Sima de los Huesos hominins

The Sima de los Huesos hominins are a 430,000-year-old population of pre-Neanderthals from the archeological site of Atapuerca, Spain. They are in the "Neanderthal clade", but fall outside Homo neanderthalensis. When first reported in 1993, these 29 individuals were about 80 percent of the human fossil record of the Middle Pleistocene. Every bone is preserved, and the unprecedented completeness of the remains sheds light on Neanderthal evolution, the classification of contemporary fossils, and variations in a single Middle Pleistocene population. Exhumation of the Sima de los Huesos hominins began in the 1980s under the direction of Emiliano Aguirre and, later, Juan Luis Arsuaga, Eudald Carbonell, and José María Bermúdez de Castro.

They have a mosaic of "classic" Neanderthal traits (apomorphies) and more "archaic" traits (plesiomorphies). Like Neanderthals, the brow ridges are inflated; the skull is not as robust in the rear, however, and has a pointed "house-like" profile instead of a rounded "bomb-like" one. Brain volume averages 1,241 cc (75.7 cu in), on the lower end of the Neanderthal range. The teeth are Neanderthal-like, with shovel-shaped incisors and taurodontism, but differ in cusp morphology. The chest and waist are broad and robust like Neanderthals, but the limbs are longer. They may have been large-bodied overall, like other archaic humans, with a height of about 170 cm (5 ft 7 in) and a weight of 90 kg (200 lb) in both sexes.

The Sima de los Huesos (bone pit) is a chamber in the Cueva Mayor–Cueva Silo cave complex at Atapuerca, and may have been a natural trap for the cave bear Ursus deningeri in particular. The Sima de los Huesos hominins may have been deposited in the pit by other humans, based on the quality of preservation and the predominance of adolescents and young adults over children and the elderly. All were buried at about the same time, and one individual may have been killed with a blunt tool. Some with severe health issues survived for a while, suggesting group care. Many individuals (especially adolescents) exhibited metabolic and nutritional diseases consistent with insufficient fat reserves during hibernation; any hibernation presumably lasted for four months.

This population produced Acheulean stone tools, as well as an industry apparently transitioning to the typically-Neanderthal Mousterian culture. They used these tools in butchering and hide- and woodworking, with the mouth as a third hand. The Sima de los Huesos hominins were buried with a single, large Acheulean handaxe, possibly a grave good with symbolic significance. Symbolic thought could indicate use of an early form of language. They may have been efficient hunters — possibly outcompeting local cave hyenas — who pursued deer, rhinoceros, horses, bison, and (sporadically) cave lions in an open woodland environment. They probably ate roots regularly, habitually squatted, and did not use fire.