Abstract:

Investigation into morphological traits of femoral shafts from Pleistocene Homo sapiens is pivotal to our understanding of human movement patterns and body size of the East Asia type. Despite the critical role these fossils play, their scarcity and uneven distribution in East Asia pose a formidable challenge to this study of morphological evolution. This paper integrates published anatomical data with a systematic examination of midshaft cross sections and overall morphological structure of Pleistocene human femoral shafts from East Asia. This study shows a consistent trend in morphological changes from the early to late Pleistocene, mirroring anatomical patterns observed globally. For instance, the mechanical shape index of the femoral shaft increases, and the cross-sectional shape transitions from anterior-posterior elongation to medial-lateral elongation suggesting an evolutionary adaptation to changes in pelvic and femoral structures. Early and middle Pleistocene femora exhibit robusticity akin to those remains from other regions likely indicative of a common hunting-gathering lifestyle.

However, into the Late Pleistocene East Asia femora display a suite of features that align with those of Late Pleistocene modern humans elsewhere, including a pronounced femoral pilaster and gluteal buttress, elongation of the midshaft cross section in an anterior-posterior direction, and a thickening of the posterior shaft wall from mid-distal to mid-proximal, enhancing anterior-posterior and lateral bending rigidity. Robusticity of East Asia femora is notably lower than that observed in Europe and west Asia. This discrepancy may be attributed to a variety of factors, such as differences in behavioral activities or body size. It is plausible that the disparity in robusticity reflects distinct evolutionary pressures and adaptive responses to specific environmental conditions and subsistence strategies prevalent in these regions. Implications of these findings extend beyond mere cataloging of morphological traits; instead they offer insights into complex interplay between genetic predispositions, environmental influences, and behavioral adaptations that have all sculpted human evolution. The study underscores the importance of regional variations in the evolutionary process and a need for a holistic approach to understanding human evolution that takes into account unique adaptations of human populations. In conclusion, the detailed analysis of Pleistocene human femora in East Asia enriches our understanding of human locomotory behavior and body size evolution as well as highlighting regional differences.

This research contributes to a more nuanced appreciation of the diverse evolutionary pathways that have shaped anatomical and physiological characteristics of modern humans. The study encourages further exploration into morphological adaptations that have emerged in response to specific environmental and behavioral challenges faced by human populations.

Key words: East Asia, Pleistocene human, Femora evolution trends, activity levels, body size variation