Masticatory function and post-pleistocene evolution in Nubia

The present research focuses on craniofacial variation in Nubia over approximately 10,000 years. Samples were grouped according to their temporal location and subsistence pattern, and represent a transition from a hunting-gathering adaptation (Mesolithic) to a transitional hunting-gathering-agricultural adaptation (A-C Group) and finally to a fully agricultural adaptation (Meroitic/X-Group/Christian). The purposes were: (1) to compare the Mesolithic sample with the later Nubian populations; and (2) to evaluate further the hypothesis that change in Nubian craniofacial morphology was due to changing functional demands associated with the progressive change in subsistence adaptation and associated behavior. The results tend to support recent views that the Nubian Mesolithic population is probably ancestral to later Nubian groups, and that the masticatory-functional hypothesis can best account for craniofacial change among the Nubians since 12,000 B.P. According to this hypothesis systematic reduction in functional demand placed on the masticatory complex from the Mesolithic led, secondarily, to an alteration of the growth of the maxillomandibular complex such that the face became progressively less robust and more inferoposteriorly located relative to the cranial vault. Both the increase in the height of the vault relative to its length, producing a more “globular” appearance, and the reduction in dental size were tertiary, compensatory responses to altered facial size and position.     

Craniofacial morphology in the Argentine Center-West: consequences of the transition to food production

The Argentine Center-West was the southernmost portion of the Andes where domestication of plants and animals evolved. Populations located in the southern portion of this area displayed a hunter-gatherer subsistence economy up to historical times, and coexisted with farmers located to the north. Archaeological and biological evidence suggests that the transition to food production was associated with the consumption of a softer diet and a more sedentary way of life. This study tests the hypothesis that diet-related factors influenced morphological differentiation, by comparing functional cranial components of farmers and hunter-gatherers. Three-dimensional changes on eight minor functional components (anteroneural, midneural, posteroneural, otic, optic, respiratory, masticatory, and alveolar) were measured on skulls derived from both subareas. Volumetric and morphometric indices were calculated to estimate the absolute and relative size of components, respectively. Results of a paired t-test indicated that farmers have a smaller craniofacial size than hunter-gatherers. The components that varied the most were masticatory and posteroneural, showing smaller absolute and relative sizes in farmers. Discriminant analyses indicated that lengths and widths were the most affected dimensions of these and other components. The pattern of differentiation, which involves specific components, enabled us to exclude differential gene flow and stochastic mechanisms as the main causes. Instead, results support the hypothesis that diet-related factors associated with both subsistence economies influenced craniofacial morphology. A proportion of the observed variation associated with size differences can be explained by two systemic factors: the lesser quality of nutrition due to a low protein content in the diet, and a decrease of growth hormone circulation induced by a lower mobility due to sedentism. However, differentiation is better explained by a localized factor: the reduction in the masticatory and posteroneural components in farmers resulted from a decrease of masticatory stresses and workload on the head and neck, linked to the consumption of a softer diet.     

NONRANDOM FACTORS IN MODERN HUMAN MORPHOLOGICAL DIVERSIFICATION: A STUDY OF CRANIOFACIAL VARIATION IN SOUTHERN SOUTH AMERICAN POPULATIONS

The causes of craniofacial variation among human populations have been the subject of controversy. In this work, we studied aboriginal populations from southern South America, the last continental region peopled by humans and with a wide range of ecological conditions. Because of these characteristics, southern South America provides a unique opportunity to study the relative importance of random and nonrandom factors in human diversification. Previous craniometric studies recognized remarkable differences among populations from this region, usually resorting to random factors as the main explanation. In contrast, here we suggest, using tests based on quantitative genetic models, that: (1) the rate of craniofacial divergence among these populations is too high and (2) the patterns of variation within and between populations are too different to be explained by genetic drift alone. In addition, the among-sample craniofacial variation is correlated with climate and diet but not with mtDNA variation. We suggest that the influence of nonrandom factors (e.g., plasticity, selection) on human craniofacial diversification in regions with large ecological variation is more important than generally acknowledged and capable to generate large craniofacial divergence in a short period of time. These results bring nonrandom factors into focus for the interpretation of human craniofacial variation.     

