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Yim AD, Cowgill L, Katz DC, Roseman CC. Variation in ontogenetic trajectories of limb dimensions in humans is attributable to both climatic effects and neutral evolution. J Hum Evol 2023; 179:103369. [PMID: 37104893 DOI: 10.1016/j.jhevol.2023.103369] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2022] [Revised: 03/26/2023] [Accepted: 03/26/2023] [Indexed: 04/29/2023]
Abstract
Previous studies showed that there is variation in ontogenetic trajectories of human limb dimensions and proportions. However, little is known about the evolutionary significance of this variation. This study used a global sample of modern human immature long bone measurements and a multivariate linear mixed-effects model to study 1) whether the variation in ontogenetic trajectories of limb dimensions is consistent with ecogeographic predictions and 2) the effects of different evolutionary forces on the variation in ontogenetic trajectories. We found that genetic relatedness arising from neutral (nonselective) evolution, allometric variation associated with the change in size, and directional effects from climate all contributed to the variation in ontogenetic trajectories of all major long bone dimensions in modern humans. After accounting for the effects of neutral evolution and holding other effects considered in the current study constant, extreme temperatures have weak, positive associations with diaphyseal length and breadth measurements, while mean temperature shows negative associations with diaphyseal dimensions. The association with extreme temperatures fits the expectations of ecogeographic rules, while the association with mean temperature may explain the observed among-group variation in intralimb indices. The association with climate is present throughout ontogeny, suggesting an explanation of adaptation by natural selection as the most likely cause. On the other hand, genetic relatedness among groups, as structured by neutral evolutionary factors, is an important consideration when interpreting skeletal morphology, even for nonadult individuals.
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Affiliation(s)
- An-Di Yim
- Department of Health and Exercise Sciences, Truman State University, 100 E Normal Ave, Kirksville, MO, USA; Department of Biology, Truman State University, 100 E Normal Ave, Kirksville, MO, USA; Department of Anthropology, University of Illinois at Urbana-Champaign, 109 Davenport Hall, 607 S Mathews Ave, Urbana, IL, USA.
| | - Libby Cowgill
- Department of Anthropology, University of Missouri, 112 Swallow Hall, Columbia, MO, USA
| | - David C Katz
- Department of Cell Biology and Anatomy, University of Calgary, 2500 University Drive NW, Calgary, Canada
| | - Charles C Roseman
- Department of Evolution, Ecology, and Behavior, University of Illinois at Urbana-Champaign, 515 Morrill Hall, 505 S Goodwin Ave, Urbana, IL, USA
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2
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Auerbach BM, Savell KRR, Agosto ER. Morphology, evolution, and the whole organism imperative: Why evolutionary questions need multi-trait evolutionary quantitative genetics. AMERICAN JOURNAL OF BIOLOGICAL ANTHROPOLOGY 2023. [PMID: 37060292 DOI: 10.1002/ajpa.24733] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/04/2022] [Revised: 03/13/2023] [Accepted: 03/14/2023] [Indexed: 04/16/2023]
Abstract
Since Washburn's New Physical Anthropology, researchers have sought to understand the complexities of morphological evolution among anatomical regions in human and non-human primates. Researchers continue, however, to preferentially use comparative and functional approaches to examine complex traits, but these methods cannot address questions about evolutionary process and often conflate function with fitness. Moreover, researchers also tend to examine anatomical elements in isolation, which implicitly assumes independent evolution among different body regions. In this paper, we argue that questions asked in primate evolution are best examined using multiple anatomical regions subjected to model-bound methods built from an understanding of evolutionary quantitative genetics. A nascent but expanding number of studies over the last two decades use this approach, examining morphological integration, evolvability, and selection modeling. To help readers learn how to use these methods, we review fundamentals of evolutionary processes within a quantitative genetic framework, explore the importance of neutral evolutionary theory, and explain the basics of evolutionary quantitative genetics, namely the calculation of evolutionary potential for multiple traits in response to selection. Leveraging these methods, we demonstrate their use to understand non-independence in possible evolutionary responses across the limbs, limb girdles, and basicranium of humans. Our results show that model-bound quantitative genetic methods can reveal unexpected genetic covariances among traits that create a novel but measurable understanding of evolutionary complexity among multiple traits. We advocate for evolutionary quantitative genetic methods to be a standard whenever appropriate to keep studies of primate morphological evolution relevant for the next seventy years and beyond.
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Affiliation(s)
- Benjamin M Auerbach
- Department of Anthropology, The University of Tennessee, Knoxville, Tennessee, USA
- Department of Ecology and Evolutionary Biology, The University of Tennessee, Knoxville, Tennessee, USA
| | - Kristen R R Savell
- Department of Biology, Sacred Heart University, Fairfield, Connecticut, USA
| | - Elizabeth R Agosto
- Department of Anatomy, Cell Biology & Physiology, Indiana University School of Medicine, Indianapolis, Indiana, USA
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3
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Cho EO, Cowgill LW, Middleton KM, Blomquist GE, Savoldi F, Tsoi J, Bornstein MM. The influence of climate and population structure on East Asian skeletal morphology. J Hum Evol 2022; 173:103268. [PMID: 36288639 DOI: 10.1016/j.jhevol.2022.103268] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2021] [Revised: 09/13/2022] [Accepted: 09/14/2022] [Indexed: 11/06/2022]
Abstract
Recent studies have shown that global variation in body proportions is more complex than previously thought as some traits formerly associated with climate adaptation are better explained by geographic proximity and neutral evolutionary forces. While the recent incorporation of quantitative genetic methodologies has improved understanding of patterns related to climate in Africa, Europe, and the Americas, Asia remains underrepresented in recent and historic studies of body form. As ecogeographic studies tend to focus on male morphology, potential sex differences in features influenced by climate remain largely unexplored. Skeletal measurements encompassing the dimensions of the skull, pelvis, limbs, hands, and feet were collected from male (n = 459) and female (n = 442) remains curated in 13 collections across seven countries in East Asia (n = 901). Osteological data were analyzed with sex and minimum temperature as covariates adjusted by autosomal single-nucleotide polymorphism population genetic distance using univariate Bayesian linear mixed models, and credible intervals were calculated for each trait. Analysis supports a relationship between specific traits and climate as well as providing the magnitude of response in both sexes. After accounting for genetic distance between populations, greater association between climate and morphology was found in postcranial traits, with the relationship between climate and the skull limited primarily to breadth measurements. Larger body size is associated with colder climates with most measurements increasing with decreased temperature. The same traits were not always associated with climate for males and females nor correlated with the same intensity for both sexes. The varied directional association with climate for different regions of the skeleton and between the sexes underscores the necessity of future ecogeographic research to holistically evaluate body form and to look for sex-specific patterns to better understand population responses to environmental stresses.
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Affiliation(s)
- Elizabeth O Cho
- Department of Anthropology, University of Missouri, Columbia, MO 65211, USA; Center for Anatomical Sciences, University of North Texas Health Science Center, Fort Worth, TX 76107, USA.
| | - Libby W Cowgill
- Department of Anthropology, University of Missouri, Columbia, MO 65211, USA
| | - Kevin M Middleton
- Division of Biological Sciences, University of Missouri, Columbia, MO 65211, USA
| | | | - Fabio Savoldi
- Orthodontics, Division of Paediatric Dentistry & Orthodontics, Faculty of Dentistry, The University of Hong Kong, Sai Ying Pun, Hong Kong S.A.R., P.R. China
| | - James Tsoi
- Dental Materials Science, Division of Applied Oral Sciences & Community Dental Care, Faculty of Dentistry, The University of Hong Kong, Sai Ying Pun, Hong Kong S.A.R., P.R. China
| | - Michael M Bornstein
- Oral and Maxillofacial Radiology, Division of Applied Oral Sciences & Community Dental Care, Faculty of Dentistry, The University of Hong Kong, Sai Ying Pun, Hong Kong S.A.R., P.R. China; Department of Oral Health and Medicine, University Center for Dental Medicine Basel UZB, University of Basel, Basel 4058, Switzerland
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Gorman J, Roberts CA, Newsham S, Bentley GR. Squatting, pelvic morphology and a reconsideration of childbirth difficulties. Evol Med Public Health 2022; 10:243-255. [PMID: 35663511 PMCID: PMC9154243 DOI: 10.1093/emph/eoac017] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2021] [Accepted: 04/19/2022] [Indexed: 11/14/2022] Open
Abstract
Childbirth is commonly viewed as difficult in human females, encompassed by the 'Obstetrical Dilemma' (OD) described by early palaeoanthropologists as an evolved trade-off between a narrow pelvis necessitated by bipedalism and a large-brained fetal head. The OD has been challenged on several grounds. We add to these challenges by suggesting humans likely squatted regularly during routine tasks prior to the advent of farming societies and use of seats. We suggest that habitual squatting, together with taller stature and better nutrition of ancestral hunter-gatherers compared with later Neolithic and industrial counterparts, obviated an OD. Instead, difficulties with parturition may have arisen much later in our history, accompanying permanent settlements, poorer nutrition, greater infectious disease loads and negligible squatting in daily life. We discuss bioarchaeological and contemporary data that support these viewpoints, suggest ways in which this hypothesis might be tested further and consider its implications for obstetrical practice. Lay Summary Human childbirth is viewed as universally difficult. Evidence from physical therapies/engineering and studies of living and ancestral humans illustrates habitual squatting widens the pelvis and could improve childbirth outcomes. Obstetrical difficulties emerged late in prehistory accompanying settled agriculture, poorer nutrition and less squatting. Specific physical exercises could improve obstetrical practice.
