1. Alexandra J. Zachwieja, Laura L. Shackelford Department of Anthropology, College of Liberal Arts and Sciences, University of Illinois at Urbana-Champaign Post-Pleistocene gracilization and the effects of terrain on the lower limbs of modern humans References Holt B. 2003. Am J Phys Anthropol 122:200-215. Marchi D. 2008. Am J Phys Anthropol 137:188-200. Marchi D, Sparacello V, Shaw C. 2011. In Pinhasi R, Stock JT, eds. Human Bioarchaeology of the Transition to Agriculture. New York: John Wiley & Sons. Pp. 317- 346. Ruff CB. 2008. In Katzenberg MA, Saunders SR, eds. Biological Anthropology of the Human Skeleton, 2 nd ed. New York: John Wiley & Sons. Pp. 183-206. Ruff CB, Trinkaus E, Walker A, Larsen CS. 1993. Am J Phys Anthropol 91:21-54. Conclusions Trend of decreased robusticity throughout time in African samples, yet East Asian Holocene samples show greater CSG values than LUP samples Differences between Andaman Islanders and Japanese/Vietnamese samples suggest that lower limb robusticity can increase as a result of activities on mountainous terrain Suggests that current paradigm of reduced post-Pleistocene robusticity may reflect sampling bias rather than a biological trend Because EUP data is of European origin, results may differ when compared to in situ regional EUP populations Future studies will expand these results by preforming separate male and female analyses, assessing the affect of elevation on robusticity, and by addressing the heritable nature of CSG data Materials 440 modern humans from the Early Upper Paleolithic (EUP; N=24), Late Upper Paleolithic (LUP; N=111) and Holocene (N=305) from regions shown in Fig. 1 Males and females combined for analyses Methods Cross-sectional geometric (CSG) properties of midshaft femur & tibia Polar moment of area (J): torsional strength & (twice) avg. bending rigidity Second moments of area: maximum (I max ) & minimum (I min ) bending rigidity Diaphyseal shape ratios (I max /I min ) J, I standardized by body mass x bone length 2 ANOVAs with post-hoc comparisons (Tukey HSD) to evaluate differences between time periods (EUP-LUP-Holocene) All geographic regions combined By region; same EUP sample for all regions due to lack of EUP fossil data for non-European areas Introduction In modern humans, lower limb robusticity decreases through the Pleistocene and Holocene, particularly in an anteroposterior (AP) direction (Holt, 2003) Related to subsistence changes and technology that reduced the human work load (Ruff, 2008; Ruff et al., 1993) Italian Neolithic samples (19-4 ka) deviate from this trend, with robusticity similar to earlier, highly mobile populations (Marchi, 2008; Marchi et al., 2011) Related to intensive subsistence activities combined with rugged terrain The current analysis evaluates diachronic changes in lower limb cortical bone in a large geographic sample to: 1.Determine if there was a post-Pleistocene decline in robusticity 2.Evaluate the consistency of this decline across geographic regions 3.Determine how terrain may have affected robusticity Results Few differences through time in strength measures of femoral or tibial midshaft when samples are not separated by region Evaluated by geographic region, few clear trends in CSG properties over time North Africa and Nile Valley samples have no decrease in robusticity in the LUP relative to available EUP samples North Africa and Nile Valley samples show only a slight decrease in Holocene samples Holocene Asian samples show trends similar to Italian Neolithics (Marchi, 2008; Marchi et. al, 2011) East Asian LUP samples are significantly more gracile than Holocene samples East Asian Holocene samples show J- and I-values more similar to available EUP samples than to Asian LUP samples Acknowledgments Thank you to J.T. Stock and C.B. Ruff for contributing data to this project on the Andaman Islanders and East Africans, respectively. EUPLUPHoloceneEUP-LUP 1 EUP-Holo 1 LUP-Holo 1 Femoral 50% J 435.1±29.2 20 472.1±14.8 78 451.7±8.5 235 -7.84-3.684.52 Femoral 50% I max 263.8±17.7 20 282.5±9.0 78 258.6±5.2 235 -6.622.019.24 Femoral 50% I min 171.2±12.7 20 189.6±6.4 78 192.4±3.7 235 -9.70-11.1-1.46 Femoral 50% I max /I min 1.56±0.06 21 1.48±0.03 102 1.38±0.02 267 5.4113.0*7.25* Tibial 50% J 484.5±38.0 12 494.7±17.0 60 440.1±8.9 220 -2.0610.112.4* Tibial 50% I max 350.3±34.9 12 315.0±15.6 60 266.6±8.2 220 11.231.418.2* Tibial 50% I min 134.5±26.9 12 179.8±12.0 60 173.5±6.3 220 -25.2-22.53.63 Tibial 50% I max /I min 2.64±0.28 12 2.13±0.12 68 2.03±0.06 247 23.930.04.93 Fig. 1. Distribution of fossil samples. Table 1. Summary statistics by time period given as mean ± s.e., n. 1 Percent difference given as [(group 1-group2)/group2]*100. * Indicates significant differences between samples after multiple-comparison corrections. Fig. 2. Differences in CSG properties by time period for REGIONAL SAMPLES. * of same color indicates significant differences between samples at α=0.05 and error bars indicate values one standard error away from the mean values * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *