Table 1. Comparison of 3 groups of theories of aging: programmed, stochastic, and quasi-programmed.

Theories	Defining feature	Purposeful?	Programmed?	Caused by ROS?	Kills via age-related diseases?	Causes death directly?	Menopause in women is	Link between aging and diseases	Use of energetic resources
Programmed	functional decline	yes	yes	mostly	unspecified	yes	programmed	unspecified	unspecified
Stochastic	functional decline	sometimes*	in some cases*	mostly	sometimes#	yes	programmed	vulnerability to diseases#	slows aging (via repair)
Quasi-programmed	hyperfunction	no	no	no	always	no	prototypical disease	manifested by diseases	fuels aging (via TOR)

According to stochastic theories, aging is caused by random accumulation of damages, errors, and “garbage” due to multiple causes including but not limited to free radicals. *Stochastic theories still accept that aging can be purposefully programmed (e.g., in salmon). ^#According to stochastic theories, aging can kill directly (by non-specified mechanisms) and also increases the vulnerability to age-related diseases.