Mobility is related to subsistence strategy (i.e., habitual activities) and other fundamental cultural aspects in extant and past human populations (e.g., Kelly, 1992; Ruff et al., 2015; Grove, 2016, 2018), as well as to various morphological and physiological characteristics (Bramble and Lieberman, 2004; Raichlen and Gordon, 2011; Raichlen et al., 2012; Raichlen and Polk, 2013; Albuquerque et al., 2015; Wallace and Garland, 2016). The ability to exploit a territory is a strong marker of the adaptation of human societies to their environment. This ability depends on both internal and external factors (e.g., Nathan et al., 2008; Kuhn et al., 2016), such as cognitive abilities, knowledge transfer, technology, population density, and physiological adaptation (inherited or not), as well as environmental factors such as climatic and topographic constraints. The way in which habitual activities are shared within human groups reflects social organization and cooperation (including mutual assistance). Here, from the study of the middle Upper Paleolithic (MUP) female skeleton from Caviglione, we investigated some of these critical aspects of human behavior by focusing on gender-specific mobility, territory occupation, and the functional adaptation of humans with traumas.

The well-preserved Caviglione 1 skeleton from Liguria, Italy, belongs to the richly documented Italian Upper Paleolithic (UP) burials, which represent a major part of the European UP sample (Fabbri and Giacobini, 2021). In 1872, Rivière discovered this skeleton in the Caviglione cave, one of the Grimaldi caves that are all located within the same cliff (Rivière, 1872a, 1872b; Hurel, 2016). The cliff is known by different names depending on the language or patois used, such as Baousse Rousse or Balzi Rossi (de Lumley, 2016a). This skeleton has been recently reassessed in a monograph (de Lumley, 2016b), with a focus on the cranial and postcranial anatomy (Chevalier and Stalens, 2016; Chevalier et al., 2016; Guipert et al., 2016a, 2016b; Voisin and Stalens, 2016a, 2016b), body size (Chevalier, 2016), and trauma (Mafart et al., 2016). The female attribution (Mallegni, 1995 from G. Giacobini personal communication, contra Verneau, 1906) was confirmed (Bruzek et al., 2016), and the Gravettian burial was dated to approximately 24 000 cal BP from the Cyclope neritea shells of its headdress (Valladas et al., 2016). The biological age of Caviglione 1 was between 30 and 47 years from the study of the cranial suture closure and dental wear (de Lumley et al., 2016). Additionally, Chevalier (2019) revealed the residual effects of trauma on the biomechanical properties of the upper limb bones and proposed a new etiological interpretation from microtomographic analysis. Caviglione 1 suffered a left radius fracture, defined as a Galeazzi fracture, probably from a fall (Chevalier, 2019). Although the fracture had healed, the distal part of the radius was not aligned with the more proximal part. In addition, the humerus showed bone structure changes caused by an unidentified severe trauma to the right shoulder, which forced Caviglione 1 to become left-handed (Chevalier, 2019). However, biomechanical investigation of the lower limb bones is also required to determine the lifestyle and living conditions of Caviglione 1 by determining her mobility pattern and to discuss the potential impact of the trauma on locomotion. The cross-sectional geometric (CSG) properties of UP human lower limbs and their dependence on mobility are well established and highlight the high level of mobility of the UP population (Holt, 2003; Ruff et al., 2006a, 2015; Ruff, 2018; Sparacello et al., 2018a). This background provides an appropriate framework to examine whether Caviglione 1 displays the expected bone structure characteristics and mobility pattern in the UP context, which is predominantly composed of males with rare females (see Supplementary Online Material [SOM] Tables S1–S5). For example, the femoral MUP sample (the largest sample considering bone type) included 16 males and 4 females. As a result, the MUP mobility pattern reflects preferentially that of males.

