Exploring the morphology of adult tibia and fibula from Sima de los Huesos site in sierra de Atapuerca, Burgos, Spain

Abstract

The analysis of the locomotor anatomy of Late Pleistocene Homo has largely focused on changes in proximal femur and pelvic morphologies, with much attention centered on the emergence of modern humans. Although much of the focus has been on changes in the proximal femur, some research has also been conducted on tibiae and, to a lesser extent, fibulae. With this in mind, we present one of the largest samples of the same population of human tibiae and fibulae from the Middle Pleistocene to determine their main characteristic traits and establish similarities and differences, primarily with those of Neanderthals and modern humans, but also with other Middle Pleistocene specimens in the fossil record. Through this study, we established that the Middle Pleistocene population from the Sima de los Huesos (Atapuerca, Burgos, Spain) had lower leg long bones similar to those of Neanderthals, although there were some important differences, such as bone length, which this fossil individuals resembled those of modern humans and not to Neanderthals. This fact is related to the crural index and leg length, even though we do not have any true association between femora and tibiae yet, it has implications for establishing locomotor efficiency and climate adaptation.

Tarsals from the Sima de los Huesos Middle Pleistocene site (Atapuerca, Burgos, Spain)

“…The study of tarsals carried out here also found similar traits in SH relative to Neandertals that differentiate both populations from recent H. sapiens. This confirms the evolutionary relationship between these two paleodemes as evolutionary sister groups as previously established by other anatomical regions (Arsuaga et al, 2014(Arsuaga et al, , 2015Rodríguez et al, 2024a). This similarity in postcranial anatomical traits between SH and Neandertals is likely related to a high degree of biomechanical stress, and to the greater general robustness of the postcranial skeleton.…”

“…The studies of the postcranial skeleton of the SH hominins have allowed to establish some traits similar among this Middle Pleistocene population and Neandertals (Arsuaga et al, 2015;Carretero et al, 1997;García-Gonz alez et al, 2024;Pablos et al, 2017;Rodríguez et al, 2024a). The study of tarsals carried out here also found similar traits in SH relative to Neandertals that differentiate both populations from recent H. sapiens.…”

“…See Table 11 for details about the identification. García-Gonz alez et al, 2024;G omez-Olivencia et al, 2007;Pablos & Arsuaga, 2024;Rodríguez et al, 2024aRodríguez et al, , 2024b.…”

Metatarsals and foot phalanges from the Sima de los Huesos Middle Pleistocene site (Atapuerca, Burgos, Spain)

“…Without a doubt, the SH population exhibits high robusticity in the postcranial skeleton in general (Arsuaga et al, 1999(Arsuaga et al, , 2015G omez-Olivencia et al, 2007;Bonmatí et al, 2010;Pablos et al, 2017;Carretero et al, 201., 2024a;García-Gonz alez et al, 2024;Rodríguez et al, 2024a), and in the metatarsal and pedal phalanges in particular. This concurs with the previously proposed large corporal size for the SH population and its primitive biotype (Arsuaga, 2010;Carretero et al, 2004).…”

“…This likely denotes the high robusticity of this Middle Pleistocene population, that is, for the same stature, the bodies are broader than current and fossil modern humans. This "wide Homo" bauplan consisting of a large thorax with broad shoulders and pelvises, and great musculature and body mass probably derives from earlier populations such as Homo ergaster/antecessor from which Homo sapiens departed (Arsuaga, 2010;Arsuaga et al, 2015;Carretero et al, 1999Carretero et al, , 2004Carretero, Rodríguez, et al, 2024b;García-Gonz alez et al, 2009;Lorenzo et al, 2015;Pablos et al, 2012;Rodríguez et al, 2024a).…”