Biomechanics and Bone Biomechanics and Bone Stress in AnthropologyStress in Anthropology

Michelle Beckhorn; Session 1; 7 May 2012; Cave

BiomechanicsBiomechanics

Application of mechanicalApplication of mechanical

principles to biological systemsprinciples to biological systems Used in anthropology to explain skeletal Used in anthropology to explain skeletal

variation among populations past and presentvariation among populations past and present Can be used to understand cultural practices Can be used to understand cultural practices

such as throwing spears, heavy workloads, such as throwing spears, heavy workloads, spatial movement, knapping, etc.spatial movement, knapping, etc.

Methods of Methods of Understanding Understanding BiomechanicsBiomechanics

Wolff’s law states simply that mechanical Wolff’s law states simply that mechanical loading influences bone structureloading influences bone structure

Bone function adaptation states that Bone function adaptation states that mechanical deformation or strain of bone mechanical deformation or strain of bone tissue occurs under mechanical loading.tissue occurs under mechanical loading. Body SizeBody Size Muscle ActivityMuscle Activity

Example: robusticity of the long bone diaphysis Example: robusticity of the long bone diaphysis between modern populations and past between modern populations and past populationspopulations

Variations to ConsiderVariations to Consider

DietDiet DiseaseDisease Age at deathAge at death GeneticsGenetics HormonesHormones GenderGender SizeSize

Aspects to consider in Aspects to consider in variationsvariations Because of the high variations within Because of the high variations within

populations, it is most accurate to populations, it is most accurate to compare sides within an individual compare sides within an individual than one individual to another.than one individual to another.

The dominant side will exhibit bone The dominant side will exhibit bone stress marks resulting from stress marks resulting from mechanical load or movement.mechanical load or movement.

Within a population, if there are Within a population, if there are many individuals with such marks, many individuals with such marks, the cultural trend can be better the cultural trend can be better assessedassessed

Cold environments can accelerate Cold environments can accelerate bone stress due to blood vessel bone stress due to blood vessel constrictionconstriction

Age at which mechanical strain Age at which mechanical strain begins affects the severity of the begins affects the severity of the bone stress. bone stress.

Early Thule of the Hudson BayEarly Thule of the Hudson Bay Supports evidence Supports evidence

of umiaksof umiaks Kayaker’s Clavicle Kayaker’s Clavicle

and humor stress and humor stress strong to heavystrong to heavy

Gender role Gender role differencesdifferences

Late startLate start Hunting changes Hunting changes

from whaling to from whaling to sealseal

90 percent left 90 percent left handednesshandedness

Evolutionary Trends in Evolutionary Trends in Bone RobusticityBone Robusticity

Over the past two million years Over the past two million years bone robusticity has decreased bone robusticity has decreased by 30%by 30%

Resulting from the decrease in Resulting from the decrease in walking long distances, walking long distances, mechanical load and mechanical load and introduction of agriculture and introduction of agriculture and industry.industry.

Increase of potential Increase of potential osteoporosis osteoporosis

Physical environment and Physical environment and effects of cultural practiceseffects of cultural practices

ConclusionConclusion Taking into consideration Taking into consideration

the variations listed, we the variations listed, we can understand how culture can can understand how culture can effect the amount of mechanical effect the amount of mechanical loads which influences bone loads which influences bone stress such as robusticity on the stress such as robusticity on the long bone.long bone.

Archaeologists can use bone Archaeologists can use bone stress marks to understand stress marks to understand evolutionary and cultural trends evolutionary and cultural trends of populations past and presentof populations past and present..

ReferencesReferences

Hawkey, Diane E., Charles F. Merbs. Hawkey, Diane E., Charles F. Merbs. Activity-induced musculoskeletal Activity-induced musculoskeletal stress markers (MSM) and subsistence strategy changes among ancient stress markers (MSM) and subsistence strategy changes among ancient Hudson Bay EskimosHudson Bay Eskimos. . International Journal of Osteoarchaeology. International Journal of Osteoarchaeology. Volume 5, Issue 4, Volume 5, Issue 4, pages 324–338, December 1995.pages 324–338, December 1995.

M. ANNE KATZENBERG, Shelly Saunders. Biological Anthropology of the Human Skeleton. John Wiley and Sons Inc. Hoboken, NJ. 2008