The most important fact about human genes is that they help to make us as big as we are and to have a central nervous system with as many connections as it has. However, there are not enough genes to determine the detailed shape and structure of that nervous system nor of the consciousness that is an aspect of that structure. Yet it is consciousness that creates our environment, its history and the direction of its future. This then provides us with a correct understanding of the relation between our genes and the shape of our lives.

Our DNA is a powerful influence on our anatomies and physiologies. In particular, it makes possible the complex brain that characterizes human beings. But having made that brain possible, the genes have made possible human nature, a social nature whose limitations and possible shapes we do not know except insofar as we know what human consciousness has already made possible. In Simone de Beauvoir’s clever but deep apothegm, a human being is “l’etre dont l’etre est de n’etre pas,” the being whose essence is in not having an essence.

History far transcends any narrow limitations that are claimed for either the power of genes or the power of the environment to circumscribe us. Like the House of Lords that destroyed its own power to limit the political development of Britain in the successive Reform Acts to which it assented, so the genes, in making possible the development of human consciousness, have surrendered their power both to determine the individual and its environment. They have been replaced by an entirely new level of causation, that of social interaction with its own laws and its own nature that can be understood and explored only through that unique form of experience, social action.

R.C. Lewontin (1991). The doctrine of DNA: Biology as Ideology