Maternal Time Allocation in Two Cooperative Childrearing Societies

This paper examines maternal trade-offs between subsistence/economic activities and caregiving, and it explores the effect of allomaternal investment on maternal time allocation and child care. I examine how nonmaternal investment in two multiple caregiving populations may offset possible risk factors associated with reductions in maternal caregiving. Behavioral observations were conducted on 8- to 12-month-old infants and their caregivers among the Aka tropical forest foragers and Ngandu farmers of Central Africa. Analysis demonstrates that mothers face trade-offs between subsistence/economic activities and infant care. Infants receive less investment when their mothers engage in subsistence/economic activities, indicating a potential risk to those infants. However, results indicate that allomothers target their assistance during times when mothers are engaged in work activities, partially offsetting potential risks associated with the maternal trade-off. The effects of intercultural variability on maternal time allocation and allomaternal investment are also explored as a means of examining the potential impact of their behaviors on infant care.     

The role of diet and temperature in shaping cranial diversification of South American human populations: an approach based on spatial regression and divergence rate tests

Aim Understanding the importance of ecological factors in the origin and maintenance of patterns of phenotypic variation among populations, in an explicit geographical context, is one of the main goals of human biology, ecology and evolutionary biology. Here we study the ecological factors responsible for craniofacial variation among human populations from South America. Location South America. Methods We studied a dataset of 718 males from 40 South American populations, coming from groups that inhabited different geographical and ecological regions. Cranial size and shape variation were studied using 30 cranial measurements. We first used spatial correlograms and interpolated maps to address spatial patterns. We then regressed the shape (principal component scores) and size variables against ecology (mean annual temperature and diet) using multiple and multivariate spatial regression. Finally, the expected magnitudes of shape and size divergence under the influence of genetic drift and mutations alone were evaluated using neutral expectation for the divergence rate. Results The spatial correlograms showed a cline affecting the entire South American distribution. Interpolated maps showed that size and allometric shape vary from south‐east to north‐west. Multiple and multivariate regression analyses suggested that diet has the largest and most significant effect on this pattern of size and allometric shape variation. Finally, the results of the divergence rate test suggested that random processes alone cannot account for the morphological divergence exhibited by cranial size and allometric shape scores among southernmost populations. Main conclusions Correlograms, spatial regression and divergence rate analyses showed that although local factors (neutral processes or local environmental conditions) are important to explain spatial interpopulation differentiation in cranial characteristics among these populations, there is significant correlation of cranial size and allometric shape variation with diet. Gene flow among human populations, or local environmental conditions, could explain spatial variation mainly at smaller spatial scales, whereas the large‐scale pattern of the South American dataset is mainly related to the high proportion of carbohydrates and low proportion of proteins consumed.     

The foams of fermentation broths. I. Some parameters of the foaming of fermentation media

The stability of foam formed during fermentation is decisively affect ed by the nature of the nutrient media used. In froth-flotation models, (a) the foam formation time, characteristic of the tendency to foam, and (b) foam subsistence time, characteristic of the stability of foams formed, have been studied. With the utilization of these two parameters, the stability of foam from aqueous solution of several surface active components of nutrient media has been noted as a function of concentrations. Further, but, without attempting completeness, the viscosity enhancing effect of carbohydrate components, and the effect of the subsistence time of their foam, upon the stability of foam have been studied together with the correlation between “standing” time after sterilization and tendency to foam. Taking soy-bean meal as a model, the stability of foam films in function of pi I, at constant concentration, has been studied. It seems that though a proper control of the factors mentioned, nutrient media with a low tendency of foaming can be formulated.     

