This study was designed to assess the mechanical properties of two calcium carbonate tempers, limestone and burnt shell. These tempers have been previously compared, in separate studies, to ...silicate-based grit or sand temper and, relative to the latter, are assumed to possess similar mechanical properties. However, their simultaneous use at the Morrison Village site begs the question: do these two calcium carbonate tempers indeed possess similar mechanical properties? In order to assess their performance characteristics, a side-by-side controlled experimental test was conducted to determine the degree of similarity in providing increased vessel strength and toughness.
Standardized ceramic test samples were systematically prepared via a set, explicit protocol. An Instron Series IX universal testing machine configured with a four-point flexural test jig was used to perform a flexural strength test of the test samples. The Instron load and deflection data were used to calculate three values related to mechanical performance: peak load, modulus of rupture, and modulus of elasticity.
All four comparative tests clearly show substantial differences in peak load, modulus of rupture, and modulus of elasticity. These differences are statistically significant for each performance attribute in every iteration of the experiment and as indicated by Mann-Whitney U Tests.
These results do not support the hypothesis that limestone and burnt shell offer the same performance characteristics. These results have implications for our understanding of prehistoric human selection of temper and the evolution of ceramic technology. Although both carbonate-based tempers are currently thought to offer the same benefits during the initial phase of pottery production, their contrasting post firing properties would have provided distinct benefits in different contexts. Future assessments of the Morrison Village ceramic assemblage should focus on residue analysis, or other functional indicators, to support or falsify this hypothesis.
The precise etiology of cam impingement continues to be incompletely understood. The prevailing hypothesis posits that the deformity arises as a developmental injury prior to skeletal maturation. ...There is a possible evolutionary role, with an aspherical femoral head affording upright humans better stability. We set out to identify the antiquity of the cam deformity to better understand the comparative roles of modern behavior and evolution in its development.
We used 249 physical specimens of femora from the Libben osteological collection, a set of bones from an ancient population who lived between the eighth and the eleventh century. These femora were photographed in four different orientations, and six specific proximal femoral angles were measured. The values were also compared with those from modern human femora using the Student t test, with a two-tailed p value of 0.05 denoting significance.
In total, 249 femora from 175 individuals were included in the final analysis. The ages of the individuals ranged between seventeen and fifty-five years. Interobserver and intraobserver correlation was good or excellent for all variables measured. Compared with modern populations, ancient human hips were significantly more anteverted (19.96° versus 12.85°; p < 0.001) and varus (true neck-shaft angle, 121.96° versus 129.23°; p < 0.001). The alpha angle was significantly lower in ancient humans (35.33° versus 45.61°; p < 0.001), and none of the ancient femora met the modern criteria for a cam deformity (an alpha angle of >50°).
It appears that the cam deformity was nonexistent among ancient humans and is perhaps predominantly a product of modern-day stresses. Further clinical investigation into behavioral modifications in adolescence is warranted to potentially prevent the development of deformity and impingement.
Von Economo neurons (VENs) are specialized projection neurons with a characteristic spindle-shaped soma and thick basal and apical dendrites. VENs have been described in restricted cortical regions, ...with their most frequent appearance in layers III and V of the anterior cingulate cortex, anterior insula, and frontopolar cortex of humans, great apes, macaque monkeys, elephants, and some cetaceans. Recently, a ubiquitous distribution of VENs was reported in various cortical areas in the pygmy hippopotamus, one of the closest living relatives of cetaceans. That finding suggested that VENs might not be unique to only a few species that possess enlarged brains. In the present analysis, we assessed the phylogenetic distribution of VENs within species representative of the superordinal clade that includes cetartiodactyls and perissodactyls, as well as afrotherians. In addition, the distribution of fork cells that are often found in close proximity to VENs was also assessed. Nissl-stained sections from the frontal pole, anterior cingulate cortex, anterior insula, and occipital pole of bowhead whale, cow, sheep, deer, horse, pig, rock hyrax, and human were examined using stereologic methods to quantify VENs and fork cells within layer V of all four cortical regions. VENs and fork cells were found in each of the species examined here with species-specific differences in distributions and densities. The present results demonstrated that VENs and fork cells were not restricted to highly encephalized or socially complex species, and their repeated emergence among distantly related species seems to represent convergent evolution of specialized pyramidal neurons. The widespread phylogenetic presence of VENs and fork cells indicates that these neuron morphologies readily emerged in response to selective forces,whose variety and nature are yet to be identified.
Upright walking absent a bent-hip-bent-knee gait requires lumbar lordosis, a ubiquitous feature in all hominids for which it can be observed. Its first appearance is therefore a central problem in ...human evolution. Atelids, which use the tail during suspension, exhibit demonstrable lordosis and can achieve full extension of their hind limbs during terrestrial upright stance. Although obviously homoplastic with hominids, the pelvic mechanisms facilitating lordosis appear largely similar in both taxa with respect to abbreviation of upper iliac height coupled with broad sacral alae. Both provide spatial separation of the most caudal lumbar(s) from the iliac blades. A broad sacrum is therefore a likely facet of earliest hominid bipedality. All tailed monkeys have broad alae. By contrast all extant apes have very narrow sacra, which promote "trapping" of their most caudal lumbars to achieve lower trunk rigidity during suspension. The alae in the tailless proconsul Ekembo nyanzae appear to have been quite broad, a character state that may have been primitive in Miocene hominoids not yet adapted to suspension and, by extension, exaptive for earliest bipedality in the hominid/panid last common ancestor. This hypothesis receives strong support from other anatomical systems preserved in Ardipithecus ramidus.
