28 results on '"Brian Villmoare"'
Search Results
2. Determination of latitude by two fixed-altitude sightings
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Brian Villmoare
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Ocean Engineering ,Oceanography - Abstract
The use of multiple observations near noon with a traditional sextant to determine a fix is common among celestial navigators. A recent invention is the fixed-angle ‘Bris sextant’ that comes with advantages, but imposes constraints due to its invariant nature. We propose a method by which both longitude and latitude can be fixed using only two sightings with such a device, each equidistant from the meridian. By modelling the solution space for the method, we explore some of the potential utility across geography and seasonal variation. Although this method was developed for use with a Bris fixed-angle sextant, it can also be conveniently used with a more traditional marine or level-bubble sextant. Because this method is computationally cumbersome, it is most convenient when used in a computer or tablet application, or with tables.
- Published
- 2022
3. The evolutionary origins of temporal discounting: an adaptive peak model shows how time and uncertainty impose constraints on selection for optimal decision-making in a temporal framework
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Brian Villmoare, David Klein, Pierre Lienard, and Timothy McHale
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The propensity of humans and non-human animals to discount future returns for short-term benefits is well established. This contrasts with the ability of organisms to unfold complex developmental sequences over months or years. Research has focused on various descriptive and predictive parameters of ‘temporal discounting’ in behavior, and researchers have proposed models to explain temporal preference in terms of rational outcomes, but the underlying cause of this phenomenon has not been deeply explored. We propose that preference for short-term reward (‘impulsivity’) may not be rational when examined from the perspective of an omniscient observer, but may be the product of the way natural selection acts on events in a temporal framework in the context of future uncertainty. Using a simple Newtonian model for time across a fitness landscape in which movement by organisms is only possible in one direction, we examine several factors that influence the ability of an organism to choose a distant reward over a more temporally proximate reward: including the temporal distance of the far reward, the relative value of the distant reward, and the effect of uncertainty about the value and presence of the distant reward. Our results indicate that an organism may choose a more distant reward, but only if it is not too far into the future, and only if it has a substantially higher-value fitness payoff relative to the short-term reward. Most notably, any uncertainty about the distant reward made it extremely unlikely for an organism to choose the delayed reward strategy compared to choosing a closer reward, even if the distant reward had a much higher payoff because events that are uncertain are only partially visible to natural selection pressures. We argue that these results explain why so many animals have difficulty making 'better' long-term rational strategies for a distant reward over the lower-value short-term reward. Uncertainty is likely to be an especially important ecological factor in promoting and biasing short-term behavioral strategies. These results help illustrate why human and non-human animals have difficulty making the more rational choice when faced with short-term and long-term rewards.
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- 2023
4. The Evolution of Everything
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Brian Villmoare
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Big History seeks to retell the human story in light of scientific advances by such methods as radiocarbon dating and genetic analysis. This book provides a deep, causal view of the forces that have shaped the universe, the earth, and humanity. Starting with the Big Bang and the formation of the earth, it traces the evolutionary history of the world, focusing on humanity's origins. It also explores the many natural forces shaping humanity, especially the evolution of the brain and behaviour. Moving through time, the causes of such important transformations as agriculture, complex societies, the industrial revolution, the enlightenment, and modernity are placed in the context of underlying changes in demography, learning, and social organization. Humans are biological creatures, operating with instincts evolved millions of years ago, but in the context of a rapidly changing world, and as we try to adapt to new circumstances, we must regularly reckon with our deep past.
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- 2022
5. William Howard Kimbel (1954-2022)
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Jeremiah E. Scott, Amy L. Rector, and Brian Villmoare
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Anthropology ,General Medicine - Published
- 2022
6. Sexual dimorphism in Homo erectus inferred from 1.5 Ma footprints near Ileret, Kenya
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Brian Villmoare, Kevin G. Hatala, and William L. Jungers
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0301 basic medicine ,Male ,Pan troglodytes ,Population ,lcsh:Medicine ,Geographic variation ,Article ,Footprint ,03 medical and health sciences ,0302 clinical medicine ,Species Specificity ,Animals ,Body Size ,Humans ,education ,Social Behavior ,lcsh:Science ,education.field_of_study ,Sex Characteristics ,Multidisciplinary ,Gorilla gorilla ,biology ,Anthropometry ,Foot ,Fossils ,Palaeontology ,lcsh:R ,Hominidae ,Pan paniscus ,biology.organism_classification ,Biological Evolution ,Kenya ,Sexual dimorphism ,030104 developmental biology ,Geography ,Sexual selection ,Homo sapiens ,Evolutionary biology ,Period (geology) ,Female ,lcsh:Q ,Skeletal anatomy ,Homo erectus ,030217 neurology & neurosurgery - Abstract
Sexual dimorphism can be one of the most important indicators of social behavior in fossil species, but the effects of time averaging, geographic variation, and differential preservation can complicate attempts to determine this measure from preserved skeletal anatomy. Here we present an alternative, using footprints from near Ileret, Kenya, to assess the sexual dimorphism of presumptive African Homo erectus at 1.5 Ma. Footprint sites have several unique advantages not typically available to fossils: a single surface can sample a population over a very brief time (in this case likely not more than a single day), and the data are geographically constrained. Further, in many cases, the samples can be much larger than those from skeletal fossil assemblages. Our results indicate that East African Homo erectus was more dimorphic than modern Homo sapiens, although less so than highly dimorphic apes, suggesting that the Ileret footprints offer a unique window into an important transitional period in hominin social behavior.
