First description of the Cro-Magnon 1 endocast and study of brain variation and evolution in anatomically modern Homo sapiens Première description de l'endocrâne de Cro-Magnon 1 et étude de la variation et de l'évolution du cerveau chez les Hommes anatomiquement modernes

Paleoneurology is an important research field for studies of human evolution. Variations in the size and shape of the endocranium are a useful means of distin- guishing between different hominin species, while brain asymmetry is related to behaviour and cognitive capaci- ties. The evolution of the hominin brain is well documen- ted and substantial literature has been produced on this topic, mostly from studies of endocranial casts, or endo- casts. However, we have only little information about var- iations in endocranial form, size and shape in fossil anatomically modern Homo sapiens (AMH) and about the evolution of the brain since the emergence of our spe- cies. One good illustration of this limited knowledge is that one of the first fossil H. sapiens discovered, in 1868, that is also one of the oldest well-preserved Euro- pean specimen has never been studied in what concerns its endocranial morphology. The first aim of this study was to propose a detailed description of the endocranial anatomy of Cro-Magnon 1, using imaging methodologies, includ- ing an original methodology to quantify endocranial asymmetries. The second aim was to compare samples of the fossil and extant AMH in order to document differ- ences in the form, size and shape of the endocasts. A decrease in absolute endocranial size since the Upper Palaeolithic was noticeable. Although both extant and older endocrania have the same anatomical layout, we nonetheless found non-allometric differences in the rela- tive size and organization of different parts of the brain. These document previously unknown intraspecific ana- tomical variations in the H. sapiens brain, demonstrating its plasticity, with some areas (frontal and occipital lobes) having been more subject to variation than others (parie- tal, temporal or cerebellar lobes). That may be due to constraints to maintain an optimal performance while reducing in size and changing in shape during our recent evolution.