肱骨骨干骨密质厚度的二维可视化及其定量分析

形态示量图是一种展示三维形态测量信息的二维可视化手段,能有效地反应骨密质厚度的分布特点。虽然现代人、更新世古老型人类和大猿的骨密质厚度分布存在差别,但全新世现代人内部是否有变异存在尚未被充分研究。本文选择全新世华中、华北地区的6个农业人群的34例右侧肱骨标本（23例男性、11例女性）,使用形态示量图对其骨干骨密质厚度的分布特征进行了全面分析。在方法上,本文比较了通过厚度最大值和生物力学长度对骨密质厚度进行标准化后分析结果的差别,并验证了主成分分析在形态示量图上的适用性。结果显示,在全新世华中、华北地区的农业人群中,男、女的厚度分布模式存在一定差异,而不同人群男性的差别并不明显。本文虽通过全新世华中、华北地区的农业人群揭示出全新世现代人在肱骨骨干骨密质厚度分布上存在一定程度的变异,但仍需在未来工作中依托本文方法,选择人群种类更丰富、标本量更大、个体变量控制更严格的材料,进一步验证或扩展本文所得结论。     

辽宁建平古人类肱骨形态结构分析

1957年,在辽宁省建平县发现了一根古人类肱骨化石,编号PA103。通过同一批龙骨中筛选的哺乳动物化石,吴汝康推断PA103应该为更新世晚期古人类,并对该化石进行了表面形态特征观察和描述。为了对PA103化石的内外结构进行更全面的了解,除了线性测量数据的对比,本文还通过计算机断层扫描技术,结合生物力学和形态示量图分析对建平古人类右侧肱骨化石PA103进行了分析。通过本研究发现,PA103骨干横断面的生物力学粗壮度和力学形状指数明显小于尼安德特人,而与同时期欧亚大陆古人类不利手侧最为接近,这说明建平人右侧肱骨可能不是惯用手,同时,建平人的行为活动应该与同时期同地区的古人类处于同一水平,而小于尼安德特人。整体来看,PA103骨干骨密质厚度和截面惯性矩与近现代人的分布模式较为接近,除局部数值增大外,其整体数值小于近现代人的平均水平,这可能与遗传或行为活动有关,由于缺少古人类化石对比数据,更详细的了解还需后期开展更多相关的研究。     

Human manipulative behavior in the Central European Late Eneolithic and Early Bronze Age: humeral bilateral asymmetry

It is assumed that the transition from the Late Eneolithic to the Early Bronze Age in Central Europe was associated with substantial changes in subsistence and the perception of gender differences. However, the archeological record itself does not entirely support this model. Alternatively, this transition may be interpreted as a continuous process. We used asymmetry in external dimensions, and asymmetry in size and distribution of cortical tissue of humeri to elucidate the nature of this transition with respect to differences in manipulative behavior. The total sample of 67 individuals representing five archaeological cultures was used. The results indicate that the pattern of asymmetry of the humeral external measurements and the cross-sectional parameters taken at 35% of humeral biomechanical length remain stable during the Late Eneolithic and Early Bronze Age. However, females of both periods show fluctuating asymmetry for all of the cross-sectional parameters, but directional asymmetry for biomechanical length. Males are nonsignificantly shifted from the line of equivalence for biomechanical length, but exhibit directional asymmetry for the cortical area and polar moment of area. Only distal articular breadth yields fluctuating asymmetry for both females and males in both periods. Thus, the transition from the Late Eneolithic to the Early Bronze Age can be seen as a continuous process that probably affected only a limited part of human activities. We interpret the differences between females and males of both periods as evidence of gender-specific activities; males might have been associated with extra-domestic agricultural labor that resulted in asymmetrical manipulative loading and females with domestic labor with symmetrical manipulative loading in both periods.     

Effects of age and occupation on cortical bone in a group of 18th-19th century British men

The effects of age and occupation on cortical bone in a group of adult males from the 18th-19th century AD skeletal collection from Christ Church Spitalfields, London, were investigated. Cortical bone was monitored using metacarpal radiogrammetry. Individual age at death was known exactly from coffin plates. Occupation for individuals was known from historical sources. Results showed that continued periosteal apposition was evident throughout adult life, but from middle age onwards this was outstripped by about 2:1 by endosteal resorption, so that there was net thinning of cortical bone. The rate of cortical thinning resembled that seen in modern European males. Cross-sectional properties, as measured by second moments of area, bore no relationship to occupation. The results may suggest that, firstly, patterns of loss of cortical bone have remained unchanged in males for at least two centuries in Britain, and secondly, that biomechanical analyses of metacarpal cortical bone may be rather insensitive indicators of intensity of manual activity.     

