# 2.2: Theory 1- Aging by Program

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• There is strong evidence supporting the suggestion that aging is in some manner programmed into each species, including humans.
• This may be controlled neurologically or hormonally through the hypothalamus.
• Other studies suggest that aging is controlled by the thymus.
• The gland atrophies at about the onset of adolescence. This implies that aging occurs more readily in the absence of the thymus gland.
• In studies cultured cells of a specific type divided a consistent number of times. This implies that the cell’s life cycle is controlled within the cell, rather than externally by the hypothalamus or thymus.
• Scientists agree that although normal cells may have a limited number of times they can divide this is only rarely, if ever, reached in the body.