Recent origin of low trabecular bone density in modern humans

Humans are unique, compared with our closest living relatives (chimpanzees) and early fossil hominins, in having an enlarged body size and lower limb joint surfaces in combination with a relatively gracile skeleton (i.e., lower bone mass for our body size). Some analyses have observed that in at least a few anatomical regions modern humans today appear to have relatively low trabecular density, but little is known about how that density varies throughout the human skeleton and across species or how and when the present trabecular patterns emerged over the course of human evolution. Here, we test the hypotheses that (i) recent modern humans have low trabecular density throughout the upper and lower limbs compared with other primate taxa and (ii) the reduction in trabecular density first occurred in early Homo erectus, consistent with the shift toward a modern human locomotor anatomy, or more recently in concert with diaphyseal gracilization in Holocene humans. We used peripheral quantitative CT and microtomography to measure trabecular bone of limb epiphyses (long bone articular ends) in modern humans and chimpanzees and in fossil hominins attributed to Australopithecus africanus, Paranthropus robustus/early Homo from Swartkrans, Homo neanderthalensis, and early Homo sapiens. Results show that only recent modern humans have low trabecular density throughout the limb joints. Extinct hominins, including pre-Holocene Homo sapiens, retain the high levels seen in nonhuman primates. Thus, the low trabecular density of the recent modern human skeleton evolved late in our evolutionary history, potentially resulting from increased sedentism and reliance on technological and cultural innovations

The first Neanderthal remains from an open-air Middle Palaeolithic site in the Levant

The late Middle Palaeolithic (MP) settlement patterns in the Levant included the repeated use of caves and open landscape sites. The fossil record shows that two types of hominins occupied the region during this period - Neandertals and Homo sapiens. Until recently, diagnostic fossil remains were found only at cave sites. Because the two populations in this region left similar material cultural remains, it was impossible to attribute any open-air site to either species. In this study, we present newly discovered fossil remains from intact archaeological layers of the open-air site 'Ein Qashish, in northern Israel. The hominin remains represent three individuals: EQH1, a nondiagnostic skull fragment; EQH2, an upper right third molar (RM3); and EQH3, lower limb bones of a young Neandertal male. EQH2 and EQH3 constitute the first diagnostic anatomical remains of Neandertals at an open-air site in the Levant. The optically stimulated luminescence ages suggest that Neandertals repeatedly visited 'Ein Qashish between 70 and 60 ka. The discovery of Neandertals at open-air sites during the late MP reinforces the view that Neandertals were a resilient population in the Levant shortly before Upper Palaeolithic Homo sapiens populated the region

Rare dental trait provides morphological evidence of archaic introgression in Asian fossil record

The recently described Denisovan hemimandible from Xiahe, China [F. Chen et al., (2019) Nature 569, 409–412], possesses an unusual dental feature: a 3-rooted lower second molar. A survey of the clinical and bioarchaeological literature demonstrates that the 3-rooted lower molar is rare (less than 3.5% occurrence) in non-Asian Homo sapiens. In contrast, its presence in Asian-derived populations can exceed 40% in China and the New World. It has long been thought that the prevalence of 3-rooted lower molars in Asia is a relatively late acquisition occurring well after the origin and dispersal of H. sapiens. However, the presence of a 3-rooted lower second molar in this 160,000-y-old fossil hominin suggests greater antiquity for the trait. Importantly, it also provides morphological evidence of a strong link between archaic and recent Asian H. sapiens populations. This link provides compelling evidence that modern Asian lineages acquired the 3-rooted lower molar via introgression from Denisovans

The functional significance of dental and mandibular reduction in Homo: A catarrhine perspective.

The reduction in dental size and mandibular robusticity is regarded as a major trend in human evolution, traditionally considered the result of the peculiar extra-oral food processing skills of Homo. The use of stone tools and fire would have allowed our ancestors to chew softer food in smaller bite size, thus relaxing the selective pressures to keep a large dentition and a robust lower jaw. This perspective assumes that differences in dental size and mandibular robusticity in hominins represent functional dissimilarities. This study uses a catarrhine comparative approach to test this fundamental assumption of the hypotheses on dental and mandibular reduction in Homo. A sample of extant catarrhines and fossil hominins was used to test for correlations between dental size, mandibular robusticity, and dietary proxies, the latter include diet quality, diet heterogeneity, feeding time, and microwear variables. The effects of phylogeny and body size were considered. Findings support the association between technological developments in Homo and reduction in incisor size and mandibular corpus robusticity, though not for premolar, molar size, and symphyseal robusticity. These results challenge the functional interpretation of postcanine reduction and symphyseal changes in the genus Homo

Locomotion in extinct giant kangaroos: were sthenurines hop-less monsters?

