A better understanding of the nature and evolution of human intelligence just possibly might help us to deal intelligently with our unknown and perilous future," writes Dr. Carl Sagan…. To help achieve this understanding Sagan begins ["The Dragons of Eden"] by looking at the evolution of intelligence in lower animals. Since larger brains can store more information, a critical point in evolutionary development occurred with the emergence of an organism that "for the first time in the history of the world had more information in its brain than in its genes." Subsequent development led to "the gradual (and certainly incomplete) dominance of brains over genes"; human intelligence resulted from "a particular property of higher primate brains."…

Sagan's frame of reference in "The Dragons of Eden" is an evolutionary one. "He who had a stone axe was more likely to win a vigorous difference of opinion. More important, he...