Eternal Riddles

Broca’s Brain: Reflections on the Romance of Science

by Carl Sagan
Random House, 347 pp., $12.95

Popularizers of science are a patchwork breed. On rare occasions a great scientist whose work is a pivot point in history, Charles Darwin for instance, has been a skillful writer of books that laymen could read with pleasure. But most scientific geniuses find popular writing difficult, and though publishers sometimes persuade them to try, the results are seldom notable. Einstein’s best book for laymen was a collaboration with Leopold Infeld. Niels Bohr struggled to explain quantum mechanics to ordinary mortals but his style was almost impenetrable. At the other extreme are writers like the legendary Isaac Asimov who, though trained in science, recognize that their talent lies not in making discoveries but in writing about science with such enthusiasm, and such obedience to that admirable maxim “eschew obfuscation,” that their books have done more for public understanding of science than twenty universities.

Somewhere in the middle are those who pursue a distinguished scientific career and also have a flair for colorful writing. One thinks of T. H. Huxley, the great science popularizer of his day, and of a long chain of British astronomers—Robert Ball, Arthur Stanley Eddington, James Jeans, Fred Hoyle, Dennis Sciama, to name a few—who took time off from professional labors to explain astronomy to the public.

In the United States the two best-known astronomers now writing books for a general audience are Robert Jastrow and Carl Sagan. Jastrow, however, has limited his attention to astronomy whereas Sagan is all over the lot. Dragons of Eden, for which he received a Pulitzer Prize, is about the evolution of human intelligence. His just-published book, Broca’s Brain, contains twenty-five short essays, dazzling in their range and eloquence.

The title essay which opens the book is a typical example of Sagan’s ability to mix science with philosophy. In the “innards” of the Musée de l’Homme, in Paris, hidden from the public, he is startled to come upon a large collection of human brains. It had been started by Paul Broca, a famous French neurologist and anthropologist, and the father of brain surgery. “Broca’s area,” on the cerebral cortex near the left temple, is a part of the brain that controls speech. Broca’s discovery of this area, Sagan reminds us, was one of the first discoveries of functional differences between the brain’s left and right hemispheres.

A bottle label catches Sagan’s eye: “P. Broca.” Yes, Broca’s own brain has found its way into the collection. Holding the container in his hands starts a sequence of fantastic thoughts in Sagan’s living brain. Is there a sense in which Broca is still in there? Will science someday find a way to scan a preserved brain and extract its memories? Would such an “ultimate breach of privacy” be a good thing?

And now Sagan asks himself if there are scientific questions that ought not to be asked. He thinks of a good example. If humanity were to destroy itself in nuclear warfare would …

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