Life Cycle

The study of the human life cycle is primarily a study of the aging process. The question of why humans age has long intrigued social and biological scientists. While a fountain of youth has yet to be discovered, public health and hygiene interventions have lengthened the human life expectancy greatly over the course of the past hundred years. And yet life expectancy varies greatly within and between societies, relating to their relative socioeconomic status, gender, reproductive history, and environment, among other factors. Biologists have estimated the human life span to be approximately 120 years; however, there are no well-documented lives of this length. This discrepancy between life expectancy and life span raises the important and complex relationship between biological and cultural determinants of aging. In effect, an understanding of the life cycle and human aging is predicated upon exploring these determinants of physical, cognitive, and social decline in later life.

All societies possess some mechanism by which to denote or mark stages in the life cycle—in particular, the transition from youth to adult and from adult to elder. Anthropologists have enumerated many formal age classification systems. Age classification systems such as age sets—groups of persons born within a set number of years and considered to be the same age—are more rigid and formalized among horticulturist and pastoralist societies; industrialized societies tend to have less formalized mechanisms to denote elder status and often rely upon physical and chronological markers of aging. Gerontologists also conceptualize age in terms of age grades, cohorts, and social age. Age grades are status differences predicated on culturally defined social ages. Cohorts are generations of people who experience similar historically defining moments that shape their experience. Social age is a way of grouping elders based on particular cultural experience, such as retirement, widowhood, or grandparenthood.