Piecing together potsherds and beads; Egypt Before the Pharaohs: The Prehistoric Foundations of Egyptian Civilization, By Michael A. Hoffman. New York: Alfred A. Knopf. $15.95.

The continuity of Egyptian civilization is staggering when we realize that the ruins of the pharaohs have given us a record of man's efforts to sustain civilization over several millenia.

In "Egypt Before the Pharaohs" Michael Hoffman examines the c. 650,000-year period before the unification of upper and lower Egypt in an attempt to provide an explanation for the comparatively sudden emergence of the rich and powerful Egyptian state.

Skillfully intermingling the history of the great prehistoric digs of the last century with a narrative account of the evidence that has been pieced together about prehistoric life, Hoffman charts the emergence of settled groups that farmed and domesticated animals. Exactly when, where, how, and why the many stages of this evolution took place is a subject of continuing debate among prehistorians and likely to remain so given the tenuous, fragile, and indefinite nature of the evidence.

Dependent upon the remnants of human settlements that have survived succeeding ages, prehistorians must reconstruct pictures of society using little more than arrowheads, tools, potshersds, beads, and a few skeletons, plus bits of geological and anthropological evidence. Because much of the evidence is destroyed as it is dug up, they also have to rely on the quality of their colleagues's work, both past and present. Often there is no way for them to be sure that what they find is a representative sampling of the range of artifacts of a given society. Dating, even using carbon-14, remains imprecise, and Hoffman calculates that one-third of all estimated dates are seriously inaccurate.

As a discussion of the scientific grounding of contemporary archaeology and the various tools used to arrive at conclusions, Hoffman's book is particularly valuable. As an occasionally disdainful attack on the less scientific work of some earlier archaeologists, it is sometimes annoying. But overall, "Egypt Before the Pharaohs" is a fascinating and extremely informative book for anyone interested in ancient Egypt or the evolution of society.