Common genetic and environmental factors among craniofacial traits in Belgian nuclear families: Comparing skeletal and soft-tissue related phenotypes

The major objective of this study was to determine the possible effects of common genetic and environmental factors among 18 craniofacial anthropometric traits, with special attention to the differences between skeletal and soft-tissue related phenotypes. The studied sample consisted of 122 nuclear families living in Brussels and included 251 males and 258 females aged from 13 to 72 years. Univariate and bivariate quantitative genetic analyses were performed using a variance components procedure implemented in SOLAR software.All phenotypes were significantly influenced by additive genetic factors with heritability estimates ranging from 0.46 (nose height) to 0.72 (external biocular breadth). Sex, age and their interactions explained 7-46% of the total phenotypic variance of the traits. Bivariate analysis revealed that several traits share a common genetic and/or environmental basis while other traits show genetic and environmental independence from one another. More and greater genetic and environmental correlations were observed among skeletal phenotypes, than among soft-tissue traits and between both categories. Apart from the tissue composition, other characteristics of the craniofacial morphology such as the orientation (e.g. heights, breadths) have shown to be important factors in determining pleiotropy and common environmental effects between some pairs of traits. In conclusion, the results confirm that overall head configuration is largely determined by additive genetic effects, and that common genetic and environmental factors affecting craniofacial size and shape are stronger for the skeletal traits than for the soft-tissue traits.     

Temporal changes in human temporomandibular joint size and shape

Measurements approximating the size of the temporomandibular joint were taken on a series of genetically homogeneous populations from early Nubia, which span almost 10,000 years and embody a shift from a primarily hunting and gathering adaptation to a completely agricultural lifeway. A generalized trend of reduction of temporomandibular joint size was observed. In addition, a decrease in sexual dimorphism was apparent for all measures of joint size; a change primarily mitigated by reductions in male dimensions. The observed variation in size and form of the temporomandibular joint is most likely the result of the reduction in masticatory muscle robusticity and resultant changes in craniofacial form which have been documented for the transition from a hunting and gathering to an agricultural subsistence in Nubia.     

Temporal variation in prehistoric Nubian crania

Much of the earlier work on the prehistory of Sudanese Nubia has emphasized discontinuity between early Nubian populations. However, recent investigations suggest the converse - that a remarkable degree of cultural and biological continuity exists among indigenous Nubian groups, perhaps as far back as the Paleolithic. Thus, cultural and biological differences between Nubian populations can be most effectively perceived as the result of in situ evolutionary development. The present analysis has two major purposes: (1) to describe the morphological differences in the craniofacial complex between indigenous Nubian populations extending from the A-Group (c. 3,400 B.C.) through the Christian (c. 1,500 A.D.) horizons; and (2) to account for these differences within an evolutionary framework. The multiple discriminant analysis of radiographically derived variables revealed a trend from a substantially lower and more elongated cranial vault to a shorter and taller vault throughout the almost 5,000 year time span. Associated with this pattern was a tendency for the face to become more inferiorly-posteriorly located with respect to the vault in the latter groups. Finally, the masseter and temporalis muscles underwent a reduction and slight relocation through time. We speculate that this trend may be associated with behavioral changes associated with transition from a hunting and gathering to a totally agricultural subsistence pattern.     

The structural and functional connectivity of the grassland plant Lychnis flos-cuculi

Understanding the relationship between structural and functional connectivity is essential for successful restoration and conservation management, particularly in intensely managed agricultural landscapes. We evaluated the relationship between structural and functional connectivity of the wetland plant Lychnis flos-cuculi in a fragmented agricultural landscape using landscape genetic and network approaches. First, we studied the effect of structural connectivity, such as geographic distance and various landscape elements (forest, agricultural land, settlements and ditch verges), on gene flow among populations as a measurement of functional connectivity. Second, we examined the effect of structural graph-theoretic connectivity measures on gene flow among populations and on genetic diversity within populations of L. flos-cuculi. Among landscape elements, forests hindered gene flow in L. flos-cuculi, whereas gene flow was independent of geographic distance. Among the structural graph-theoretic connectivity variables, only intrapopulation connectivity, which was based on population size, had a significant positive effect on gene flow, that is, more gene flow took place among larger populations. Unexpectedly, interpopulation connectivity of populations, which takes into account the spatial location and distance among populations, did not influence gene flow in L. flos-cuculi. However, higher observed heterozygosity and lower inbreeding was observed in populations characterised by higher structural interpopulation connectivity. This finding shows that a spatially coherent network of populations is significant for maintaining the genetic diversity of populations. Nevertheless, lack of significant relationships between gene flow and most of the structural connectivity measures suggests that structural connectivity does not necessarily correspond to functional connectivity.     