The extinct \u27sthenurine\u27 family of giant Kangaroos, up to three times larger than living Kangaroos, were able to walk on two feet, according to new research. Abstract Sthenurine kangaroos (Marsupialia, Diprotodontia, Macropodoidea) were an extinct subfamily within the family Macropodidae (kangaroos and rat-kangaroos). These “short-faced browsers” first appeared in the middle Miocene, and radiated in the Plio-Pleistocene into a diversity of mostly large-bodied forms, more robust than extant forms in their build. The largest (Procoptodon goliah) had an estimated body mass of 240 kg, almost three times the size of the largest living kangaroos, and there is speculation whether a kangaroo of this size would be biomechanically capable of hopping locomotion. Previously described aspects of sthenurine anatomy (specialized forelimbs, rigid lumbar spine) would limit their ability to perform the characteristic kangaroo pentapedal walking (using the tail as a fifth limb), an essential gait at slower speeds as slow hopping is energetically unfeasible. Analysis of limb bone measurements of sthenurines in comparison with extant macropodoids shows a number of anatomical differences, especially in the large species. The scaling of long bone robusticity indicates that sthenurines are following the “normal” allometric trend for macropodoids, while the large extant kangaroos are relatively gracile. Other morphological differences are indicative of adaptations for a novel type of locomotor behavior in sthenurines: they lacked many specialized features for rapid hopping, and they also had anatomy indicative of supporting their body with an upright trunk (e.g., dorsally tipped ischiae), and of supporting their weight on one leg at a time (e.g., larger hips and knees, stabilized ankle joint). We propose that sthenurines adopted a bipedal striding gait (a gait occasionally observed in extant tree-kangaroos): in the smaller and earlier forms, this gait may have been employed as an alternative to pentapedal locomotion at slower speeds, while in the larger Pleistocene forms this gait may have enabled them to evolve to body sizes where hopping was no longer a feasible form of more rapid locomotion

Musculoskeletal Markers: A Comparison Of The Influence Of Three Biological Factors On Robusticity

Research suggests that musculoskeletal markers (MSMs) can provide information about the lives of deceased individuals. The majority of studies focus on single factors that influence the morphology of MSMs in pre-modern societies (i.e., medieval, hunter-gatherers, preindustrial, etc.). This study analyzes MSMs of modern skeletons of 72 females and 83 males from the United States whose ages at death range from 30 to 89 to understand the relationship between various biological factors and MSM morphology. Eight MSMs (attachments of pectoralis major, deltoid, brachialis, supinator, iliopsoas, gluteus maximus, quadriceps, and soleus) were analyzed and categorized as phases zero, one, two, or three depending on the degree of robusticity, with phase zero showing no robusticity and phase three being the most robust. Odds ratio estimates, chi square tests, & Mann-Whitney U tests were used to assess the relationship of the MSMs with age, sex, and estimated body mass. Results show that four of the eight MSMs have significant relationships with estimated body mass and/or age: the deltoid, brachialis, iliopsoas, and quadriceps tendon. Interestingly, four MSMs, the left quadriceps tendon, the right pectoralis major, the right gluteus maximus, and the right soleus show a significant relationship between sex and MSM robusticity. The results for the relationship between sex and MSM robusticity were not able to show specifically whether males or females were more likely to have more robust MSMs

Lower limb bone shape and structure among populations of differing lifestyles: Effects of biomechanical stress and inferences of activity