Biomechanical approach to the reconstruction of activity patterns in Neolithic Western Liguria, Italy

This paper investigates the changes in upper and lower limb robusticity and activity patterns that accompanied the transition to a Neolithic subsistence in western Liguria (Italy). Diaphyseal robusticity measures were obtained from cross-sectional geometric properties of the humerus and femur in a sample of 16 individuals (eight males and eight females) dated to about 6,000-5,500 BP. Comparisons with European Late Upper Paleolithics (LUP) indicate increased humeral robusticity in Neolithic Ligurian (NEOL) males, but not in females, with a significant reduction in right-left differences in both sexes. Sexual dimorphism in robusticity increases in upper and lower limb bones. Regarding the femur, while all female indicators of bending strength decrease steadily through time, values for NEOL males approach those of LUP. This suggests high, and unexpected, levels of mechanical stress for NEOL males, probably reflecting the effects of the mountainous terrain on lower limb remodeling. Comparisons between NEOL males and a small sample of LUP hunter-gatherers from the same area support this interpretation. In conclusion, cross-sectional geometry data indicate that the transition to Neolithic economies in western Liguria did not reduce functional requirements in males, and suggest a marked sexual division of labor involving a more symmetrical use of the upper limb, and different male-female levels of locomotory stress. When articulated with archaeological, faunal, paleopathological, and ethnographic evidence, these results support the hypothesis of repetitive, bimanual use of axes tied to pastoral activities in males, and of more sedentary tasks linked to agriculture in females.     

Humeral cross-sectional morphology from 18th century Quebec prisoners of war: Limits to activity reconstruction

This study uses measures of cross-sectional robusticity and asymmetry (based on humeral areal and inertial cross-sectional components) to test a prediction from bone remodeling theory that a physically active 18th century Quebec prisoner of war sample (N = 25) should have more robust and asymmetrical humeri than a nonphysically active 20th century New Mexico suburbanite sample (N = 27). Narrative accounts document that prisoners of war engaged in labor-intensive activities, and these activities were confirmed by observations of osteoarthritis and other pathologies. The suburbanite sample, for the most part, did not engage in such activities. The prisoners had higher levels of pathology than the suburbanites (e.g., 80% vs. 22% osteoarthritis; F = 17.95, P < 0.01). For robusticity, the populations did not differ significantly in total area, cortical area, moment areas of inertia about the mediolateral plane, or polar moment area of inertia. The Quebec prison sample did have significantly higher values for moment areas of inertia about the anteroposterior plane. For asymmetry, the populations did not differ in any values (total area, cortical area, moment areas of inertia about the mediolateral plane, moment areas of inertia about the anteroposterior plane, or polar moment of inertia). Thus, examinations of cross-sectional robusticity and asymmetry failed to conclusively confirm the hypothesis that intensive labor leads to changes in humeral morphology. Possible explanations for the lack of differences are discussed, such as poor diet impeding bone remodeling. Nevertheless, the one significant finding suggests that cross-sectional shape is more useful in reconstructing activity patterns than amount of bone in a cross section. Results from this study join those from other recent investigations to suggest that additional controls are required before cross-sectional differences may be confidently attributed to activity patterns.     

Ontogenetic adaptation to bipedalism: age changes in femoral to humeral length and strength proportions in humans, with a comparison to baboons

The increase in lower/upper limb bone length and strength proportions in adult humans compared to most other anthropoid primates is commonly viewed as an adaptation to bipedalism. The ontogenetic development of femoral to humeral proportions is examined here using a longitudinal sample of 20 individuals measured radiographically at semiannual or annual intervals from 6 months of age to late adolescence (a subset of the Denver Growth Study sample). Anthropometric data (body weights, muscle breadths) were also available at each examination age. Results show that while femoral/humeral length proportions close to those of adults are already present in human infants, characteristically human femoral/humeral diaphyseal strength proportions only develop after the adoption of bipedalism at about 1 year of age. A rapid increase in femoral/humeral strength occurs between 1 and 3 years, followed by a slow increase until mid-late adolescence, when adult proportions are reached. When age changes in material properties are factored in, femoral strength shows an almost constant relationship to body size (body mass.bone length) after 5 years of age, while humeral strength shows a progressive decline relative to body size. Femoral/humeral length proportions increase slightly throughout growth, with no apparent change in growth trajectory at the initiation of walking, and with a small decline in late adolescence due to later growth in length of the humerus. A sex difference in femoral/humeral strength proportions (females greater) but not length proportions, develops early in childhood. Thus, growth trajectories in length and strength proportions are largely independent, with strength proportions more responsive to actual changes in mechanical loading. A cross-sectional ontogenetic sample of baboons (n=30) illustrates contrasting patterns of growth, with much smaller age changes in proportions, particularly strength proportions, although there is some indication of an adaptation to altered limb loadings early in baboon development.     

