I believe we have no idea what might be possible on this "Space Ship Earth."
It is tempting to predict that the more we understand the wide-ranging effects of genetic differences on all human characteristics—especially behavioral ones—our cultural, ethical, legal, and personal ways of thinking about ourselves will have to undergo profound changes in response. Perhaps criminal proceedings will consider genetic background. Parents, presented with the genetic sequence of their children, will be faced with difficult decisions about reproduction. These hopes or fears are often exaggerated. In some ways, our thinking may need to change—for example, when we consider the meaning behind the fundamental American principle that all men are created equal. Human beings differ, and like all evolved organisms they differ genetically. The Declaration of Independence predates Darwin and Mendel, but it is hard to imagine that Jefferson—whose genius encompassed botany as well as moral philosophy—would have been alarmed to learn about the genetic diversity of organisms. One of the most important things modern genetics has taught us is that almost all human behavior is too complex to be nailed down, even from the most complete genetic information, unless we’re looking at identical twins. The science of nature and nurture has demonstrated that genetic differences among people are vital to human moral equality, freedom, and self-determination, not opposed to them. As Mordecai Kaplan said about the role of the past in Jewish theology, genetics gets a vote, not a veto, in the determination of human behavior. We should indulge our fascination with nature–nurture while resisting the temptation to oversimplify it.
Increasingly, people are beginning to realize that asking how much heredity or environment influence a particular trait is not the right approach. The reality is that there is not a simple way to disentangle the multitude of forces that exist. These influences include genetic factors that interact with one another, environmental factors that interact such as social experiences and overall culture, as well as how both hereditary and environmental influences intermingle. Instead, many researchers today are interested in seeing how genes modulate environmental influences and vice versa.
Currently, researchers are embarking on the companion to the Human Genome Project—the Human Epigenome Project.
DM: To me, there’s been a surprising amount of hype related to epigenetic inheritance. That’s because there is some evidence that the experiences we have in the course of our lives can change our epigenetic states and those epigenetic states can then be transmitted to the next generation. This has caused a bit of an uproar among some biologists. They are unsure about what to do with this new finding, because it calls to mind a pre-Darwinian biologist named Lamarck who argued that evolution occurs when the experiences we have change our bodies and we pass those bodily changes on to our offspring.