Publications by authors named "Fernando Ramirez-Rozzi"

31 Publications

The same growth pattern from puberty suggests that modern human diversity results from changes during pre-pubertal development.

Sci Rep 2021 Mar 1;11(1):4817. Epub 2021 Mar 1.

UMR 7206 Ecoanthropology, MNHN, CNRS, UP, Musée de l'Homme, 17 place du Trocadéro, 75016, Paris, France.

Patterns of human growth established for one population have rarely been tested in other populations. In a previous study, three growth curves from puberty were modelled for each sex in a longitudinal study of a Caucasian population based on stature, age at peak of growth and biological maturation. Each curve represents the canalisation of growth associated with the type of puberty. The high precision (± 3 cm) of individual adult stature predictions shows that growth kinetics are already set up at puberty and are canalised depending on biological maturity. Our aim is to assess whether this model can be extrapolated to other populations to test whether growth canalisation is a population-dependent phenomenon or if the model reflects a canalisation pattern specific to our species. The modelled curves predicted adult stature with the same high degree of precision in basketball players and the Baka pygmies. Therefore, (1) the relationship between growth kinetics and age at maturity is similar in all populations and (2) growth according to pubertal stages follows the same canalisation patterns in the populations despite the wide differences in their average adult statures. It suggests that morphological diversity in modern humans results from processes taking place in early development.
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http://dx.doi.org/10.1038/s41598-021-84327-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7921106PMC
March 2021

A comprehensive survey of Retzius periodicities in fossil hominins and great apes.

J Hum Evol 2020 12 15;149:102896. Epub 2020 Oct 15.

Institute of Human Origins, School of Human Evolution and Social Change, Arizona State University, Tempe, AZ 85287, USA.

Recent studies have provided great insight into hominin life history evolution by utilizing incremental lines found in dental tissues to reconstruct and compare the growth records of extant and extinct humans versus other ape taxa. Among the hominins, studies that have examined Retzius periodicity (RP) variation have come to contradictory conclusions in some instances. To clarify RP variation among hominins and better place this variation in its broader evolutionary context, we conduct the most comprehensive analysis of published RP values for hominins and great apes to date. We gathered all available data from the literature on RP data from extant humans, great apes, and fossil hominins and assessed their variation using parametric and nonparametric analyses of variance. We also performed phylogenetic generalized least-squares regressions of RP data for these taxa as well as a larger set of hominoids for which RP data have been published against data for body mass, encephalization, and mean semicircular canal radius (a proxy for metabolic rate). Our results show that modern humans have a mean RP significantly differing from that of other hominins. Pongo also is significantly different from nearly all other taxa in all analyses. Our results also demonstrate that RP variation among hominins scales with respect to body mass, encephalization, and semicircular canal radius similarly to other hominids but that modern humans and Pongo stand out in this regard. Operating within the hypothesis that RP reflects autonomic biorhythms that regulate multiple life history variables, our results reinforce the idea that Homo sapiens has evolved a life history distinct from other hominins, even from other members of Homo, and suggest that many of these life history differences may be driven by hypothalamic output from the brain.
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http://dx.doi.org/10.1016/j.jhevol.2020.102896DOI Listing
December 2020

Age-related tooth wear in African rainforest hunter-gatherers.

Am J Phys Anthropol 2019 12 10;170(4):622-628. Epub 2019 Oct 10.

Departament de Biologia Evolutiva, Ecologia i Ciencies Ambientals, Secció Zoologia i Antropologia Biològica, Universitat de Barcelona, Barcelona, Spain.

Objectives: Central African small-scale foragers subsist primarily on hunting game activities and wild plant-food gathering. Starch-rich tubers are underground storage organs (USOs) and staple food resources in savanna and tropical rainforests. However, little is known about the effect of USO consumption on tooth wear development in living hunter-gatherers. We report age- and sex-dependent tooth wear rates in forest-dwelling Baka Pygmies with well-documented wild-yam-tuber-based diet to explore the long-term impact of USO mechanical hardness and abrasiveness on the wearing down of the teeth.

Materials And Methods: Percentages of dentine exposure (PDEs) of permanent left mandibular first molars (M ) were recorded using in vivo high-resolution replicas of Baka individuals (aged 8-33 years), inhabiting Le Bosquet district in Cameroon (Western Africa). Regression and covariance analyses were used to test the effect of individual aging by sex on PDE rates.

Results: We found a strong increase of PDE by age among Baka individuals. No evidence of sexual dimorphism in wear patterns suggests similar sex-related dietary and masticatory demands during growth. Overall, greatest dentine exposure values ≈4% denote unexpected slow wear down rates for foraging diets relying on USO consumption.

Discussion: The low molar wear rates with age found in Baka Pygmies contrast with extensive wear rates in savanna-dwelling foragers, reflecting differences in thermal processing techniques affecting fracture toughness and grittiness of mechanically challenging foods. Our findings reveal that culture-specific dietary proclivities influence tooth wear among foraging behaviors with important implications in hominin dietary versatility and abrasive stress on chewing surfaces.
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http://dx.doi.org/10.1002/ajpa.23934DOI Listing
December 2019

Tooth dimensions and body size in a Pygmy population.

Ann Hum Biol 2019 Sep 16;46(6):467-474. Epub 2019 Oct 16.

Departamento de Biotecnología, Facultad de Ciencias, Universidad de Alicante, Alicante, Spain.

