Uncovering the adult morphology of the forearm bones from the Sima de los Huesos Site in Atapuerca (Spain), with comments on biomechanical features

Abstract

The forearm skeleton is composed of two bones: the radius and the ulna. This is closely related to manipulative movements. The ulna is part of the elbow joint, whereas the radius and ulna together with the scaphoid and lunate bones, form the wrist joints. Thus, morphofunctional analysis of the adult Sima de los Huesos (SH) forearm bones, provides clues about manipulative activities in one Pleistocene population. From 1976 to the present, over 7000 human fossils have been recovered from the SH site. The radial sample comprised 98 labeled fragments, of which 49 belonged to adult individuals, representing at least 7 individuals. The ulnar sample included 31 labeled adult fossils representing at least nine individuals. In this study, we describe the SH radii and ulnae and analyze their functional implications for manipulative and forearm movements. We confirmed that the SH radii are long and curved, with variations in robusticity and radial tuberosity orientation. The SH ulnae are characterized by an anteriorly oriented trochlear notch, a massive olecranon process, an obliquely oriented radial notch, a blunt and short supinator crest, a gracile and curved diaphysis, and a round and anteriorly oriented pronator crests. In general, they exhibit Neanderthal morphology. The SH collection provides a unique opportunity to conduct morphological analyses of these bones in the Middle Pleistocene population.

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

“…The body mass index for the tarso-metatarsal skeleton of foot 1 and foot 2 calculated here as the body mass (in kg) divided by height squared (in m) is 27.74 which could suggests some overweight according to the International Obesity Task Force (Cole & Lobstein, 2012). This fact suggests that the musculature of this individual, and that from all the individuals from SH, is higher to that observed in recent modern humans because the corporal cylinder is broader than in recent populations (Arsuaga et al, 1999;Carretero et al, 2018;Carretero, Rodríguez, et al, 2024b;García-Gonz alez et al, 2024;G omez-Olivencia et al, 2010;Rodríguez et al, 2016Rodríguez et al, , 2018Rodríguez et al, , 2024b. 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.…”

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

“…SH, Sima de los Huesos. Carretero et al, 2018;García-Gonz alez et al, 2024;G omez-Olivencia et al, 2010;Rodríguez et al, 2018Rodríguez et al, , 2016Rodríguez et al, , 2024b. This individual denotes the high robusticity of the SH Middle Pleistocene population, that is, for the same stature, the bodies are broader than those of modern and fossil 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.…”

How the Sima de los Huesos was won

“…The narrow body of H. sapiens would be a peculiarity developed exclusively by our species. One of the most notable aspects of the collection of human fossils recovered in the Sima de los Huesos until 1997 was the large number of remains corresponding to the limb skeleton , Carretero, Rodríguez, et al, 2024bGarcía-Gonz alez et al, 2024, this volume;Rodríguez et al, 2024aRodríguez et al, , 2024b. The fossil record of human evolution is rich in teeth, jaws and crania, but relatively poor in the rest of the bones of the skeleton, especially in the fossil record of the genus Homo prior to the Neanderthals.…”