The European UP population underwent a marked change in mobility following the Last Glacial Maximum (20 ka; Holt, 2003; Shackelford, 2007). Climatic shifts toward colder temperatures greatly impacted the subsistence behavior of UP human populations and reduced mobility. The human population in the Early Upper Paleolithic (EUP; 40–20 ka) was highly mobile and mobile to a greater extent than that in the Late Upper Paleolithic (LUP; 20–10 ka). Mobility in the UP and Holocene has been extensively explored from assessments of the lower limb, including diaphyseal long bone shape (i.e., relative bending strength) and robusticity (i.e., bone strength relative to body size; see Ruff and Larsen, 2014; Holt et al., 2018a, for a synthetic view). A decrease in midshaft cross-sectional femoral strength and an increase in circularity indicate a decrease in mobility; these bone structure changes were observed from the EUP to LUP and Mesolithic in European populations (Holt, 2003) and from the EUP to LUP in European, Asian, and African populations (Shackleford, 2007). By collecting a large European sample of modern humans in the context of major economic and social changes, Ruff et al. (2015) and Holt et al. (2018a) highlighted a significant decline in the femoral and tibial strength and shape ratio from the hunter–gatherers of the UP and Mesolithic to the more sedentary Holocene populations. These authors confirmed the decline in lower limb bone strength over time (Ruff et al., 1993, 2006b; Holt, 1999, 2003; Ruff, 2005), persisting through the Iron/Roman period (ca. 2000 years). The adoption of food production during the Neolithic was probably a driving force behind the decrease in mobility, leading to the major bone structure changes (Ruff et al., 2015). However, not all bones and biomechanical parameters show the same pattern of changes over time, and the change has not been linear (Holt et al., 2018a). Recently, Sparacello et al. (2018a) explored changes in the mobility pattern derived from lower limb characteristics during the Pleistocene–Holocene transition, based on European (and specifically Ligurian) samples as well as modern athletes. The European sample exhibited no differences in the tibiofibular complex, an indicator of mobility (Shaw and Stock, 2009a; Rantalainen et al., 2010; Marchi and Shaw, 2011; Sparacello et al., 2018a) between the MUP (30–20 ka) and LUP (20–10 ka). Specifically, both groups exhibited a high mobility level. The multifactorial analyses indicated that neither group exhibited biomechanical characteristics similar to those of field hockey players or runners despite the supposedly more intensive exploitation of mountainous terrain by LUP individuals (requiring extensive foot eversion/inversion, as in field hockey players) and level terrain (the plain) by MUP individuals (requiring little foot eversion/inversion, as in runners). Most individuals in both groups were classified as modern runners. Within the Ligurian sample, found in a mountainous setting, the mobility patterns of the LUP and MUP groups were similar; however, a larger sample size is necessary for more robust interpretation (Sparacello et al., 2018a). To date, the well-preserved Ligurian skeleton of Caviglione 1 has not been included in such a study.

Many factors, including physical behavior, can affect lower limb bone structure (e.g., Sparacello and Marchi, 2008; Pearson et al., 2014; Holt et al., 2018a). While mobility plays a major role in bone modeling, the unevenness of the terrain (Sparacello and Marchi, 2008; Holt and Whittey, 2019), variations in body size and body shape (Ruff, 2000; Shaw and Stock, 2011; Pearson et al., 2014), workload (Holt et al., 2018a), genetic and hormonal factors, and the influence of aging (Lovejoy et al., 2003; Pearson and Lieberman, 2004) might play a crucial role in bone adaptation during an individual's lifespan. Additionally, bone properties may be differentially influenced by changes in lifestyle; for example, femoral robusticity and shape are differently affected by changes in the level of mobility (Sparacello and Marchi, 2008). Moreover, the same structural properties may provide distinct functional interpretations in lower limb bones. Sparacello et al. (2018a) underlined the lack of significant differences between the tibial shape ratio in EUP and LUP individuals, which contrasts with the results of the femur shape ratio (see Holt, 2003). These results suggest that a combination of variables and bones is conductive to a thorough interpretation of UP human mobility based on lower limb analysis.