The relationship between tooth size and stature has been analysed extensively at the interspecies level but has received less attention at the intraspecies level. The relationship between these two parameters does not seem to be the same among modern human populations. The aim of this study is to analyse the relationship between tooth dimensions and body measurements in the Baka Pygmies. Height, weight, and tooth dimensions were obtained for 45 adult Baka females and 17 males from Le Bosquet (Cameroon). Correlations were obtained between the variables and compared to results for other human populations. The Baka population is distinctive in the small number of significant correlations. Only two buccolingual diameters among Baka females show any significant correlation with height. The lack of significant correlations between tooth dimensions and body dimensions among the Baka means that changes in body size are accompanied by random variations in tooth dimensions. The absence of correlations may be accounted for by the impact of environmental effects on the somatic growth of the Baka producing a Pygmy phenotype adapted to live in the forest. It is worth noting that many correlations become significant when sexes are pooled.
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http://dx.doi.org/10.1080/03014460.2019.1673482DOI Listing
September 2019

Carbon and nitrogen isotopic signatures of hair, nail, and breath from tropical African human populations.

Rapid Commun Mass Spectrom 2019 Nov;33(22):1761-1773

Leverhulme Centre for Human Evolutionary Studies, Department of Archaeology, University of Cambridge, Fitzwilliam Street, Cambridge, CB2 1QH, UK.

Rationale: Stable isotopic analyses are increasingly used to study the diets of past and present human populations. Yet, the carbon and nitrogen isotopic data of modern human diets collected so far are biased towards Europe and North America. Here, we address this gap by reporting on the dietary isotopic signatures of six tropical African communities: El Molo, Turkana (Kerio), Luhya (Webuye), Luhya (Port Victoria), and Luo (Port Victoria) from Kenya, and Baka from Cameroon; representing four subsistence strategies: fishing, pastoralism, agriculturalism, and hunter-gatherer.

Methods: We used an elemental analyser coupled in continuous-flow mode to an isotope ratio mass spectrometer to measure the carbon and nitrogen isotopic ratios of hair (n = 134) and nail (n = 80) and the carbon isotopic ratios of breath (n = 184) from these communities, as well as the carbon and nitrogen isotopic ratios of some food samples from the Kenyan communities.

Results: We expand on the known range of δ C values in human hair through the hunter-gatherer Baka, with a diet based on C plants, and through the agriculturalist Luhya (Webuye), with a diet based on C plants. In addition, we found that the consumption of fish from East African lakes is difficult to detect isotopically due to the combined effects of high nitrogen isotopic ratios of plants and the low nitrogen isotopic ratios of fish. Finally, we found that some of the communities studied are markedly changing their diets through increasing sedentism and urbanisation.

Conclusions: Our findings contribute substantially to the understanding of the environmental, demographic, and economic dynamics that affect the dietary landscape of different tropical populations of Africa. These results highlight the importance of studying a broader sample of human populations and their diet, with a focus on their precise context - from both isotopic and more general anthropological perspectives.
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http://dx.doi.org/10.1002/rcm.8524DOI Listing
November 2019

Reproduction in the Baka pygmies and drop in their fertility with the arrival of alcohol.

Proc Natl Acad Sci U S A 2018 07 18;115(27):E6126-E6134. Epub 2018 Jun 18.

UMR 5288 Laboratoire Anthropologie Moléculaire et Imagerie de Synthèse, CNRS, Faculté de Chirurgie Dentaire, 92120 Montrouge, France

To understand the diversity of human growth and development from an evolutionary point of view, there is an urgent need to characterize the life-history variables of vanishing forager societies. The small body size of the Baka pygmies is the outcome of a low growth rate during infancy. While the ages at sexual maturity, menarche, and first delivery are similar to those in other populations, fertility aspects are unknown. In the Le Bosquet district in Cameroon, thanks to systematic birth records kept from 1980 onwards, we were able to assign ages to individuals with certainty. This study, based on chronological records and on data collected from 2007 to 2017, presents life-history variables related to fertility and mortality among the Baka pygmies: total fertility rate, age-specific fertility rate, completed family size, reproductive span, age at menopause, and infant and juvenile mortality. The Baka present low infant and juvenile mortality, and their fertility pattern differs from that of other forager societies in the higher age-specific fertility rates found in the two lower age classes. Future studies will need to assess whether this particular pattern and the short interbirth interval are related to highly cooperative childrearing, which in the Baka is associated with slow growth. The fertility rate has fallen drastically since 2011, and this matches the arrival of cheap alcohol in the community. Our data provide a first-hand record of the impact of alcohol on fertility in a hunter-gatherer society which appears to be seriously compromising the survival of the Baka.
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http://dx.doi.org/10.1073/pnas.1719637115DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6142234PMC
July 2018

Earliest Animal Cranial Surgery: from Cow to Man in the Neolithic.

Sci Rep 2018 04 19;8(1):5536. Epub 2018 Apr 19.

IRD - Musée de l'Homme, 17 place du Trocadéro, 75116, Paris, France.

The earliest cranial surgery (trepanation) has been attested since the Mesolithic period. The meaning of such a practice remains elusive but it is evident that, even in prehistoric times, humans from this period and from the Neolithic period had already achieved a high degree of mastery of surgical techniques practiced on bones. How such mastery was acquired in prehistoric societies remains an open question. The analysis of an almost complete cow cranium found in the Neolithic site of Champ-Durand (France) (3400-3000 BC) presenting a hole in the right frontal bone reveals that this cranium underwent cranial surgery using the same techniques as those used on human crania. If bone surgery on the cow cranium was performed in order to save the animal, Champ-Durant would provide the earliest evidence of veterinary surgical practice. Alternatively, the evidence of surgery on this cranium can also suggest that Neolithic people practiced on domestic animals in order to perfect the technique before applying it to humans.
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http://dx.doi.org/10.1038/s41598-018-23914-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5908843PMC
April 2018

Dental size variability in Central African Pygmy hunter-gatherers and Bantu-speaking farmers.