Chimpanzee subsistence technology: Materials and skills

Beyond reviewing basic data on Primate technological behavior, the aim of this report is to document the nature of chimpanzee technical skills by examining some of the mental as well as physical expertise which chimpanzees bring to bear on subsistence activities. This task is approached along several avenues: first, an outline is drawn of current knowledge about chimpanzee subsistence technology throughout Africa; second, a sketch is made of technological variability in several chimpanzee populations; third, the results of a personal investigation into the skills needed by chimpanzees to probe for insects are provided; and fourth, a comparison is made of the baboon, chimpanzee and human techniques used to exploit termites as a food resource. Instead of focusing on the unique features of human subsistence technology, the report attempts to show that many technical skills are and probably were firmly rooted in Primate prehistory, well before the advent of the earliest hominids. An integrated model of technological achievements among extant Primates, based on a sample of African cercopithecid, pongid and hominid populations representing stages in a phylogentic sequence, is offered as a foundation for reconstructing the gradual evolution of primate subsistence technology. This approach is intended to provoke contemplation and discussion among those investigators of human behavior and society who favor the thesis that the criterion of technology, together with the cultural transmission of technical skills, separates the human from the nonhuman Primates.     

Ecology of Children’s Growth: An Example from Transitional Populations of the Brazilian Amazon

The intense environmental and social changes taking place in Amazonia make this a key area for health studies of populations transitioning to a cosmopolitan lifestyle and market economy. Caboclos are among those populations. They comprise the majority of rural Brazilian Amazon peoples. At present there is limited information about their patterns of growth and health. In this paper, anthropometric data on Caboclo children from three groups living in different environments are presented and discussed within a bioanthropological framework. Caxiuanã, Aracampina, and Santana have a combined population of 1,069 people. Caxiuanã relies more on subsistence activities for survival and Santana more on commerce, while Aracampina uses both subsistence strategies. Compared to US children, Caboclo are generally shorter and lighter in all age groups. However, their weight-for-height is above the 50th percentile. In relation to skinfolds, age groups 0–2, 6–8, and 9–11 years present statistically significant differences among the three communities. Caxiuanã children have the smallest and Aracampina children have the largest skinfolds. While seasonal and environmental differences may account for some of the observed variation in growth and fatness patterns, socioeconomic factors also play a key role in the trends observed. Thus, an ecological model provides the best framework for explaining these findings. Caxiuanã children are small and thin as a result of their combined poor environment and limited access to cash, western goods, and health care. Aracampina and Santana’s fuller access to such socioeconomic influences and richer ecology results in taller and fatter children. Understanding similar interactions between ecology and social factors will be fundamental to developing sustainable health initiatives among rural Amazonian populations.     

Comparison of craniofacial features of major human groups

Distance analysis and factor analysis, based on Q-mode correlation coefficients, were applied to 23 craniofacial measurements in 1,802 recent and prehistoric crania from major geographical areas of the Old World. The major findings are as follows: 1) Australians show closer similarities to African populations than to Melanesians. 2) Recent Europeans align with East Asians, and early West Asians resemble Africans. 3) The Asian population complex with regional difference between northern and southern members is manifest. 4) Clinal variations of craniofacial features can be detected in the Afro-European region on the one hand, and Australasian and East Asian region on the other hand. 5) The craniofacial variations of major geographical groups are not necessarily consistent with their geographical distribution pattern. This may be a sign that the evolutionary divergence in craniofacial shape among recent populations of different geographical areas is of a highly limited degree. Taking all of these into account, a single origin for anatomically modern humans is the most parsimonious interpretation of the craniofacial variations presented in this study. © 1996 Wiley-Liss, Inc.     

Sexual dimorphism in stature and women's work: a phylogenetic cross-cultural analysis.

The following cultural variables were tested for their association with sexual dimorphism: sexual division of labor, type of subsistence (hunting and agriculture), and polygyny. The transmission of these traits among populations was investigated. All the traits were found to be associated with phylogeny, indicating that they are inherited from mother to daughter populations. A cross-cultural comparative method was used which controls for the statistical effects of similarity due to common ancestry (Galton's problem). Cross-cultural variation in sexual dimorphism in stature is negatively associated with women's contribution to subsistence. Women are taller, relative to men, in societies where women contribute more to food production. This may be because female nutritional status is better in these societies. No relationship was found between sexual dimorphism and other aspects of subsistence or polygyny. These results are discussed in relation to other studies of sexual dimorphism in modern and archaeological populations, and in relation to cross-cultural variation in sex-biased parental investment.     

