This chapter deals with the symbiotic and evolutionary bases of human health. It argues that modern medicine should reflect the new understanding of humans as multigenomic beings with an ancient evolutionary history. It suggests that health must be seen in the context of microecology (the cell communities of the body) and evolutionary change. This chapter shows that a new science, “medical symbiotics,” might be organized, planned, and funded that would study health from a cosmic and microecological standpoint.