Am J Phys Anthropol 2018 07 22;166(3):671-681. Epub 2018 Mar 22.

Departament de Biologia Evolutiva, Ecologia i Ciencies Ambientals, Secció Zoologia i Antropologia Biològica, Universitat de Barcelona, Barcelona, 08028, Spain.

Objectives: Odontometric studies of African populations show high within-group variation in tooth size. Overall, North Africans exhibit smaller dimensions than groups from eastern and southern sub-Saharan regions, but no previous studies have analyzed the full dental metrics among extant African Pygmy hunter-gatherers and Bantu-speaking farmers. Furthermore, the population variability in tooth crown sizes from equatorial rainforest regions remains to be elucidated.

Materials And Methods: The mesiodistal and buccolingual diameters of the permanent teeth (I1-M2) were measured in vivo using high-resolution replicas from Baka Pygmies and Mvae and Yassa Bantu-speakers from Cameroon (western Africa). Analyses of variance were used to record sex-related and population-level differences in tooth sizes, and a principal component analysis of geometrically scaled measures was used to plot the odontometric variability among groups.

Results: Cameroonian Baka Pygmies differ in dental size from their Bantu-speaking neighbors. Molar teeth are larger in Pygmies than in Bantu individuals, while the anterior dentition is larger in the Bantu. Baka males exhibit significantly larger teeth than females, whereas sexual dimorphism in non-Pygmies is only present in the anterior dentition.

Discussion: Odontometric patterns and the degree of sexual dimorphism in dental size differ among Central African groups, indicating adaptation to their different forager and farmer lifestyles. In particular, the admixture of Bantu-speakers in Baka populations is smaller than that in other western Pygmy groups. The greater dental phenetic diversity in Baka compared to that of the smaller-toothed farmers suggests that ecogenetic and microevolutionary factors are influencing a particular divergence scenario.
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http://dx.doi.org/10.1002/ajpa.23458DOI Listing
July 2018

Diversity in tooth eruption and life history in humans: illustration from a Pygmy population.

Sci Rep 2016 06 16;6:27405. Epub 2016 Jun 16.

AMIS UMR 5288 CNRS - Université Paris V. Faculté de Chirurgie Dentaire, 1 rue Maurice Arnoux, 92120 Montrouge, France.

Life history variables (LHV) in primates are closely correlated with the ages of tooth eruption, which are a useful proxy to predict growth and development in extant and extinct species. However, it is not known how tooth eruption ages interact with LHV in polymorphic species such as modern humans. African pygmies are at the one extreme in the range of human size variation. LHV in the Baka pygmies are similar to those in standard populations. We would therefore expect tooth eruption ages to be similar also. This mixed (longitudinal and cross-sectional) study of tooth eruption in Baka individuals of known age reveals that eruption in all tooth classes occurs earlier than in any other human population. Earlier tooth eruption can be related to the particular somatic growth in the Baka but cannot be correlated with LHV. The link between LHV and tooth eruption seems disrupted in H. sapiens, allowing adaptive variations in tooth eruption in response to different environmental constraints while maintaining the unique human life cycle.
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http://dx.doi.org/10.1038/srep27405DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4910065PMC
June 2016

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

PLoS One 2013 19;8(12):e84804. Epub 2013 Dec 19.

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.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0084804PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3868657PMC
July 2014

Brief communication: Molar development and crown areas in early Australopithecus.

Am J Phys Anthropol 2012 Aug 24;148(4):632-40. Epub 2012 May 24.

Center for Craniofacial Molecular Biology, Herman Ostrow School of Dentistry, University of Southern California, Los Angeles, CA 90033, USA.

Recent studies suggest that the hypodigms representing the two earliest Australopithecus (Au. anamensis and Au. afarensis) form an ancestor-descendant lineage. Understanding the details of this possible transition is important comparative evidence for assessing the likelihood of other examples of ancestor-descendant lineages within the hominin clade. To this end we have analyzed crown and cusp base areas of high resolution replicas of the mandibular molars of Au. anamensis (Allia Bay and Kanapoi sites) and those of Au. afarensis (Hadar, Laetoli, and Maka). We found no statistically significant differences in crown areas between these hypodigms although the mean of M(1) crowns was smaller in Au. anamensis, being the smallest of any Australopithecus species sampled to date. Intraspecies comparison of the areas of mesial cusps for each molar type using Wilcoxon signed rank test showed no differences for Au. anamensis. Significant differences were found between the protoconid and metaconid of Au. afarensis M(2)s and M(3)s. Furthermore, the area formed by the posterior cusps as a whole relative to the anterior cusps showed significant differences in Au. afarensis M(1)s and in Au. anamensis M(2)s but no differences were noted for M(3)s of either taxon. Developmental information derived from microstructural details in enamel shows that M(1) crown formation in Au. anamensis is similar to Pan and shorter than in H. sapiens. Taken together, these data suggests that the overall trend in the Au. anamensis-Au. afarensis transition may have involved a moderate increase in M(1) crown areas with relative expansion of distal cusps.
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http://dx.doi.org/10.1002/ajpa.22089DOI Listing
August 2012

Different cranial ontogeny in Europeans and Southern Africans.