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Affiliation(s)
- John Gorman
- Independent Scholar, Greenhead, Brampton, Northumberland CA8 7HX, UK
| | - Charlotte A Roberts
- Department of Archaeology, Durham University, Dawson Building, South Road, Durham DH1 3LE, UK
| | - Sally Newsham
- Department of Gynaecology, North Cumbria Integrated Care NHS Foundation Trust, Cumbria CA2 7HY, UK
| | - Gillian R Bentley
- Department of Anthropology, Durham University, Dawson Building, South Road, Durham DH1 3LE, UK
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Haeusler M, Grunstra ND, Martin RD, Krenn VA, Fornai C, Webb NM. The obstetrical dilemma hypothesis: there's life in the old dog yet. Biol Rev Camb Philos Soc 2021; 96:2031-2057. [PMID: 34013651 PMCID: PMC8518115 DOI: 10.1111/brv.12744] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2020] [Revised: 05/06/2021] [Accepted: 05/10/2021] [Indexed: 12/17/2022]
Abstract
The term 'obstetrical dilemma' was coined by Washburn in 1960 to describe the trade-off between selection for a larger birth canal, permitting successful passage of a big-brained human neonate, and the smaller pelvic dimensions required for bipedal locomotion. His suggested solution to these antagonistic pressures was to give birth prematurely, explaining the unusual degree of neurological and physical immaturity, or secondary altriciality, observed in human infants. This proposed trade-off has traditionally been offered as the predominant evolutionary explanation for why human childbirth is so challenging, and inherently risky, compared to that of other primates. This perceived difficulty is likely due to the tight fit of fetal to maternal pelvic dimensions along with the convoluted shape of the birth canal and a comparatively low degree of ligamentous flexibility. Although the ideas combined under the obstetrical dilemma hypothesis originated almost a century ago, they have received renewed attention and empirical scrutiny in the last decade, with some researchers advocating complete rejection of the hypothesis and its assumptions. However, the hypothesis is complex because it presently captures several, mutually non-exclusive ideas: (i) there is an evolutionary trade-off resulting from opposing selection pressures on the pelvis; (ii) selection favouring a narrow pelvis specifically derives from bipedalism; (iii) human neonates are secondarily altricial because they are born relatively immature to ensure that they fit through the maternal bony pelvis; (iv) as a corollary to the asymmetric selection pressure for a spacious birth canal in females, humans evolved pronounced sexual dimorphism of pelvic shape. Recently, the hypothesis has been challenged on both empirical and theoretical grounds. Here, we appraise the original ideas captured under the 'obstetrical dilemma' and their subsequent evolution. We also evaluate complementary and alternative explanations for a tight fetopelvic fit and obstructed labour, including ecological factors related to nutrition and thermoregulation, constraints imposed by the stability of the pelvic floor or by maternal and fetal metabolism, the energetics of bipedalism, and variability in pelvic shape. This reveals that human childbirth is affected by a complex combination of evolutionary, ecological, and biocultural factors, which variably constrain maternal pelvic form and fetal growth. Our review demonstrates that it is unwarranted to reject the obstetrical dilemma hypothesis entirely because several of its fundamental assumptions have not been successfully discounted despite claims to the contrary. As such, the obstetrical dilemma remains a tenable hypothesis that can be used productively to guide evolutionary research.
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Affiliation(s)
- Martin Haeusler
- Institute of Evolutionary MedicineUniversity of ZurichWinterthurerstrasse 190Zürich8057Switzerland
| | - Nicole D.S. Grunstra
- Konrad Lorenz Institute (KLI) for Evolution and Cognition ResearchMartinstrasse 12Klosterneuburg3400Austria
- Department of Evolutionary BiologyUniversity of ViennaUniversity Biology Building (UBB), Carl Djerassi Platz 1Vienna1030Austria
- Mammal CollectionNatural History Museum ViennaBurgring 7Vienna1010Austria
| | - Robert D. Martin
- Institute of Evolutionary MedicineUniversity of ZurichWinterthurerstrasse 190Zürich8057Switzerland
- The Field Museum1400 S Lake Shore DrChicagoIL60605U.S.A.
| | - Viktoria A. Krenn
- Institute of Evolutionary MedicineUniversity of ZurichWinterthurerstrasse 190Zürich8057Switzerland
- Department of Evolutionary AnthropologyUniversity of ViennaUniversity Biology Building (UBB), Carl Djerassi Platz 1Vienna1030Austria
| | - Cinzia Fornai
- Institute of Evolutionary MedicineUniversity of ZurichWinterthurerstrasse 190Zürich8057Switzerland
- Department of Evolutionary AnthropologyUniversity of ViennaUniversity Biology Building (UBB), Carl Djerassi Platz 1Vienna1030Austria
| | - Nicole M. Webb
- Institute of Evolutionary MedicineUniversity of ZurichWinterthurerstrasse 190Zürich8057Switzerland
- Senckenberg Research Institute and Natural History Museum FrankfurtSenckenberganlage 25Frankfurt am Main60325Germany
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Abstract
Homo erectus is the first hominin species with a truly cosmopolitan distribution and resembles recent humans in its broad spatial distribution. The microevolutionary events associated with dispersal and local adaptation may have produced similar population structure in both species. Understanding the evolutionary population dynamics of H. erectus has larger implications for the emergence of later Homo lineages in the Middle Pleistocene. Quantitative genetics models provide a means of interrogating aspects of long-standing H. erectus population history narratives. For the current study, cranial fossils were sorted into six major palaeodemes from sites across Africa and Asia spanning 1.8-0.1 Ma. Three-dimensional shape data from the occipital and frontal bones were used to compare intraspecific variation and test evolutionary hypotheses. Results indicate that H. erectus had higher individual and group variation than Homo sapiens, probably reflecting different levels of genetic diversity and population history in these spatially disperse species. This study also revealed distinct evolutionary histories for frontal and occipital bone shape in H. erectus, with a larger role for natural selection in the former. One scenario consistent with these findings is climate-driven facial adaptation in H. erectus, which is reflected in the frontal bone through integration with the orbits.
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Affiliation(s)
- Karen L Baab
- Department of Anatomy, College of Graduate Studies, Midwestern University, Glendale, AZ 85308, USA
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Pomeroy E, Stock JT, Wells JCK. Population history and ecology, in addition to climate, influence human stature and body proportions. Sci Rep 2021; 11:274. [PMID: 33431970 PMCID: PMC7801440 DOI: 10.1038/s41598-020-79501-w] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2020] [Accepted: 12/09/2020] [Indexed: 01/29/2023] Open
Abstract
Worldwide variation in human stature and limb proportions is widely accepted to reflect thermal adaptation, but the contribution of population history to this variation is unknown. Furthermore, stature and relative lower limb length (LLL) show substantial plastic responses to environmental stressors, e.g., nutrition, pathogen load, which covary with climate. Thus ecogeographic patterns may go beyond temperature-based selection. We analysed global variation in stature, sitting height and absolute and relative LLL using large worldwide samples of published anthropometric data from adult male (n = 571) and female (n = 268) populations in relation to temperature, humidity, and net primary productivity (NPP). Population history was modeled using spatial eigenvector mapping based on geographic distances reflecting the hypothesized pattern for the spread of modern humans out of Africa. Regression models account for ~ 50% of variation in most morphological variables. Population history explains slightly more variation in stature, sitting height and LLL than the environmental/climatic variables. After adjusting for population history, associations between (usually maximum) temperature and LLL are consistent with Allen's "rule" and may drive similar relationships with stature. NPP is a consistent negative predictor of anthropometry, which may reflect the growth-limiting effects of lower environmental resource accessibility (inversely related to NPP) and/or pathogen load.
