Activity-related changes in geometry of the proximal femurA study of two Near Eastern samplesKevin G. Hatala1,2, Steven E. Churchill3, Jaime Ullinger4, Susan Guise Sheridan51Hominid Paleobiology Doctoral Program, 2Center for the Advanced Study of Hominid Paleobiology, Department of Anthropology, The George Washington University, 3Department of Evolutionary Anthropology, Duke University, 4Department of Anthropology, The Ohio State University, 5Department of Anthropology, University of Notre Dame
The reconstruction of behaviors of past populations is a central goal of bioarchaeology. A common technique used to accomplish this goal is the analysis of cross-sectional bone geometry to reconstruct activity patterns. The often-cited but still disputed “Wolff’s Law” generally states that living bone tissue is added in areas of high mechanical demand and resorbed in areas of low demand (Ruff et al. 2006). Analyses of cross-sectional geometry examine the amount and distribution of cortical bone , as they should reflect the magnitude and orientation of habitual mechanical loads during life.
The goal of this research is to assess the correlations between bone geometry and archaeological and historical evidence for activity in two prehistoric Near Eastern samples. Doing so will provide an examination of how cross-sectional bone geometry reflects activity patterns in past populations, especially in fragmentary and commingled skeletal samples.
Comparisons of Geometric Properties:
Comparisons of Geometric Ratios:
For every geometric property and ratio, differences in between-group comparisons were statistically significant (p<0.05 in Student’s t-tests). The St. Stephen’s sample showed significantly greater mean values for every geometric property, as well as the IX/IY ratio. The Bab edh-Dhra’ sample showed a greater mean IMAX/IMIN ratio.
We would like to thank Dr. Damiano Marchi and Dr. Tracy Kivell for their advice and encouragement over the course of this project. This research was supported by the NSF-REU (SES 0649088), the Duke University Undergraduate Research Support Office, Trinity College Research Forum, Summer Research in Biological Anthropology at the University of Notre Dame Scholarship in the Liberal Arts, a Smithsonian Institution Pre-doctoral Fellowship, and a Sigma Xi Grant-in-Aid of Research. Thanks to Dr. Susan Guise Sheridan for use of the collection and laboratory as well as for her support and encouragement.
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1 Provided for free at: http://rsb.info.nih.gov/nih-image/
2 Available at: http://www.hopkinsmedicine.org/FAE/mmacro.htm
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Materials and Methods:
Due to the fragmentary nature of the two samples, the subtrochanteric region was the only location that could be sufficiently analyzed. This region is defined as 1-2 cm below the lesser trochanter (Trinkaus and Ruff 1999) and is shown in Figure 2.
Figure 2. Location of the Subtrochanteric Region of the Femur
(Indicated by the red transverse line)
Sample size equaled 42 adult femora in the Bab edh-Dhra’ sample and 57 adult femora in the St. Stephen’s sample.
All femora were physically cross-sectioned at the subtrochanteric region, and digital images were taken of the proximal femur cross-sections. Example images are shown in Figure 3.
Figure 3. Cross-sectional Images of Proximal Femora
Digital Images were imported into the ImageJ program1and analyzed using MomentMacro2. The computer program measured second moments of area about the x, y, maximum, and minimum axes. Size-standardization was accomplished by dividing geometric properties by an estimate of body mass based upon femoral head diameter.