Effects of spaceflight on rat humerus geometry, biomechanics, and biochemistry

The effects of a 12.5-day spaceflight (Cosmos 1887 biosatellite) on the geometric, biomechanical, and biochemical characteristics of humeri of male specific pathogen-free rats were examined. Humeri of age-matched basal control, synchronous control, and vivarium control rats were contrasted with the flight bones to examine the influence of growth and space environment on bone development. Lack of humerus longitudinal growth occurred during the 12.5 days in spaceflight. In addition, the normal mid-diaphysial periosteal appositional growth was affected; compared with their controls, the spaceflight humeri had less cortical cross-sectional area, smaller periosteal circumferences, smaller anterior-posterior periosteal diameters, and smaller second moments of area with respect to the bending and nonbending axes. The flexural rigidity of the flight humeri was comparable to that of the younger basal control rats and significantly less than that of the synchronous and vivarium controls; the elastic moduli of all four groups, nonetheless, were not significantly different. Generally, the matrix biochemistry of the mid-diaphysial cross sections showed no differences among groups. Thus, the spaceflight differences in humeral mechanical strength and flexural rigidity were probably a result of the differences in humeral geometry rather than material properties.     

Understanding muscle markers: aggregation and construct validity

Musculoskeletal markers are frequently used to reconstruct past lifestyles and activity patterns. Yet, the reliability of muscle marker measurements has been called into question because they allegedly fail to correlate with cross-sectional properties and exercise patterns, and are confounded by body size. In this study, the principle of aggregation was used to sum muscle markers over 7 insertion sites (4 humeral, 2 radial, and 1 ulnar) and examine the effects on them of body size, age, sex, and cross-sectional properties. Analyses were made of a sample of 91 (66 males, 25 females) Native British Columbians (3500-1500 years BP) and 18th century Quebec prisoners. Muscle markers were measured using three-point observer rating scales; size was measured by standard methods; age and sex were determined through pelvic, cranial, and dental morphology; and cross-sectional properties were calculated from radiographs. Whereas any single muscle marker component failed to correlate with age, size, sex, or cross-sections, aggregate muscle marker correlated with: age, r = 0.49; size, r = 0.38; sex, r = 0.40; and, cross-sections, r = 0.38; P < 0.001. Older individuals had greater muscle markers, as did larger individuals, males, and those with more robust cross-sections. Based on partial correlations and regression analyses, age was the best overall predictor of aggregate muscle marker.     

Compact bone distribution and biomechanics of early hominid mandibles.

This investigation explores the effects of compact bone distribution on the biomechanical properties of the postcanine mandibular corpus of the fossil hominid taxa Australopithecus africanus and Paranthropus robustus. The mandibles of extant great apes, modern humans, and the fossil hominids are examined by computed tomography (CT), and compact bone contours are used to calculate cross-sectional biomechanical properties (cortical area, second moments of area, and Bredt's formula for torsional strength). The relative amount of compact bone is comparable in the modern and fossil mandibles, but the mechanical properties of A. africanus and P. robustus jaws are distinct in terms of the ratio of minimum to maximum second moments of area. This difference most likely represents a structural response to elevated torsional moments in the fossil hominids. Although the relative amount of compact bone in cross-section does not differ significantly between taxa by statistical criteria, A. africanus utilizes less cortical bone than P. robustus in the same manner in which Pongo is separated from the condition in other extant large-bodied hominoids. It has been suggested that the phenomenon of mandibular "robusticity" (expressed as an index of corpus breadth/corpus height) may be an effect of postcanine megadontia and/or reduced canine size in the australopithecines. Results presented here, however, indicate that it is unlikely that either factor adequately accounts for mandibular size and shape variation in early hominids.     

