The popular notion that the natural world maintains an invariant balance without perturbation by industrial civilization is invalid. Environmental changes in the aftermath of Pleistocene glaciation were dramatic and pervasive, and continued in varying guise throughout the Holocene interglacial, which has been coincident in duration with the rise of modern human cultures. Holocene conditions have been influenced by the progress of physical processes and biotic migrations set in motion by deglaciation, by climatic fluctuations still poorly understood, and by the behavior of aboriginal peoples who achieved widespread manipulation of their evolving environments even as they learned to adapt to them. Because cumulative Holocene environmental changes are largely irreversible, future sustainability of the human condition is dependent upon further and wiser development of human culture. All hopes for return to an irretrievable past are quixotic.