Juho-Antti Junno

Gradual decline in mobility with the adoption of food production in Europe

Significance Declining mobility levels following the Pleistocene had profound effects on human demography, social organization, and health, but the exact timing and pace of this critical change are unknown. Here we examine direct evidence for changing mobility levels from limb bone structural characteristics in a large sample of European skeletons spanning the past 30,000 y. Our results show that mobility first declined during the Neolithic, at the onset of food production, but that the decline was gradual, continuing for several thousand years as agriculture intensified. No change in relative limb strength occurred during the past 2,000 y. Thus, the more gracile modern human skeleton is a result of increased sedentism tied to food production, not subsequent mechanization and industrialization. Increased sedentism during the Holocene has been proposed as a major cause of decreased skeletal robusticity (bone strength relative to body size) in modern humans. When and why declining mobility occurred has profound implications for reconstructing past population history and health, but it has proven difficult to characterize archaeologically. In this study we evaluate temporal trends in relative strength of the upper and lower limb bones in a sample of 1,842 individuals from across Europe extending from the Upper Paleolithic [11,000–33,000 calibrated years (Cal y) B.P.] through the 20th century. A large decline in anteroposterior bending strength of the femur and tibia occurs beginning in the Neolithic (∼4,000–7,000 Cal y B.P.) and continues through the Iron/Roman period (∼2,000 Cal y B.P.), with no subsequent directional change. Declines in mediolateral bending strength of the lower limb bones and strength of the humerus are much smaller and less consistent. Together these results strongly implicate declining mobility as the specific behavioral factor underlying these changes. Mobility levels first declined at the onset of food production, but the transition to a more sedentary lifestyle was gradual, extending through later agricultural intensification. This finding only partially supports models that tie increased sedentism to a relatively abrupt Neolithic Demographic Transition in Europe. The lack of subsequent change in relative bone strength indicates that increasing mechanization and urbanization had only relatively small effects on skeletal robusticity, suggesting that moderate changes in activity level are not sufficient stimuli for bone deposition or resorption.

Temporal Trends in Vertebral Size and Shape from Medieval to Modern-Day

Human lumbar vertebrae support the weight of the upper body. Loads lifted and carried by the upper extremities cause significant loading stress to the vertebral bodies. It is well established that trauma-induced vertebral fractures are common especially among elderly people. The aim of this study was to investigate the morphological factors that could have affected the prevalence of trauma-related vertebral fractures from medieval times to the present day. To determine if morphological differences existed in the size and shape of the vertebral body between medieval times and the present day, the vertebral body size and shape was measured from the 4th lumbar vertebra using magnetic resonance imaging (MRI) and standard osteometric calipers. The modern samples consisted of modern Finns and the medieval samples were from archaeological collections in Sweden and Britain. The results show that the shape and size of the 4th lumbar vertebra has changed significantly from medieval times in a way that markedly affects the biomechanical characteristics of the lumbar vertebral column. These changes may have influenced the incidence of trauma- induced spinal fractures in modern populations.

Application of the anatomical method to estimate the maximum adult stature and the age‐at‐death stature

This study focuses on the age adjustment of statures estimated with the anatomical method. The research material includes 127 individuals from the Terry Collection. The cadaveric stature (CSTA)-skeletal height (SKH) ratios indicate that stature loss with age commences before SKH reduction. Testing three equations to estimate CSTA at the age at death and CSTA corrected to maximum stature from SKH indicates that the age correction of stature should reflect the pattern of age-related stature loss to minimize estimation error. An equation that includes a continuous and linear age correction through the entire adult age range [Eq. (1)] results in curvilinear stature estimation error. This curvilinear stature estimation error can be largely avoided by applying a second linear equation [Eq. (2)] to only individuals older than 40 years. Our third equation [Eq. (3)], based on younger individuals who have not lost stature, can be used to estimate maximum stature. This equation can also be applied to individuals of unknown or highly uncertain age, because it provides reasonably accurate estimates until about 60/70 years at least for males.