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- 2019
7. EarlyHomoand the role of the genus in paleoanthropology
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Brian Villmoare
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Male ,0301 basic medicine ,Hominidae ,03 medical and health sciences ,Phylogenetics ,Genus ,biology.animal ,Animals ,Humans ,0601 history and archaeology ,Clade ,Phylogeny ,060101 anthropology ,biology ,Fossils ,Paleontology ,Vertebrate ,06 humanities and the arts ,Biological evolution ,biology.organism_classification ,Biological Evolution ,030104 developmental biology ,Geography ,Evolutionary biology ,Anthropology ,Paleoanthropology ,Female ,Taxonomy (biology) ,Anatomy - Abstract
The history of the discovery of early fossils attributed to the genus Homo has been contentious, with scholars disagreeing over the generic assignment of fossils proposed as members of our genus. In this manuscript I review the history of discovery and debate over early Homo and evaluate the various taxonomic hypotheses for the genus. To get a sense of how hominin taxonomy compares to taxonomic practice outside paleoanthropology, I compare the diversity of Homo to genera in other vertebrate clades. Finally, I propose a taxonomic model that hews closely to current models for hominin phylogeny and is consistent with taxonomic practice across evolutionary biology.
- Published
- 2018
8. Early Homo at 2.8 Ma from Ledi-Geraru, Afar, Ethiopia
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William H. Kimbel, Erin N. DiMaggio, David R. Braun, Brian Villmoare, Kaye E. Reed, J Ramón Arrowsmith, John Rowan, Christopher J. Campisano, and Chalachew Seyoum
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Paleontology ,Multidisciplinary ,Fossil Record ,Australopithecus ,Genus ,Evolutionary biology ,Lineage (evolution) ,Biological evolution ,Biology ,biology.organism_classification - Abstract
Finding Homo nearly 3 million years ago The fossil record of humans is notoriously patchy and incomplete. Even so, skeletal remains and artifacts unearthed in Africa in recent decades have done much to illuminate human evolution. But what is the origin of the genus Homo ? Villmoare et al. found a fossil mandible and teeth from the Afar region in Ethiopia. The find extends the record of recognizable Homo by at least half a million years, to almost 2.8 million years ago. The morphological traits of the fossil align more closely with Homo than with any other hominid genus. DiMaggio et al. confirm the ancient date of the site and suggest that these early humans lived in a setting that was more open and arid than previously thought. Science , this issue p. 1352 , p. 1355
- Published
- 2015
9. Craniofacial modularity, character analysis, and the evolution of the premaxilla in early African hominins
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Michael J. Depew, Jennifer L. Fish, Christopher J. Dunmore, Brian Villmoare, Shaun Kilpatrick, and Nadja Oertelt
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Premaxilla ,Fossils ,Skull ,Hominidae ,Context (language use) ,Anatomy ,Biology ,biology.organism_classification ,Biological Evolution ,Paranthropus robustus ,medicine.anatomical_structure ,Incisor ,Face ,Anthropology ,Maxilla ,medicine ,Animals ,Paranthropus ,Ecology, Evolution, Behavior and Systematics ,Paranthropus boisei - Abstract
Phylogenetic analyses require evolutionarily independent characters, but there is no consensus, nor has there been a clear methodology presented on how to define character independence in a phylogenetic context, particularly within a complex morphological structure such as the skull. Following from studies of craniofacial development, we hypothesize that the premaxilla is an independent evolutionary module with two integrated characters that have traditionally been treated as independent. We test this hypothesis on a large sample of primate skulls and find evidence supporting the premaxilla as an independent module within the larger module of the palate. Additionally, our data indicate that the convexity of the nasoalveolar clivus and the contour of the alveolus are integrated within the premaxilla. We show that the palate itself is composed of two distinct modules: the FNP-derived premaxillae and the mxBA1-derived maxillae and palatines. Application of our data to early African hominin facial morphology suggests that at least three separate transitions contributed to robust facial morphology: 1) an increase in the size of the post-canine dentition housed within the maxillae and palatines, 2) modification of the premaxilla generating a concave clivus and reduced incisor alveolus, and 3) modification of the zygomatic, shifting the zygomatic root and lateral face anteriorly. These data lend support to the monophyly of Paranthropus boisei and Paranthropus robustus, and provide mounting evidence in favor of a Paranthropus clade. This study also highlights the utility of applying developmental evidence to studies of morphological evolution.
