A majority of evolutionary biologists believe that we now can envision our biological predecessors--not the first, but nearly the first, living beings on Earth. Life from an RNA World is about these vanished forebears, sketching them in the distant past just as their workings first began to resemble our own. The advances that have made such a pursuit possible are rarely discussed outside of bio-labs. So here, says author Michael Yarus, is an album for interested non-biologists, an introduction to our relatives in deep time, slouching between the first rudimentary life on Earth and...