It is known that activity-related stresses and mechanical loadings affect adult bone morphology. The purpose of this study is to examine how well presumed subsistence-related activities correlate with bone morphology; In addition, this study will investigate the degree to which sex differences can be explained by differences in mechanical loaDing If such differences in expression are apparent between males and females within a population, then it can be speculated that the sexes were participating in different activities---or at least in activities that yielded different mechanical loadings; Although there have been several biomechanical studies that have looked at the relationship between skeletal morphology and physical activities, this study takes a different approach in two ways. First, this study will examine temporal trends in adult lower limb phenotypes that are known to be mechanically sensitive and flexible within populations under different subsistence economies in order to analyze the accuracy to which such phenotypes can reflect presumed activity levels based on known subsistence practices. In short---to examine how well the skeletal data (i.e. morphology indicative of activity) correlates with the archaeological evidence of subsistence practices; Second, the relationship between the expression of lower limb flexible traits and maturation in immature individuals will be analyzed. The purpose of this is to examine how and when such traits are expressed during skeletal maturation, and to determine if the expression of such traits are strictly related to skeletal growth and development, or if they can be explained from a biosocial and/or bioarchaeological perspective. (Abstract shortened by UMI.)

Three-Dimensional Analysis of the Development of Upper Arm Musculoskeletal Stress Markers in Late Adolescents and Young Adults of Archaic and Mississippian Populations of Tennessee

This study compares three methods for the evaluation of morphology of musculoskeletal attachment sites. Two methods were macroscopic and the third was microscopic, utilizing three-dimensional laser scanning and fractal analysis The morphology of 19 upper limb attachment sites was observed in 33 males aged 15 and 30+ years, dating to the Archaic and Mississippian periods from the southeastern U.S. It was hypothesized that 1) the microscopic method would identify subtler differences than the macroscopic methods; 2) enthesis development would be greater in the Mississippian population due to the increased subsistence workload, even among younger individuals; and 3) late adolescents would show similar patterns of enthesis development as their older counterparts. The microscopic method failed to show the same patterns observed with the macroscopic methods. The majority of variation was between the two macroscopic methods but little difference was seen between the two methods. In the Archaic sample most activity was found among the older age sets whereas in thee Mississippian sample, it was found in the younger age sets, including late adolescents. Most differences seen were in scoring Robusticity rather than Osteolytic or Osteophytic Activity. In all instances, late adolescents in this study followed the general pattern set by the other age sets. The results of this study suggest that three-dimensional scans, at this point may not be optimal for MSM research. Additional research scrutinizing the way MSM are scored and how bone response to mechanical strain is needed before more confident interpretations can be made based on the data

Age at death determination from morphological changes in the clavicle: from adolescence to adulthood - the impact of environmantal factors

