Bioenergetic perspectives on Neanderthal thermoregulatory and activity budgets

The study of adaptation in Neanderthals is confounded by equifinality – the existence of multiple adaptive pathways to the same morphological end state – manifest as an inability to discriminate between equally likely selective agents behind a given trait. The capacious chests of Neanderthals serve as one example, possibly representing an adaptation either to cold or to high activity levels. While single features may be adaptive in multiple contexts, their relative adaptive value may vary greatly between contexts. Without means of evaluating competing adaptive arguments, we have little hope of identifying the primary selective agents that operated on Neanderthal body form. Bioenergetics provides a basis for quantifying the costs and benefits of various adaptive solutions to a given environmental challenge – thus providing potential for resolving issues of equifinality. Evaluating claims of cold-adapted morphology in Neanderthals involves determining the energetic costs of adhering to Bergmann's and Allen's rules. Skin surface area (SA) is the major determinant of basal metabolic rate (BMR) in mammals, thus estimating Neanderthal SA allows an estimate of the caloric cost of their coldadapted body form. Clinical equations exist for estimating SA from stature and mass, but these have never been tested on humans of extreme (i.e., “hyper-arctic”) body form. A half-size reconstruction of a male European Neanderthal was used to test the utility of these formulae: results indicate that they can be used confidently to predict Neanderthal SA. Based on Neanderthals for whom mass and stature can be reasonably estimated, mean SA is greater than that of Inuit of comparable stature, and suggests higher BMRs in Neanderthals than reported in previous studies.

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