Brain shape and thermoregulation: a quantitative approach

Brain thermoregulation is a debated topic in human physiology and evolution. Despite the high energy loadings associated with brain metabolism in humans, specific thermoregulatory mechanisms are unknown. Paleoneurological evidence based onto fossil record cannot give direct information on metabolism. However, correlations between thermoregulation and brain morphology can provide partial indications on this issue. Heat dissipation depends upon many factors, including geometry. Therefore, investigating the relationship between brain shape and heat dissipation patterns can supply indirect information on brain evolution in hominids. Here we present a computational approach to describe the patterns of heat dissipation in endocranial casts, providing tools to quantify species-specific differences. As case-study, we used samples from humans and chimpanzees, supplying results from intra-specific and inter-specific variation. Numerical modelling and thermic maps are used to describe the values of heat dissipation on the endocranial maps, and methods of comparison of the differences are evaluated accordingly. Absolute and relative variations are considered in terms of value distribution and residuals from expected models. The results show that this approach is effective in evidencing local and general differences between the species-specific heat dissipation patterns, providing a quantitative tool for investigating possible relationships between brain morphology and heat management in paleoneurology.

Keywords: brain metabolism, heat dissipation, paleoneurology

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