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

Abstract

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. mobility | Europe | Neolithic | bone strength

Limb Bone Structural Proportions and Locomotor Behavior in A.L. 288-1 ("Lucy")

“…The modern human sample used in comparisons of femoral/humeral strength and strength/articular proportions was derived from an ongoing study of Upper Paleolithic to 20th century European skeletal samples [68, 69]. Sample sizes vary between 838 and 1756, depending on the comparison (S2 Table).…”

Calcaneal Quantitative Ultrasound Indicates Reduced Bone Status Among Physically Active Adult Forager-Horticulturalists

“…Reductions in trabecular bone volume fraction of the metatarsal head, calcaneus, femoral head, and metacarpal head have similarly been documented among modern humans compared to other extant apes. Within the genus Homo , earlier studies documented a decline in postcranial skeletal strength relative to body size throughout the Pleistocene, but recent studies suggest this decline occurred in the later Pleistocene or Holocene . Biomechanical correlates of habitual bipedality per se thus cannot fully account for modern human skeletal gracility.…”

Physical activity alters limb bone structure but not entheseal morphology

“…Physical activity is essential for individual health and survival (Lieberman, 2013), it can be a driving force behind phenotypic evolution (Wallace et al, 2010; Raichlen and Polk, 2013), and it is a nexus that links features of economy, technology, and social relations (Kelly, 2013). For these reasons, paleoanthropological investigations of the lifeways of our ancient ancestors often aim to glean information about their levels of physical activity, typically by analyzing their skeletal remains (e.g., Villotte et al, 2010; Lieverse et al, 2013; Shaw and Stock, 2013; Chirchir et al, 2015; Ruff et al, 2015). Two skeletal features are assumed to be especially informative: (1) the quantity and distribution of bone within the limb elements, and (2) the morphology of muscle and tendon attachments sites, or entheses (Jurmain et al, 2012; Larsen, 2015).…”