Versatile though he is, [Sagan] is simply not enough saturated in his subject [in "The Dragons of Eden: Speculations on the Evolution of Human Intelligence"] to speculate; what he can do is summarize and, to a limited degree, correlate the results of scattered and tentative modern research on the human brain. The research, from electroencephalograms of dreamers to endocranial casts of fossil skulls, is in progress, and Mr. Sagan, like the rest of us, must wait for sweeping conclusions. "If this result is confirmed, it would be quite an important finding," he writes in one iffy spot, and, in another, complains, "Very little work has been done in this field to date." He speaks of "many potential near-term developments in brain chemistry which hold great promise both for good and for evil," shamelessly woolgathers about how "one day we will have surgically implanted in our brains small replaceable...