Tese de mestrado. Biologia (Biologia Humana e Ambiente). Universidade de Lisboa, Faculdade de Ciências, 2011A determinação da idade à morte é um dos principais desafios que se apresentam numa identificação individual a partir de restos humanos ósseos. Obter a idade que o indivíduo tinha aquando da morte é uma tarefa complicada e que vai aumentando de grau de dificuldade à medida que a idade do indivíduo aumenta. Até ao final da sua formação e erupção, os dentes representam indicadores muito precisos da idade (Hillson, 1996). Durante a infância e adolescência, o comprimento dos ossos longos e a fusão epifisária aparecem como as formas mais fiáveis da determinação da idade. A partir dos 18 anos, o terceiro molar está muitas vezes já erupcionado, e muitas das principais epifises começam a estar fundidas à medida que o corpo deixa de crescer (Cardoso, 2008). A partir desta altura a precisão dos métodos começa a decaír drasticamente e após os 30 anos os indicadores usados para determinar a idade em indivíduos adultos prendem-se com degeneração dos ossos, degeneração esta que está muito menos dependente de factores genéticos e muito mais dependente de factores ambientais, como a nutrição, o clima e principalmente a actividade física (Scheuer e Black, 2000). Existem vários estudos que estabelecem um padrão de fusão para a epífise esternal da clavícula para indivíduos adolescentes e jovens adultos, através da análise de restos ósseos (e.g. Stevenson, 1924; Todd e D’Errico, 1928; MacLaughlin, 1990; Black e Scheuer, 1996; Veschi e Facchini, 2002; Coqueugniot e Weaver, 2007; Shirley e Jantz, 2010), Com este trabalho pretendeu-se desenvolver uma métodologia que permita de uma forma tão precisa quanto possivel, determinar a idade a morte de esqueletos (provenientes de contexto arqueológico ou forense) através da análise da clavícula, nomeadamente do processo de fusão da epífise esternal. Foram estudados esqueletos de tres colecções osteologicas distintas. A colecção de esqueletos identificados do Museu Bocage em Lisboa, que contém indivíduos nascidos em meados do século 20, e representa uma população eminentemente urbana (Cardoso, 2006); a colecção do Museu Antropológico da Universidade de Coimbra, com indivíduos nascidos no inicio do século 20 provenientes de uma população rural (Fernandes, 1985); foi ainda estudada uma colecção de esqueletos conservada no Museu de História Natural de Londres, a colecção de Spitalfields, mais antiga que as anteriores, pois contém esqueletos que viveram em meados do século 18, numa zona muito industrializada de Londres (Molleson et al., 1993). No total foram estudados 246 esqueletos (125 do sexo masculino e 121 do sexo feminino), divididos da seguinte forma pelas 3 colecções: 138 de Coimbra (74 do sexo masculino e 64 do sexo feminino), 87 de Lisboa (40 do sexo masculino e 47 do sexo feminino) e 21 da colecção inglesa (11 do sexo masculino e 10 do sexo feminino). A comparação de idade entre as colecções revelou diferenças significativas entre Lisboa e as restantes duas, sendo os indivíduos de Lisboa mais jovens. Não se encontraram diferenças entre Coimbra e Spitalfields. Uma análise analoga para a robustez, apenas revelou diferenças entre Lisboa e Coimbra, com os indivíduos de Lisboa a serem em media menos robustos. Os dados recolhidos, foram o comprimento máximo da diafise e o perímetro ao meio de modo a obter o índice de robustez. As clavículas foram classificadas quanto ao seu grau de fusão da epífise com 3 escalas diferentes: a) 3 Fases, que e a divisão mais frequentemente usada, e o mais simples de aplicar, pois apenas diferencia o desenvolvimento da epífise em : não fundido (Fase 1), ou seja sem floco epifisario; em fusão (Fase 2), isto e com floco visível e fundido (Fase 3) quando este está completamente fundido e não se vislumbra qualquer linha de fusão; b) 4 Fases, que e mais complexo que o anterior: não fundido (Fase 1); se o floco cobre menos de 50% da superfície de epífise (Fase 2), se cobre 50% ou mais da epífise (Fase 3) (Figura 4) e fase 4 se a fusão é completa. c) O método de 5 Fases divide a fase Não fundido das outras escalas em duas fases: não fundido com billowing marcado (Fase 1) e não fundido com billowing pouco profundo (Fase 2); as restantes fases (3,4 e 5) sao iguais ao método de 4 estádios. Várias técnicas estatísticas foram utilizadas, para comparar as colecções (ANOVA, Kruskal- Wallis e Mann-Withney-Wilcoxon), e para caracterizar as passagens de grau e comparar os graus entre si (análise de transição e análise de sobrevivência por Kaplan-Meier), e por último usada a regressão Ordinal Logistica para modelar os dados e obter as probabilidades de estimação da idade. Todo o trabalho estatístico foi efectuado com recurso a softwares especificos, nomeadamente STATA e R. De referir que todos os pressupostos dos testes foram estudados e respeitados, embora não se mostrem detalhes neste trabalho. A análise de transição revelou que como se esperava os indivíduos do sexo feminino passam para um grau de fusão superior numa idade, em média, inferior aos do sexo masculino. Ou seja, a fusão ocorre mais cedo. A mesma análise mostra que os indivíduos de Lisboa maturam mais rapidamente que os das outras duas colecções. A utilização das técnicas de análise de sobrevivência de Kaplan-Meier, revelaram diferenças significativas entre todos os graus dos métodos de 3 e 4 etapas. No método de 5 etapas não foi possivel separar os graus mais baixos, sendo pois aconselhável a sua junção. A modelação por regressão ordinal logística forneceu vários modelos significativos, com uma boa capacidade explicativa, usando a idade categorizada em 7 classes (15-17; 18-20; 21-23; 24- 26;27-29; 30-32; 33-35), e a variável grau de fusão (Stage) do método em 3 e 4 estados. Estes modelos procuraram aumentar a flexibilidade de aplicação do método. Como exemplo mostra-se em detalhe o modelo com o grau em 3 estados e as outras variáveis no modelo (sexo e robustez). Antes de proceder à obtenção de probabilidade de estimação da idade, introduziu-se a variável colecção para tentar confirmar a tendência de maturação mais cedo dos indivíduos da colecção de Lisboa (de referir que esta variável não pode fazer parte do modelo final sob pena