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Affiliation(s)
- Emma Pomeroy
- Department of Archaeology, University of Cambridge, Downing Street, Cambridge, CB2 3DZ, UK.
| | - Jay T Stock
- Department of Anthropology, University of Western Ontario, London, ON, N6A 5C2, Canada
| | - Jonathan C K Wells
- UCL Great Ormond Street Institute of Child Health, University College London, Great Ormond Street, London, WC1N 3JH, UK
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Kenyon-Flatt B, Conaway MA, Lycett SJ, von Cramon-Taubadel N. The relative efficacy of the cranium and os coxa for taxonomic assessment in macaques. AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 2020; 173:350-367. [PMID: 32594518 DOI: 10.1002/ajpa.24100] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/23/2019] [Revised: 02/07/2020] [Accepted: 05/20/2020] [Indexed: 11/08/2022]
Abstract
OBJECTIVES The cranium is generally considered more reliable than the postcranium for assessing primate taxonomy, although recent research suggests that pelvic shape may be equally reliable. However, little research has focused on intrageneric taxonomic discrimination. Here, we test the relative taxonomic efficacy of the cranium and os coxa for differentiating two macaque species, with and without considering sexual dimorphism. MATERIALS AND METHODS Geometric morphometric analyses were performed on cranial and os coxa landmarks for 119 adult Macaca fascicularis, M. mulatta, and Chlorocebus pygerythrus. Among-group shape variation was examined using canonical variates analyses. Cross-validated discriminant function analysis provided rates of correct group classification. Additionally, average morphological distances were compared with neutral genetic distances. RESULTS Macaque species were clearly differentiated, both cranially and pelvically, when sex was not considered. Males were more often correctly classified based on the os coxa, while female classification rates were high for both morphologies. Female crania and male os coxa were differentiated approximately the same as genetic distance, while male crania were more similar (convergent), and female os coxa were more divergent than expected based on genetic distance. DISCUSSION The hypothesis that cranial and os coxal shape can be used to discriminate among macaque species was supported. The cranium was better at differentiating females, while the os coxa was better at differentiating male macaques. Hence, there is no a priori reason for preferring the cranium when assessing intragenetic taxonomic relationships, but the effects of high levels of sexual dimorphism must be corrected for to accurately assess taxonomic signatures.
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Affiliation(s)
- Brittany Kenyon-Flatt
- Buffalo Human Evolutionary Morphology Lab, Department of Anthropology, University at Buffalo, Buffalo, New York, USA
| | - Mark A Conaway
- Buffalo Human Evolutionary Morphology Lab, Department of Anthropology, University at Buffalo, Buffalo, New York, USA
| | - Stephen J Lycett
- Department of Anthropology, University at Buffalo, Buffalo, New York, USA
| | - Noreen von Cramon-Taubadel
- Buffalo Human Evolutionary Morphology Lab, Department of Anthropology, University at Buffalo, Buffalo, New York, USA
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9
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Longman DP, Wells JCK, Stock JT. Human athletic paleobiology; using sport as a model to investigate human evolutionary adaptation. AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 2020; 171 Suppl 70:42-59. [PMID: 31957878 PMCID: PMC7217212 DOI: 10.1002/ajpa.23992] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/01/2019] [Revised: 10/29/2019] [Accepted: 12/12/2019] [Indexed: 11/11/2022]
Abstract
The use of sport as a conceptual framework offers unprecedented opportunities to improve our understanding of what the body does, shedding new light on our evolutionary trajectory, our capacity for adaptation, and the underlying biological mechanisms. This approach has gained traction over recent years. To date, sport has facilitated exploration not only of the evolutionary history of our species as a whole, but also of human variation and adaptation at the interindividual and intraindividual levels. At the species level, analysis of lower and upper limb biomechanics and energetics with respect to walking, running and throwing have led to significant advances in the understanding of human adaptations relative to other hominins. From an interindividual perspective, investigation of physical activity patterns and endurance running performance is affording greater understanding of evolved constraints of energy expenditure, thermoregulatory energetics, signaling theory, and morphological variation. Furthermore, ultra-endurance challenges provoke functional trade-offs, allowing new ground to be broken in the study of life history trade-offs and human adaptability. Human athletic paleobiology-the recruitment of athletes as study participants and the use of contemporary sports as a model for studying evolutionary theory-has great potential. Here, we draw from examples in the literature to provide a review of how the use of athletes as a model system is enhancing understanding of human evolutionary adaptation.
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Affiliation(s)
- Daniel P. Longman
- School of Sport, Exercise and Health SciencesLoughborough UniversityLoughboroughUK
| | | | - Jay T. Stock
- Department of AnthropologyUniversity of Western OntarioLondonOntarioCanada
- Department of ArchaeologyMax Planck Institute for the Science of Human HistoryJenaGermany
- Department of ArchaeologyUniversity of CambridgeCambridgeUK
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10
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Savell KRR. Evolvability in human postcranial traits across ecogeographic regions. AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 2020; 172:110-122. [PMID: 31912894 DOI: 10.1002/ajpa.24004] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/29/2019] [Revised: 11/19/2019] [Accepted: 12/20/2019] [Indexed: 11/08/2022]
Abstract
OBJECTIVES Though recent quantitative genetic analyses have indicated that directional selection appears to be acting on limb lengths and measures of body size in modern humans, these studies assume equal evolvability across modern human groups. However, differences in trait covariance structure due to ancient migration patterns and/or selection may limit the evolvability of populations further from Africa. This study therefore explores patterns of human evolvability across ecogeographic regions. MATERIALS AND METHODS Mean evolvability, respondability, conditional evolvability, and autonomy were calculated from variance-covariance matrices of limb length and body size measures representing 14 human groups spanning four ecogeographic regions. Measures of evolvability were compared across groups and regions, and the minimum sample size, inaccuracy, and bias were calculated for each. RESULTS When compared between regions, humans demonstrate significant differences between indices of evolvability across regions. Despite the relatively recent evolution of modern humans, several measures of evolvability show a strong negative correlation with latitude across regions, demonstrating a reduction in genetic variance that is potentially reflective of human migration and/or response to selection. CONCLUSIONS These results demonstrate the importance of establishing patterns of evolvability prior to additional quantitative genetic analyses, and emphasize the influence of sample size on the accuracy of estimated evolvability measures. These findings also suggest that while modern human groups share similar covariance structures, there is evidence for emergent differentiation in evolvability and respondability between human groups across ecogeographic regions, further complicating our ability to apply results derived from modern human groups to ancient hominin lineages.
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11
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Waxenbaum EB, Warren MW, Holliday TW, Byrd JE, Cole TM. Ecogeographic patterns in fetal limb proportions. AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 2019; 169:93-103. [PMID: 30848485 DOI: 10.1002/ajpa.23814] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/19/2018] [Revised: 02/06/2019] [Accepted: 02/19/2019] [Indexed: 11/11/2022]
Abstract
OBJECTIVES Humans generally comply with the ecological rule of Allen (1877), with populations from tropical environments exhibiting body proportions in which limb segments are long relative to trunk height compared to temperate groups. This study tests whether ecogeographic differences in intralimb proportions are identifiable among two modern fetal samples of differing ancestry. MATERIALS AND METHODS Data are derived from radiographic measurements of long bone diaphyseal length and crown-heel length (CHL) of contemporary, spontaneously aborted fetuses of African Americans ("black") of assumed African (tropical) ancestry and European Americans ("white") of assumed European (temperate) ancestry (n = 184). Population individual limb elements, brachial, and crural indices are compared via analyses of covariance (ANCOVA). Potential patterns of divergent allometric growth are quantified through principal components analysis (PCA). RESULTS African ancestral distal limb elements were consistently, albeit slightly, longer than those of European ancestry, relative to CHL. None of the ANCOVA interactions with ancestry are statistically significant for limb indices. The radius was the only single element that displayed a statistically significant ancestry effect (p = 0.0435) equating to a 1 mm difference. PCA highlights that upper limbs demonstrate negative allometry and lower limbs demonstrate positive allometry with sample-specific multivariate growth patterns being nearly identical. Differences in growth allometry late in gestation make little contribution to observed differences in adult limb proportions. DISCUSSION No statistically significant ecogeographic patterns were appreciated among intralimb proportions between these groups during the fetal period. This study contributes to a greater appreciation of phenotypic plasticity, ecogeographic variation in ontogeny, and the evolution of modern human diversity.
