It was the best idea I would ever have, I realized, as soon as I had it – a true eureka experience – while teaching a graduate seminar early in my career. I had been struggling with an intellectual issue as I had never done before, seeking insight that would enable me to test a provocative – even radical – new theoretical perspective on the ways in which the experiences children have while growing up shape who they become later in life. My best idea would not only revolutionize my thinking, but would stimulate a second important insight.

My training in and early research on human development was rather traditional, founded on the commonsense idea that there are good ways of caring for children that promote their well-being – or “optimal” development – and bad ways that foster problematic functioning. Thus, sensitive-responsive parenting, provided by economically secure and happily married parents, fosters children's emotional security, intellectual competence, and social skills, resulting, eventually, in an adult able to love and to work in productive and satisfying ways. In contrast, marital discord, economic insufficiency, and detached, intrusive, insensitive, or harsh parenting foster the opposite. These views were founded on classic developmental perspectives, including psychoanalytic, attachment, and social-learning theories.

But my thinking began to change after reading a fascinating anthropology paper that a colleague, Pat Draper, had written and left with me many months earlier. Pat's work introduced me to life-history theory, a branch of evolutionary biology which stipulates that ALL living things have the same fundamental goal – and it is not to be rich, happy, or healthy, but, rather, to pass their genes on to future generations. And that the best way to get this job of life done depends on the conditions in which the living organism finds itself, humans included. Notably, then, there is no optimal development. So what my training had taught me regarding what qualified as “good” parenting, “healthy” family life, and “optimal” child development turned out, when examined from the perspective of life-history theory and evolutionary biology, to be best only under particular circumstances, but not others.