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The Dragons of Eden: Speculations on the Evolution of Human Intelligence

by Carl Sagan
Random House, 263 pp., $8.95

The intellectual landmines laid for us by Charles Darwin more than a century ago continue to explode. As each cloud of dust settles back around us, we begin to see a little more clearly the ways in which the history of humanity interlocks with and reflects the continued presence of patterns apparent in the history of nature. Yet each of these novel insights in turn finds itself resisted by those who have a major investment in the uniqueness of the human species, and who feel themselves threatened by any new analogies between the human species and other kinds of animals—most particularly, between the modes of life and experience of human beings (their psyche and ethos) and those of other primates and higher animals. At times, the passions aroused in the resulting controversies even remind us of the outburst that greeted the original publication of The Origin of Species in 1859: recall, for instance, last year’s angry exchanges in response to Edward Wilson’s book, Sociobiology.

From the standpoint of the development of ideas in the long term, however, these opponents seem to have been living in something of a fool’s paradise. When Darwin finally let The Descent of Man go to press in 1871—his argument in the Origin had been discreetly silent about the evolutionary status of human beings—he claimed explicitly only that “Man still bears in his bodily frame the indelible stamp of his lowly origin.” As a result, the first scientific and philosophical battles about human evolution were all fought out around the morphological features of different species, around fossil bones and brainpans, the beaks of finches and the necks of giraffes. And since the scientific case for the animal ancestry of the human species had been largely made out on morphological grounds, it seemed possible for a while to resist the further encroachment of evolutionary ideas by adopting a policy of containment. Evolution had to do, not with ethos or psyche, but with morphe alone. The mental and moral sciences could continue to hold themselves aloof from the natural sciences. Geist remained distinct from Natur. The methodological dualism which Kant had substituted for the ontological dualism of earlier Cartesian natural philosophy still seemed to protect human history from any danger of being engulfed in natural history.

This defense line was, at best, a temporary one. As early as 1838, Darwin himself had been thinking of ways in which his vision of man as part of a single creation with all other animals could be extended into psychology also. In private notebooks that remained unpublished in the Cambridge University Library until the 1970s he confessed himself a “materialist” in his views about the function of the human brain as the organ of higher mental activities. Yet he understood well enough how much damage would be done to the reception of his evolutionary theories by any public profession of these views: not least from memories of the storm provoked by William Lawrence’s …

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