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Affiliation(s)
- Erin B Waxenbaum
- Department of Anthropology, Northwestern University, Evanston, Illinois
| | - Michael W Warren
- Department of Anthropology, University of Florida, Gainesville, Florida
| | - Trenton W Holliday
- Department of Anthropology, Tulane University, New Orleans, Louisiana
- Evolutionary Studies Institute, University of the Witwatersrand, Wits, Republic of South Africa
| | - John E Byrd
- Defense POW/MIA Accounting Agency, Central Identification Laboratory, Hickam AFB, Hawaii
| | - Theodore M Cole
- Department of Biomedical Sciences, University of Missouri - Kansas City, Kansas City, Missouri
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12
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von Cramon-Taubadel N. Multivariate morphometrics, quantitative genetics, and neutral theory: Developing a "modern synthesis" for primate evolutionary morphology. Evol Anthropol 2019; 28:21-33. [PMID: 30652384 DOI: 10.1002/evan.21761] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2018] [Revised: 08/17/2018] [Accepted: 11/29/2018] [Indexed: 01/07/2023]
Abstract
Anthropologists are increasingly turning to explicit model-bound evolutionary approaches for understanding the morphological diversification of humans and other primate lineages. Such evolutionary morphological analyses rely on three interconnected conceptual frameworks; multivariate morphometrics for quantifying similarity and differences among taxa, quantitative genetics for modeling the inheritance and evolution of morphology, and neutral theory for assessing the likelihood that taxon diversification is due to stochastic processes such as genetic drift. Importantly, neutral theory provides a framework for testing more parsimonious explanations for observed morphological differences before considering more complex adaptive scenarios. However, the consistency with which these concepts are applied varies considerably, which mirrors some of the theoretical obstacles faced during the "modern synthesis" of classical population genetics in the early 20th century. Here, each framework is reviewed and some potential stumbling blocks to the full conceptual integration of multivariate morphometrics, quantitative genetics, and neutral theory are considered.
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Affiliation(s)
- Noreen von Cramon-Taubadel
- Department of Anthropology, Buffalo Human Evolutionary Morphology Lab, University at Buffalo, SUNY, Buffalo, New York
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13
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Abstract
In humans, patterns of cranial variation mirror genetic diversity globally, implicating population history as a key driver of cranial disparity. Here, we demonstrate that the magnitude of genetic diversity within 12 extant ape taxa explains a large proportion of cranial shape variation. Taxa that are more genetically diverse tend to be more cranially diverse also. Our results suggest that neutral evolutionary processes such as mutation, genetic drift, and gene flow are reflected in both genetic and cranial diversity in apes. This work provides a perspective on intraspecific cranial variation in apes which has important implications for interpreting selective and developmental pressures on the cranium and for understanding shape variation in fossil hominin crania. Natural selection, developmental constraint, and plasticity have all been invoked as explanations for intraspecific cranial variation in humans and apes. However, global patterns of human cranial variation are congruent with patterns of genetic variation, demonstrating that population history has influenced cranial variation in humans. Here we show that this finding is not unique to Homo sapiens but is also broadly evident across extant ape species. Specifically, taxa that exhibit greater intraspecific cranial shape variation also exhibit greater genetic diversity at neutral autosomal loci. Thus, cranial shape variation within hominoid taxa reflects the population history of each species. Our results suggest that neutral evolutionary processes such as mutation, gene flow, and genetic drift have played an important role in generating cranial variation within species. These findings are consistent with previous work on human cranial morphology and improve our understanding of the evolutionary processes that generate intraspecific cranial shape diversity within hominoids. This work has implications for the analysis of selective and developmental pressures on the cranium and for interpreting shape variation in fossil hominin crania.
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Agostini G, Holt BM, Relethford JH. Bone functional adaptation does not erase neutral evolutionary information. AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 2018; 166:708-729. [DOI: 10.1002/ajpa.23460] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/18/2017] [Revised: 02/26/2018] [Accepted: 03/01/2018] [Indexed: 12/15/2022]
Affiliation(s)
- Gina Agostini
- Mayo Clinic/ASU Obesity Solutions, School of Human Evolution and Social ChangeArizona State UniversityTempe Arizona
| | - Brigitte M. Holt
- Department of AnthropologyUniversity of Massachusetts AmherstAmherst Massachusetts
| | - John H. Relethford
- Department of AnthropologyState University of New York at OneontaOneonta New York
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15
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Reyes-Centeno H, Rathmann H, Hanihara T, Harvati K. Testing Modern Human Out-of-Africa Dispersal Models Using Dental Nonmetric Data. CURRENT ANTHROPOLOGY 2017. [DOI: 10.1086/694423] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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16
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Betti L. Human Variation in Pelvic Shape and the Effects of Climate and Past Population History. Anat Rec (Hoboken) 2017; 300:687-697. [PMID: 28297180 DOI: 10.1002/ar.23542] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2016] [Revised: 08/30/2016] [Accepted: 10/20/2016] [Indexed: 12/13/2022]
Abstract
The human pelvis is often described as an evolutionary compromise (obstetrical dilemma) between the requirements of efficient bipedal locomotion and safe parturition of a highly encephalized neonate, that has led to a tight fit between the birth canal and the head and body of the foetus. Strong evolutionary constraints on the shape of the pelvis can be expected under this scenario. On the other hand, several studies have found a significant level of pelvic variation within and between human populations, a fact that seems to contradict such expectations. The advantages of a narrow pelvis for locomotion have recently been challenged, suggesting that the tight cephalo-pelvic fit might not stem from the hypothesized obstetrical dilemma. Moreover, the human pelvis appears to be under lower constraints and to have relatively higher evolvability than other closely related primates. These recent findings substantially change the way in which we interpret variation in the human pelvis, and help make sense of the high diversity in pelvic shape observed within and among modern populations. A lower magnitude of covariance between functionally important regions ensured that a wide range of morphological variation was available within populations, enabling natural selection to generate pelvic variation between populations living in different environments. Neutral processes such as genetic drift and differential migration also contributed to shaping modern pelvic diversity during and after the expansion of humans into and across the various continents. Anat Rec, 300:687-697, 2017. © 2017 Wiley Periodicals, Inc.
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Affiliation(s)
- Lia Betti
- Centre for Research in Evolutionary, Social and Inter-Disciplinary Anthropology, Department of Life Sciences, University of Roehampton, London, SW15 4JD, UK
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17
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Femoral neck-shaft angle and climate-induced body proportions. AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 2017; 164:720-735. [DOI: 10.1002/ajpa.23311] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/23/2017] [Revised: 08/23/2017] [Accepted: 08/29/2017] [Indexed: 01/25/2023]
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18
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Agostini G, Rasoazanabary E, Godfrey LR. The befuddling nature of mouse lemur hands and feet at Bezà Mahafaly, SW Madagascar. Am J Primatol 2017; 79. [PMID: 28605033 DOI: 10.1002/ajp.22680] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2016] [Revised: 03/14/2017] [Accepted: 05/15/2017] [Indexed: 11/11/2022]
Abstract
The reddish-gray mouse lemur (Microcebus griseorufus) possesses striking phenotypic and behavioral variation. This project investigates differences in autopod proportions in neighboring populations of M. griseorufus from the Special Reserve at Bezà Mahafaly in southwest Madagascar. One population resides in an environment generally preferred by M. griseorufus-a spiny forest with large-trunked trees, vertically-oriented supports, and more open ground, while the other resides in a gallery forest with abundant small, often horizontal peripheral branches in high canopy. We demonstrate significant interpopulation differences in autopod morphophology despite no evidence of divergence in mitochondrial cytochrome b. We test two hypotheses regarding ultimate causation. The first, based on the Fine Branch Arborealism Hypothesis (FBAH), holds that autopod differences are related to different locomotor practices in the two environments, and the second, based on the Narrow Niche Hypothesis (NNH), holds that the observed differences reflect a relaxation (from ancestral to descendant conditions) of selective pressure for terrestrial locomotion and/or use of large, vertical supports combined with positive selection for locomoting in peripheral branch settings. Our data conform well to FBAH expectations and show some support for the NNH. Individuals from the gallery forest possess disproportionally long posterior digits that facilitate locomotion on small, flexible canopy supports while individuals from the spiny forest possess shorter posterior digits and a longer pollex/hallux that increase functional grasping diameter for large vertical supports and facilitate efficient ground locomotion. Focal individual data confirm differences in how often individuals descend to the ground and use vertical supports. We further show that predispersal juveniles, like adults, possess autopod morphologies suited to their natal forest. We explore two proximate mechanisms that could generate these cheiridial differences. The first posits an in vivo plastic response to different locomotor behaviors, the second posits differences that manifest in early development.