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- 2014
10. Australopithecus africanus
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Brian Villmoare
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- 2017
11. Australopithecus garhi
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Brian Villmoare
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- 2017
12. Hominin track assemblages from Okote Member deposits near Ileret, Kenya, and their implications for understanding fossil hominin paleobiology at 1.5 Ma
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Kelly R. Ostrofsky, Roshna E. Wunderlich, Heather L. Dingwall, David R. Braun, John W.K. Harris, Kevin G. Hatala, Brian Villmoare, Neil T. Roach, Brian G. Richmond, David J. Green, and Anna K. Behrensmeyer
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010506 paleontology ,Pleistocene ,Trace fossil ,01 natural sciences ,Paleontology ,Ichnology ,East africa ,Animals ,0601 history and archaeology ,Social Behavior ,Ecology, Evolution, Behavior and Systematics ,0105 earth and related environmental sciences ,060101 anthropology ,Fossil Record ,biology ,Fossils ,Paleobiology ,Hominidae ,06 humanities and the arts ,computer.file_format ,biology.organism_classification ,Biological Evolution ,Kenya ,Archaeology ,Anthropology ,RDFa ,Homo erectus ,computer ,Geology ,Locomotion - Abstract
Tracks can provide unique, direct records of behaviors of fossil organisms moving across their landscapes millions of years ago. While track discoveries have been rare in the human fossil record, over the last decade our team has uncovered multiple sediment surfaces within the Okote Member of the Koobi Fora Formation near Ileret, Kenya that contain large assemblages of ∼1.5 Ma fossil hominin tracks. Here, we provide detailed information on the context and nature of each of these discoveries, and we outline the specific data that are preserved on the Ileret hominin track surfaces. We analyze previously unpublished data to refine and expand upon earlier hypotheses regarding implications for hominin anatomy and social behavior. While each of the track surfaces discovered at Ileret preserves a different amount of data that must be handled in particular ways, general patterns are evident. Overall, the analyses presented here support earlier interpretations of the ∼1.5 Ma Ileret track assemblages, providing further evidence of large, human-like body sizes and possibly evidence of a group composition that could support the emergence of certain human-like patterns of social behavior. These data, used in concert with other forms of paleontological and archaeological evidence that are deposited on different temporal scales, offer unique windows through which we can broaden our understanding of the paleobiology of hominins living in East Africa at ∼1.5 Ma.
- Published
- 2016
13. Pleistocene footprints show intensive use of lake margin habitats by Homo erectus groups
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Andrew Du, Neil T. Roach, Anna K. Behrensmeyer, Brian Villmoare, Kevin G. Hatala, David R. Braun, Brian G. Richmond, Jonathan Reeves, Kelly R. Ostrofsky, and John W.K. Harris
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Geologic Sediments ,010506 paleontology ,Taphonomy ,Pleistocene ,Hominidae ,Fauna ,Foraging ,01 natural sciences ,Article ,Animals ,Body Size ,Humans ,0601 history and archaeology ,0105 earth and related environmental sciences ,060101 anthropology ,Multidisciplinary ,biology ,Fossils ,Ecology ,06 humanities and the arts ,biology.organism_classification ,Kenya ,Archaeology ,Habitat ,Paleoecology ,Homo erectus - Abstract
Reconstructing hominin paleoecology is critical for understanding our ancestors’ diets, social organizations and interactions with other animals. Most paleoecological models lack fine-scale resolution due to fossil hominin scarcity and the time-averaged accumulation of faunal assemblages. Here we present data from 481 fossil tracks from northwestern Kenya, including 97 hominin footprints attributed to Homo erectus. These tracks are found in multiple sedimentary layers spanning approximately 20 thousand years. Taphonomic experiments show that each of these trackways represents minutes to no more than a few days in the lives of the individuals moving across these paleolandscapes. The geology and associated vertebrate fauna place these tracks in a deltaic setting, near a lakeshore bordered by open grasslands. Hominin footprints are disproportionately abundant in this lake margin environment, relative to hominin skeletal fossil frequency in the same deposits. Accounting for preservation bias, this abundance of hominin footprints indicates repeated use of lakeshore habitats by Homo erectus. Clusters of very large prints moving in the same direction further suggest these hominins traversed this lakeshore in multi-male groups. Such reliance on near water environments and possibly aquatic-linked foods, may have influenced hominin foraging behavior and migratory routes across and out of Africa.
