Aubrey de Grey, a leading researcher in the field of aging, defines aging as follows:
“a collection of cumulative changes to the molecular and cellular structure of an adult organism, which result in essential metabolic processes, but which also, once they progress far enough, increasingly disrupt metabolism, resulting in pathology and death.”
The second law of thermodynamics explains that systems tend towards greater entropy, or disorder. Usually, the general metabolism alters after he “youth” period and the body degenerates (catabolizes) at a faster rate than it regenerates (anabolizes).
Brain and muscle cells decrease, and some newly created cells may not be as viable, due, for example, to transcription errors in the DNA that forms the code for the makeup of an individual.
Proteins that constitute cells and our skin are also affected with age, which is what causes wrinkles. Others believe that a natural clock tells the body via hormones to shut down and cease operating, a belief supported by the existence of such systems at the cellular level in the form of programmed cell death.
Yet another theory suggests that collagen cross-linking of proteins inhibits passage of materials and causes aging.
Artificially induced senescence, as a means of control over artificially created humans, or androids, is a central plot motivation in the renowned 1982 science fiction film “Blade Runner”, loosely based on Philip K. Dick’s (1968) novel “Do Androids Dream of Electric Sheep?”.