Abstract

Rest in poikilothermic animals is an adaptation of the organism to adjust to the geophysical cycles, a doubtless valuable function for all animals. In this review, we argue that the function of steep could be trivial. for mammals and birds because steep does, not provide additional advantages over simple rest. This conclusion can be reached by using the null hypothesis and parsimony arguments. First, we develop some theoretical and empirical considerations supporting the absence of specific effects after steep deprivation. Then, we question the adaptive value of steep traits by using non-coding DNA as a metaphor that shows that the complexity in the design is not a definitive proof of adaptation. We then propose that few, if any, phenotypic selectable traits do exist in steep. Instead, the selection of efficient waking has been the major determinant of the most significant aspects in steep structure. In addition, we suggest that the regulation of steep is only a mechanism to enforce rest, a state that was challenged after the development of homeothermy. As a general conclusion, there is no direct answer to the problem of why we steep; only an explanation of why such a complex set of mechanisms is used to perform what seems to be a simple function. This explanation should be reached by following the evolution of wakefulness rather than that of steep. Steep could have additional functions secondarily added to the trivial. one, although, in this case, the necessity and sufficiency of these steep functions should be demonstrated. (c) 2007 Elsevier Ltd. All rights reserved.