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In Our DNA? It is increasingly clear that our behaviors are not hard-wired into our genes. By Stuart A. Newman Behaviors are innate or environmentally induced novel or habitual actions by humans or other organisms that, at a minimum, involve interactions between the nervous system and other organs. A gene specifies the sequence of subunits of a single RNA or protein molecule. How is it possible for specific behaviors to be associated with particular genes? Can anything significant be learned from such associations? One persistent view, increasingly discredited in recent years, is that genes collectively provide a blueprint or software program for the generation of all organismal characters—anatomical structures, but also behaviors—and variant genes are lines of code of alternative programs. So, for example, two recent reports in the journal Nature Genetics described evidence that variations within any of 11 DNA regions in the human genome have a strong association with schizophrenia, bipolar disorder, or both.1 One of the studies’ authors was quoted as stating, “Our findings are a significant advance in our knowledge of the underlying causes of psychosis—especially in relation to the development and function of the brain.”2 The expectation that such genetic associations will provide insight into how the brain generates normal or abnormal behaviors is directly connected to belief in the notion of a genetic program. No one would assert that learning the chemical Volume 24 Number 6

composition of a piece of tile from a medieval mosaic represents a significant advance in understanding the meaning of the art work. But when it comes to living organisms which operate individually and socially on multiple spatial and temporal scales and have assumed their present forms and behavior patterns over billions of years, genetically reductionist explanations can unfortunately still be advanced without evoking derision. The acceptance of this bizarre way of thinking, which is even more prevalent in the scientific and medical professions than in lay society, derives from a particular theory of evolution that has prevailed over the past century. Referred to as the Modern Synthesis, it links Darwin’s idea of natural selection as the generator of all inherited traits to the notion that genes and their variants are the only

significant determinants passed from one generation to the next. All standard features of an organism, e.g., the five fingers of the human hand or the propensity of humans to live in social groups, are consequently considered adaptations. By this argument, pathological behaviors that are endemic to many societies, like racism and rape, are likely to be adaptations as well (or sometimes negative but understandable misappropriation of adaptive behaviors).3,4 And now that a “genetic basis” is claimed to have been discerned for psychosis, it is all but certain that some evolutionary psychologist is laboring to uncover its benefits on the prehistoric savannah. Fortunately, a new concept of evolution is now taking hold. In various subdisciplines like “evolutionary developmental biology”5 and “ecological developmental biology”6 there is increasing receptivity to the idea of a loose, nonprogrammatic relation between the phenotype (particularly the behavioral phenotype) and the genotype. This includes an openness to the notion that the external environment may influence the development of inherently plastic living systems,7 not in arbitrary ways, but in ways constrained by the forming systems’ inherent modes of action.8 The “Baldwin effect,” the name given to a GeneWatch 13

Profile for Council for Responsible Genetics

GeneWatch Vol. 24 No. 6  

Behavioral Genetics

GeneWatch Vol. 24 No. 6  

Behavioral Genetics

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