Childhood Experience and the Expression of Genetic Potential: What Childhood Neglect Tells Us About Nature and Nurture

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More than 200,000 years ago, the first homo sapiens, our genetic ancestors, began to spread across the planet. For 99 percent of the time our species has been on this planet, we lived in small hunter-gatherer clans. Humans lived with few material possessions, no written language, no complex world economy, advanced technologies or systems of governance. The major predator of humans was (and remains) other humans — usually from competing clans or bands. The lifespan was short, infant mortality high and the overall population of on the planet only slowly increased over tens of thousands of years. How different our Earth is today! Only one of thousands of mammals on the planet, humankind — slow, naked and weak creatures, biologically suited to few of the Earth's many climates and ecosystems — ultimately came to dominate the planet. Humankind is now capable of living in all of the planet's climates and harsh environments. No longer bound by cold, absence of natural grains or migrating herds, the natural boundaries of sea and sky, we humans — unlike any other of the planet's species — have created our own world. We have learned to cultivate natural grains and fruits — and now alter their genome; to domesticate and now, create, other animal species; from our own genetic capacity to make complex associations, symbolic representations and 40 basic sounds we have created 10,000 languages, and invented writing; we have invented belief systems, styles of governance, housing, economies — we have invented ourselves. We have made our own world with its own rules. In good ways and in bad, we stand out from all other species. So much so that we often forget that we are ultimately accountable to the laws of nature. Yet we are biological creatures, bound by the laws of nature to a time-limited existence. We are conceived and born, live our lives and then we die. From conception to death, our biological matrix organizes in remarkably complex ways to create multiple organ systems — bone and muscle, heart and liver, senses and brain. These biological systems allow each of us to move through space and time in a host of natural and, now, man-made, environments, interacting in complex ways with a diversity of biological creatures and environments. Within that single lifetime the range and variety in how we live is stunning. Genetically-comparable humans can live as Inuit in the tundra of Nunavut, a banker on Wall Street, a hunter-gatherer in the rainforest in Brazil. At times, a life is lived with grace and beauty, sharing with and caring for others, creating ideas, objects and concepts never before known on this planet. And at other times humans are cruel, ruthless and destructive — both random and systematic in the ways we destroy, hate and kill. How is this possible in the same species?

This question has been at the heart of centuries of debate on the "nature" of humankind. Are we born evil — natural born killers or the most creative and compassionate of all animals? Are we both? Does our best and our worst come from our genes or from our learning? Nature or nurture? These questions have tainted political, sociocultural and scientific processes for thousands of years. Its simplicity — suggesting that the essence of a person is the inevitable product of one or the other — genes or learning — is seductive. The human mind tends to prefer simple linear explanations rather than complex ambiguity. Unfortunately, simple categorical explanations of humankind feed destructive belief systems and deflect from a healthy process of inquiry about our true complexity. We now know more about our genes and more about the influence of experience on shaping biological systems that ever before. What do these advances tell us about the nature or nurture debate? Simply, they tell us that this is a foolish argument. Humans are the product of nature and nurture. Genes and experience are interdependent. Genes are merely chemicals and without "experience" — with no context, no microenviromental signals to guide their activation or deactivation —create nothing. And "experiences" without a genomic matrix cannot create, regulate or replicate life of any form. The complex process of creating a human being —and humanity — requires both. The amazing malleability and adaptability of humankind is allowed by our genetically-mediated capacity to perceive and respond to myriad environmental cues including the complex social-emotional milieu created when humans live together; and the organ most sensitive and responsive to the environment is the human brain.