- Published
- 2016
14. Morphological Integration, Evolutionary Constraints, and Extinction: A Computer Simulation-Based Study
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Brian Villmoare
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education.field_of_study ,Extinction ,Variation (linguistics) ,Morphological integration ,Fitness landscape ,Evolutionary biology ,Population ,Survivability ,Biology ,education ,Simulation based ,Ecology, Evolution, Behavior and Systematics ,Selection (genetic algorithm) - Abstract
It is well known that there is a strong relationship among the environment, selection, and extinction, but the underlying role of genetics and genetic constraints in contributing to extinction is less appreciated. Integration of characters may enhance survivability for species, providing that selective pressure is parallel with the patterns of morphological integration. However, we hypothesize that, if the direction of selection shifts, integration may also prevent populations from responding quickly enough to the new directions of selection. This would lead to the inability to find a successful adaptive solution, causing downward pressure on the population, and ultimately, extinction. We test this model with a computer simulation, using an adaptive landscape model. We generate populations of varying levels of multivariate integration and generate selection pressures to test the ability of the populations to respond to selection both parallel and orthogonal to the axis of maximum variation. In these simulations, more highly integrated populations survived longer when selection was in the direction of maximum variation. However, when selection was closer to orthogonal to the axis of maximum variation, extinction was more rapid in highly integrated populations. These results suggest that integration may play a strong role in both survivability and extinction. Tightly integrated populations are highly persistent when selection pressure is close to the axis of maximum variation, which is expected to frequently be the case since integration is likely often a product of selection. However, these highly integrated taxa are more susceptible to extinction when the direction of selection shifts, and is closer to orthogonal to the axis of maximum variation.
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- 2012
15. Footprints reveal direct evidence of group behavior and locomotion in Homo erectus
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Heather L. Dingwall, Neil T. Roach, Kevin G. Hatala, David J. Green, John W.K. Harris, Brian Villmoare, Kelly R. Ostrofsky, David R. Braun, Roshna E. Wunderlich, and Brian G. Richmond
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0301 basic medicine ,Direct evidence ,Hominidae ,Lineage (evolution) ,Walking ,Article ,Footprint ,03 medical and health sciences ,Gait (human) ,Animals ,Body Size ,Humans ,0601 history and archaeology ,Bipedalism ,Social Behavior ,Gait ,060101 anthropology ,Multidisciplinary ,biology ,Ecology ,Foot ,Fossils ,06 humanities and the arts ,biology.organism_classification ,Biological Evolution ,Biomechanical Phenomena ,030104 developmental biology ,Homo erectus ,Locomotion ,Social behavior - Abstract
Bipedalism is a defining feature of the human lineage. Despite evidence that walking on two feet dates back 6–7 Ma, reconstructing hominin gait evolution is complicated by a sparse fossil record and challenges in inferring biomechanical patterns from isolated and fragmentary bones. Similarly, patterns of social behavior that distinguish modern humans from other living primates likely played significant roles in our evolution, but it is exceedingly difficult to understand the social behaviors of fossil hominins directly from fossil data. Footprints preserve direct records of gait biomechanics and behavior but they have been rare in the early human fossil record. Here we present analyses of an unprecedented discovery of 1.5-million-year-old footprint assemblages, produced by 20+ Homo erectus individuals. These footprints provide the oldest direct evidence for modern human-like weight transfer and confirm the presence of an energy-saving longitudinally arched foot in H. erectus. Further, print size analyses suggest that these H. erectus individuals lived and moved in cooperative multi-male groups, offering direct evidence consistent with human-like social behaviors in H. erectus.
- Published
- 2015
16. Satb2, modularity, and the evolvability of the vertebrate jaw
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Victor Tarabykin, Michael J. Depew, Olga V. Britanova, Jennifer L. Fish, Katja Köbernick, Claudia Compagnucci, and Brian Villmoare
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Modularity (networks) ,education.field_of_study ,biology ,Mechanism (biology) ,Population ,Xenopus ,Vertebrate ,Anatomy ,biology.organism_classification ,Evolvability ,stomatognathic diseases ,stomatognathic system ,Evolutionary biology ,biology.animal ,Amniote ,education ,Ecology, Evolution, Behavior and Systematics ,Loss function ,Developmental Biology - Abstract
SUMMARY Modularity is a key mechanism bridging development and evolution and is fundamental to evolvability. Herein, we investigate modularity of the Vertebrate jaw with the aim of understanding mechanisms of its morphological evolution. Conservation of the basic structural bauplan of Vertebrate jaws led to a Hinge and Caps model, in which polarity in the patterning system of developing jaws predicts modularity. We have tested the hypothesis that the Satb2+ cell population delineates a developmental module within the mandibular jaw. Satb2 is expressed in the mesenchyme of the jaw primordia that gives rise to distal elements of both the upper and lower jaws. Loss of Satb2 specifically affects structural elements of the distal (incisor) domain, reflecting the integration of these elements as well as their independence from other mandibular domains. Reducing Satb2 dosage leads to an increase in variation in mandibular length, providing insight into the developmental potential to generate variation. Inter-taxa comparisons reveal that the Satb2 domain is conserved within gnathostomes. We complement previous loss of function studies in mice with gene knock-down experiments in Xenopus, providing evidence for functional conservation of Satb2 in regulating size. Finally, we present evidence that the relative size of the amniote mandibular Satb2+ domain varies in relation to epithelial Fgf8 expression, suggesting a mechanism for evolutionary change in this domain. Taken together, our data support the Hinge and Caps model and provide evidence that Satb2 regulates coordinated distal jaw modules that are subject to evolutionary modification by signals emanating from the Hinge.
