Seeking to demolish the “either/or” of genetic determinism vs. environmentalism, Moore (Developmental Psychology/Pitzer College) sounds a clarion—indeed, somewhat strident—call for recognition that genetic and environmental factors interact throughout life to form human traits.
Media hype surrounding the genome project has led the public to believe that there are genes for specific traits: that IQ is largely inherited, for example, and identical twins separated at birth reveal remarkable similarities in behavior. Nothing could be farther from the truth, Moore asserts, providing counterexamples. Some, like the rare appearance of mismatched eye color (to demonstrate that eye color is not a genetic certainty), seem a bit of a stretch. Others, like the notable differences in coat coloration and behavior of cloned rams, indeed make it clear that identical fertilized eggs are subjected to different environments from the moment they are implanted in their surrogate ewe mothers. Moore is also to be commended for his clarifying revisionist history of biology, showing embryology shunted off from the “modern synthesis” that united Darwinian natural selection with population genetics and gene theory. But he is also guilty of some sins of omission. He limits his discussion of genetic diseases to a few like PKU or Wilson’s disease that can be counteracted by dietary measures, which suggests environmental control. He neglects to mention single-gene-dominant diseases like Huntington’s that occur notwithstanding any intervention. Further, he has nothing to say about the role in early development of so-called “master genes,” which ensure that cells in a particular location “know” that they are destined to be arms and not legs. This means that at times—and timing is one of the great mysteries of development—genes become all-important and mutations at this time result in irreversible consequences: a missing limb, a deformed head, a maldeveloped brain.
Moore sometimes overstates his case, but perhaps his real value here lies in pointing out how much we don’t know about the calculus of development.