In The Monkey Puzzle, John Gribbin and Jeremy Cherfas make the case for what may be the most important discovery about human origins since Darwin's day. That the human species is descended from tree-dwelling creatures that thrived in tropical forest 35 million years ago is well established. But just how, when, and where those ancestors changed through evolutionary processes into a variety of apes, including ourselves, has been less clear. Now, recent breakthroughs in the field of genetics have allowed scientists to develop with what they feel to be unambiguous precision a set of techniques for mapping the human route out of the past.