Femoral shaft waist distribution and its relationship to behavioral reconstructions in fossil hominins
FRIEDL, L., SLÁDEK, V., HOLLIDAY, T. Femoral shaft waist distribution and its relationship to behavioral reconstructions in fossil hominins. Chicago, IL, USA, 2009.
|Anglický název:||Femoral shaft waist distribution and its relationship to behavioral reconstructions in fossil hominins|
|Autoři:||Mgr. Lukáš Friedl , Mgr. Vladimír Sládek Ph.D. , Trenton Holliday|
|Abstrakt EN:||Femoral midshaft is commonly used in biomechanical analyses for assessing behavior of fossil hominins. Besides midshaft’s practical advantages (its well-defined, accurate location across species, large available samples, limited impact of muscular structures), there is doubt as to how well it represents biomechanical phenomena. Here we examine the distribution of the femoral shaft waist (defined as the weakest point along the shaft and expressed as the %BML location with the smallest polar moment of area) relative to midshaft to address the question as to whether the midshaft reflects the same biomechanical phenomena in all specimens. Our sample consists of 53 recent humans of unknown sex and age. A-P and M-L diameters were measured on the left femoral shaft from 65% to 35% BML in 1% BML steps. Polar moment of area (J) was estimated following Pearson et al. (2006). The position of minimum value was then recorded. Results show that the level of femoral shaft waist is normally distributed (Shapiro-Wilk’s test, p=0.35) with mean, median, and mode located slightly proximal to midshaft. However, there is high variability in its location (SD=7.6), with midshaft ± 5% BML representing minimum J for only 51% of our sample. We found no relationship between waist location and factors of bone length and body size; however, we did find a positive relationship between minimum J and M-L diameter (r=0.68), suggesting that A-P diameter variability has less influence on waist location. We then employed a method we previously used (Sládek et al. 2008) to assess if such variability influences our ability to reconstruct midshaft J for incomplete femora. We find that J can be reliably calculated between 44% and 64% of BML assuming midshaft is its true value (the same range holds true for 53% BML level, which is the median and modal value in our sample).|