Effects of Leisure-Time Physical Activity on Vertebral Dimensions in the Northern Finland Birth Cohort 1966

Vertebral fractures are a common burden amongst elderly and late middle aged people. Vertebral cross-sectional area (CSA) is a major determinant of vertebral strength and thus associated with vertebral fracture risk. Previous studies suggest that physical activity affects vertebral CSA. We aimed to investigate the relationship between leisure-time physical activity (LTPA) from adolescence to middle age and vertebral dimensions in adulthood. We utilized the Northern Finland Birth Cohort 1966, of which 1188 subjects had records of LTPA at 14, 31 and 46 years, and had undergone lumbar magnetic resonance imaging (MRI) at the mean age of 47 years. Using MRI data, we measured eight dimensions of the L4 vertebra. Socioeconomic status, smoking habits, height and weight were also recorded at 14, 31 and 46 years. We obtained lifetime LTPA (14–46 years of age) trajectories using latent class analysis, which resulted in three categories (active, moderately active, inactive) in both genders. Linear regression analysis was used to analyze the association between LTPA and vertebral CSA with adjustments for vertebral height, BMI, socioeconomic status and smoking. High lifetime LTPA was associated with larger vertebral CSA in women but not men. Further research is needed to investigate the factors behind the observed gender-related differences.

Low trabecular bone density in recent sedentary modern humans

OBJECTIVES Research on a limited number of samples suggests that trabecular bone density (i.e., bone volume fraction, BVF) within specific articulations is lower among more sedentary Holocene agricultural populations compared with Holocene foragers, implying that activity levels have a significant effect on trabecular BVF. However, it is unclear to what extent BVF differs among groups with varying activity levels and how general this phenomenon is across multiple limb articulations. Here, we test two hypotheses that: (i) sedentary populations have lower BVF compared with active populations across limb articulations; and (ii) these declines are more uniform in the lower limb (because of its more direct relationship to mobility), and more variable in the upper limb. MATERIALS AND METHODS We estimated BVF in seven lower and upper limb articulations of five Holocene population samples with subsistence strategies spanning from foraging through horticultural to industrial using pQCT (peripheral Quantitative Computed Tomography). RESULTS Both hypotheses are largely supported. First, the most active groups have significantly greater BVF in most limb elements compared with more sedentary groups. Second, all sedentary groups have relatively similar (and lower) BVF in the lower limb but show more variation in upper limb articulations. CONCLUSIONS These results suggest that a decline in activity levels associated with the adoption of agriculture and industrialization significantly contributed to the reduction in BVF in recent modern humans, but specific behavioral changes, particularly in the upper limb, also affected these patterns.

Estimation of African apes’ body size from postcranial dimensions

We examine how African apes’ postcranial skeletal dimensions and their combinations are related to body size, as represented by trunk volume, within sex-specific samples of a total of 39 central chimpanzees (Pan troglodytes troglodytes) and 34 western gorillas (Gorilla gorilla gorilla). We examine this relationship by determining the strength of the correlation between selected skeletal dimensions and trunk volume. The findings indicate that sex should be taken into account when possible. Most two-predictor models perform better than most single-predictor models. Interspecific regressions based on log-transformed variables and sex/species-specific regression based on raw variables perform about equally well.

Cortical bone thickness can adapt locally to muscular loading while changing with age

Mechanical loading of muscle action is concentrated at muscle attachment sites; thus there may be a potential for site-specific variation in cortical bone thickness. Humeri from an early 20th-century Finnish (Helsinki) and two medieval English (Newcastle, Blackgate and York, Barbican) populations were subjected to pQCT scanning to calculate site-specific cross-sectional cortical bone area (CA) for four locations and to measure cortical thickness at muscle attachment sites and non-attachment sites. We found that CA at 80% of humerus length was significantly reduced compared to more distal cross-sections, which can be due to reduced stresses at the proximal shaft. The principal direction of loading at 80% humerus length was towards mediolateral plane, likely due to fixing the humerus close to the torso. At 35% the main direction of loading was towards anteroposterior plane, reflecting elbow flexing forces. The principal direction of loading varied between populations, sides and sexes at 50% humerus length due to preference between elbow and shoulder joint; thus this location might be useful when trying to infer differences in activity. These changes are likely due to overall shaft adaptation to forces acting at the humerus. In addition, we found a potential for site-specific variation in cortical thickness; cortical bone at muscle attachment sites was significantly thicker compared to non-attachment sites. Lastly, CA at 35% of humerus length and cortical thickness at non-attachment sites decreased with age. These results underline the importance of muscle loading for bone mass preservation as well as indicate that a site-specific variation of bone mass is possible.

Influence of physical activity on vertebral size

Dear Editors, The role of vertebral cross-sectional area (CSA) is widely recognised as an essential factor for vertebral strength [1], and the knowledge about the factors behind vertebral size could be vital for the further prevention of vertebral fractures. Physical activity and mechanical loadings have major effects on bone structure and cross-sectional geometry [2]. To clarify the role of loading induced adaptations on vertebral size, we utilised Northern Finland Birth Cohort 1986 (NFBC 1986) population. The present analyses include 380 members who answered the question concerning physical activity both at 16 and 19 years and participated in lumbar spine MRI at a mean age of 21 years. The research protocol was reviewed by the Ethics Committee of the University Hospital of Oulu. MRI scans were obtained with a 1.5-T unit (Sigma, General Electric, Milwaukee, WI, USA) with a Phased Array CTL Spine Coil (USA Instruments, Aurora, OH, USA). We measured mediolateral and anteroposterior dimensions from the fourth lumbar vertebra (L4) to estimate vertebral size and to calculate the CSA of the vertebral body. Physical activity was evaluated with a question about participation in moderate-to-vigorous physical activity (MVPA), causing at least some sweating and shortness of breath. Subjects were classified into three physical activity

Influence of physical activity on vertebral strength during late adolescence

BACKGROUND CONTEXT Reduced vertebral strength is a clear risk factor for vertebral fractures. Men and women with vertebral fractures often have reduced vertebral size and bone mineral density (BMD). Vertebral strength is controlled by both genetic and developmental factors. Malnutrition and low levels of physical activity are commonly considered to result in reduced bone size during growth. Several studies have also demonstrated the general relationship between BMD and physical activity in the appendicular skeleton. PURPOSE In this study, we wanted to clarify the role of physical activity on vertebral bodies. Vertebral dimensions appear to generally be less pliant than long bones when lifetime changes occur. We wanted to explore the association between physical activity during late adolescence and vertebral strength parameters such as cross-sectional size and BMD. STUDY DESIGN The association between physical activity and vertebral strength was explored by measuring vertebral strength parameters and defining the level of physical activity during adolescence. PATIENT SAMPLE The study population consisted of 6,928 males and females who, at 15 to 16 and 19 years of age, responded to a mailed questionnaire inquiring about their physical activity. A total of 558 individuals at the mean age of 21 years underwent magnetic resonance imaging (MRI) scans. METHODS We measured the dimensions of the fourth lumbar vertebra from the MRI scans of the Northern Finland Birth Cohort 1986 and performed T2* relaxation time mapping, reflective of BMD. Vertebral strength was based on these two parameters. We analyzed the association of physical activity on vertebral strength using the analysis of variance. RESULTS AND CONCLUSIONS We observed no association between the level of physical activity during late adolescence and vertebral strength at 21 years.

Effect of occupational physical activities on vertebral dimensions in midlife in the Northern Finland Birth Cohort 1966

Objectives The vertebral cross-sectional area (CSA) is a major determinant of vertebral strength. Since leisure-time physical activity (LTPA) is known to affect vertebral CSA, we hypothesised that engagement in physical activity at work might have similar effects on vertebral size. We aimed to examine the association between various adulthood occupational physical activities (OPA) and vertebral CSA, and to evaluate the association between OPA intensity and vertebral CSA. Methods We used the prospective population-based Northern Finland Birth Cohort 1966. Our sample consisted of 712 participants with a mean age of 46.8 years. We assessed their engagement in various individual physical work activities at the ages of 31 and 46, and created overall OPA categories (high, moderate and low intensity), which we used in the analyses to study their association with vertebral CSA in middle age. Linear regression was used as the statistical method with adjustments for LTPA, vertebral height, body mass index and smoking. Results A statistically significant association was found between occupational sitting and smaller vertebral CSA in men, but only at the age of 31 (49.2 mm2 smaller among those who sit often vs rarely (95% CI −96.0 to −2.4)). No significant differences were detected between OPA categories and vertebral CSA (p>0.05). Thus, we found no consistent association between OPA and vertebral size among either sex. Conclusions OPA seems to have very little effect on vertebral size. Our results suggest that the effect of LTPA on vertebral size is different to that of OPA.