Edited by author 06-08-2001 04:13 PM
From David Mankins on separate list:

_Microcosmos_, but Lynn Margulis and Dorion Sagan. Short (but very unfair) summary: we're really not much more than walking colonies of cooperating bacteria.

A quick peek at Amazon shows that Margulis has a number of more recent books on the same theme, but _Microcosmos_ is the only one I've read.

(Margulis, incidentally, collaborated with James Lovelock on the original statement of the Gaia Hypothesis.)