Most studies on human mobility in the UP and Holocene (e.g., Holt, 2003; Shackelford, 2007; Ruff et al., 2015; Sparacello et al., 2018a; Holt et al., 2018a, 2018b) have used the cross-sectional properties of weight-bearing long bones (the femur and tibia); the fibula, considered a non- or poor-weight-bearing bone (Takabe et al., 1984; McNeil et al., 2009), is rarely included (Marchi et al., 2011; Sparacello et al., 2014, 2018a). The biomechanical properties of MUP fibulas are presented only in Sparacello et al. (2018a), in which all individuals are male (Barma Grande 2, 5 and 6; Bausso da Torre 1 and 2). Moreover, the CSG properties of UP metatarsals have not yet been studied. Nevertheless, the involvement of these bones in walking should prompt their inclusion in mobility studies. Both bones (the fibula and first metatarsal) respond to distinct mechanical loads during locomotion; therefore, they merit consideration when predicting mobility. The fibula is exposed to different mechanical stresses generated by various foot movements. Foot eversion/inversion occurs during frequent directional changes and when crossing uneven terrain (e.g., mountains); in field hockey players (Marchi and Shaw, 2011) and some Paleolithic and Neolithic groups (Marchi et al., 2011; Sparacello et al., 2014, 2018a), these movements alter the biomechanical properties of the fibula (i.e., reinforce the fibula). Additionally, the first ray of the foot is a fundamental structure of the forefoot (Morton, 1935; Christensen and Jennings, 2009; Hansen, 2009). The first metatarsal in humans experiences high pressure during the push-off phase of bipedal walking, acting as a fulcrum for propulsion. The human foot exhibits high metatarsophalangeal joint angles (mean = 48°) during the stance phase of bipedal walking (Fernández et al., 2016), during which the head of the first metatarsal is directly (or indirectly, through a shoe) in contact with the ground and the metatarsal is subvertical to the ground. The ground reaction force at the metatarsal head produces significant diaphysis stresses that may generate functional adaptation. Indeed, Griffin and Richmond (2005) noted that CSG properties properly reflect the level of pressure experienced by the first metatarsal in the majority of activities. Macintosh and Stock (2019) highlighted the specific diaphyseal shape of the first metatarsal due to running activities, characterized by repetitive low-impact loading. However, the other biomechanical parameters assessed from this foot bone showed no significant differences between runners, soccer players, rowers, and nonathletic individuals.

The comparative analysis of the MUP Caviglione 1 was not previously performed in UP CSG studies (see Holt, 2003; Shackelford, 2007; Ruff et al., 2015; Sparacello et al., 2018a; Holt et al., 2018a, 2018b). Our aim is to determine whether the biomechanical properties of the lower limb of Caviglione 1 (female with bone trauma) are consistent with previous UP cross-sectional results. Specifically, we investigate (1) whether this female exhibited the same high level of mobility as males, which comprise the majority of the UP sample; (2) whether she exhibited bone structure adaptations (i.e., bone modeling) to a mountainous environment during its lifespan (the past environment, including a large coastal plain in front of the Baousse Rousse cliff, differs from the present environment; de Lumley, 2016a); and (3) whether Caviglione 1's upper limb bone pathologies impacted lower limb bone structure and mobility. This is the first UP study to include the CSG properties of the femur, tibia, fibula, and first metatarsal, i.e., four bones experiencing distinct mechanical loads, to investigate mobility (Fig. 1).

If Caviglione 1 exhibits an overall structural pattern highly similar to other UP individuals, especially Ligurian UP individuals, we could deduce that sex and upper limb trauma are not limiting factors for high levels of mobility, or at least that we have no proof of the impact of trauma on mobility, and that locomotor behavior included the ability to cross in mountainous terrain. This structural pattern should include high femoral and tibial robusticity and shape indices compared to those of sedentary groups and high relative fibular robusticity, as observed in extinct human groups living in mountainous regions.