Suckling of the baby at the breast enhances milk production. Development is a lifelong process into adulthood. After that period, aging occurs. Gerontology is the study of aging. One theory of aging suggests that aging has a genetic basis.
Cells can divide only so many times.
As we grow older, it may be that more cells age and die. Also, some cell lines may die before that maximum number of cell divisions has been reached. Some people may have genes that code for efficient enzymes that remove free radicals, causing the individuals to live longer. A second theory of aging suggests that a hormonal decline can affect many different organ systems. The immune system no longer performs as well, which is perhaps why cancer is more prevalent in the elderly.