The effect of swimming activity on bone architecture in growing rats

The effect of non-habitual physical activity on bone architecture in the rat humeral shaft was examined. Two groups of rats were trained to swim for 1 h a day, for 20 weeks, at two training levels. The control group consisted of sedentary rats. Parameters of cross-sectional bone morphology (cross-section areas, principal area moments of inertia and their ratio) were used to evaluate the response of bone architecture to mechanical loading. The strength of bone was assessed by measuring the ultimate compressive force and stress. The cortical cross-section area and principal moments of inertia were found to be significantly higher in the swimming groups than in the controls. Examination of the ratio between the major and minor moments of inertia revealed a pronounced change in the shape of the bone cross-section which became more rounded following swimming training. The ultimate compressive force was significantly higher in the swimming rats while the changes in ultimate stress were not significant. Our results indicate a gain of bone strength due to increased periosteal apposition and modified bone tissue distribution. The marked changes in bone morphology are attributed to the different nature of the forces and moments exerted on the humerus during swimming compared to those prevailing during normal locomotion.     

Cortical bone maintenance and geometry of the tibia in prehistoric children from Nubia's Batn el Hajar

The relationship between advancing age in adults and patterns of cortical bone maintenance has been extensively documented for archaeological populations (Dewey, et al., 1969; Van Gerven et al., 1969; Perzigian, 1973). Most recently, this research has been expanded to include a more thorough consideration of the geometric properties of bone in relationship to adult age changes (Martin and Atkinsin, 1977; Ruff and Hayes, 1983). To date, however, few studies have documented subadult patterns of cortical bone maintenance in archaeological populations and none have incorporated the relationship between patterns of cortical bone loss and gain and the changing geometric properties of growing bone. Using a sample of 172 tibias from children excavated from the Medieval Christian site of Kulubnarti, located in Nubia's Batn el Hajar, the present research examines the relationship between percent cortical area, bone mineral content, and cross-sectional moments of inertia. Among these children, bone mineral content increases steadily from birth in spite of a reduction in percent cortical area during early and late childhood. It appears, therefore, that tissue quality of the bone is not adversely affected by the reduction. Furthermore, the reduction in percent cortical area in later childhood corresponds to a dramatic increase in bending strength measured by cross-sectional moments of inertia. Thus, whether this cortical reduction is due entirely or in part to either normal modeling or nutritional stress, the tissue and organ quality of the bone is not adversely affected.     

Second metacarpal midshaft geometry in an historic cemetery sample

Study of bone mass at the second metacarpal midshaft has contributed to our understanding of skeletal growth and aging within and between populations and has relied extensively on noninvasive techniques and in particular radiogrammetric data. This study reports age, sex, and side variation in size and shape data acquired from direct measurement of cross-sections obtained from a large (n = 356), homogeneous skeletal sample. Correlation analysis and three-way ANOVA of size-adjusted data confirm general impressions of patterned variation in this element: males have absolutely but not necessarily relatively larger bones than females; the right side is larger than the left, though a larger than expected proportion (approximately 25%) of left metacarpals exhibits greater values than the right; and bone mass but not strength (in males) declines with age. Contrary to the widely accepted assumption of circularity for this location, direct measurement of cross-sectional geometry confirms previous biplanar radiogrammetric conclusions regarding the noncircularity of the second metacarpal midshaft and identifies a significant difference between males and females, with the latter having a more cylindrical diaphysis. Deviation of the axes of maximum and minimum bending strength associated with noncircularity suggests a distribution of bone mass to resist bending moments perpendicular to the distal palmar arch, though this conclusion awaits more robust study of the functional anatomy of the metacarpal diaphysis. Am J Phys Anthropol 106:157–167, 1998. © 1998 Wiley-Liss, Inc.     

The relationship between musculoskeletal stress markers and biomechanical properties of the humeral diaphysis

Musculoskeletal stress markers (MSM) at entheses and bone biomechanical properties are used in activity reconstructions. The effect of physical activity on bone biomechanical properties is well established but the relative role of physical activity on MSM is less well known. In this article, it is hypothesized that the same causal mechanisms should affect MSM development as those responsible for bone biomechanical properties. Further, there should be a correlation between MSMs and bone cross-sectional properties as both are considered to reflect physical activity. This was tested using three skeletal samples: early 20th century Finnish (Helsinki) and two medieval English (Blackgate and York) populations. Torsional/average bending rigidity (J) for four cross-sectional locations at 80, 65, 50, and 35% of humeral length from the distal end was calculated and pectoralis major, teres major, and deltoid were scored for MSM. Correlations between MSM and size-standardized J were significant for many comparisons, although they were stronger in males than in females, especially on the right side. In ANOVAs, sample was found to be a significant influence on the right side in both sexes. Using an aggregated MSM score, covariance between J and high MSM scores was again stronger in males. Covariance between J and MSM was found both at cross-sectional locations under muscle insertions and at more distant locations, demonstrating both direct and general effects of muscular loadings applied to diaphyses. Thus, the two types of skeletal markers appear to be related to similar underlying mechanical factors, but effects may also be sex- and sample-specific.     

