There are many possible orderings of events of the human life cycle. For convenience, the life cycle may be said to begin with fertilization and then proceed through prenatal growth and development, birth, postnatal growth and development, maturity, senescence, and death. In truth, however, the course of life is cyclical —the onset of sexual maturation in the adolescent boy or girl, or death is each as much of a fundamental attribute as are conception or birth. As human ecologists we look at life from the perspective of the population. People grow, mature, age, and die even as new individuals are conceived and born. Declaring one moment, such as fertilization, to be a beginning to life is arbitrary in a continuous cycle that passes through many stages, both in the individual person and in generation after generation. The Circle of Life is composed of extensive networks of interacting biological and cultural variables. These extensive biocultural networks are woven into a hugely complicated matrix that sustains existing life, makes it grow, develop, and mature. The matrix of networks is the ecology upon which all humanity depends for sustainable production and reproduction into new generations. [Barry Bogin]