PLoS One 2012 27;7(4):e35917. Epub 2012 Apr 27.

División Antropología, Facultad de Ciencias Naturales y Museo, Universidad Nacional de La Plata - CONICET, La Plata, Buenos Aires, Argentina.

Modern human populations differ in developmental processes and in several phenotypic traits. However, the link between ontogenetic variation and human diversification has not been frequently addressed. Here, we analysed craniofacial ontogenies by means of geometric-morphometrics of Europeans and Southern Africans, according to dental and chronological ages. Results suggest that different adult cranial morphologies between Southern Africans and Europeans arise by a combination of processes that involve traits modified during the prenatal life and others that diverge during early postnatal ontogeny. Main craniofacial changes indicate that Europeans differ from Southern Africans by increasing facial developmental rates and extending the attainment of adult size and shape. Since other studies have suggested that native subsaharan populations attain adulthood earlier than Europeans, it is probable that facial ontogeny is linked with other developmental mechanisms that control the timing of maturation in other variables. Southern Africans appear as retaining young features in adulthood. Facial ontogeny in Europeans produces taller and narrower noses, which seems as an adaptation to colder environments. The lack of these morphological traits in Neanderthals, who lived in cold environments, seems a paradox, but it is probably the consequence of a warm-adapted faces together with precocious maturation. When modern Homo sapiens migrated into Asia and Europe, colder environments might establish pressures that constrained facial growth and development in order to depart from the warm-adapted morphology. Our results provide some answers about how cranial growth and development occur in two human populations and when developmental shifts take place providing a better adaptation to environmental constraints.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0035917PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3338763PMC
September 2012

A new method for relative Sr determination in human teeth enamel.

J Anthropol Sci 2011 1;89:153-60. Epub 2011 Jul 1.

Centro de Investigaciones Opticas, (CONICET La Plata, CIC), CC 124, 1900, La Plata, Argentina.

We present a new method to determine Sr/Ca changes in hard dental tissues based on laser ablation and spectroscopic detection. By using femtosecond Laser Induced Breakdown Spectroscopy (fs-LIBS), we micro mapped the relative amount of strontium in the enamel of three human lower third molar. We also analyzed the Sr/Ca ratio along the striae of Retzius. Results show that microlibs allows detection of variation in relative Sr/Ca ratio through enamel. The same values of Sr/Ca ratio were found along a single stria. The method has a precision better than 95% and is sensitive enough to detect Sr/Ca ratio variations among striae and within stria. Fs-LIBS generates information in a fast and simple way that can be used by non-specialists to make inferences about diet or mobility in human populations and fossil hominids.
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http://dx.doi.org/10.4436/jass.89012DOI Listing
April 2012

Diversity among African pygmies.

PLoS One 2010 Oct 26;5(10):e13620. Epub 2010 Oct 26.

UPR 2147 CNRS, Paris, France.

Although dissimilarities in cranial and post-cranial morphology among African pygmies groups have been recognized, comparative studies on skull morphology usually pull all pygmies together assuming that morphological characters are similar among them and different with respect to other populations. The main aim of this study is to compare cranial morphology between African pygmies and non-pygmies populations from Equatorial Africa derived from both the Eastern and the Western regions in order to test if the greatest morphological difference is obtained in the comparison between pygmies and non-pygmies. Thirty three-dimensional (3D) landmarks registered with Microscribe in four cranial samples (Western and Eastern pygmies and non-pygmies) were obtained. Multivariate analysis (generalized Procrustes analysis, Mahalanobis distances, multivariate regression) and complementary dimensions of size were evaluated with ANOVA and post hoc LSD. Results suggest that important cranial shape differentiation does occur between pygmies and non-pygmies but also between Eastern and Western populations and that size changes and allometries do not affect similarly Eastern and Western pygmies. Therefore, our findings raise serious doubt about the fact to consider African pygmies as a homogenous group in studies on skull morphology. Differences in cranial morphology among pygmies would suggest differentiation after divergence. Although not directly related to skull differentiation, the diversity among pygmies would probably suggest that the process responsible for reduced stature occurred after the split of the ancestors of modern Eastern and Western pygmies.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0013620PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2964320PMC
October 2010

Molar crown development in Australopithecus afarensis.

J Hum Evol 2010 Feb 30;58(2):201-6. Epub 2009 Dec 30.

Center for Craniofacial Molecular Biology, University of Southern California School of Dentistry, Los Angeles CA 90033 USA.

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http://dx.doi.org/10.1016/j.jhevol.2009.11.007DOI Listing
February 2010

Cutmarked human remains bearing Neandertal features and modern human remains associated with the Aurignacian at Les Rois.

J Anthropol Sci 2009 ;87:153-85

UPR 2147, Dynamique de l'Evolution Humaine, CNRS, 44 Rue de l'Amiral Mouchez, 75014 Paris, France.

The view that Aurignacian technologies and their associated symbolic manifestations represent the archaeologicalproxy for the spread of Anatomically Modern Humans into Europe, is supported by few diagnostic human remains, including those from the Aurignacian site of Les Rois in south-western France. Here we reassess the taxonomic attribution of the human remains, their cultural affiliation, and provide five new radiocarbon dates for the site. Patterns of tooth growth along with the morphological and morphometric analysis of the human remains indicate that a juvenile mandible showing cutmarks presents some Neandertal features, whereas another mandible is attributed to Anatomically Modern Humans. Reappraisal of the archaeological sequence demonstrates that human remains derive from two layers dated to 28-30 kyr BP attributed to the Aurignacian, the only cultural tradition detected at the site. Three possible explanations may account for this unexpected evidence. The first one is that the Aurignacian was exclusively produced by AMH and that the child mandible from unit A2 represents evidence for consumption or, more likely, symbolic use of a Neandertal child by Aurignacian AMH The second possible explanation is that Aurignacian technologies were produced at Les Rois by human groups bearing both AMH and Neandertal features. Human remains from Les Rois would be in this case the first evidence of a biological contact between the two human groups. The third possibility is that all human remains from Les Rois represent an AMH population with conserved plesiomorphic characters suggesting a larger variation in modern humans from the Upper Palaeolithic.
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September 2009

Megadontia, striae periodicity and patterns of enamel secretion in Plio-Pleistocene fossil hominins.

