The premise that bones grow and remodel throughout life to adapt to their mechanical environment is often called Wolff's law. Wolff's law, however, is not always true, and in fact comprises a variety of different processes that are best considered separately. Here we review the molecular and physiological mechanisms by which bone senses, transduces, and responds to mechanical loads, and the effects of aging processes on the relationship (if any) between cortical bone form and mechanical function. Experimental and comparative evidence suggests that cortical bone is primarily responsive to strain prior to sexual maturity, both in terms of the rate of new bone growth (modeling) as well as rates of turnover (Haversian remodeling). Rates of modeling and Haversian remodeling, however, vary greatly at different skeletal sites. In addition, there is no simple relationship between the orientation of loads in long bone diaphyses and their cross-sectional geometry. In combination, these data caution against assuming without testing adaptationist views about form-function relationships in order to infer adult activity patterns from skeletal features such as cross-sectional geometry, cortical bones density, and musculo-skeletal stress markers. Efforts to infer function from shape in the human skeleton should be based on biomechanical and developmental models that are experimentally tested and validated.

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The Aging of Wolff’s “Law”: Ontogeny and Responses to Mechanical Loading in Cortical Bone

Knee osteoarthritis (OA) is believed to be highly prevalent today because of recent increases in life expectancy and body mass index (BMI), but this assumption has not been tested using long-term historical or evolutionary data. We analyzed long-term trends in knee OA prevalence in the United States using cadaver-derived skeletons of people aged ≥50 y whose BMI at death was documented and who lived during the early industrial era (1800s to early 1900s; n = 1,581) and the modern postindustrial era (late 1900s to early 2000s; n = 819). Knee OA among individuals estimated to be ≥50 y old was also assessed in archeologically derived skeletons of prehistoric hunter-gatherers and early farmers (6000-300 B.P.; n = 176). OA was diagnosed based on the presence of eburnation (polish from bone-on-bone contact). Overall, knee OA prevalence was found to be 16% among the postindustrial sample but only 6% and 8% among the early industrial and prehistoric samples, respectively. After controlling for age, BMI, and other variables, knee OA prevalence was 2.1-fold higher (95% confidence interval, 1.5-3.1) in the postindustrial sample than in the early industrial sample. Our results indicate that increases in longevity and BMI are insufficient to explain the approximate doubling of knee OA prevalence that has occurred in the United States since the mid-20th century. Knee OA is thus more preventable than is commonly assumed, but prevention will require research on additional independent risk factors that either arose or have become amplified in the postindustrial era.

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Knee osteoarthritis has doubled in prevalence since the mid-20th century

Warfare has traditionally been considered unique to humans. It has, therefore, often been explained as deriving from features that are unique to humans, such as the possession of weapons or the adoption of a patriarchal ideology. Mounting evidence suggests, however, that coalitional killing of adults in neighboring groups also occurs regularly in other species, including wolves and chimpanzees. This implies that selection can favor components of intergroup aggression important to human warfare, including lethal raiding. Here I present the principal adaptive hypothesis for explaining the species distribution of intergroup coalitional killing. This is the "imbalance-of-power hypothesis," which suggests that coalitional killing is the expression of a drive for dominance over neighbors. Two conditions are proposed to be both necessary and sufficient to account for coalitional killing of neighbors: (1) a state of intergroup hostility; (2) sufficient imbalances of power between parties that one party can attack the other with impunity. Under these conditions, it is suggested, selection favors the tendency to hunt and kill rivals when the costs are sufficiently low. The imbalance-of-power hypothesis has been criticized on a variety of empirical and theoretical grounds which are discussed. To be further tested, studies of the proximate determinants of aggression are needed. However, current evidence supports the hypothesis that selection has favored a hunt-and-kill propensity in chimpanzees and humans, and that coalitional killing has a long history in the evolution of both species.

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Evolution of coalitionary killing.

This paper reviews the mechanisms of injury and the types of fractures that most commonly affect the human skeleton, presents descriptive protocols for cranial and postcranial fractures adapted from clinical and forensic medicine, and summarizes anatomically the injuries most likely to be found in archaeological skeletons along with their most common causes and complications. Mechanisms of injury are categorized as direct and indirect trauma, stress, and fracture that occurs secondary to pathology. These are considered to be the proximate, or most direct, causes of injury and they are influenced by intrinsic biological factors such as age and sex, and extrinsic environmental factors, both physical and sociocultural, that may be thought of as the ultimate, or remote, causes of injury. Interpersonal conflict may be one of those causes but the skeletal evidence itself is rarely conclusive and must therefore be evaluated in its individual, populational, sociocultural, and physical context. A cautionary tale regarding parry fractures is presented as an illustration. Yrbk Phys Anthropol 40:139–170, 1997. © 1997 Wiley-Liss, Inc.