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Affiliation(s)
- Gina Agostini
- Department of Anthropology, University of Massachusetts Amherst, Amherst, Massachusetts
| | | | - Laurie R Godfrey
- Department of Anthropology, University of Massachusetts Amherst, Amherst, Massachusetts
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19
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Hammond AS, Royer DF, Fleagle JG. The Omo-Kibish I pelvis. J Hum Evol 2017; 108:199-219. [PMID: 28552208 DOI: 10.1016/j.jhevol.2017.04.004] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2017] [Revised: 04/13/2017] [Accepted: 04/15/2017] [Indexed: 12/13/2022]
Abstract
Omo-Kibish I (Omo I) from southern Ethiopia is the oldest anatomically modern Homo sapiens skeleton currently known (196 ± 5 ka). A partial hipbone (os coxae) of Omo I was recovered more than 30 years after the first portion of the skeleton was recovered, a find which is significant because human pelves can be informative about an individual's sex, age-at-death, body size, obstetrics and parturition, and trunk morphology. Recent human pelves are distinct from earlier Pleistocene Homo spp. pelves because they are mediolaterally narrower in bispinous breadth, have more vertically oriented ilia, lack a well-developed iliac pillar, and have distinct pubic morphology. The pelvis of Omo I provides an opportunity to test whether the earliest modern humans had the pelvic morphology characteristic of modern humans today and to shed light onto the paleobiology of the earliest humans. Here, we formally describe the preservation and morphology of the Omo I hipbone, and quantitatively and qualitatively compare the hipbone to recent humans and relevant fossil Homo. The Omo I hipbone is modern human in appearance, displaying a moderate iliac tubercle (suggesting a reduced iliac pillar) and an ilium that is not as laterally flaring as earlier Homo. Among those examined in this study, the Omo I ischium is most similar in shape to (but substantially larger than) that of recent Sudanese people. Omo I has features that suggest this skeleton belonged to a female. The stature estimates in this study were derived from multiple bones from the upper and lower part of the body, and suggest that there may be differences in the upper and lower limb proportions of the earliest modern humans compared to recent humans. The large size and robusticity of the Omo I pelvis is in agreement with other studies that have found that modern human reduction in postcranial robusticity occurred later in our evolutionary history.
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Affiliation(s)
- Ashley S Hammond
- Center for Advanced Study of Human Paleobiology, Department of Anthropology, George Washington University, Washington, DC, 20052, USA.
| | - Danielle F Royer
- Department of Cell and Developmental Biology, University of Colorado, Denver, CO, 80204, USA
| | - John G Fleagle
- Department of Anatomical Sciences, Stony Brook University, Stony Brook, NY, 11794, USA
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20
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Jantz RL, Meadows Jantz L. Limb bone allometry in modern Euro-Americans. AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 2017; 163:252-263. [DOI: 10.1002/ajpa.23203] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/31/2016] [Revised: 02/03/2017] [Accepted: 02/20/2017] [Indexed: 01/29/2023]
Affiliation(s)
- R. L. Jantz
- Department of Anthropology; University of Tennessee; Knoxville Tennessee 37996-0720
| | - L. Meadows Jantz
- Department of Anthropology; University of Tennessee; Knoxville Tennessee 37996-0720
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21
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Kurki HK. Bilateral Asymmetry in the Human Pelvis. Anat Rec (Hoboken) 2017; 300:653-665. [DOI: 10.1002/ar.23546] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2016] [Revised: 09/26/2016] [Accepted: 12/19/2016] [Indexed: 12/14/2022]
Affiliation(s)
- Helen K. Kurki
- Department of Anthropology; University of Victoria; Victoria BC V8W 2Y2 Canada
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22
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Brzobohatá H, Krajíček V, Horák Z, Velemínská J. Sexual Dimorphism of the Human Tibia through Time: Insights into Shape Variation Using a Surface-Based Approach. PLoS One 2016; 11:e0166461. [PMID: 27846265 PMCID: PMC5112946 DOI: 10.1371/journal.pone.0166461] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2016] [Accepted: 10/28/2016] [Indexed: 01/08/2023] Open
Abstract
In this paper we present a three-dimensional (3D) morphometrical assessment of human tibia sexual dimorphism based on whole bone digital representation. To detect shape-size and shape differences between sexes, we used geometric morphometric tools and colour-coded surface deviation maps. The surface-based methodology enabled analysis of sexually dimorphic features throughout the shaft and articular ends of the tibia. The overall study dataset consisted of 183 3D models of adult tibiae from three Czech population subsets, dating to the early medieval (9-10th century) (N = 65), early 20th century (N = 61) and 21st-century (N = 57). The time gap between the chronologically most distant and contemporary datasets was more than 1200 years. The results showed that, in all three datasets, sexual dimorphism was pronounced. There were some sex-dimorphic characteristics common to all three samples, such as tuberosity protrusion, anteriorly bowed shaft and relatively larger articular ends in males. Diachronic comparisons also revealed substantial shape variation related to the most dimorphic area. Male/female distinctions showed a consistent temporal trend regarding the location of dimorphic areas (shifting distally with time), while the maximal deviation between male and female digitized surfaces fluctuated and reached the lowest level in the 21st-century sample. Sex determination on a whole-surface basis yielded the lowest return of correct sex assignment in the 20th-century group, which represented the lowest socioeconomic status. The temporal variation could be attributed to changes in living conditions, the decreasing lower limb loading/labour division in the last 12 centuries having the greatest effect. Overall, the results showed that a surface-based approach is successful for analysing complex long bone geometry.
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Affiliation(s)
- Hana Brzobohatá
- Department of Prehistorical Archaeology, Institute of Archaeology of the Academy of Sciences, Prague, Czech Republic
| | - Václav Krajíček
- Department of Software and Computer Science Education, Faculty of Mathematics and Physics, Charles University in Prague, Prague, Czech Republic
- Department of Anthropology and Human Genetics, Faculty of Science, Charles University in Prague, Prague, Czech Republic
| | - Zdeněk Horák
- Laboratory of Biomechanics, Faculty of Mechanical Engineering, Czech Technical University, Prague, Czech Republic
| | - Jana Velemínská
- Department of Anthropology and Human Genetics, Faculty of Science, Charles University in Prague, Prague, Czech Republic
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23
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Tracking modern human population history from linguistic and cranial phenotype. Sci Rep 2016; 6:36645. [PMID: 27833101 PMCID: PMC5105118 DOI: 10.1038/srep36645] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2016] [Accepted: 10/19/2016] [Indexed: 12/27/2022] Open
Abstract
Languages and genes arguably follow parallel evolutionary trajectories, descending from a common source and subsequently differentiating. However, although common ancestry is established within language families, it remains controversial whether language preserves a deep historical signal. To address this question, we evaluate the association between linguistic and geographic distances across 265 language families, as well as between linguistic, geographic, and cranial distances among eleven populations from Africa, Asia, and Australia. We take advantage of differential population history signals reflected by human cranial anatomy, where temporal bone shape reliably tracks deep population history and neutral genetic changes, while facial shape is more strongly associated with recent environmental effects. We show that linguistic distances are strongly geographically patterned, even within widely dispersed groups. However, they are correlated predominantly with facial, rather than temporal bone, morphology, suggesting that variation in vocabulary likely tracks relatively recent events and possibly population contact.
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24
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Abstract
Variation in body form among human groups is structured by a blend of natural selection driven by local climatic conditions and random genetic drift. However, attempts to test ecogeographic hypotheses have not distinguished between adaptive traits (i.e., those that evolved as a result of selection) and those that evolved as a correlated response to selection on other traits (i.e., nonadaptive traits), complicating our understanding of the relationship between climate and morphological distinctions among populations. Here, we use evolutionary quantitative methods to test if traits previously identified as supporting ecogeographic hypotheses were actually adaptive by estimating the force of selection on individual traits needed to drive among-group differentiation. Our results show that not all associations between trait means and latitude were caused by selection acting directly on each individual trait. Although radial and tibial length and biiliac and femoral head breadth show signs of responses to directional selection matching ecogeographic hypotheses, the femur was subject to little or no directional selection despite having shorter values by latitude. Additionally, in contradiction to ecogeographic hypotheses, the humerus was under directional selection for longer values by latitude. Responses to directional selection in the tibia and radius induced a nonadaptive correlated response in the humerus that overwhelmed its own trait-specific response to selection. This result emphasizes that mean differences between groups are not good indicators of which traits are adaptations in the absence of information about covariation among characteristics.
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25
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Tobolsky VA, Kurki HK, Stock JT. Patterns of directional asymmetry in the pelvis and pelvic canal. Am J Hum Biol 2016; 28:804-810. [PMID: 27224219 DOI: 10.1002/ajhb.22870] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2015] [Revised: 03/18/2016] [Accepted: 05/01/2016] [Indexed: 12/13/2022] Open
Abstract
OBJECTIVES The human pelvis is unique among modern taxa for supporting both parturition of large brained young and obligate bipedalism. Though much work has focused on pelvic development and variation, little work has explored the presence or absence of asymmetry in the pelvis despite well-known patterns of asymmetry in other skeletal regions. This study investigated whether patterns of directional asymmetry (DA) could be observed in the pelvis or pelvic canal. METHODS Seventeen bilaterally paired osteometric measurements of the os coxae (34 measures in total) were taken from 128 skeletons (female n = 65, male n = 63) from recent human populations in five geographic regions. Paired sample t-tests and Mann-Whitney U-tests were used to investigate DA. RESULTS Results from a pooled sample of all individuals showed that the pelvis exhibited a left-bias in DA. In contrast, the pelvic canal exhibited a pattern in which the anterior canal exhibited a right-bias and the posterior canal exhibited a left-bias. Neither sex nor populational differences in DA were observed in the pelvis or pelvic canal. CONCLUSIONS The varying patterns of asymmetry uncovered here accord with prior work and may indicate that loading from the trunk and legs place differing stresses on the pelvis and canal, yielding these unequal asymmetries. However, this is speculative and the possible influence of genetics, biomechanics, and nutritional status on the development of pelvic and canal asymmetries presents a rich area for future study. Additionally, the potential influence of pelvic canal asymmetry on obstetric measures of pelvic capacity merits future research. Am. J. Hum. Biol. 28:804-810, 2016. © 2016Wiley Periodicals, Inc.