- Published
- 2011
17. Selection, Morphological Integration, and Strepsirrhine Locomotor Adaptations
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William L. Jungers, Jennifer L. Fish, and Brian Villmoare
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medicine.anatomical_structure ,Morphological integration ,Evolutionary biology ,Mechanism (biology) ,Modularity (biology) ,medicine ,Hindlimb ,Anatomy ,Forelimb ,Adaptation ,Biology ,Ecology, Evolution, Behavior and Systematics ,Selection (genetic algorithm) - Abstract
Clades with taxa that have multiple locomotor adaptations represent a direct way to test the relationship between adaptation and integration. If integration is influenced by functional requirements, integration should be most apparent where selection is strongest and less evident where selection has been relaxed. If integration is primarily regulated by genetic constraints, integration should be present irrespective of selection pressures. Here we use patterns of integration in the strepsirrhine fore- and hind limbs as a test case. Strepsirrhine locomotion is relatively well-studied, and there are multiple clades that share different locomotor modes. We found that quadrupeds have greater limb integration than vertical leapers. These results suggest that variation can be expressed if selection for integration is relaxed. However, an unexpected pattern was revealed, in which there appears to be some broader regulatory mechanism controlling overall limb integration. Our tests identified a strong correlation between integration of the forelimb and integration of the hind limb. This broader mechanism may be evidence of the primitive genetic control of limb integration.
- Published
- 2011
18. The evolutionary origin and population history of the grauer gorilla
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D. Troy Case, Caley M. Orr, Amandine B. Eriksen, Scott E. Burnett, Matthew W. Tocheri, Neil T. Roach, Shannon C. McFarlin, William L. Jungers, Zelalem Assefa, Brian Villmoare, Colin P. Groves, Daniela C. Kalthoff, René Dommain, and Sascha Senck
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0106 biological sciences ,0301 basic medicine ,Male ,Range (biology) ,Population ,Gorilla ,Biology ,Subspecies ,Environment ,010603 evolutionary biology ,01 natural sciences ,03 medical and health sciences ,Critically endangered ,biology.animal ,Animals ,Africa, Central ,education ,Phylogeny ,education.field_of_study ,Gorilla gorilla ,Ecology ,Fossils ,Population size ,Foot Bones ,Africa, Eastern ,biology.organism_classification ,Eastern gorilla ,Biological Evolution ,030104 developmental biology ,Population bottleneck ,Anthropology ,Female ,Anatomy - Abstract
Gorillas living in western central Africa (Gorilla gorilla) are morphologically and genetically distinguishable from those living in eastern central Africa (Gorilla beringei). Genomic analyses show eastern gorillas experienced a significant reduction in population size during the Pleistocene subsequent to geographical isolation from their western counterparts. However, how these results relate more specifically to the recent biogeographical and evolutionary history of eastern gorillas remains poorly understood. Here we show that two rare morphological traits are present in the hands and feet of both eastern gorilla subspecies at strikingly high frequencies (>60% in G. b. graueri; ∼28% in G. b. beringei) in comparison with western gorillas (
- Published
- 2015
19. PALEOANTHROPOLOGY. Response to Comment on 'Early Homo at 2.8 Ma from Ledi-Geraru, Afar, Ethiopia'
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Brian, Villmoare, William H, Kimbel, Chalachew, Seyoum, Christopher J, Campisano, Erin, DiMaggio, John, Rowan, David R, Braun, J Ramon, Arrowsmith, and Kaye E, Reed
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Animals ,Humans ,Hominidae ,Biological Evolution - Abstract
Hawks et al. argue that our analysis of Australopithecus sediba mandibles is flawed and that specimen LD 350-1 cannot be distinguished from this, or any other, Australopithecus species. Our reexamination of the evidence confirms that LD 350-1 falls outside of the pattern that A. sediba shares with Australopithecus and thus is reasonably assigned to the genus Homo.