A comparison of primate, carnivoran and rodent limb bone cross-sectional properties: are primates really unique?

The cross-sectional properties of mammalian limb bones provide an important source of information about their loading history and locomotor adaptations. It has been suggested, for instance, that the cross-sectional strength of primate limb bones differs from that of other mammals as a consequence of living in a complex arboreal environment (Kimura, 1991, 1995). In order to test this hypothesis more rigorously, we have investigated cross-sectional properties in samples of humeri and femora of 71 primate species, 30 carnivorans and 59 rodents. Primates differ from carnivorans and rodents in having limb bones with greater cross-sectional strength than mammals of similar mass. This might imply that primates have stronger bones than carnivorans and rodents. However, primates also have longer proximal limb bones than other mammals. When cross-sectional dimensions are regressed against bone length, primates appear to have more gracile bones than other mammals. These two seemingly contradictory findings can be reconciled by recognizing that most limb bones experience bending as a predominant loading regime. After regressing cross-sectional strength against the product of body mass and bone length, a product which should be proportional to the bending moments applied to the limb, primates are found to overlap considerably with carnivorans and rodents. Consequently, primate humeri and femora are similar to those of nonprimates in their resistance to bending. Comparisons between arboreal and terrestrial species within the orders show that the bones of arboreal carnivorans have greater cross-sectional properties than those of terrestrial carnivorans, thus supporting Kimura's general notion. However, no differences were found between arboreal and terrestrial rodents. Among primates, the only significant difference was in humeral bending rigidity, which is higher in the terrestrial species. In summary, arboreal and terrestrial species do not show consistent differences in long bone reinforcement, and Kimura's conclusions must be modified to take into account the interaction of bone length and cross-sectional geometry.     

External-internal relationships in humeri of modern human females

With data from an early twentieth century human skeletal collection, this exploratory study investigates associations between inner cortical and medullary cavity structures and outer shaft and epiphyseal features of a long bone. Humeri are measured directly in both whole bone and transverse section contexts; data along 2 axes at 2 sites are obtained. Twenty-two probable females, with an age range concentrated in middle adulthood, comprise the sample. Correlations between multiple external and internal bone measurements are analyzed, with the aim of yielding information on the physical nature of bone and on the effects of different measurement types, locations, and orientations for bone relationships. The study also examines whether prediction of inner humeral dimensions from outer measurements would be appropriate. Results indicate biepicondylar width and maximum length as the strongest external correlates of cortical dimensions. Contrasting with studies on the proximal femur, the humeral head shows external size changeability, mostly in the transverse plane, in response to modeling forces shared with the shaft. Epiphyseal measures are more highly associated with absolute rather than percent, and areal rather than linear, cortical variables. Medullary cavity dimensions are not significantly correlated with whole bone measures. Most associations demonstrate shape or proportion influences rather than a shared effect of linear body size. Regarding location and orientation, the distal site and medial-lateral axis display the strongest correlations among external and internal bone dimensions. In light of the demonstrated correlation patterns, prediction of humeral cortical quantity from external bone measures in living and skeletal populations would benefit from utilizing (1) biepicondylar width and maximum length; (2) an absolute, areal cortical measure; (3) a distal location; and (4) a medial-lateral orientation.     