de o modelo apenas poder predizer idades dentro destas três colecções). A variável colecção mostrou-se significativa, e mostrou que um indivíduo com o mesmo grau de fusão, mesma robustez e mesmo sexo, tem uma possibilidade maior de ser mais velho se pertencer a uma colecção que não a de Lisboa. Ficamos então com um modelo que se traduz em 6 equações: G(y ≤ 1) = 1.8001 – (1.5599 ∗ Stage 2 + 3.4719 ∗ Stage 3 + 0.0911 ∗ Robusticity − 0.1701 ∗ Sex) G(y ≤ 2_ = 2.9810 – (1.5599 ∗Stage 2 + 3.4719 ∗ Stage 3 + 0.0911 ∗ Robusticity − 0.1701 ∗ Sex) G(y ≤ 3_ = 4.0323 – (1.5599 ∗Stage 2 + 3.4719 ∗ Stage 3 + 0.0911 ∗ Robusticity − 0.1701 ∗ Sex) G(y ≤ 4_ = 4.9407 – (1.5599 ∗Stage 2 + 3.4719 ∗ Stage 3 + 0.0911 ∗ Robusticity − 0.1701 ∗ Sex) G(y ≤ 5_ = 5.6435 – (1.5599 ∗Stage 2 + 3.4719 ∗ Stage 3 + 0.0911 ∗ Robusticity − 0.1701 ∗ Sex) G(y ≤ 6_ = 6.4021 – (1.5599 ∗Stage 2 + 3.4719 ∗ Stage 3 + 0.0911 ∗ Robusticity − 0.1701 ∗ Sex) As variáveis Stage2, Stage3, robustez e sexo, devem ser substituidas pelos valores do indivíduo. Por exemplo se tivermos um indivíduo do sexo masculino (0), com grau de fusão 2, e robustez 22, devemos substituir estes valores nas equações (e necessário ter em conta que o facto de a variável Stage ser ordinal com 3 categorias, torna necessário a sua transformação em variável dummy, pelo que neste caso teríamos que substituir nas equações por Stage2=1, Stage3=0). Cada uma das equações dá-nos um valor que nos permite obter a probabilidade cumulativa do indivíduo estar nessa classe de idade ou abaixo dela. Por exemplo ao substituir na equação G (y≤3) obtemos o valor de 0.4673, do qual temos que obter a probabilidade. Podemos fazê-lo de duas formas: ou com o comando do R pnorm(valor) ou com a formula do Excel dist.normp (valor). Neste caso pnorm(0.4673)=0.6798 que significa que o nosso desconhecido tem uma probabilidade de 68% de estar incluido ou abaixo da classe 3, ou seja abaixo dos 23 anos. Uma vez que estamos a trabalhar com probabilidades cumulativas, para calcular a probabilidade de estar numa determinada classe temos que subtrair as probabilidades anteriores. Assim, voltando ao nosso exemplo, para obter a P (y=3) temos que subtrair P (y≤2) a ja calculada P (y≤3). Ficamos então com P (y=3) =0.68-0.28=0.40. portanto o nosso desconhecido tem assim cerca de 40% de probabilidades de ter entre 21 e 23 anos. Os resultados apontam para uma tendência secular de aceleração do desenvolvimento, havendo uma diferença significativa entre a maturação dos indivíduos de Lisboa e os das outras duas colecções. Os indivíduos de Lisboa apresentam uma maturação mais cedo e mais rapidamente, podendo esta diferença ser devida às melhores condições de vida da Lisboa de meados do século 20, relativamente a zonas rurais de Coimbra no inicio do século 20, ou mesmo da Londres do século 18. Este tipo de tendências seculares no desenvolvimento tem sido documentado (Lin, et al, 2006; Ahmed and Warner, 2007), e ligado a mudança de condições de vida. De facto, Hawley e colaboradores (2009) estabeleceram uma ligação estatisticamente significativa na maturação, entre criancas da África do Sul num periodo de 40 anos. O estudo atribui a aceleração da maturação às importantes melhorias das condições de vida ocorridas no seio daquela população da cidade de Pretoria, naquele período. Shirley e Jantz (2010) também documentaram esta tendência na maturação esquelética, ao compararem as colecções McCormick (final do século 20) e Hamman-Todd (inicio do século 20), nomeadamente nos indivíduos do sexo masculino. A estratégia de modelação adoptada, permitiu atingir o principal objectivo proposto que foi o de obter um novo método, que fosse estatisticamente robusto para estimar a idade a morte. Este trabalho apresenta resultados que apontam para uma tendência secular de aceleração na maturação esquelética. É demonstrado que indivíduos mais recentes, com melhores condições de vida, têm um desenvolvimento mais cedo e mais acelerado. Os métodos apresentados são estatisticamente significativos, mas acima de tudo são flexíveis e fáceis de utilizar quer sejam em contexto arqueológico ou forense.This paper describes a new method for age at death estimation using the epiphyseal union at the medial end of the clavicle. Individuals from 3 human skeletal collections with ages between 15 and 35 were used in a total of 246 specimens – 125 males and 121 females. The Spitalfields collection represents a 1750’s sample from industrial London, whereas the Coimbra’s specimens represent a largely rural population and range from late nineteen to early twentieth century, and the Lisbon collection is the most recent (mid to late twentieth century) and representative of a more typical urban population. Clavicles were scored according to three classification schemes, a 3 stage scheme (1-unfused, 2-fusing and 3-fused), a 4stage scheme(1- unfused; 2-fusing with flake covering under 50% of epiphysis, 3-fusing with flake covering 50% or more of epiphysis, 4-fused), and 5 stage scheme(1-unfused with marked billowing; 2- unfused with shallow billowing; 3-fusing with flake covering under 50% of epiphysis; 4-fusing with flake covering 50% or more of epiphysis; 5-fused). Maximum length and perimeter at the middle of the shaft were also measured to establish the robustcity index. Collections were compared by age and robusticity, and transition analysis and survival analysis were used to compare mean age of attainment for maturation/fusion stages. Ordinal Logistic Regression was used to establish several probabilistic models for age ate death estimation. Results show that there is a secular tendency for the development to be earlier in more recent individuals (Lisbon) when compared to the other collections. Robusticity was found to significantly influence the fusion of the epiphyses, unlike sex. Modeling techniques demonstrated that a 5 degree method is not suitable to our data, since there are no differences between the first 2 stages. The extracted models with 3 and 4 stages provide reliable probabilities for age at death given a certain stage of fusion. Modeling techniques proved to a very useful tool as they allow introducing several factors that influence the variation that we are trying to describe