J Anat 2008 Aug;213(2):148-58

Center for Craniofacial Molecular Biology, School of Dentistry, University of Southern California, Los Angeles, USA.

Early hominins formed large and thick-enamelled cheek-teeth within relatively short growth periods as compared with modern humans. To understand better the developmental basis of this process, we measured daily enamel increments, or cross striations, in 17 molars of Plio-Pleistocene hominins representing seven different species, including specimens attributed to early Homo. Our results show considerable variation across species, although all specimens conformed to the known pattern characterised by greater values in outer than inner enamel, and greater cuspal than cervical values. We then compared our results with the megadontia index, which represents tooth size in relation to body mass, for each species to assess the effect of daily growth rates on tooth size. Our results indicate that larger toothed (megadont) taxa display higher rates or faster forming enamel than smaller toothed hominins. By forming enamel quickly, large tooth crowns were able to develop within the constraints of shorter growth periods. Besides daily increments, many animals express long-period markings (striae of Retzius) in their enamel. We report periodicity values (number of cross striations between adjacent striae) in 14 new specimens of Australopithecus afarensis, Paranthropus aethiopicus, Paranthropus boisei, Homo habilis, Homo rudolfensis and Homo erectus, and show that long-period striae express a strong association with male and average male-female body mass. Our results for Plio-Pleistocene hominins show that the biological rhythms that give rise to long-period striae are encompassed within the range of variation known for modern humans, but show a lower mean and modal value of 7 days in australopithecines. In our sample of early Homo, mean and modal periodicity values were 8 days, and therefore similar to modern humans. These new data on daily rates of enamel formation and periodicity provide a better framework to interpret surface manifestations of internal growth markings on fossil hominin tooth crowns. Importantly, our data on early hominin cross striation variation may now contribute towards solving difficult taxonomic diagnoses where much may depend on fragmentary molar remains and enamel structure.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2526111PMC
http://dx.doi.org/10.1111/j.1469-7580.2008.00938.xDOI Listing
August 2008

East-West cranial differentiation in pre-Columbian populations from Central and North America.

J Hum Evol 2008 Mar 26;54(3):296-308. Epub 2007 Nov 26.

División Antropología del Museo de La Plata (FCNyM, UNLP), Paseo del Bosque s/n, 1900 La Plata, Argentina.

In a recent study we found that crania from South Amerindian populations on each side of the Andes differ significantly in terms of craniofacial shape. Western populations formed one morphological group, distributed continuously over 14,000km from the Fuegian archipelago (southern Chile) to the Zulia region (northwestern Venezuela). Easterners formed another group, distributed from the Atlantic Coast up to the eastern foothills of the Andes. This differentiation is further supported by several genetic studies, and indirectly by ecological and archaeological studies. Some authors suggest that this dual biological pattern is consistent with differential rates of gene flow and genetic drift operating on both sides of the Cordillera due to historical reasons. Here we show that such East-West patterning is also observable in North America. We suggest that the "ecological zones model" proposed by Dixon, explaining the spread of the early Americans along a Pacific dispersal corridor, combined with the evolution of different population dynamics in both regions, is the most parsimonious mechanism to explain the observed patterns of within- and between-group craniofacial variability.
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http://dx.doi.org/10.1016/j.jhevol.2007.08.011DOI Listing
March 2008

Allometries throughout the late prenatal and early postnatal human craniofacial ontogeny.

Anat Rec (Hoboken) 2007 Sep;290(9):1112-20

División Antropología, Facultad de Ciencias Naturales y Museo, Universidad Nacional de La Plata, La Plata, Argentina.

Craniofacial shape changes throughout the late prenatal and early postnatal ontogeny (32-47 weeks of gestational age) were explored. The purpose was to evaluate whether the skull follows an allometric growth pattern, as was observed in other ontogenetic periods, and to assess shape variation patterns for the cranial vault, cranial base, and face. Thirty three-dimensional landmarks were registered in 54 skulls. Wire-frames were built with landmarks to observe shape variation in the following cranial components: anteroneural, midneural, posteroneural, optic, respiratory, masticatory, and alveolar. The landmark configurations were subjected to generalized Procrustes analyses, and the shape coordinates obtained were subjected to Principal Components Analyses. Multivariate regression of the shape variables (the principal components) on the size vector (the centroid size) was performed to assess allometries. Transformation grids were constructed to identify how cranial components interact across ontogeny. Results indicated that highly significant shape changes depend on size changes. Important shape variation in the vault, small variation in the cranial base, and no variation in the face were observed. Brain growth is proposed to be the major influence on craniofacial shape change, which produces a relative elongation and compression of midneural and posteroneural components. The cranial base elongates by intrinsic factors and affects position of the face. Ontogenetically, the cranial base seems to be independent with respect to brain growth, in contrast to what has been suggested in comparisons at higher taxonomic levels.
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http://dx.doi.org/10.1002/ar.20581DOI Listing
September 2007

Crown-formation time in Neandertal anterior teeth revisited.

