Biological theories
Programmed theories say aging is built into our genes. Leonard Hayflick found human cells divide only about 50 times—the Hayflick limit—linked to shortening telomeres at chromosome ends. Denham Harman's free radical theory blames accumulating oxidative damage, and wear-and-tear theories compare us to machines. A 2013 Cell paper synthesized nine "hallmarks of aging."
Psychological and social theories
Psychologically, Erikson's integrity vs. despair and Baltes's selection-optimization-compensation are key. Socially, disengagement theory says older adults and society mutually withdraw; activity theory says staying active brings satisfaction; continuity theory stresses maintaining past patterns; and exchange theory looks at shrinking resources. For work transitions, see retirement theory.
FAQ
- How do disengagement and activity theory differ?
- Disengagement sees withdrawal as natural; activity theory says staying engaged leads to well-being.
- Can aging be stopped?
- No, but exercise, nutrition, and social engagement support healthy aging.
Sources reviewed: 2026-10-26
References
- Hayflick, L., & Moorhead, P. S. (1961). The serial cultivation of human diploid cell strains. Experimental Cell Research, 25(3), 585–621.
- Harman, D. (1956). Aging: A theory based on free radical and radiation chemistry. Journal of Gerontology, 11(3), 298–300.
- López-Otín, C., et al. (2013). The hallmarks of aging. Cell, 153(6), 1194–1217.
- Cumming, E., & Henry, W. E. (1961). Growing Old: The Process of Disengagement. Basic Books.