 | | conditions, either grow unalike through the development of natural characteristics which had lain dormant at first, or else they continue their lives, keeping time like two watches, hardly to be thrown out of accord except by some physical jar. Nature is far stronger than nurture within the limited range that I have been careful to assign to the latter.
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Galton noted the high correspondence among identical twins for such things as toothaches, onset of disease, and time of death. The twins he studied tended to marry less often than the general population, which led him to suppose that they may have been infertile. "The one point in which similarity is rare is handwriting. I cannot account for this," Galton wrote. It was a matter of particular interest to him, since most of his reporting was conducted by correspondence.
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Galton wrote in an age that had been deeply influenced by the environmentalism of John Stuart Mill, who attributed his own amazing intellect to the early training he had received from his father. The reviews of Galton's book
Hereditary Genius: An Inquiry Into Its Laws and Consequence
were scalding.
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"My only fear is that my evidence seems to prove too much and may be discredited on that account, as it seems contrary to all experience that nurture should go for so little," Galton wrote, as he anticipated the reaction to his classic twin experiments.
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There is no evidence that twins have lower fertility than the general population. As for handwriting, Galton may have been confounded by the phenomenon of "mirror-image" twins, who write with opposite hands. Identical twins who write with the same hand usually have extremely similar handwriting.
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In some respects, the response to Galton's work is mirrored in the reviews that greeted Richard Herrnstein and Charles Murray's
The Bell Curve
in the United States more than a century later. Many of the same themes, in particular the heritability of intelligence, prompted angry responses to both books.
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