- Published
- 2015
20. Biomechanical studies of the zygoma: A review of in vivo (italic) and FEM studies of the lateral orbital wall and zygomatic arch
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Brian G. Richmond, Paul C. Dechow, Barth W. Wright, Annemarie Gundel, Amanda L. Smith, Dennis E. Slice, Ian R. Grosse, Kelly Tamvada, Gerhard W. Weber, Leslie Pryor Smith, Mark A. Spencer, Kristian J. Carlson, Lee R. Berger, Darryl J. de Ruiter, Justin A. Ledogar, Craig D. Byron, Stefano Benazzi, Callum F. Ross, Qian Wang, Brian Villmoare, and David S. Strait
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genetic structures ,Zygomatic region ,Anatomy ,Biochemistry ,eye diseases ,medicine.anatomical_structure ,Lateral orbital wall ,Genetics ,medicine ,Zygomatic arch ,sense organs ,Craniofacial skeleton ,Molecular Biology ,Geology ,Biotechnology - Abstract
The zygomatic region and lateral orbital wall are important structural components of the primate craniofacial skeleton, providing attachment for muscles, housing and protecting the eye, and resisti...
- Published
- 2015
21. Metric and non-metric randomization methods, geographic variation, and the single-species hypothesis for Asian and African Homo erectus
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Brian Villmoare
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Percentile ,Asia ,Hominidae ,Population Dynamics ,Population ,Sampling Studies ,Random Allocation ,Species Specificity ,Resampling ,Statistics ,Animals ,education ,Ecology, Evolution, Behavior and Systematics ,Statistical hypothesis testing ,Analysis of Variance ,education.field_of_study ,Geography ,biology ,Fossils ,Data Collection ,Skull ,Paleontology ,biology.organism_classification ,Biological Evolution ,Euclidean distance ,Data Interpretation, Statistical ,Anthropology ,Africa ,Metric System ,Homo erectus ,Null hypothesis ,Demography - Abstract
This paper proposes a statistical test of the single-species hypothesis using non-metric characters as a complement to statistical tests using more traditional metric characters. The sample examined is that of Asian and African Homo erectus. The paleoanthropological community is divided on the taxonomic distinction of these fossils, with workers arguing both for and against the species-level distinction between Asian and African populations. Previous arguments have focused on patterns of apparent morphological differentiation between the African and Asian cranial samples. To assess this question, three tests were performed that compared the range of variation in the fossil sample to a single-species group with a similar geographic distribution; this comparative sample was composed of 221 modern humans from Africa and Asia. For the first test, 23 metric characters were analyzed on the fossil and comparative samples. Using resampling procedures, the variation for these characters was examined, recreating 1000 samples from the human analogs and comparing the CV distributions of these samples to the CVs of the fossil group. The second test used the metric data to calculate a Euclidean distance between the African and Asian fossil samples. This distance was compared to a distribution of Euclidean distances calculated between 1000 randomly selected samples of African and Asian modern humans. For the third test, a grading scale was created for ten non-metric characters that encompassed the total morphological variation found in the fossil and modern human samples. The Manhattan distance between the Asian and African fossil samples was calculated and compared to a distribution of distances calculated between 1000 randomly selected samples of African and Asian moderns. The first two tests, using the metric data, failed to falsify the null hypothesis. However, in the third test, using non-metric data, the total Manhattan distance for the fossil sample approached the 100th percentile of the resampled distances calculated from the moderns. The implications of the contrasting results are discussed.
- Published
- 2005
22. Continuous dental eruption identifies Sts 5 as the developmentally oldest fossil hominin and informs the taxonomy of Australopithecus africanus
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Kevin L. Kuykendall, Brian Villmoare, Conrad S. Brimacombe, and Todd C. Rae
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Anterior tooth ,Aging ,Models, Biological ,Tooth Eruption ,Tooth root ,South Africa ,stomatognathic system ,medicine ,Prognathism ,Animals ,Tooth Root ,Australopithecus africanus ,Ecology, Evolution, Behavior and Systematics ,Dentition ,biology ,Fossils ,Hominidae ,Anatomy ,biology.organism_classification ,medicine.disease ,Biological Evolution ,Australopithecus ,Anthropology ,Dental eruption ,Taxonomy (biology) ,Female ,Tomography, X-Ray Computed - Abstract
The relatively small Australopithecus africanus specimen Sts 5 has figured prominently in taxonomic debates, and the determination of this specimen as a young male or an elderly female has the potential to offer a great deal of resolution on this question. Sts 5 has been argued to be either a small, immature male or a mature female based on a variety of characters. A proposed model of continuous root remodeling and angular change for heavily worn dentition may account for the extremely short tooth roots, particularly for the anterior dentition, that Sts 5 demonstrates. The anterior tooth roots of Sts 5 are oriented vertically (relative to the alveolar plane), unlike those found in most other apes, humans, and fossil specimens, in which the tooth roots are roughly parallel with the plane of the nasoalveolar clivus. Computed tomography (CT) data of adult apes were examined and a relationship between the angle of the anterior tooth roots and their length was discovered, caused by heavily worn anterior dentition continuing to erupt to maintain occlusion. The extremely short and vertically oriented anterior roots observed in Sts 5 thus suggest that the specimen represents an aged female specimen with extremely worn dentition. Interestingly, this reorientation of anterior tooth roots helps account for the unusual nasoalveolar contour of Sts 5. The remodeling associated with the heavily worn teeth and reoriented roots thus resolves the taxonomic question raised by analyses identifying unusual prognathism of this small specimen.
