This book is a milestone in our understanding of the origin of life on earth and its subsequent early development. Its editor, J. E. Schopf, assembled an interdisciplinary team of 24 experts, the Precambrian Paleobiology Research Group (PPRG), who worked together for 14 months. Their official report, the volume reviewed here, has the following stated goals: first, to report the original research results obtained by the PPRG; second, to provide an in-depth summary of relevant data; third, to provide an integrated assessment of current evidence on the early history of life; and fourth, to highlight unsolved problems. T h e book succeeds admirably in achieving these goals.