Bone preservation in an archaeological burial assemblage: the effects of time, soil pH, age, and sex
McCraw, Kimberly Ann
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This project examined the differences in skeletal preservation from several mound sites in the West Central Illinois Valley, spanning the Late Archaic to Late Woodland periods, from approximately 2500 B.C to A.D. 1000: Koster Mounds, containing Early Archaic to Middle Archaic burials from approximately 8700 B.C. to 800 B.C.; Peisker Mounds, containing Early Woodland burials from approximately 625 B.C. to 230 B.C.; Gibson Mounds, containing Archaic, Hopewell, and Late Woodland burials starting 50 B.C. to A.D. 400; and Helton Mounds, containing Late Woodland burials from approximately A.D. 830 to A.D. 1200. The intrinsic factors of bone density and age and sex of the individual were compared statistically with bone inventories and osseous taphonomic conditions to determine if these factors affected preservation. Based on extant inventories each skeleton was scored on the percent of standard measurements possible to take, 24 cranial, 10 mandibular, and 44 postcranial measurements, following Buikstra and Ubelaker (1994), as a proxy for individual element completeness for major portions of the skeleton. Additionally, this project examined more specifically the preservation of the os coxa. The five commonly used areas for sexing (the ventral arc, subpubic concavity, ischiopubic ramus ridge, greater sciatic notch, and preauricular sulcus), following Buikstra and Ubelaker (1994) and Phenice (1969), were examined and scored independently. Three commonly used areas for aging (the pubic symphysis, auricular surface, and acetabulum) following Brooks and Suchey (1990), Phenice (1969) and Calce (2012) were examined and scored independently. Soil samples were collected from two sites and analyzed to determine if soil pH affects the preservation rates of skeletons differently. To assess the amount of data lost in older skeletal assemblages the author tested the hypotheses that (1) denser skeletal portions are most likely to be well-preserved, (2) mature adult males are more likely to be well-preserved than mature adult females, (3) mature adults will be more well-preserved than the remains of juveniles and old adults, and (4) skeletons from more recent time periods will be more well-preserved than skeletons from earlier time periods. The results of the study show, that while there are many factors that influence preservation of skeletal assemblages in the archaeological record, certain factors are more important than others when it comes to skewing the archaeological record. Sex of the individual does not appear significantly to affect the rate of preservation, while age at death and duration of burial, especially when looking at infants compared to adults and individuals buried during the Archaic period compared to individuals buried during the Middle and Late Woodland period, do affect preservation.