditions. Furthermore, the influence of grit-laden food suggests that a high-quality meat diet from butchering processes could have fueled evolutionary changes in brain size.

Age-related variability in buccal dental-microwear in Middle and Upper Pleistocene human populations

Age-related variability in buccal dental-microwear in Middle and Upper Pleistocene human populations Infants are thought to present a different buccal microwear pattern than adults and these, therefore, are generally analyzed separately. However, El-Zaatari & Hublin [2009] showed that occlusal texture in Neandertal and modern human juvenile populations did not differ from their elders. The microwear patterns of a sample of 193 teeth, corresponding to 61 individuals of Homo heidelbergensis, H. neanderthalensis and anatomically modern humans (AMH), were analyzed revealing that AMH infants up to 14 years old differ from older individuals in having fewer scratch densities, whereas the Neandertals have a much more variable microwear pattern. Age-at-death and dental age since emergence showed similar though somewhat diverging results, especially in the infant and subadult samples. Differences observed between the Neandertals and modern humans could be reflecting differential wearing patterns or distinct enamel structure and resistance to hard food items consumption. Interpopulation differences in striation densities were not apparent in either subadult or adult individuals, only adult Neandertals (26-45 yrs. old) showed fewer striations than the younger age groups. The AMH sample revealed a gradual cumulative pattern of striation density with age, suggestive of a non-abrupt change in diet. Policzkowe mikrostarcie zębów wykazuje charakterystyczne, trwałe i zależne od diety cechy. Na materiałach historycznych wykazano [Pérez-Pérez et al. 1994], że w analizie trzeba uwzględniać również wiek osobnika, szczególnie u dzieci, które mają zarówno zęby mleczne, jak i świeżo wyrżnięte zęby stałe. W populacjach górnoplejstoceńskich zbadano jednak tylko mikrostarcie na zgryzowych powierzchniach zębów. Ostatnio El-Zaatari & Hublin [2009] stwierdzili brak związanych z wiekiem różnic w nierównościach szkliwa, i to zarówno w populacjach neandertalskich, jak i u człowieka anatomicznie nowoczesnego (AMH), wobec czego grupy reprezentowane zębami mlecznymi można analizować łącznie ze stałymi [Gamza 2010]. Dla populacji historycznych wykazano, że wzór mikrostarcia stabilizuje się około 13 roku życia, niezależnie od zęba (m2, M1, M2). Nie próbowano jednak badać procesu tej stabilizacji u prehistorycznych łowców-zbieraczy. Celem tej pracy jest ustalenie, w jakim wieku wzór policzkowego mikrostarcia stabilizuje się u środkowo- i górnoplejstoceńskich osobników i przetestowanie różnic między wzorem mikrostarcia u dorosłych oraz u dzieci i osobników dorastających. Badana próba zawierała 836 wysokiej rozdzielczości odlewów zębowych, dostępnych na uniwersytecie w Barcelonie. Zęby należały do 174 osobników z trzech populacji: Homo heidelbergensis, H. neanderthalensis i H. sapiens (AMH). Zęby, na których nie zachowało się policzkowe mikrostarcie lub od osobników o nieustalonym wieku wyeliminowano, podobnie jak wszystkie zęby przednie. Ostatecznie próba liczyła 193 zęby 59 osobników. Wiek zębowy od momentu wyrżnięcia obliczano za Skinnerem [1997]. Dla AMH wiek wyrzynania przyjmowano za Ubelakerem [1979] i Williamsem [2006], a dla H. neanderthalensis i H. heidelbergensis - za Gramat & Heim [2003]. Powierzchnie policzkowe zębów były skanowane SEM zgodnie ze standardową procedurą [Pérez-Pérez et al. 2003, Galbany et al. 2009]. Z obrazów SEM wycięte zostały fragmenty szkliwa o powierzchni 0,56 mm2, na których zliczano rysy przy pomocy półautomatycznego oprogramowania. Uwzględniano gęstość, długość i odchylenie standardowe długości wszystkich zauważonych prążków w kategoriach ich orientacji (pionowe, poziome, mezjo-dystalne i dysto-mezjalne oraz wszystkich orientacji łącznie. Przedstawiana analiza dotyczy jednak tylko ogólnej gęstości prążkowania. W analizie statystycznej wykorzystano SPSS 15. Poniewaz gęstość prążkowania ma rozkład normalny, do porównań międzygrupowych zastosowano testy parametryczne (ANOVA). We wszystkich trzech badanych populacjach osobniki w wieku poniżej 5 lat wykazywały gęstość prążków podobną do osobników dorosłych. Choć u neandertalczyków w wieku 6-13 lat gęstość prążkowania wyraźnie malała, co mogło korespondować z wyrzynaniem się M1, w grupie AMH dzieci miały rzadsze prążki niż starsze osobniki i wykazywały ciągły wzrost gęstości z wiekiem. Zmienność mikrostarcia u osobników w wieku dziecięcym może być związana z procesem przechodzenia na pokarm stały, który u AMH polegał na stopniowym włączaniu do diety twardszych składników, jak również obróbki termicznej [Hadingham 1979, Pfeiffer 1986, Nakazawa et al. 2009]. Z tej pracy płyną następujące wnioski: Wzór policzkowego mikrostarcia jest charakterystyczny dla każdej populacji i odzwierciedla długotrwałe zwyczaje żywieniowe. Uwzględniać należy wiek w chwili śmierci, szczególnie dla osobników przed 13 rokiem życia. Przejście od diety dziecięcej na dorosłą mogło zachodzić stopniowo u AMH, podczas gdy u neandertalczyka wcześnie ujawnia się wzrost gęstości prążków, prawdopodobnie odzwierciedlając przechodzenie na dietę z produktami wywołującymi większą abrazję. Zmienność wewnątrzpopulacyjna - czasowa, geograficzna i klimatyczna - może oznaczać, że te czynniki mogły wpływać na dostępność różnych składników pokarmu.