Morphological differentiation of aboriginal human populations from Tierra del Fuego (Patagonia): implications for South American peopling

This study aims to integrate the craniofacial morphological variation of southern South American populations with the results of mtDNA haplogroup variation, to discuss the South America peopling. Because the causes of morphological differentiation of Fueguian populations are still a controversial subject, the comparison with neutral variation could contribute to elucidate them. Samples of human remains from South America regions were used to analyze the evolutionary relationships. Several craniofacial traits observed in frontal and lateral view were analyzed by means of geometric morphometrics techniques, and the evolutionary relationships based on morphological and molecular data were established in base to ordination analyses. The results from the facial skeleton agree with those obtained from mtDNA haplogroup frequencies, with La Pampa/Chaco samples detached from the Patagonian samples. Hence, the same mechanism that accounts for the pattern of frequency of haplogroups could explain the variation found in facial skeleton among the samples. It is suggested that such geographic pattern of craniofacial and molecular diversity may reflect the effect of genetic drift that occurred in the small founding populations isolated by distance or geographic barriers. Conversely, the results obtained using the traits from the lateral view slightly differ from the molecular results, showing differences between southernmost Patagonian and the other samples. Therefore, mechanisms other than genetic drift (e.g., natural selection) could have acted to shape the pattern observed in some craniofacial structures present in the lateral view, characterized by the fact that the southernmost Patagonian samples display the most robust and dolichocephalic crania.     

Heterozygosity and craniofacial dimensions of Zapotec school children from a subsistence community in the valley of Oaxaca, southern Mexico

Gene flow is associated with differences in craniofacial and postcranial dimensions among indigenous populations of southern Mexico. This study compares four craniofacial dimensions in 322 children from families which have an average inbreeding coefficient of 0.01 and 36 children from families which have an inbreeding coefficient of zero (more heterozygous) in a Zapotec speaking community. In addition, two indices were computed. With sex and chronological age constant, there is a statistically significant difference between more and less heterozygous children in bizygomatic diameter. Differences in biparietal diameter and fronto-occipital length reflect the same tendency. The differences probably reflect more an effect of heterozygosity on these dimensions than facial dissimilarity of the populations from which the new genetic materials were drawn because gene flow was from related groups of Indians (e.g., Mixtec) in southern Mexico. Hence, midface growth and overall normal size appear to be affected by fluctuation in level of heterozygosity.     

Effect of bite force and diet composition on craniofacial diversification of Southern South American human populations

Ecological factors can be important to shape the patterns of morphological variation among human populations. Particularly, diet plays a fundamental role in craniofacial variation due to both the effect of the nutritional status—mostly dependent on the type and amount of nutrients consumed—on skeletal growth and the localized effects of masticatory forces. We examine these two dimensions of diet and evaluate their influence on morphological diversification of human populations from southern South America during the late Holocene. Cranial morphology was measured as 3D coordinates defining the face, base and vault. Size, form, and shape variables were obtained for 474 adult individuals coming from 12 samples. Diet composition was inferred from carious lesions and δ¹³C data, whereas bite forces were estimated using traits of main jaw muscles. The spatial structure of the morphological and ecological variables was measured using correlograms. The influence of diet composition and bite force on morphometric variation was estimated by a spatial regression model. Cranial variation and diet composition display a geographical structure, while no geographical pattern was observed in bite forces. Cranial variation in size and form is significantly associated with diet composition, suggesting a strong effect of systemic factors on cranial growth. Conversely, bite forces do not contribute significantly to the pattern of morphological variation among the samples analyzed. Overall, these results show that an association between diet composition and hardness cannot be assumed, and highlight the complex relationship between morphological diversification and diet in human populations. Am J Phys Anthropol 155:114–127, 2014. © 2014 Wiley Periodicals, Inc.     

