Ana Mateos

The first hominin of Europe

The earliest hominin occupation of Europe is one of the most debated topics in palaeoanthropology. However, the purportedly oldest of the Early Pleistocene sites in Eurasia lack precise age control and contain stone tools rather than human fossil remains. Here we report the discovery of a human mandible associated with an assemblage of Mode 1 lithic tools and faunal remains bearing traces of hominin processing, in stratigraphic level TE9 at the site of the Sima del Elefante, Atapuerca, Spain. Level TE9 has been dated to the Early Pleistocene (approximately 1.2–1.1 Myr), based on a combination of palaeomagnetism, cosmogenic nuclides and biostratigraphy. The Sima del Elefante site thus emerges as the oldest, most accurately dated record of human occupation in Europe, to our knowledge. The study of the human mandible suggests that the first settlement of Western Europe could be related to an early demographic expansion out of Africa. The new evidence, with previous findings in other Atapuerca sites (level TD6 from Gran Dolina), also suggests that a speciation event occurred in this extreme area of the Eurasian continent during the Early Pleistocene, initiating the hominin lineage represented by the TE9 and TD6 hominins.

Differences between Neandertal and modern human infant and child growth models

Studying the emergence of distinctive human growth patterns is essential to understanding the evolution of our species. The large number of Neandertal fossils makes this species the best candidate for a comparative study of growth patterns in archaic and modern humans. Here, Neandertal height growth during infancy and early childhood is described using a mathematical model. Height growth velocities for individuals five years old or younger are modelled as age functions based on different estimates of height and age for a set of ten Neandertal infants and children. The estimated heights of each Neandertal individual are compared with those of two modern human populations based on longitudinal and cross-sectional data. The model highlights differences in growth velocity during infancy (from the age of five months onward). We find that statural growth in Neandertal infants is much slower than that seen in modern humans, Neandertal growth is similar to modern humans at birth, but decreases around the third or fourth month. The markedly slower growth rates of Neandertal infants may be attributable to ontogenetic constraints or to metabolic stress, and contribute to short achieved adult stature relative to modern humans.

Neandertal growth: what are the costs?

Energetic approaches have been increasingly used to address key issues in Neandertal palaeoecology and palaeobiology. Previous research has focused exclusively on the energy requirements of adults and highlights the high energy demands of these individuals compared with modern humans. Less attention has been paid to the energy requirements of sub-adult Neandertals, even though this age group could provide clues for a better understanding of Neandertal life history. Accordingly, herein, we estimate the energy costs of maintenance and growth in Neandertal infants and children from one to six years of age and compare these costs with values for modern humans. Statural growth models for two modern human populations (Beasain and Evenki) and an average Neandertal model population are used to establish weight growth models. In turn, these models of body weight growth are used to estimate key components of energetic variables (basal metabolic rate, total energy expenditure, energy of growth and daily energy requirements). Between three and six years of age, Neandertal children have slightly lower basal and growth energy costs than do modern humans of the same age, due primarily to their smaller body mass and slower growth rates. The reduction in energy allocated to growth is likely the result of metabolic adaptations to other somatic factors and thermal stress. Data from contemporary human infants and children suggest that even mild cold stress increases non-shivering thermogenesis, thus elevating metabolic needs by 50% or more. These results suggest that thermal stress likely played a strong role in shaping the delayed developmental patterns and lower energy allocated to growth during early life in Neandertals relative to Homo sapiens.