Up from Dragons: The Evolution of Human Intelligence. (Nonfiction).(Brief Article)

JOHN SKOYLES AND DORION SAGAN. McGraw-Hill, $27.95 (440p) ISBN 0-07-137825-1

When Carl Sagan published The Dragons of Eden in 1977, his speculations on the development of the human brain drew on the still-nascent field of neuroscience. Now science writer Dorion Sagan (Carl's son) and brain theorist Skoyles present a follow-up that includes not only new discoveries about brain functions but also a coherent theory as to how and why humans developed the intelligence that sets them apart from other primates. Key to this evolution, they argue, are two facts: the plasticity of the brain (particularly in the prefrontal cortex), which means that it "is not fixed in what it …