This article introduces one type of comprehensive complex systems model to explain why humanity continues to be frustrated by its lack of progress toward sustainability. Human overconsumption has now raised concern over the depletion of resources and environmental decay to critical levels that threaten the integrity of the human species, the planet's biodiversity and the global ecosystem in general. The focus on biopsychosocial explanations of human unsustainability is framed to encourage an interdisciplinary approach to problem solving towards a global bioethics. (...) This framework relies on three essential elements: the first concerns the notion that human overconsumption behavior is principally driven by an unconscious set of evolutionary predispositions to survive and prosper; the second element focuses on our unique psychological make-up, which at its core is universal and naturally selected over a geologic period that spans at least the 200–250 million-year natural history of mammals; the third component of the biopsychosocial model is the human evolutionary predisposition to seek out and participate in social behavior. This third element is selected because of the reciprocal benefits of cooperating with others for the purpose of enhancing everyone's survival. These three components have an evolved interrelationship and interdependence from which the full complement of human behavior emerges. Moreover, these three factors constitute the root causes of human overconsumption behavior and the basis for our unsustainable nature. This article argues that the biopsychosocial explanation of human unsustainability can adequately characterize virtually any kind of human and social phenomena that involve the exploitation of resources. Examples, such as the origins and effects of media and advertising, politics, education and religion on overconsumption, are discussed. The final section attempts to demonstrate that a comprehensive approach that unifies biological, psychological and social parameters toward solving the human unsustainability problem can be achieved. (shrink)