The importance of considering fibular robusticity when inferring the mobility patterns of past populations

In this chapter we investigate the lower limb structural rigidity (using cross-sectional geometric properties of the diaphyseal midshaft) within a sample of 124 individuals from the Late Upper Paleolithic, Neolithic and Iron Age from Italy, Medieval Germany, and twenty-first Century Britain (long distance runners, field hockey players, and sedentary controls). Late Upper Paleolithic, Neolithic and Iron Age samples were settled in rugged areas, whereas the other samples inhabited plain areas. The aim of this study is to assess whether fibular diaphyseal properties reflect mobility patterns or terrain properties in past populations. Both fibular rigidity and relative fibular rigidity ratio (fibula/tibia) have been analyzed. Results reveal that Late Upper Paleolithic, Neolithic and Iron Age samples show high fibular rigidity and have values of relative fibular rigidity that are most similar to modern hockey players. The relative fibular diaphyseal rigidity of hockey players has been previously explained as the consequence of their dynamic and repetitive change of direction. Late Upper Paleolithic and Neolithic individuals are thought to have been highly terrestrially mobile, while Iron Age people were probably fairly sedentary. However, all of the three groups lived in areas of uneven terrain. We conclude that fibular rigidity and relative fibular rigidity are influenced by factors that increase foot eversion/inversion such as frequent directional changes and uneven terrain. The results of this study suggest that inclusion of the fibula provides a valuable additional perspective that complements traditional predictions of mobility patterns based on the femur or the tibia alone