J Hum Evol 2007 Jul 10;53(1):108-13; discussion 114-8. Epub 2007 May 10.

UPR 2147, Dynamique de l'Evolution Humaine, CNRS, 44, rue de l'Amiral Mouchez, 75014 Paris, France.

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http://dx.doi.org/10.1016/j.jhevol.2007.01.009DOI Listing
July 2007

Developmental connections between cranial components and the emergence of the first permanent molar in humans.

J Anat 2007 Apr;210(4):406-17

UPR 2147 Dynamique de l'Evolution Humaine, CNRS, Paris, France.

The age of emergence of the first molar (M1) is a developmental event correlated with many variables of primate life history, such as adult brain size. The evolution of human life history is characterized by the inclusion of childhood, which takes place between weaning and M1 emergence. Children still depend on adults for nutrition due to their small digestive system and their immature brains. By contrast, juveniles are not dependent because of M1 emergence, which enables shifting to adult type diet, and attainment of nearly adult brain size. In this study, developmental connections between M1 emergence and growth of cranial components were explored in two ways in order to understand the developmental basis of their evolutionary connections: (1) differences in growth trajectories of cranial components with respect to M1 emergence and (2) differences between individuals with and without fully emerged M1. Growth of anteroneural, midneural, posteroneural, otic, optic, respiratory, masticatory and alveolar cranial components was analysed in human skulls of individuals aged 0-20 years and in an adult reference skull. Volumetric indices were calculated to estimate size. Two subsamples were selected in order to focus on the transition between deciduous and permanent dentition: those with full deciduous dentition and before M1 reaches the occlusal plane; and those who present M1 in full emergence and no other cheek-tooth at the occlusal plane. The principal results were as follows. (1) Trajectories fitted using the whole sample are characterized by an inflection point that takes place before M1 emergence for neural components and around M1 emergence for facial components. (2) Associations between growth and age tend to be strong in those with full deciduous dentition, and weak in those who present M1 in full emergence. (3) Individuals who present M1 in full emergence are larger than those with full deciduous dentition. (4) Growth of components linked to the central nervous system is not linear until M1 emergence. Individuals who present M1 in full emergence are only larger than individuals with full deciduous dentition by 4-5% of adult size. (5) The alveolar component does not show increments between full deciduous dentition and M1 emergence. (6) When volumetric indices were standardized by age, the growth trajectories of individuals with full deciduous dentition and of those with M1 were not decoupled. In general terms, M1 emergence does not show a strong association with growth of the components that may explain differences in life histories. However, the main changes in neural and alveolar components occur in the first 3 years of life, which may be developmentally connected with M1 crown formation.
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http://dx.doi.org/10.1111/j.1469-7580.2007.00701.xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2100294PMC
April 2007

Variation in enamel development of South African fossil hominids.

J Hum Evol 2006 Dec 5;51(6):580-90. Epub 2006 Aug 5.

Institute for Human Evolution, School of GeoSciences, University of the Witwatersrand, Johannesburg, South Africa.

Dental tissues provide important insights into aspects of hominid palaeobiology that are otherwise difficult to obtain from studies of the bony skeleton. Tooth enamel is formed by ameloblasts, which demonstrate daily secretory rhythms developing tissue-specific structures known as cross striations, and longer period markings called striae of Retzius. These enamel features were studied in the molars of two well known South African hominid species, Australopithecus africanus and Paranthropus robustus. Using newly developed portable confocal microscopy, we have obtained cross striation periodicities (number of cross striations between adjacent striae) for the largest sample of hominid teeth reported to date. These data indicate a mean periodicity of seven days in these small-bodied hominids. Important differences were observed in the inferred mechanisms of enamel development between these taxa. Ameloblasts maintain high rates of differentiation throughout cervical enamel development in P. robustus but not in A. africanus. In our sample, there were fewer lateral striae of Retzius in P. robustus than in A. africanus. In a molar of P. robustus, lateral enamel formed in a much shorter time than cuspal enamel, and the opposite was observed in two molars of A. africanus. In spite of the greater occlusal area and enamel thickness of the molars of both fossil species compared with modern humans, the total crown formation time of these three fossil molars was shorter than the corresponding tooth type in modern humans. Our results provide support for previous conclusions that molar crown formation time was short in Plio-Pleistocene hominids, and strongly suggest the presence of different mechanisms of amelogenesis, and thus tooth development, in these taxa.
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http://dx.doi.org/10.1016/j.jhevol.2006.05.007DOI Listing
December 2006

Variation of functional cranial components in six Anthropoidea species.

Zoology (Jena) 2006 3;109(3):231-43. Epub 2006 Jul 3.

Centro de Investigaciones en Genética Básica y Aplicada (CIGEBA, FCV, UNLP), La Plata, Argentina.

Sixty male crania from three Platyrrhini and three Catarrhini genera were measured by means of the craniofunctional method. The aim was to analyze functional components of the skull and relate their function and the degree of encephalization to life history variables. We recognized two major and eight minor functional components. The objectives were to test (1) if within-taxa (Platyrrhini or Catarrhini) and/or between-taxa (Platyrrhini and Catarrhini) comparisons showed minor-component differentiation; and (2) if encephalization affects both primate groups differently. After standardization by size and scaling, 15 possible within-taxa and between-taxa comparisons were made. We found a strong phylogenetic signal, i.e., cranial differences were not randomly distributed, with the between-taxa variation being greater than within-taxa. Both hypotheses tested were accepted since: (1) There was no random variation between functional cranial components. They followed definite patterns for ancestral and derived traits. (2) Encephalization was present in all scaled comparisons, with Platyrrhini showing a higher degree of encephalization than Catarrhini. We conclude that major and minor craniofunctional components should be considered as correlated traits related to life history, because we found different patterns between platyrrhines and catarrhines, and within species of both taxa.
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http://dx.doi.org/10.1016/j.zool.2006.02.002DOI Listing
October 2006

East-West cranial differentiation in pre-Columbian human populations of South America.