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Affiliation(s)
- Victoria A Tobolsky
- Division of Biological Anthropology, Department of Archaeology and Anthropology, University of Cambridge, Cambridge, UK.,Department of Human Evolutionary Biology, Harvard University, Cambridge, Massachusetts, 02138
| | - Helen K Kurki
- Department of Anthropology, University of Victoria, Victoria, British Columbia, Canada, V8W 3P5
| | - Jay T Stock
- Division of Biological Anthropology, Department of Archaeology and Anthropology, University of Cambridge, Cambridge, UK
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26
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Gruss LT, Schmitt D. The evolution of the human pelvis: changing adaptations to bipedalism, obstetrics and thermoregulation. Philos Trans R Soc Lond B Biol Sci 2016; 370:20140063. [PMID: 25602067 DOI: 10.1098/rstb.2014.0063] [Citation(s) in RCA: 85] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
The fossil record of the human pelvis reveals the selective priorities acting on hominin anatomy at different points in our evolutionary history, during which mechanical requirements for locomotion, childbirth and thermoregulation often conflicted. In our earliest upright ancestors, fundamental alterations of the pelvis compared with non-human primates facilitated bipedal walking. Further changes early in hominin evolution produced a platypelloid birth canal in a pelvis that was wide overall, with flaring ilia. This pelvic form was maintained over 3-4 Myr with only moderate changes in response to greater habitat diversity, changes in locomotor behaviour and increases in brain size. It was not until Homo sapiens evolved in Africa and the Middle East 200 000 years ago that the narrow anatomically modern pelvis with a more circular birth canal emerged. This major change appears to reflect selective pressures for further increases in neonatal brain size and for a narrow body shape associated with heat dissipation in warm environments. The advent of the modern birth canal, the shape and alignment of which require fetal rotation during birth, allowed the earliest members of our species to deal obstetrically with increases in encephalization while maintaining a narrow body to meet thermoregulatory demands and enhance locomotor performance.
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Affiliation(s)
| | - Daniel Schmitt
- Department of Evolutionary Anthropology, Duke University, Durham, NC, USA
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27
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Kurki HK, Decrausaz SL. Shape variation in the human pelvis and limb skeleton: Implications for obstetric adaptation. AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 2015; 159:630-8. [PMID: 26699269 DOI: 10.1002/ajpa.22922] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/28/2015] [Revised: 11/26/2015] [Accepted: 11/28/2015] [Indexed: 12/22/2022]
Abstract
OBJECTIVES Under the obstetrical dilemma (OD) hypothesis, selection acts on the human female pelvis to ensure a sufficiently sized obstetric canal for birthing a large-brained, broad shouldered neonate, while bipedal locomotion selects for a narrower and smaller pelvis. Despite this female-specific stabilizing selection, variability of linear dimensions of the pelvic canal and overall size are not reduced in females, suggesting shape may instead be variable among females of a population. Female canal shape has been shown to vary among populations, while male canal shape does not. Within this context, we examine within-population canal shape variation in comparison with that of noncanal aspects of the pelvis and the limbs. MATERIALS AND METHODS Nine skeletal samples (total female n = 101, male n = 117) representing diverse body sizes and shapes were included. Principal components analysis was applied to size-adjusted variables of each skeletal region. A multivariate variance was calculated using the weighted PC scores for all components in each model and F-ratios used to assess differences in within-population variances between sexes and skeletal regions. RESULTS Within both sexes, multivariate canal shape variance is significantly greater than noncanal pelvis and limb variances, while limb variance is greater than noncanal pelvis variance in some populations. Multivariate shape variation is not consistently different between the sexes in any of the skeletal regions. DISCUSSION Diverse selective pressures, including obstetrics, locomotion, load carrying, and others may act on canal shape, as well as genetic drift and plasticity, thus increasing variation in morphospace while protecting obstetric sufficiency.
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Affiliation(s)
- Helen K Kurki
- Department of Anthropology, University of Victoria, Victoria, BC, V8P 5C2, Canada
| | - Sarah-Louise Decrausaz
- Division of Biological Anthropology, Department of Archaeology and Anthropology, University of Cambridge, Cambridge, CB2 3QG
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28
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Katz DC, Grote MN, Weaver TD. A mixed model for the relationship between climate and human cranial form. AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 2015; 160:593-603. [DOI: 10.1002/ajpa.22896] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/03/2015] [Revised: 10/18/2015] [Accepted: 10/31/2015] [Indexed: 11/11/2022]
Affiliation(s)
- David C. Katz
- Department of AnthropologyUniversity of CaliforniaDavis CA95616
| | - Mark N. Grote
- Department of AnthropologyUniversity of CaliforniaDavis CA95616
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29
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Liebenberg L, L'Abbé EN, Stull KE. Population differences in the postcrania of modern South Africans and the implications for ancestry estimation. Forensic Sci Int 2015; 257:522-529. [PMID: 26584515 DOI: 10.1016/j.forsciint.2015.10.015] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2015] [Revised: 09/07/2015] [Accepted: 10/18/2015] [Indexed: 10/22/2022]
Abstract
The cranium is widely recognized as the most important skeletal element to use when evaluating population differences and estimating ancestry. However, the cranium is not always intact or available for analysis, which emphasizes the need for postcranial alternatives. The purpose of this study was to quantify postcraniometric differences among South Africans that can be used to estimate ancestry. Thirty-nine standard measurements from 11 postcranial bones were collected from 360 modern black, white and coloured South Africans; the sex and ancestry distribution were equal. Group differences were explored with analysis of variance (ANOVA) and Tukey's honestly significant difference (HSD) test. Linear and flexible discriminant analysis (LDA and FDA, respectively) were conducted with bone models as well as numerous multivariate subsets to identify the model and method that yielded the highest correct classifications. Leave-one-out (LDA) and k-fold (k=10; FDA) cross-validation with equal priors were used for all models. ANOVA and Tukey's HSD results reveal statistically significant differences between at least two of the three groups for the majority of the variables, with varying degrees of group overlap. Bone models, which consisted of all measurements per bone, resulted in low accuracies that ranged from 46% to 63% (LDA) and 41% to 66% (FDA). In contrast, the multivariate subsets, which consisted of different variable combinations from all elements, achieved accuracies as high as 85% (LDA) and 87% (FDA). Thus, when using a multivariate approach, the postcranial skeleton can distinguish among three modern South African groups with high accuracy.
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Affiliation(s)
- Leandi Liebenberg
- Department of Anatomy, University of Pretoria, Arcadia, South Africa; Department of Basic Medical Sciences, University of the Free State, Bloemfontein, South Africa.
| | - Ericka N L'Abbé
- Department of Anatomy, University of Pretoria, Arcadia, South Africa
| | - Kyra E Stull
- Department of Anthropology, Idaho State University, Pocatello, ID, USA
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30
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Betti L, Lycett SJ, von Cramon-Taubadel N, Pearson OM. Are human hands and feet affected by climate? A test of Allen's rule. AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 2015; 158:132-40. [DOI: 10.1002/ajpa.22774] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/12/2014] [Revised: 05/12/2015] [Accepted: 05/14/2015] [Indexed: 01/02/2023]
Affiliation(s)
- Lia Betti
- Centre for Research in Evolutionary and Environmental Anthropology, Department of Life Sciences, University of Roehampton; London SW15 4JD UK
| | - Stephen J. Lycett
- Department of Anthropology; University at Buffalo, SUNY; Buffalo NY 14261
| | | | - Osbjorn M. Pearson
- Department of Anthropology; University of New Mexico; Albuquerque NM 87131
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31
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Stock JT. The skeletal phenotype of "negritos" from the Andaman Islands and Philippines relative to global variation among hunter-gatherers. Hum Biol 2015; 85:67-94. [PMID: 24297221 DOI: 10.3378/027.085.0304] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/02/2013] [Indexed: 11/05/2022]
Abstract
The "negrito hypothesis" suggests that populations of small-bodied foragers in South and Southeast Asia who share common phenotypic characteristics may also share a common, ancient origin. The key defining characteristics of the "negrito" phenotype, small body size, dark skin, and tightly curled hair, have been interpreted as linking these populations to sub-Saharan Africans. The underlying assumption of this interpretation is that the observed phenotypic similarities likely reflect shared ancestry rather than phenotypic convergence. Current genetic evidence is inconclusive, as it both demonstrates that negrito populations have genetic affinities with neighboring populations but also rare and ancient variation that suggests considerable isolation. This study investigates the skeletal phenotype of Andaman Islanders and Aeta foragers from the Philippines in the context of the phenotypic variation among other hunter-gatherers globally, to test whether they show a common, unique physique apart from small body size. Particular emphasis is placed on the comparison of negrito phenotypes to African, Asian, and Australian hunter-gatherer diversity to investigate phenotypic similarities to other populations globally. The results demonstrate that despite sharing small adult stature, the Andaman Islanders and Aeta show variation in body dimensions. In particular, the Andaman Islanders share a pattern of narrow bi-iliac breadth and short upper limbs with the Khoisan (Later Stone Age Southern Africans), whereas the Aeta and Efé show broader bi-iliac breadths relative to lower limb lengths. Although general similarities in size and proportions remain between the Andamanese and Aeta, differences in humero-femoral indices and arm length between these groups and the Efé demonstrate that there is not a generic "pygmy" phenotype. Our interpretations of negrito origins and adaptation must account for this phenotypic variation.
