Bioarchaeology Study Guide

📖 Core Concepts Bioarchaeology – scientific study of human/animal biological remains from archaeological sites to reconstruct health, diet, lifestyle, mortality, and social conditions. Paleodemography – building demographic profiles (age, sex, mortality) using skeletal age‑estimation methods and life tables. Non‑specific stress markers – skeletal or dental lesions (e.g., enamel hypoplasia, porotic hyperostosis, Harris lines) that record childhood physiological stress but do not pinpoint a specific disease. Wolff’s Law – bone tissue remodels: increased mechanical load → thicker/stronger bone; inactivity/disease → bone loss. Stable isotope biogeochemistry – ratios of heavy/light isotopes (δ¹³C, δ¹⁵N, δ¹⁸O, δ³⁴S) measured in collagen or apatite to infer diet, trophic level, water source, and mobility. Biocultural bioarchaeology – integrates biological data with cultural context, treating bodies as products of both biology and society. Ethical framework – NAGPRA, respectful handling of remains, and emerging guidelines for digital documentation. --- 📌 Must Remember Age estimation Children: dental eruption, ossification, long‑bone length. Adults: pubic symphysis, auricular surface, sternal end of 4th rib, dental attrition → grouped “young (20‑35), middle (35‑50), old (50+)”. Sex determination – pelvis (sub‑pubic angle > 90° = female; < 90° = male) and robust cranial features; > 95 % accuracy with population‑specific discriminant functions. Enamel hypoplasia (LEH) – transverse pits/furrows formed 1–7 yr (up to 13 yr for 3rd molars) → record of childhood disease or malnutrition. Harris lines – transverse high‑density bands in long bones, appear 2–3 yr, rare after 5 yr; thicker after severe/prolonged stress. δ¹³C ranges – C₃ plants: −22 ‰ to −34 ‰; C₄ plants: −9 ‰ to −16 ‰. δ¹⁵N trophic shift – +3–4 ‰ per trophic level; higher values → more animal protein. Perimortem vs post‑mortem fracture – perimortem: clean, linear, no weathering; post‑mortem: weathered, irregular, no healing. NAGPRA – legal right of Native American tribes to reclaim ancestral remains and cultural items. --- 🔄 Key Processes Building a life table Collect age‑sex estimates → sort individuals into age‑cohorts → calculate survivorship (lx) and mortality (dx). Estimating childhood stress using LEH Identify LEH on tooth crowns → note tooth type & position → correlate with known eruption ages → infer timing of stress episode. Stable isotope sampling Extract collagen (δ¹³C, δ¹⁵N) or apatite (δ¹³C, δ¹⁸O) → measure δ values vs standards (VPDB for C, AIR for N, VSMOW for O) → interpret diet/mobility. Sex determination workflow Examine pelvis → if ambiguous, assess cranial traits → apply discriminant function (if metric data available). Assessing trauma chronology Observe fracture edge morphology → check for periosteal reaction (healing) → classify as perimortem, antemortem, or post‑depositional. --- 🔍 Key Comparisons Enamel hypoplasia vs. Dental caries LEH: linear pits, form during enamel formation, record past stress. Caries: cavities formed after eruption, indicate present‑day carbohydrate exposure. C₃ vs. C₄ plants (δ¹³C) C₃: more negative δ¹³C (−22 to −34 ‰); typical forest, temperate crops. C₄: less negative δ¹³C (−9 to −16 ‰); tropical grasses, maize, millet. Perimortem vs. Post‑mortem fractures Perimortem: clean breaks, no weathering, possible hemorrhage. Post‑mortem: weathered, irregular, no healing signs. Porotic hyperostosis vs. Cribra orbitalia Both reflect vascular changes; traditionally linked to iron‑deficiency anemia, now viewed as broader stress (nutrition, infection). --- ⚠️ Common Misunderstandings “LEH = disease” – LEH records any physiological stress (illness, malnutrition, weaning), not a specific disease. “Higher δ¹⁵N always means meat consumption” – Elevated δ¹⁵N can also result from marine protein, manure‑fertilized crops, or legume intake (low δ¹⁵N). “Wolff’s law predicts larger bones always mean hard labor” – Bone size reflects cumulative loading; genetics and age can dominate over occupational stress. “All porotic lesions equal anemia” – Modern research shows they may reflect multiple stressors, including parasitic infection. --- 🧠 Mental Models / Intuition Isotope “color wheel” – Imagine δ¹³C as a blue‑red scale (C₃ = blue, C₄ = red); mixing shades in a collagen sample tells you the proportion of each diet component. Bone as a “dynamic scaffold” – Think of bone like a building under renovation: load → workers (osteoblasts) add material; no load → workers leave, scaffold thins. Age‑sex “two‑key lock” – Pelvic angle and cranial robustness are the two keys that together open the “sex” lock; missing one key reduces confidence. --- 🚩 Exceptions & Edge Cases Sexing pre‑pubertal skeletons – Dimorphic traits are undeveloped; sex estimation is unreliable. δ¹³C offset in apatite – Apatite values are +14 ‰ relative to collagen; must adjust when comparing tissue types. High δ¹⁵N in vegetarian diets – Manure‑fertilized crops or marine fish consumption can raise δ¹⁵N without meat intake. Harris lines in girls – While more common in boys, severe stress can produce them in females; do not assume gender bias. --- 📍 When to Use Which Age estimation – Use dental eruption for children < 12 yr; switch to epiphyseal fusion & long‑bone length for early teens; apply degenerative pelvic/rib markers for adults. Sex determination – Prioritize pelvis; if pelvis fragmented, supplement with cranial metrics; resort to aDNA only when morphological data insufficient. Isotope system – δ¹³C: diet type (C₃ vs C₄). δ¹⁵N: trophic level / protein source. δ¹⁸O: water source / mobility. δ³⁴S: marine vs terrestrial protein. Stress markers – Use LEH for childhood stress timing; Harris lines for early‑childhood growth interruptions; porotic lesions for chronic anemia/vascular stress. --- 👀 Patterns to Recognize Clustered LEH on first molars → weaning stress or early‑life disease episode. Consistent high δ¹³C across a site → community reliance on C₄ agriculture (e.g., maize). Mixed high δ¹⁵N & high δ³⁴S → marine‑based diet. Perimortem cut marks on long bones + associated burial reduction → possible ritual sacrifice. --- 🗂️ Exam Traps Choosing “enamel hypoplasia = iron‑deficiency anemia” – distractor; LEH records any stress, not a specific deficiency. Assuming “higher δ¹³C always means poorer diet” – false; C₄ crops can be nutritious; focus on cultural context. Identifying any osteoarthritis as occupational stress – age‑related OA is common; need age control. Equating “porotic hyperostosis = anemia” – oversimplified; may reflect infection or other stressors. Selecting perimortem fracture based solely on clean edge – must also consider lack of weathering and healing; post‑mortem fractures can be sharp if recent. ---