Primate subsistence patterns: Collector-predators and gatherer-hunters

Hominization via predation has become a pervasive anthropological theme in recent years. Indeed, the assumption that hunting behavior originated within the primate phylogenetic sequence as a “human” subsistence pattern has generated numerous subsidiary hypotheses about how secondary traits were initiated, propagated or enhanced when a terrestrial, savanna-dwelling, meat-eating hominid line emerged from an arboreal, forest-dwelling, plant-eating ancestral stock. New field evidence on the behavioral and organizational features of subsistence in nonhuman and human primates now provides the basis for reconsidering these views.Many monkey, ape and human populations no longer seem to fit the stereotyped images sketched in past decades, when little or no comparative information was available to anthropologists. The discrepancy between the old concepts and new facts is particularly evident in Sub-Saharan Africa, where numerous primate taxa have been studied in climatically and biotically similar zones. In this region alone, more than 364 cases of predation, involving 22 different species of mammalian prey, have been recorded among at least 10 supposedly “vegetarian” baboon and chimpanzee populations dispersed between Ethiopia and South Africa. Furthermore, many of the human populations living within this same region—such as the Mbuti pygmies, the Hadza and the Kalahari bushmen—have been characterized as “hunters” but actually subsist for the most part on foods other than meat. These basic facts about collector-predator and Gatherer-hunter subsistence patterns are a mere beginning, however, for popular conceptions of primate lifestyles are eroding swiftly along many axes of investigation. It is becoming clear, for instance, that many primates—from prosimians to humans—are actually omnivores even though anthropologists have persistently miscast them as frugivores or carnivores. This false dichotomization of nonhuman versus human diets has led to a series of equally erroneous dichotomies in nonhuman versus human behavior. Thus, the possession of culture, technology, language and other similarly amorphous traits, many of which were in fact derived from this presumed shift in subsistence, have become entrenched as concepts of human uniqueness. In recent years, however, many new discoveries in primatology, and in ethnography and archeology, have weakened the theoretical structure to which “man-the-hunter” has been pinned. It is probable that savanna-dwelling, tool-using, seed-eating, scavenging and other independent schemes can now be replaced by a single, much simpler model wherein subsistence shifts among both nonhuman and human primates are perceived as smooth transitions within a graded continuum of evolution. Thus, the central objective of this report is to show that the subsistence activities of several extant cercopithecid, pongid and hominid populations in Africa can be arranged along an integrated spectrum which reflects gradual processes in the evolution of primate behavior and organization. This spectrum serves as the crux for a unifying model of behavioral evolution, and can in turn be broken down into a linked series of subsidiary models which elucidate specific aspects of primate prehistory.     

Family resemblance for components of craniofacial size and shape

Path analysis is used to analyze family resemblance for eight principal components extracted from 30 anthropometric measurements of the craniofacial complex. Based on likelihood ratio tests, the null hypothesis of no assortative mating is rejected for the nasal height component. The null hypothesis of no common sibling environmental effect is rejected for the cranial size, craniofacial breadth, and nasal height components. Finally, the hypothesis that transmission from both mother and father is equal to 1/2, consistent with simple autosomal polygenic inheritance, is rejected for components corresponding to craniofacial breadth and upper facial height, thus implicating some effect of familial environment. Transmissibility is higher for components related to cranial size and facial height than for those related to facial breadth or ear dimensions.     

On stone age human diet

Diet is part of a larger adaptational process. In terms of evolution, effective subsistence adaptation is expected to enhance selectively the inclusive fitness of those individuals who carry them out. Especially with regard to the “neolithic revolution”, the Stone Ages in Central Europe and the Near East were a period of dietary change with a switch from a foraging to a producing subsistence strategy. Several assumptions do exist on dietary behaviour and resulting lifestyle through the Stone Ages, culminating in the suggestion that in the Neolithic, the role of energy as a limiting factor for human populations gave way to other factors like fats and proteins. Research on Stone Age human populations led to informations on very general trends, and the skeletal record is far from being complete. However, considering the available morphological and archaeometric data, there is at present to need to assume continuing tension between population numbers and food ressources. There are no indications that the neolithic subsistence was on the expense of dietary quality. Also, cost/benefit balances in terms of energy should have been met. The conclusion is the invention and introduction of agriculture being a fitness maximizing process in terms of adaptive dietary behaviour in a changing environment.