Trauma analysis in paleopathology

▪ Abstract Traumatic injuries in ancient human skeletal remains are a direct source of evidence for testing theories of warfare and violence that are not subject to the interpretative difficulties posed by literary creations such as historical records and ethnographic reports. Bioarchaeological research shows that throughout the history of our species, interpersonal violence, especially among men, has been prevalent. Cannibalism seems to have been widespread, and mass killings, homicides, and assault injuries are also well documented in both the Old and New Worlds. No form of social organization, mode of production, or environmental setting appears to have remained free from interpersonal violence for long.

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A bioarchaeological perspective on the history of violence

Osteoarthritis is among the most common pathological conditions in skeletal collections and is the most frequent musculoskeletal disorder in contemporary populations. Jurmain (1991) has previously published in this journal a brief review of skeletal perspectives on osteoarthritis. Subsequent studies by osteologists and medical researchers have added considerably to understanding of the aetiology and patterning of osteoarthritis. Thus, it is timely to present an updated review that expands and supports conclusions discussed in the earlier review. In short, osteoarthritis aetiology is multifactorial, with age being the main influence on the onset and severity of osteoarthritis. Genetic influences also play a large role in the severity of osteoarthritis, especially in the lower limbs. Weight, although playing a significant role for modern populations, seems to have had very minimal effects on prehistoric populations. Sex differences may often be a consequence of hormones, body size and anatomy, rather than activity related. Finally, intense activity starting at a young age still may influence osteoarthritis, especially in the upper limbs. Future directions discussed include within-body comparisons, animal studies, and examining patterns in large populations. Copyright © 2007 John Wiley & Sons, Ltd.

Osteoarthritis revisited: a contemporary review of aetiology

Although degenerative joint disease is an old and exceedingly common problem, clinical investigators have not reached a consensus regarding the etiology of this disease. Comparative osteological analysis of the knee, hip, shoulder, and elbow joints of 789 individuals from four human skeletal populations (Black and White Americans, Pueblo Indians, and Alaskan Eskimos) indicates that age of onset, frequency, and location of degenerative changes are directly related to the nature and degree of environmentally associated stress, as reflected by the variable life styles of the populations sampled. Eskimos have the earliest onset and most severe involvement for all four joints studied, the right side is usually more affected than the left, and Blacks are more frequently involved than Whites in the knee, shoulder, and elbow. Functional stress, when constant and severe in nature, becomes the primary focus of degenerative disease, but other background contributing agents such as age, sex, and hormonal influence must not be ignored.

Stress and the etiology of osteoarthritis

Human skeletal research aimed at reconstructing past activities has had a long and checkered history. In recent years, in fact, it has been embraced as a kind of “Holy Grail” by an entire subfield of human osteology. The quest, however, has proven more hazardous than most of us would have imagined. Many types of bone changes have been proposed as “markers” of activity, occupation, or mechanical stress. Three major research areas have been thought to show the most promise and, consequently, have been most actively pursued: osteoarthritis, musculoskeletal stress markers, and cross-sectional bone geometry.As might be expected, most contributors to this volume focus on pathological conditions as identified in human remains. As has been widely recognized, some of the bone changes seen in osteoarthritis that have routinely been used to reconstruct activity are also sometimes pathological. In addition, much of the complex physiolog-ical change that occurs at muscle attachment sites (entheses) also involves inherently pathological processes—a basic consideration that has not yet been generally acknowledged by bioarchaeologists. In recent years many paleopathologists have actively pursued this type of research under the broad rubric of what Jane Buikstra

Bioarchaeology's Holy Grail: The Reconstruction of Activity

Of science and stories osteoarthritis - clinical and osteological approaches osteoarthritis and activity - occupational and sports studies osteoarthritis - anthropological interpretations enthesophaties and other osteological indicators of activity trauma studies of bone geometry - the shape of things to come? defining the limits of interpretation.

Robert Jurmain

Papers

Knee osteoarthritis has doubled in prevalence since the mid-20th century

Osteoarthritis revisited: a contemporary review of aetiology

Stress and the etiology of osteoarthritis

Bioarchaeology's Holy Grail: The Reconstruction of Activity

Stories from the Skeleton: Behavioral Reconstruction in Human Osteology