For millennia, humans have speculated how the physical and living elements on the surface of the Earth combine, with gods and goddesses frequently posited to embody specific elements. The notion that the Earth, itself, is alive was a regular theme of Greek philosophy and religion. Early scientific interpretations of the Earth system began in the field of geology, initially in the Middle EastFielding H. Garrison, An introduction to the history of medicine, W.B. Saunders, 1921. and China, and largely focused on aspects such as the age of the Earth and the large-scale processes involved in mountain and ocean formation. As geology developed as a science, understanding of the interplay of different facets of the Earth system increased, leading to the inclusion of factors such as the Earth's interior, planetary geology and living systems.