- Published
- 2013
23. From Australopithecus to Homo : the transition that wasn't
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Brian Villmoare and William H. Kimbel
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0301 basic medicine ,Technology ,Hominidae ,Ancient history ,General Biochemistry, Genetics and Molecular Biology ,03 medical and health sciences ,Paleontology ,Cultural Evolution ,Animals ,Humans ,0601 history and archaeology ,060101 anthropology ,Fossil Record ,Tool Use Behavior ,biology ,Fossils ,Brain ,Articles ,06 humanities and the arts ,Biological evolution ,Hand ,biology.organism_classification ,Biological Evolution ,030104 developmental biology ,Australopithecus ,Human taxonomy ,General Agricultural and Biological Sciences - Abstract
Although the transition from Australopithecus to Homo is usually thought of as a momentous transformation, the fossil record bearing on the origin and earliest evolution of Homo is virtually undocumented. As a result, the poles of the transition are frequently attached to taxa (e.g. A. afarensis, at ca 3.0 Ma versus H. habilis or H. erectus, at ca 2.0–1.7 Ma) in which substantial adaptive differences have accumulated over significant spans of independent evolution. Such comparisons, in which temporally remote and adaptively divergent species are used to identify a ‘transition’, lend credence to the idea that genera should be conceived at once as monophyletic clades and adaptively unified grades. However, when the problem is recast in terms of lineages, rather than taxa per se , the adaptive criterion becomes a problem of subjectively privileging ‘key’ characteristics from what is typically a stepwise pattern of acquisition of novel characters beginning in the basal representatives of a clade. This is the pattern inferred for species usually included in early Homo , including H. erectus , which has often been cast in the role as earliest humanlike hominin. A fresh look at brain size, hand morphology and earliest technology suggests that a number of key Homo attributes may already be present in generalized species of Australopithecus , and that adaptive distinctions in Homo are simply amplifications or extensions of ancient hominin trends. This article is part of the themed issue ‘Major transitions in human evolution’.
- Published
- 2016
24. Satb2, modularity, and the evolvability of the vertebrate jaw
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Jennifer L, Fish, Brian, Villmoare, Katja, Köbernick, Claudia, Compagnucci, Olga, Britanova, Victor, Tarabykin, and Michael J, Depew
- Subjects
Fibroblast Growth Factor 8 ,Xenopus ,Gene Dosage ,Gene Expression Regulation, Developmental ,Genetic Variation ,Mandible ,Matrix Attachment Region Binding Proteins ,Zebrafish Proteins ,Biological Evolution ,Mesoderm ,Mice ,Animals ,RNA, Messenger ,Chickens ,Zebrafish ,Transcription Factors - Abstract
Modularity is a key mechanism bridging development and evolution and is fundamental to evolvability. Herein, we investigate modularity of the Vertebrate jaw with the aim of understanding mechanisms of its morphological evolution. Conservation of the basic structural bauplan of Vertebrate jaws led to a Hinge and Caps model, in which polarity in the patterning system of developing jaws predicts modularity. We have tested the hypothesis that the Satb2+ cell population delineates a developmental module within the mandibular jaw. Satb2 is expressed in the mesenchyme of the jaw primordia that gives rise to distal elements of both the upper and lower jaws. Loss of Satb2 specifically affects structural elements of the distal (incisor) domain, reflecting the integration of these elements as well as their independence from other mandibular domains. Reducing Satb2 dosage leads to an increase in variation in mandibular length, providing insight into the developmental potential to generate variation. Inter-taxa comparisons reveal that the Satb2 domain is conserved within gnathostomes. We complement previous loss of function studies in mice with gene knock-down experiments in Xenopus, providing evidence for functional conservation of Satb2 in regulating size. Finally, we present evidence that the relative size of the amniote mandibular Satb2+ domain varies in relation to epithelial Fgf8 expression, suggesting a mechanism for evolutionary change in this domain. Taken together, our data support the Hinge and Caps model and provide evidence that Satb2 regulates coordinated distal jaw modules that are subject to evolutionary modification by signals emanating from the Hinge.
