Physiologic time: A hypothesis

•We present a scaling hypothesis to justify the physiologic time allometry relation (AR) and explore its implications.•The allometry coefficient and exponent are shown to covary and are consequently not universal.•The physiologic time AR is a consequence of a speciesʼ physiology being maximally efficient resulting from scaling and minimum entropy generation.

The scaling of respiratory metabolism with body size in animals is considered by many to be a fundamental law of nature. One apparent consequence of this law is the scaling of physiologic time with body size, implying that physiologic time is separate and distinct from clock time. Physiologic time is manifest in allometry relations for lifespans, cardiac cycles, blood volume circulation, respiratory cycle, along with a number of other physiologic phenomena. Herein we present a theory of physiologic time that explains the allometry relation between time and total body mass averages as entailed by the hypothesis that the fluctuations in the total body mass are described by a scaling probability density.