Homo 2006 30;57(2):133-50. Epub 2006 Mar 30.

Departamento Científico de Antropología del Museo de La Plata, Universidad Nacional de La Plata, 1900 La Plata, Argentina.

South Amerindians are frequently thought of as a rather biologically homogeneous megapopulation. However, when native South Americans are assessed by information coming from DNA variability analysis, they resolve into two, major distinct entities of Eastern and Western zones. The purpose of this study is to investigate if the same dual pattern emerges from craniometric data. We approached this question by means of functional craniometric variables. We found strong evidence that Westerners and Easterners constitute two distinct and independent microevolutionary universes when cranial morphology is assessed. The existence of a third universe, Northwest, cannot be completely ruled out, but needs further investigation. We also discovered that Westerners and Easterners present similar degrees of internal variation, contrary to the findings of geneticists and molecular biologists. Palaeoamericans seem to be more similar to Easterners than to Westerners and North-Westerners. Our results suggest that this East-West cranial differentiation is more probably the result of differential rates of genetic drift and gene flow acting on each side of the Cordillera. However, different intensities of gene flow between Palaeoamericans and Amerindians in the highlands and in the lowlands cannot be completely dismissed as a possible explanation for the differentiation found.
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http://dx.doi.org/10.1016/j.jchb.2005.12.003DOI Listing
December 2006

A cross-sectional study of human craniofacial growth.

Ann Hum Biol 2005 May-Jun;32(3):390-6

Dynamique de l'Evolution Humaine, Centre National de la Recherche Scientifique, Paris, France.

It is generally accepted that different cranial regions do not follow the same growth pattern. In this study, size changes of the functional cranial components (FCCs) in 228 human skulls of age at death between 0 and 20 years were evaluated. The skull is considered as divided into anteroneural, midneural, posteroneural, otic, optic, respiratory, masticatory and alveolar FCCs. Age-related changes of FCCs were assessed by fitting curves with the smoothing spline method, and quantifying the proportional increments at different stages. All FCCs show a high growth rate in the first 3-5 years of life. Two groups of growth trajectories can be distinguished. The anteroneural, midneural, posteroneural and optic FCCs are more advanced at all stages; they show a high growth rate before 3-5-years-old and a low rate later. This difference is less pronounced in the group comprising the respiratory, masticatory and otic FCCs. The alveolar FCC shows an independent pattern. The similarities among FCCs of the two groups are best explained by their common embryological origin. In contrast, the participation in a common function cannot be associated with the co-ordinated variation, given that the masticatory and alveolar FCCs show independent trajectories.
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http://dx.doi.org/10.1080/03014460400027441DOI Listing
December 2005

Cranial growth in normal and low-protein-fed Saimiri. An environmental heterochrony.

J Hum Evol 2005 Oct;49(4):515-35

UPR 2147 Dynamique de l'volution humaine (CNRS), 44, rue de l'Amiral Mouchez, 75014 - Paris, France.

Protein malnutrition has a significant and measurable effect on the rate and timing of growth. Heterochrony is generally viewed as the study of evolutionary changes in the relative rates and timing of growth and development. Although changes in growth commonly result from experimental manipulations of diet, nobody has previously attempted to explain such changes from a heterochronic perspective. We use a heterochronic perspective to compare a group of squirrel monkeys fed a low-protein diet to individuals on a high-protein diet, but, in contrast to previous works, we focus particularly on the effects of environmental and not genetic factors. In the present study, Gould's (1977) and Godfrey and Sutherland's (1996) methodologies for studying heterochrony, as well as geometric morphometrics, are used to compare two groups of Saimiri sciureus boliviensis. Two groups of Saimiri were constructed on the basis of the protein content in their diets: a high-protein group (HP) (N=12) and a low-protein group (LP) (N=12). All individuals are males born in captivity. Two major functional components of the skull, the neurocranium and the face, were analysed. Four minor components were studied in each major component. Comparison of craniofacial ontogeny patterns based on major and minor components suggests that changes in the skull of LP animals can be explained by heterochrony. The skull of LP animals exhibits isomorphism produced by proportioned dwarfism. Our results suggest that heterochrony can be environmentally, rather than exclusively genetically, induced. The study of genetic assimilation (Waddington, 1953, 1956; see Scharloo, 1991; Hallgrimsson et al., 2002) has demonstrated that environmentally induced phenotypes often have a genetic basis, and thus parallel changes can be easily induced genetically. It is possible that proportioned dwarfism is far more common than currently appreciated.
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http://dx.doi.org/10.1016/j.jhevol.2005.06.002DOI Listing
October 2005

South Amerindian craniofacial morphology: diversity and implications for Amerindian evolution.

Am J Phys Anthropol 2005 Dec;128(4):747-56

UPR 2147, Dynamique de l'Evolution Humaine, CNRS, 75014 Paris, France.

