As a complement to the four volumes of the naturalist suite, this essay on low biological energies was needed to explore the transitions between quantum mechanics and statistical physics at work in the integration-level units of the living - proteins, the cell, and the animal. From questioning to questioning the coordination of cellular activity, marine historian and naturalist Claude ROUQUETTE embarks on a navigation at sight, to plumb the depths of low energies in order to take stock of the complex processes in biological evolution, intimately associated with the transformations of civilization.