Caves and Culture Spurlock, Linda B; Prufer, Olaf H; Pigott, Thomas R
2013
eBook
A collection of the last forty years of research on Ohio's caves and rockshelters Caves and Culture seeks to address a number of important problems, specifically the use of rockshelters by humans ...through time and transcontinental continuities. It presents new and updated, unreported research from such Ohio caves and rockshelters as Stow Rockshelter (Stow), Peters Cave (Ross County), Hendricks Cave (Wyandotte County), and Chesser Cave (Athens), among others. Caves and Culture is primarily focused on the archaeological research of Dr. Olaf H. Prufer and his associates as they investigated and explored caves in Ohio since 1964. Spurlock and her co-editors report, sometimes reclaim, and frequently reinterpret data that will be useful to the understanding of Ohio archaeology for decades to come. Anyone with interest in local or regional (Midwestern or midcontinental) prehistory will appreciate this exploration into Ohio's history.
Purpose This study was designed to assess the mechanical properties of two calcium carbonate tempers, limestone and burnt shell. These tempers have been previously compared, in separate studies, to ...silicate-based grit or sand temper and, relative to the latter, are assumed to possess similar mechanical properties. However, their simultaneous use at the Morrison Village site begs the question: do these two calcium carbonate tempers indeed possess similar mechanical properties? In order to assess their performance characteristics, a side-by-side controlled experimental test was conducted to determine the degree of similarity in providing increased vessel strength and toughness. Methods Standardized ceramic test samples were systematically prepared via a set, explicit protocol. An Instron Series IX universal testing machine configured with a four-point flexural test jig was used to perform a flexural strength test of the test samples. The Instron load and deflection data were used to calculate three values related to mechanical performance: peak load, modulus of rupture, and modulus of elasticity. Results All four comparative tests clearly show substantial differences in peak load, modulus of rupture, and modulus of elasticity. These differences are statistically significant for each performance attribute in every iteration of the experiment and as indicated by Mann-Whitney U Tests. Conclusions These results do not support the hypothesis that limestone and burnt shell offer the same performance characteristics. These results have implications for our understanding of prehistoric human selection of temper and the evolution of ceramic technology. Although both carbonate-based tempers are currently thought to offer the same benefits during the initial phase of pottery production, their contrasting post firing properties would have provided distinct benefits in different contexts. Future assessments of the Morrison Village ceramic assemblage should focus on residue analysis, or other functional indicators, to support or falsify this hypothesis.
The femur and pelvis of Ardipithecus ramidus have characters indicative of both upright bipedal walking and movement in trees. Consequently, bipedality in Ar. ramidus was more primitive than in later ...AUSTRALOPITHECUS: Compared with monkeys and Early Miocene apes such as Proconsul, the ilium in Ar. ramidus is mediolaterally expanded, and its sacroiliac joint is located more posteriorly. These changes are shared with some Middle and Late Miocene apes as well as with African apes and later hominids. However, in contrast to extant apes, bipedality in Ar. ramidus was facilitated by craniocaudal shortening of the ilium and enhanced lordotic recurvature of the lower spine. Given the predominant absence of derived traits in other skeletal regions of Ar. ramidus, including the forelimb, these adaptations were probably acquired shortly after divergence from our last common ancestor with chimpanzees. They therefore bear little or no functional relationship to the highly derived suspension, vertical climbing, knuckle-walking, and facultative bipedality of extant African apes.
During the North American Late Archaic Period, people produced ceramic vessels from clay and stone vessels from soapstone. While both ceramic and soapstone vessels proliferated across eastern North ...America, the former evolved and endured into the subsequent periods, while the latter declined. Here, we conducted an experiment to assess heating effectiveness between soapstone and ceramic vessels. We examined heating rate, ability to boil, heat retention, and thermal shock resistance. We predicted that if cooking performance contributed to the decline of soapstone vessels, then they would perform poorly relative to ceramic vessels. Our results did not support that hypothesis and revealed soapstone vessels were significantly more likely to reach a boil. We consider three other related factors: (1) sourcing and production costs; (2) subsistence change; and (3) exchange and mobility, which may have contributed to the decline of the soapstone cooking vessel and the continued investment in ceramic technology.
•Stone weapon tips can exhibit microscopic linear impact traces (MLITs)•Some North American Late Pleistocene Clovis points in association with mammoths have MLITs.•These MLITs are seen as evidence of ...those points’ having been used to strike those mammoths.•We experimentally show MLITs can form on Clovis points impacting foliage and sediment.•MLITs on Clovis points cannot be automatically taken as evidence of a successful mammoth hunt.
Stone weapon tips can exhibit microscopic linear impact traces (MLITs), as a result of the tip impacting abrasive materials, including stone fragments from the tip itself that detached upon impact. Experiments have demonstrated that MLITs can form via the use of a variety of weapon systems, stone point types, and targets. MLITs found on North American Late Pleistocene Clovis points in association with proboscideans at the Colby and Lange/Ferguson sites are seen as evidence of those points’ having been used to hunt and strike those animals. However, there is experimental evidence to suggest that MLITs can occur for reasons other than successfully hitting a prey target. To explore alternate explanations for MLITs, we conducted an experiment whereby we launched replica Clovis points via atlatl and dart into sediment and foliage. Microwear analysis documented a total of 52 MLITs on the 10 experimental points with a range of three to eight areas of MLITs on any individual point. The MLITs this experiment generated were visually similar to those experimentally produced when Clovis points were launched into elephant carcasses. Equifinality in experimental MLIT formation suggests that multiple hypotheses can potentially explain the presence of Clovis point MLITs at Colby and Lange/Ferguson, possibly from hunting misses into sediment and foliage here or at other prior locales.
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