Age, sex, and grip strength determine architectural bone parameters assessed by peripheral quantitative computed tomography (pQCT) at the human radius

The purpose of this study was to estimate the relation of some noninvasively derived mechanical characteristics of radial bone including architectural parameters for bone strength to grip strength and muscle cross-section. Sixty-three males between 21 and 78yr of age and 101 females between 18 and 80yr of age were measured at the nondominant forearm using peripheral quantitative computed tomography (pQCT). We assessed the integral bone mineral density (BMD(I)) and content (BMC(I)) by pQCT at the distal and at the mid-shaft radius. Integral bone area (Area(I)), cortical thickness (C-th), and a newly proposed index for bone strength; the stress-strain index (SSI) were also calculated. The dynamometrically measured maximum grip strength was taken as a mechanical loading parameter and muscle cross-section as a substitute for it. Sex, grip strength, BMC(I) and BMD(I) (distal radius) were identified in a multiple regression analysis to significantly predict bone strength as expressed by SSI, after adjusting for all other independent variables, including age and sex (p<0.0001). Grip strength was closest related to age, sex, BMD(I) and SSI(p) of the distal radius. The cross-sectional area of muscle was not significantly determining the grip strength within the analysis model. In conclusion, our results suggested that architectural parameters at the distal radius were better related to grip strength than to cross-sectional muscle area in both males and females. Maximum muscle strength as estimated by grip strength might be a stronger determinant of mechanical characteristics of bones as compared with cross-sectional muscle area.     

Activity-related skeletal change in medieval humeri: cross-sectional and architectural alterations

This paper examines humeral cross-sectional properties in two different samples of later medieval date: a group of blade-injured males from the sites of Towton, North Yorkshire, and Fishergate in the City of York, England, and a comparative group of nonblade-injured males also from the site of Fishergate in York. CT image slices were taken of the humeral shaft at 20%, 35%, 50%, 65%, and 80% from the distal end to investigate population differences in levels and patterns of mechanical loading. Bilateral asymmetry is investigated and comparisons are made with different populations of varying activity levels. Architectural changes such as humeral torsion are also investigated to determine the relationship between architectural changes and biomechanical efficiency. Results show significant differences in diaphyseal robusticity between the Towton sample and the comparative population, as well as significant differences in diaphyseal shape both between limbs within the Towton sample and between blade-injured samples. Population differences were also identified in the level of bilateral asymmetry, further demonstrating the differences in movement and activity patterns both between and within samples. These variations may relate to distinctive, more strenuous weapon use and differences in strenuous movement patterns in the two groups.     

Patterns of humeral asymmetry among Late Pleistocene humans

Human humeral diaphyseal asymmetry in midshaft and mid-distal rigidity is assessed through the Late Pleistocene in samples of late archaic (Neandertal) and early modern humans. It is considered with respect to directionality (handedness), levels of asymmetry, body size and sexual differences. The overall Late Pleistocene sample indicates a right-handed preference in frequencies (right: 74.8%, left: 15.0%, ambiguous: 10.3%), which are similar to those of recent human samples. Average levels of humeral asymmetry are elevated relative to Holocene samples through all but the small Middle Paleolithic modern human and eastern Eurasian late Upper Paleolithic samples. Humeral asymmetry is especially high among the males relative to the females, and the possibility of a division of labor between uni-manual tasks (mostly male) and bi-manual tasks (mostly female) is considered. At the same time, there is a general pattern of increased asymmetry with larger body size, but it remains unclear to what extent it reflects body size versus sexual effects on bilateral humeral loading. There do not appear to have been substantial changes in humeral asymmetry through time, indicating a continuity of similar manual behavioral patterns through the Late Pleistocene, despite considerable changes in technology through the Late Pleistocene.     

Muscle markers revisited: activity pattern reconstruction with controls in a central California Amerind population

Anthropologists frequently use musculoskeletal stress markers to reconstruct past activity patterns. Yet, researchers have called into question the reliability of muscle marker measurements in part because body size and age affect muscle marker scores. In this study, the author examined an aggregate upper limb muscle marker to determine if after controlling for the effects of body size and age, one could reconstruct activity patterns of a prehistoric Amerind population. Analyses were made of a sample of 102 (43 males, 59 females) prehistoric central California Amerinds. Muscle markers were measured using two-point observer rating scales; body size was measured by humeral articular surfaces; age and sex were determined previously through standard procedures. Using sex separated rankings and partial correlations, disaggregated muscle markers were examined for correlations with age and size to determine if specific muscle markers may be useful in pinpointing to activity patterns. Aggregate upper limb muscle marker correlated with: age, r = 0.44; humeral size, r = 0.44; and sex, r = 0.43; Ps < 0.001. Older individuals had greater muscle markers, as did larger individuals, and males. Rankings seemed to be confounded by the effect size had on the muscle markers. However, based on partial correlations controlling for size and age, the differences that remained between males and females could be used to reconstruct male activities of throwing in hunting and interpersonal aggression acts.