Are genes destiny? Have adenine, cytosine, guanine and thymine replaced Lachesis, Clotho and Atropos as the weavers of our fate?

It is as futile to ask how much of the phenotype of an organism is due to nature and how much to its nurture as it is to determine how much of the area of a rectangle is due to its length and how much to its height. Phenotype and area are joint products. The spectacular success of genomics, unfortunately, threatens to re-awaken belief in genes as the principal determinants of human behavior. This paper develops the thesis that gene expression is modified by environmental inputs and that the impact of the environment on a given organism is modified by its genome. Genes set the boundaries of the possible; environments parse out the actual.