The most compelling models concerning the peopling of the Americas consider that modern Amerindians share a common biological pattern, showing affinities with populations of the Asian Northeast. The aim of the present study was to assess the degree of variation of craniofacial morphology of South American Amerindians in a worldwide context. Forty-three linear variables were analyzed on crania derived from American, Asian, Australo-Melanesian, European, South-Saharan African, and Polynesian regions. South America was represented by seven Amerindian samples. In order to understand morphologic diversity among Amerindians of South America, variation was estimated using regions and local populations as units of analysis. Variances and F(ST) values were calculated for each unit, respectively. Both analyses indicated that morphologic variation in Southern Amerindians is extremely high: an F(ST) of 0.01531 was obtained for Southern Amerindians, and values from 0.0371-0.1205 for other world regions. Some aspects linked to the time and mode of the peopling of the Americas and various microevolutionary processes undergone by Amerindians are discussed. Some of the alternatives proposed to explain this high variation include: a greater antiquity of the peopling than what is mostly accepted, a peopling by several highly differentiated waves, an important effect of genetic drift, and gene flow with Paleoamericans. A combination of some of these alternatives explains at least some of the variation.
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http://dx.doi.org/10.1002/ajpa.20235DOI Listing
December 2005

Functional-cranial approach to the influence of economic strategy on skull morphology.

Am J Phys Anthropol 2005 Dec;128(4):757-71

Secció d'Antropologia, Facultat de Biologia, Universitat de Barcelona, 08028 Barcelona, Spain.

Environmental factors are assumed to play an important role in the shaping of craniofacial morphology. Here we propose a statistical approach which can be of utility in estimating the magnitude and localization of a particular nongenetic factor upon the specific functional components of the skull. Our analysis is a combination of previous attempts of apportionment of variance and the application of craniofunctional theory. The effect of subsistence strategy on craniofacial functional components was studied on 18 populations of hunter-gatherers and farmers from South America. Results demonstrate that the environmental factors studied likely influenced the masticatory component's size and shape. Even when this effect is not large enough to clearly differentiate among subsistence strategies (since whole craniofacial variation among populations remains greater), the method used here provides interesting clues to localize plastic or adaptive responses to external stimuli.
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http://dx.doi.org/10.1002/ajpa.20161DOI Listing
December 2005

Cranial sutures and craniometric points detected on MRI.

Surg Radiol Anat 2005 Mar 29;27(1):64-70. Epub 2004 Oct 29.

Laboratoire d'Anatomie de l'UFR Laennec, Rue Guillaume Paradin, 69312 , Lyon Cedex 08, France.

The main goal of the study was to determine on MRI the cranial sutures, the craniometric points and craniometric measurements, and to correlate these results with classical anthropometric measurements. For this purpose, we reviewed 150 cerebral MRI examinations considered as normal (Caucasian population aged 20-49 years). For each examination we individualized 11 craniometric landmarks (Glabella, Bregma, Lambda, Opisthocranion, Opisthion, Basion, Inion, Porion, Infra-orbital, Eurion) and three measurements. Measurements were also calculated independently on 498 dry crania (Microscribe 3-DX digitizer). To validate the MRI procedure, we measured four dry crania by MRI and with compass or digital caliper gauges. Cranial sutures always appeared without signal (black), whatever the MRI sequence used, and they are better visualized with a 5 mm slice thickness (compact bone overlapping). Slice dynamic analysis and multiplanar reformatting allowed the detection of all craniometric points, some of these being more difficult to detect than others (Porion, Infra-orbital). The measurements determined by these points were as follows: Vertex-Basion height=135.66+/-6.56 mm; Eurion-Eurion width=141.17+/-5.19 mm; Glabella-Opisthocranion length=181.94+/-6.40 mm. On the midline T1-weighted sagittal image, all median craniometric landmarks can be individualized and the Glabella-Opisthocranion length, Vertex-Basion height and parenchyma indices can be calculated. Craniometric points and measurements between these points can be estimated with a standard cerebral MRI examination, with results that are similar to anthropometric data.
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http://dx.doi.org/10.1007/s00276-004-0283-6DOI Listing
March 2005

The Neolithic transition in Europe and North Africa. The functional craneology contribution.

Anthropol Anz 2004 Jun;62(2):129-45

UPR 2147 "Dynamique de l'Evolution Humaine", Centre National de la Recherche Scientifique, Paris, France.

The origin and mode of the process that led to food production in Europe and North Africa is a matter intensively discussed. It is not clear in the transition to the Neolithic in these regions if it results by a migration of peoples from the Near East, by changes in the behaviour of local populations, or by an interaction of both processes. Morphological changes in Europe and North Africa, from the Upper Palaeolithic to modern periods were assessed. A method based on the Functional Matrix Hypothesis was carried out, which implies that the bone shape is modified by the related soft tissues. Absolute and relative size and shape changes were estimated on two major--neural and facial--and eight minor--anteroneural, midneural, posteroneural, otic, optic, respiratory, masticatory and alveolar--functional cranial components (FCC). ANOVA and Canonical Correlation analyses indicate that neither a temporal trend nor a pattern characteristic of each region is evidenced. But a shift is observed between the Upper Palaeolithic groups and the later samples. Size is greater in the Upper Palaeolithics. Shape is modified because Upper Palaeolithics have greater midneural and masticatory FCCs, and smaller optic FCC. The greater masticatory volume is associated to wider faces in hunter-gatherers. Our study cannot enable to conclude if the morphological shift is caused by a replacement or by a change in the local populations, however, the morphological changes can be attributed to the reduced mobility and the masticatory stress since the Neolithic period.
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June 2004