- Published
- 2012
25. CT-based study of internal structure of the anterior pillar in extinct hominins and its implications for the phylogeny of robust Australopithecus
- Author
-
William H. Kimbel and Brian Villmoare
- Subjects
Synapomorphy ,Multidisciplinary ,biology ,Hominidae ,Fossils ,Zoology ,Biological Sciences ,biology.organism_classification ,Monophyly ,Australopithecus ,Phylogenetics ,Africa ,Animals ,sense organs ,Parallel evolution ,Clade ,Tomography, X-Ray Computed ,Australopithecus africanus ,Phylogeny - Abstract
The phylogeny of the early African hominins has long been confounded by contrasting interpretations of midfacial structure. In particular, the anterior pillar, an externally prominent bony column running vertically alongside the nasal aperture, has been identified as a homology of South African species Australopithecus africanus and Australopithecus robustus . If the anterior pillar is a true synapomorphy of these two species, the evidence for a southern African clade of Australopithecus would be strengthened, and support would be given to the phylogenetic hypothesis of an independent origin for eastern and southern African “robust” australopith clades. Analyses of CT data, however, show that the internal structure of the circumnasal region is strikingly different in the two South African australopith species. In A. africanus the anterior pillar is a hollow column of cortical bone, whereas in A. robustus it is a column of dense trabecular bone. Although Australopithecus boisei usually lacks an external pillar, it has internal morphology identical to that seen in A. robustus . This result supports the monophyly of the “robust” australopiths and suggests that the external similarities seen in the South African species are the result of parallel evolution.
- Published
- 2011
26. Response to Comment on 'Early Homo at 2.8 Ma from Ledi-Geraru, Afar, Ethiopia'
- Author
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Kaye E. Reed, Brian Villmoare, Chalachew Seyoum, David R. Braun, John Rowan, Erin N. DiMaggio, J Ramón Arrowsmith, William H. Kimbel, and Christopher J. Campisano
- Subjects
Australopithecus sediba ,Multidisciplinary ,Geography ,biology ,Australopithecus ,Genus ,Evolutionary biology ,biology.organism_classification - Abstract
Hawks et al . argue that our analysis of Australopithecus sediba mandibles is flawed and that specimen LD 350-1 cannot be distinguished from this, or any other, Australopithecus species. Our reexamination of the evidence confirms that LD 350-1 falls outside of the pattern that A. sediba shares with Australopithecus and thus is reasonably assigned to the genus Homo .
- Published
- 2015
27. Anatomical Network Analysis Shows Decoupling of Modular Lability and Complexity in the Evolution of the Primate Skull
- Author
-
Brian Villmoare, Borja Esteve-Altava, Rui Diogo, Julia C. Boughner, and Diego Rasskin-Gutman
- Subjects
Primates ,Science ,Zoology ,Network theory ,Biology ,medicine ,Animals ,Phylogeny ,Cognitive science ,Modularity (networks) ,Multidisciplinary ,Functional integration (neurobiology) ,business.industry ,Skull ,Modular design ,Biological Evolution ,Constraint (information theory) ,Evolvability ,medicine.anatomical_structure ,Evolutionary developmental biology ,Medicine ,business ,Research Article - Abstract
Modularity and complexity go hand in hand in the evolution of the skull of primates. Because analyses of these two parameters often use different approaches, we do not know yet how modularity evolves within, or as a consequence of, an also-evolving complex organization. Here we use a novel network theory-based approach (Anatomical Network Analysis) to assess how the organization of skull bones constrains the co-evolution of modularity and complexity among primates. We used the pattern of bone contacts modeled as networks to identify connectivity modules and quantify morphological complexity. We analyzed whether modularity and complexity evolved coordinately in the skull of primates. Specifically, we tested Herbert Simon’s general theory of near-decomposability, which states that modularity promotes the evolution of complexity. We found that the skulls of extant primates divide into one conserved cranial module and up to three labile facial modules, whose composition varies among primates. Despite changes in modularity, statistical analyses reject a positive feedback between modularity and complexity. Our results suggest a decoupling of complexity and modularity that translates to varying levels of constraint on the morphological evolvability of the primate skull. This study has methodological and conceptual implications for grasping the constraints that underlie the developmental and functional integration of the skull of humans and other primates.
- Published
- 2015
28. A companion to biological anthropology - Edited by Clark Spencer Larsen
- Author
-
Brian Villmoare
- Subjects
History ,Arts and Humanities (miscellaneous) ,Anthropology ,Biological anthropology ,Environmental ethics - Published
- 2012
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