This paper proposes a view: terrestrial life did not evolve by escaping water, but by engineering biological mechanisms to preserve internal aqueous conditions. We reframe essential physiological systems — such as skin, kidneys, lungs, and cuticles — as components of a mobile life-support system, or ‘mobile aquarium,’ designed to sustain ancestral aquatic equilibrium in a dehydrating environment. The theory applies universally to all known life forms — including animals, plants, fungi, bacteria, and archaea — none of which exhibit active cellular function without water. Drawing on evidence from comparative physiology, developmental biology, molecular genetics, and extremophile adaptations, this synthesis reinterprets terrestrial evolution as a persistent negotiation with water dependence. The implications span multiple domains, including medicine, astrobiology, and the search for origins of life. The theory invites empirical testing and critical examination.
David Shadi (Mon,) studied this question.