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Affiliation(s)
- Jay T Stock
- Phenotypic Adaptability, Variation and Evolution Research Group, Department of Archaeology and Anthropology, University of Cambridge, Cambridge CB2 3DF, UK
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32
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Sexual dimorphism of the pelvic girdle from 3D images of a living Spanish sample from Castilla-La Mancha. HOMO-JOURNAL OF COMPARATIVE HUMAN BIOLOGY 2015; 66:149-57. [DOI: 10.1016/j.jchb.2015.01.001] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/01/2014] [Accepted: 01/14/2015] [Indexed: 11/19/2022]
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33
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Hruschka DJ, Hadley C, Brewis AA, Stojanowski CM. Genetic population structure accounts for contemporary ecogeographic patterns in tropic and subtropic-dwelling humans. PLoS One 2015; 10:e0122301. [PMID: 25816235 PMCID: PMC4376747 DOI: 10.1371/journal.pone.0122301] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2014] [Accepted: 02/19/2015] [Indexed: 01/15/2023] Open
Abstract
Contemporary human populations conform to ecogeographic predictions that animals will become more compact in cooler climates and less compact in warmer ones. However, it remains unclear to what extent this pattern reflects plastic responses to current environments or genetic differences among populations. Analyzing anthropometric surveys of 232,684 children and adults from across 80 ethnolinguistic groups in sub-Saharan Africa, Asia and the Americas, we confirm that body surface-to-volume correlates with contemporary temperature at magnitudes found in more latitudinally diverse samples (Adj. R2 = 0.14-0.28). However, far more variation in body surface-to-volume is attributable to genetic population structure (Adj. R2 = 0.50-0.74). Moreover, genetic population structure accounts for nearly all of the observed relationship between contemporary temperature and body surface-to-volume among children and adults. Indeed, after controlling for population structure, contemporary temperature accounts for no more than 4% of the variance in body form in these groups. This effect of genetic affinity on body form is also independent of other ecological variables, such as dominant mode of subsistence and household wealth per capita. These findings suggest that the observed fit of human body surface-to-volume with current climate in this sample reflects relatively large effects of existing genetic population structure of contemporary humans compared to plastic response to current environments.
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Affiliation(s)
- Daniel J. Hruschka
- School of Human Evolution and Social Change, Arizona State University, Tempe, Arizona, United States of America
- * E-mail:
| | - Craig Hadley
- Department of Anthropology, Emory University, Atlanta, Georgia, United States of America
| | - Alexandra A. Brewis
- School of Human Evolution and Social Change, Arizona State University, Tempe, Arizona, United States of America
| | - Christopher M. Stojanowski
- School of Human Evolution and Social Change, Arizona State University, Tempe, Arizona, United States of America
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von Cramon-Taubadel N, Lycett SJ. A comparison of catarrhine genetic distances with pelvic and cranial morphology: implications for determining hominin phylogeny. J Hum Evol 2014; 77:179-86. [PMID: 25439629 DOI: 10.1016/j.jhevol.2014.06.009] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2013] [Revised: 02/28/2014] [Accepted: 06/12/2014] [Indexed: 11/15/2022]
Abstract
Inferring the evolutionary history of the hominins is necessarily reliant on comparative analyses of fossilized skeletal anatomy. However, the reliability of different primate skeletal regions for recovering phylogenetic relationships is currently poorly understood. Historically, postcranial variation has largely been conceived of as reflecting locomotory and postural adaptation. The shape of the os coxae is central to such discussions given the divergent morphology displayed by the bipedal hominin pelvis relative to other primate taxa. While previous cladistic studies have suggested that postcranial and cranial datasets do not differ in terms of their propensity for homoplasy, methodological issues such as the numbers of characters and their quantification make it difficult to evaluate these findings. Here, we circumvent these problems by constructing morphological distance matrices based on cranial, mandibular and os coxae three-dimensional shape. Statistical comparisons of these morphological distance matrices against a single genetic distance matrix for 11 catarrhine taxa show that cranial and os coxae shape reflect genetic relationships better than the mandible when humans are included, and that the cranium and os coxae do not differ statistically in terms of their genetic correlations. When humans were excluded from the analyses, all three anatomical regions were equally strongly correlated with genetic distance. Moreover, a second analysis focusing solely on os coxae variation of 16 taxa demonstrated that os coxae shape correctly recovers catarrhine taxonomic relationships at the sub-family level, even when humans are included. Taken together, our results suggest that there is no a priori reason to favor cranial shape data over os coxae morphology when inferring the genetic relationships of extant or extinct primate taxa. Morphological similarities between humans and other primates differ depending on the skeletal element, suggesting that combining skeletal elements into a single analysis may provide more accurate reconstructions of genetic relationships.
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Affiliation(s)
| | - Stephen J Lycett
- Department of Anthropology, University at Buffalo, SUNY, New York 14261-0005, USA
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Roseman CC, Auerbach BM. Ecogeography, genetics, and the evolution of human body form. J Hum Evol 2014; 78:80-90. [PMID: 25456824 DOI: 10.1016/j.jhevol.2014.07.006] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2014] [Revised: 05/23/2014] [Accepted: 07/24/2014] [Indexed: 12/30/2022]
Abstract
Genetic resemblances among groups are non-randomly distributed in humans. This population structure may influence the correlations between traits and environmental drivers of natural selection thus complicating the interpretation of the fossil record when modern human variation is used as a referential model. In this paper, we examine the effects of population structure and natural selection on postcranial traits that reflect body size and shape with application to the more general issue of how climate - using latitude as a proxy - has influenced hominin morphological variation. We compare models that include terms reflecting population structure, ascertained from globally distributed microsatellite data, and latitude on postcranial phenotypes derived from skeletal dimensions taken from a large global sample of modern humans. We find that models with a population structure term fit better than a model of natural selection along a latitudinal cline in all cases. A model including both latitude and population structure terms is a good fit to distal limb element lengths and bi-iliac breadth, indicating that multiple evolutionary forces shaped these morphologies. In contrast, a model that included only a population structure term best explained femoral head diameter and the crural index. The results demonstrate that population structure is an important part of human postcranial variation, and that clinally distributed natural selection is not sufficient to explain among-group differentiation. The distribution of human body form is strongly influenced by the contingencies of modern human origins, which calls for new ways to approach problems in the evolution of human variation, past and present.
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Affiliation(s)
- Charles C Roseman
- Department of Anthropology, University of Illinois, Urbana, IL 61802, USA.
| | - Benjamin M Auerbach
- Department of Anthropology, The University of Tennessee, Knoxville, TN 37996, USA
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Pickrell JK, Reich D. Toward a new history and geography of human genes informed by ancient DNA. Trends Genet 2014; 30:377-89. [PMID: 25168683 PMCID: PMC4163019 DOI: 10.1016/j.tig.2014.07.007] [Citation(s) in RCA: 94] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2014] [Revised: 07/21/2014] [Accepted: 07/28/2014] [Indexed: 12/12/2022]
Abstract
Genetic information contains a record of the history of our species, and technological advances have transformed our ability to access this record. Many studies have used genome-wide data from populations today to learn about the peopling of the globe and subsequent adaptation to local conditions. Implicit in this research is the assumption that the geographic locations of people today are informative about the geographic locations of their ancestors in the distant past. However, it is now clear that long-range migration, admixture, and population replacement subsequent to the initial out-of-Africa expansion have altered the genetic structure of most of the world's human populations. In light of this we argue that it is time to critically reevaluate current models of the peopling of the globe, as well as the importance of natural selection in determining the geographic distribution of phenotypes. We specifically highlight the transformative potential of ancient DNA. By accessing the genetic make-up of populations living at archaeologically known times and places, ancient DNA makes it possible to directly track migrations and responses to natural selection.