Tooth wear and feeding ecology in mountain gorillas from Volcanoes National Park, Rwanda

OBJECTIVESnEcological factors have a dramatic effect on tooth wear in primates, although it remains unclear how individual age contributes to functional crown morphology. The aim of this study is to determine how age and individual diet are related to tooth wear in wild mountain gorillas (Gorilla beringei beringei) from Volcanoes National Park, Rwanda.nnnMATERIAL AND METHODSnWe calculated the percent of dentine exposure (PDE) for all permanent molars (M1-M3) of known-age mountain gorillas (Nu2009=u200923), to test whether PDE varied with age using regression analysis. For each molar position, we also performed stepwise multiple linear regression to test the effects of age and percentage of time spent feeding on different food categories on PDE, for individuals subject to long-term observational studies by the Dian Fossey Gorilla Fund Internationals Karisoke Research Center.nnnRESULTSnPDE increased significantly with age for both sexes in all molars. Moreover, a significant effect of gritty plant root consumption on PDE was found among individuals. Our results support prior reports indicating reduced tooth wear in mountain gorillas compared to western gorillas, and compared to other known-aged samples of primate taxa from forest and savanna habitats.nnnDISCUSSIONnOur findings corroborate that mountain gorillas present very low molar wear, and support the hypothesis that age and the consumption of particular food types, namely roots, are significant determinants of tooth wear variation in mountain gorillas. Future research should characterize the mineral composition of the soil in the Virunga habitat, to test the hypothesis that the physical and abrasive properties of gritty foods such as roots influence intra- and interspecific patterns of tooth wear.

Dental microwear textural analysis as an analytical tool to depict individual traits and reconstruct the diet of a primate

OBJECTIVESnDental microwear is a promising tool to reconstruct animals diet because it reflects the interplay between the enamel surface and the food items recently consumed. This study examines the sources of inter-individual variations in dietary habits in a free-ranging population of mandrills (Mandrillus sphinx) using a combination of feeding monitoring and in vivo dental microwear textural analysis (DMTA).nnnMETHODSnWe investigated the impact of seasonality and individual traits on four DMTA parameters. In parallel, we further studied the influence of the physical properties of the food items consumed on these four parameters, using three proxies (mechanical properties, estimates of phytolith and external grit contents).nnnRESULTSnWe found that seasonality, age, and sex all impact DMTA parameters but those results differ depending on the facet analyzed (crushing vs. shearing facets). Three DMTA parameters (anisotropy, complexity, and heterogeneity of complexity) appear sensitive to seasonal variations and anisotropy also differs between the sexes while textural fill volume tends to vary with age. Moreover, the physical properties of the food items consumed vary seasonally and also differ depending on individual sex and age.nnnCONCLUSIONnConsidering the interplay between the tested variables and both dental microwear and diet, we reaffirm that food physical properties play a major role in microwear variations. These results suggest that DMTA parameters may provide valuable hints for paleoecological reconstruction using fragmentary fossil dental remains.

Phylogenetic signal in molar dental shape of extant and fossil catarrhine primates.

Morphology has been widely used for inferring the phylogenies of numerous taxonomic groups. Recent molecular studies performed on extant non-human primates, however, have cast doubt on the reliability of cranial and postcranial characters for characterizing evolutionary affinities. Because molecular evidence is often not available for fossil specimens, detecting phylogenetic signals in anatomical features is of great relevance. Here we have analyzed molar (M1 and M2) crown shape by means of geometric morphometrics in a large sample of both extant and fossil Miocene catarrhine primates to detect the phylogenetic signal in molar morphometry. Results support that molar shape carries a strong phylogenetic signal, mostly at the superfamily level but also to some extent at the family level. Dietary factors, however, appear to have less influence, especially for M2. The Miocene Pliopithecoidea, Cercopithecoidea, and Hominoidea superfamilies clearly grouped according to the expected taxonomic affinities with the extant groups, although some discrepancies were found depending on the tooth considered. Our findings suggest that although molar crown shape can be used as a reliable proxy for establishing taxonomic affinities of catarrhine fossil primates with extant groups, a significant amount of interspecific variation exists, indicative of derived adaptations at the genus or species level.

First molar size and wear within and among modern hunter-gatherers and agricultural populations

Apart from reflecting modern human dental variation, differences in dental size among populations provide a means for studying continuous evolutionary processes and their mechanisms. Dental wear, on the other hand, has been widely used to infer dietary adaptations and variability among or within diverse ancient human populations. Few such studies have focused on modern foragers and farmers, however, and diverse methods have been used. This research aimed to apply a single, standardized, and systematic quantitative procedure to measure dental size and dentin exposure in order to analyze differences among several hunter-gatherer and agricultural populations from various environments and geographic origins. In particular, we focused on sexual dimorphism and intergroup differences in the upper and lower first molars. Results indicated no sexual dimorphism in molar size and wear within the studied populations. Despite the great ethnographic variation in subsistence strategies among these populations, our findings suggest that differences in sexual division of labor do not affect dietary wear patterns.