There are two modern evolutionary theories of mammal senescence: Programmed theories
contend that mammals purposely limit their lifespans because doing so creates an evolutionary advantage.
Non-programmed theories contend that each mammal specie only needs a particular lifespan and
therefore only evolved and retained the capability for attaining that lifespan. Arguments over the evolutionary
nature of aging have now existed for more than 150 years and for reasons described here
may never be definitively resolved.
The programmed/ non-programmed question is critical to medical research because the theories have
grossly different predictions regarding the biological mechanisms associated with the aging process
and therefore, the nature of age-related diseases and conditions.
This article describes and compares two approaches for avoiding the need to obtain resolution on the evolutionary basis of
senescence in order to identify and characterize the biological mechanisms responsible for aging and therefore the nature
of highly age-related diseases.