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Affiliation(s)
- Joseph K Pickrell
- New York Genome Center, New York, NY, USA; Department of Biological Sciences, Columbia University, New York, NY, USA.
| | - David Reich
- Department of Genetics, Harvard Medical School, Boston, MA, USA; Howard Hughes Medical Institute, Harvard Medical School, Boston, MA, USA; Broad Institute of the Massachusetts Institute of Technology (MIT) and Harvard, Cambridge, MA, USA.
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The interaction of neutral evolutionary processes with climatically-driven adaptive changes in the 3D shape of the human os coxae. J Hum Evol 2014; 73:64-74. [PMID: 24935167 DOI: 10.1016/j.jhevol.2014.02.021] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2013] [Revised: 02/03/2014] [Accepted: 02/04/2014] [Indexed: 11/21/2022]
Abstract
Differences in the breadth of the pelvis among modern human populations and among extinct hominin species have often been interpreted in the light of thermoregulatory adaptation, whereby a larger pelvic girdle would help preserve body temperature in cold environments while a narrower pelvis would help dissipate heat in tropical climates. There is, however, a theoretical problem in interpreting a pattern of variation as evidence of selection without first accounting for the effects of neutral evolutionary processes (i.e., mutation, genetic drift and migration). Here, we analyse 3D configurations of 27 landmarks on the os coxae of 1494 modern human individuals representing 30 male and 23 female populations from five continents and a range of climatic conditions. We test for the effects of climate on the size and shape of the pelvic bone, while explicitly accounting for population history (i.e., geographically-mediated gene flow and genetic drift). We find that neutral processes account for a substantial proportion of shape variance in the human os coxae in both sexes. Beyond the neutral pattern due to population history, temperature is a significant predictor of shape and size variation in the os coxae, at least in males. The effect of climate on the shape of the pelvic bone, however, is comparatively limited, explaining only a small percentage of shape variation in males and females. In accordance with previous hypotheses, the size of the os coxae tends to increase with decreasing temperature, although the significance of the association is reduced when population history is taken into account. In conclusion, the shape and size of the human os coxae reflect both neutral evolutionary processes and climatically-driven adaptive changes. Neutral processes have a substantial effect on pelvic variation, suggesting such factors will need to be taken into account in future studies of human and fossil hominin coxal variation.
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von Cramon-Taubadel N. The microevolution of modern human cranial variation: implications for hominin and primate evolution. Ann Hum Biol 2014; 41:323-35. [DOI: 10.3109/03014460.2014.911350] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
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Betti L. Sexual dimorphism in the size and shape of the os coxae and the effects of microevolutionary processes. AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 2013; 153:167-77. [DOI: 10.1002/ajpa.22410] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/03/2013] [Revised: 09/16/2013] [Accepted: 10/13/2013] [Indexed: 11/08/2022]
Affiliation(s)
- Lia Betti
- Division of Biological Anthropology; Department of Archaeology and Anthropology; University of Cambridge; Cambridge CB2 3QG UK
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41
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Kurki HK. Skeletal variability in the pelvis and limb skeleton of humans: Does stabilizing selection limit female pelvic variation? Am J Hum Biol 2013; 25:795-802. [DOI: 10.1002/ajhb.22455] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2013] [Revised: 08/16/2013] [Accepted: 08/19/2013] [Indexed: 12/21/2022] Open
Affiliation(s)
- Helen K. Kurki
- Department of Anthropology; University of Victoria; Victoria British Columbia Canada V8W 2Y2
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von Cramon-Taubadel N, Stock JT, Pinhasi R. Skull and limb morphology differentially track population history and environmental factors in the transition to agriculture in Europe. Proc Biol Sci 2013; 280:20131337. [PMID: 23902904 DOI: 10.1098/rspb.2013.1337] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
The Neolithic transition in Europe was a complex mosaic spatio-temporal process, involving both demic diffusion from the Near East and the cultural adoption of farming practices by indigenous hunter-gatherers. Previous analyses of Mesolithic hunter-gatherers and Early Neolithic farmers suggest that cranial shape variation preserves the population history signature of the Neolithic transition. However, the extent to which these same demographic processes are discernible in the postcranium is poorly understood. Here, for the first time, crania and postcranial elements from the same 11 prehistoric populations are analysed together in an internally consistent theoretical and methodological framework. Results show that while cranial shape reflects the population history differences between Mesolithic and Neolithic lineages, relative limb dimensions exhibit significant congruence with environmental variables such as latitude and temperature, even after controlling for geography and time. Also, overall limb size is found to be consistently larger in hunter-gatherers than farmers, suggesting a reduction in size related to factors other than thermoregulatory adaptation. Therefore, our results suggest that relative limb dimensions are not tracking the same demographic population history as the cranium, and point to the strong influence of climatic, dietary and behavioural factors in determining limb morphology, irrespective of underlying neutral demographic processes.
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Affiliation(s)
- Noreen von Cramon-Taubadel
- Department of Anthropology, School of Anthropology and Conservation, University of Kent, Canterbury CT2 7NR, UK.
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Kurki HK. Bony pelvic canal size and shape in relation to body proportionality in humans. AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 2013; 151:88-101. [PMID: 23504988 DOI: 10.1002/ajpa.22243] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/26/2012] [Revised: 01/14/2013] [Accepted: 01/20/2013] [Indexed: 11/06/2022]
Abstract
Obstetric selection acts on the female pelvic canal to accommodate the human neonate and contributes to pelvic sexual dimorphism. There is a complex relationship between selection for obstetric sufficiency and for overall body size in humans. The relationship between selective pressures may differ among populations of different body sizes and proportions, as pelvic canal dimensions vary among populations. Size and shape of the pelvic canal in relation to body size and shape were examined using nine skeletal samples (total female n = 57; male n = 84) from diverse geographical regions. Pelvic, vertebral, and lower limb bone measurements were collected. Principal component analyses demonstrate pelvic canal size and shape differences among the samples. Male multivariate variance in pelvic shape is greater than female variance for North and South Africans. High-latitude samples have larger and broader bodies, and pelvic canals of larger size and, among females, relatively broader medio-lateral dimensions relative to low-latitude samples, which tend to display relatively expanded inlet antero-posterior (A-P) and posterior canal dimensions. Differences in canal shape exist among samples that are not associated with latitude or body size, suggesting independence of some canal shape characteristics from body size and shape. The South Africans are distinctive with very narrow bodies and small pelvic inlets relative to an elongated lower canal in A-P and posterior lengths. Variation in pelvic canal geometry among populations is consistent with a high degree of evolvability in the human pelvis.
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Affiliation(s)
- Helen K Kurki
- Department of Anthropology, University of Victoria, STN CSC, Victoria, BC, Canada, V8W 2Y2.
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Betti L, von Cramon-Taubadel N, Manica A, Lycett SJ. Global geometric morphometric analyses of the human pelvis reveal substantial neutral population history effects, even across sexes. PLoS One 2013; 8:e55909. [PMID: 23409086 PMCID: PMC3567032 DOI: 10.1371/journal.pone.0055909] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2012] [Accepted: 01/03/2013] [Indexed: 12/27/2022] Open
Abstract
Recent applications of population genetic models to human craniodental traits have revealed a strong neutral component to patterns of global variation. However, little work has been undertaken to determine whether neutral processes might also be influencing the postcranium, perhaps due to substantial evidence for selection and plastic environmental responses in these regions. Recent work has provided evidence for neutral effects in the pelvis, but has been limited in regard to shape data (small numbers of linear measurements) and restricted only to males. Here, we use geometric morphometric methods to examine population variation in the human os coxae (pelvic bone) in both males and females. Neutrality is examined via apportionment of variance patterns and fit to an Out-of-Africa serial founder effect model, which is known to structure neutral genetic patterns. Moreover, we compare males and females directly, and the true versus false pelvis, in order to examine potential obstetrical effects. Our results indicate evidence for substantial neutral population history effects on pelvic shape variation. They also reveal evidence for the effect of obstetrical constraints, but these affect males and females to equivalent extents. Our results do not deny an important role for selection in regard to specific aspects of human pelvic variation, especially in terms of features associated with body size and proportions. However, our analyses demonstrate that at a global level, the shape of the os coxae reveals substantial evidence for neutral variation. Our analyses thus indicate that population variation in the human pelvis might be used to address important questions concerning population history, just as the human cranium has done.
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Affiliation(s)
- Lia Betti
- Department of Anthropology, School of Anthropology and Conservation, University of Kent, Canterbury, United Kingdom.
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Auerbach BM. Skeletal variation among early Holocene North American humans: Implications for origins and diversity in the Americas. AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 2012; 149:525-36. [DOI: 10.1002/ajpa.22154] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/11/2012] [Accepted: 08/27/2012] [Indexed: 11/10/2022]
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