Recommended: Alone in the Universe

For decades now there have been attempts to detect signals from intelligent life from nearby stars, all so far to no avail. John Gribbin argues, in his new book Alone in the Universe: Why Our Planet Is Unique, that while simple life may emerge on any planet that has a tolerable environment (not too hot, not too cold, with liquid water), complex multi-cellular life and certainly intelligent life is probably so rare that we may be the only example in our galaxy, despite the enormous number of stars and planets in our galaxy. He details the many things, and the many accidents of nature, that make our planet unique.

He also points out, with detailed discussion, exactly why intelligent life, and indeed all life on earth, is so tenuous. Not only do we live under the threat of major asteroid hits of the sort that have wiped out most species on earth several times before, but we are threatened by climate change not only from our own technological progress, but also from major super-volcanoes (like an exploding Yellowstone)  and major outpourings of lava such as formed the Siberian traps 250 million years ago.

This is a fascinating book to read, full of complex detail about how Earth was formed and why not many planets share our metals-rich surface, our shielding magnetic field, our relatively stable orbit, and dozens of other features that have provided enough protection and enough evolutionary pressures to drive the evolution of intelligent life.