CAA Conference

The endocraneal volume has been considered as a key feature in hominin evolution and more specifically in Homo evolution. As a general rule, the brain size has experienced a considerable increase from H. habilis to anatomically modern humans (AMH). Nevertheless, traditionally, it has been considered that the biggest brain belonged to the Neanderthal. In order to explain such difference in size, several factors have been invoked, but the most recurrent has been Bergmann's ecogeographic rule. It predicts that individuals of bigger size will be found at larger distances from the Equator.This paper has two aims: 1) to evaluate if the Neanderthal's endocraneal volume is significantly bigger than that of AMH; 2) to test if the differences in body mass (BM) and endocraneal volume (EV) are related to latitude (LAT) and/or time (TIME). For the first aim, we have used ANOVA test (post hoc Bonferroni) and Lubischew's test, a test generated to evaluate overlapping); and for the second one, we have analyzed the relation between body mass (BM), EV and encephalization quotient (EQ) as dependent variables, with LAT and TIME as independent variables, by the means of both, correlation and regression analyses. On the other hand, we have carried out a visual assessment, by the use of GIS, of the endocraneal volume's values, once the diffusion of the sample's distribution has been analyzed (Tukey's hinge). The results of this study show that Neanderthal and AMH have a brain size that makes them indistinguishable from a statistical point of view and also that the overlapping between both samples is very high (45.22%). On the other hand, Neanderthal has provided two statistically significant relationships: EV on TIME and BM on TIME. Meanwhile, AMH has supplied only one with a slope statistically different from zero: that between BM and LAT. Finally, the regression analyses between EV on TIME (Neanderthal) has given a very low slope value (b = -2.351; P < 0.001) and BM on TIME (Neanderthal) closer to zero (b = -0.126; P < 0.002). From these results we can draw the next conclusions. AMH seems to fit in the ecogeographic assumptions while Neanderthal's variability seems to respond rather to a temporal pattern. This means that the most recent neanderthals hold bigger brain and body sizes. Nevertheless, it is relevant to point out that the brain size maintains a slower pace than the body size. This fact can be related to an evolutionary constrain for increasing the brain size in spite of increasing the whole body mass.