Are humans a galactic oddity, or will complex life with human abilities
develop on planets with environments that remain habitable for long
enough? In a clear, jargon-free style, two leading researchers in the
burgeoning field of astrobiology critically examine the major
evolutionary steps that led us from the distant origins of life to the
technologically advanced species we are today.
Are the key events that took life from simple cells to astronauts unique
occurrences that would be unlikely to occur on other planets? By
focusing on what life does - it's functional abilities - rather than
specific biochemistry or anatomy, the authors provide plausible answers
to this question. Systematically exploring the various pathways that led
to the complex biosphere we experience on planet Earth, they show that
most of the steps along that path are likely to occur on any world
hosting life, with only two exceptions: One is the origin of life
itself - if this is a highly improbable event, then we live in a rather
"empty universe". However, if this isn't the case, we inevitably live in
a universe containing a myriad of planets hosting complex as well as
microbial life - a "cosmic zoo". The other unknown is the rise of
technologically advanced beings, as exemplified on Earth by humans. Only
one technological species has emerged in the roughly 4 billion years
life has existed on Earth, and we don't know of any other technological
species elsewhere. If technological intelligence is a rare, almost
unique feature of Earth's history, then there can be no visitors to the
cosmic zoo other than ourselves.
Schulze-Makuch and Bains take the reader through the history of life on
Earth, laying out a consistent and straightforward framework for
understanding why we should think that advanced, complex life exists on
planets other than Earth. They provide a unique perspective on the
question that puzzled the human species for centuries: are we alone?
