Late Pleistocene modern human (LPMH) femora from Europe and West Asia exhibit distinctive morphological and cross-sectional geometric features that distinguish them from archaic Homo and recent modern humans (McCown and Keith, 1939; Trinkaus, 1976, 1984, 2005a, 2006; Kennedy, 1984; Ruff et al., 1993, 2015a; Trinkaus and Ruff, 1999, 2012; Holt, 2003; Shackelford, 2007; Wei et al., 2017). Specifically, these femora often exhibit 1) a variably developed pilaster, i.e., the prominent crest of bone running along the posterior midshaft, separated from the medial and lateral shaft by flat or concave surfaces and supporting the linea aspera. The pilaster is positioned in the mid-proximal to mid-distal posterior surface of the diaphyseal region (Trinkaus, 2005b). This feature may relate to the increased anteroposterior/mediolateral diaphyseal strength at the midshaft and an anteroposteriorly elongated or mediolaterally narrowed oval shape of midshaft cross sections (Trinkaus, 2005b; Xing et al., 2021) and 2) a prominent gluteal buttress (McCown and Keith, 1939; Trinkaus, 2005a, 2005b, 2006; Wei et al., 2021a). These distinctive features are absent in archaic Homo and modern humans, thus providing valuable insights into the evolutionary changes in locomotor behavior and body shape during the Late Pleistocene (Carlson and Marchi, 2014; Ruff et al., 2022).

Compared to the extensive investigations conducted on LPMH femora from Europe (Shackelford and Trinkaus, 2002; Shackelford, 2007; Trinkaus and Ruff, 2012; Ruff et al., 2015a), our current knowledge of femoral morphology in mainland East Asia remains limited. Two femora from Tianyuan Cave in northern China dated to 39–42 ka cal BP display typical characteristics observed in other LPMHs from Europe, including prominent pilasters, distinct gluteal buttresses, and the absence of a medial buttress (Shang and Trinkaus, 2010; Wei et al., 2017). Another assemblage of femoral material dating from a similar period (Li et al., 2018) was discovered at the Upper Cave of Zhoukoudian in northern China. These femora are characterized by a well-developed pilaster and an anteroposteriorly elongated oval shape at the midshaft cross section, aligning them with the femoral morphology of modern humans (Trinkaus and Ruff, 2012; Xing et al., 2021). Unfortunately, the material from the Upper Cave was lost during World War II, and no detailed studies have been conducted beyond the original morphological descriptions by Weidenreich (1941) and the quantification of the perimeter contour using the remaining casts (Ruff et al., 2022). By contrast, the Late Pleistocene Maomaodong femora (14.5 ± 12 ka cal BP) from southern China exhibit typical early modern human features, including a prominent linea aspera, a well-developed pilaster, and a mediolaterally narrow midshaft cross section (Wei et al., 2021a). A recent analysis of the Late Pleistocene Maludong femur from southern China, dated to 14 ka cal BP, revealed that it exhibits internal femoral morphology consistent with that of derived modern humans (Wei et al., 2022). Specifically, the Maludong femur displays an anteroposteriorly elongated oval shape and an increase in the anteroposterior/mediolateral diaphyseal strength of the cross section just proximal to the midshaft (Wei et al., 2022). Further research is warranted to investigate the morphological variation in LPMHs from the East Asian mainland as these previous studies have been limited in scope.

Here, we present a comprehensive morphological description and a comparative analysis of two partial femora discovered from the Tongtianyan Cave in Liujiang city, southern China. These femora were originally excavated in 1958 alongside a complete cranium, 10 vertebrae, and a right os coxae, all of which belonged to the same individual (Wu, 1959; Liu et al., 2014). The individual has been identified as a ∼40-year-old male, with a height of 161 cm and weight of 50.9 kg (Wu, 1959, 1997; Wu et al., 1984; Rosenberg, 2002; Liu et al., 2010; Ruff et al., 2018, 2022). The body weight of the Liujiang individual was estimated using femoral head superoinferior breadth and the equation described in Ruff et al. (2018). Previous investigations of the cranium have revealed several modern human-like features, including a flat face, rectangular orbit, round brain, enlarged cranial volume, high vault, and an overall cranial shape resembling Cro-Magnon 1 (Wu, 1959; Liu and Zeng, 1996; Cui, 2014). In contrast to the extensive studies conducted on the Liujiang cranium, the initial report only provided a preliminary description of the preservation of the femora and length measurements (Wu, 1959). In a recent study by Xing et al. (2021) on the Huanglongdong femora, the cross-sectional geometry and contour shapes of midshaft and subtrochanteric cross sections of the Liujiang femora were included for comparative purposes. However, the study by Xing et al. (2021) did not include a description of the surface features of the Liujiang femora. Additionally, as the Liujiang femora were used only for purposes of comparison, length estimation, standard orientation, and detailed comparisons for these femora were not provided (Xing et al., 2021).

The flowstone and mammalian remains found in the Tongtianyan Cave have been dated using uranium-series (U-series) and accelerator mass spectrometry 14C methods. However, these investigations have produced conflicting results, with chronological age estimates ranging from older than ∼67 ka (Yuan et al., 1986) to 111–139 ka (Shen et al., 2002) or even 153–280 ka (Wang et al., 2004). The relationship between the flowstone and the Liujiang human remains uncertain. Nevertheless, the presence of modern human–like features in the Liujiang individual (see above; Wu, 1959; Rosenberg, 2002; Liu et al., 2010) implies a LPMH dating of around 67 ka.

In this study, our objective is to enhance our understanding of the femoral anatomy of LPMHs from the East Asian mainland by conducting a detailed reanalysis of the partial femora from Liujiang. We aim to provide a comprehensive interpretation of the morphology of the Liujiang femora by thoroughly examining their surface features, estimating their length, and conducting a comprehensive analysis of their cross-sectional geometric properties along the entire diaphysis. By contextualizing the Liujiang femora within the broader spectrum of intragroup and intergroup femoral variation among other Eurasian and African Pleistocene hominins, we contribute valuable insights to the taxonomic attribution and behavioral analysis of the Liujiang hominin.