If we make this readjustment to view Homo sapiens as an ultimate in oddball rarity, and life at bacterial grade as the common expression of a universal phenomenon, then we could finally ask the truly fundamental question raised by the prospect of Martian fossils. If life originates as a general property of the material universe under certain conditions (probably often realized), then how much can the basic structure and constitution of life vary from place to independent place?

"War of the Worldviews", p. 352 - Leonardo's Mountain of Clams and the Diet of Worms (1998)