Evolutionary scientists have been trying to form a consolidated theory of ageing since the 1890's.
Enquiry into the evolution of ageing aims to explain why a detrimental process such as ageing would evolve, and why there is so much variability in the lifespans of living organisms. The classical theories of evolution (mutation accumulation, antagonistic pleiotropy, and disposable soma) suggest that environmental factors such as predation, accidents, disease, starvation, etc. ensure that most organisms living in natural settings will not live until old age, and so there will be very little pressure to conserve genetic changes that increase longevity. Natural selection will instead strongly favor genes which ensure early maturation and rapid reproduction, and the selection for genetic traits which promote molecular and cellular self-maintenance will decline with age for most organisms.
One theory is that random deleterious mutations can be minimised if lifeforms have limited lifespans, but no theory yet explains how mutations can affect fitness at different ages and the evolution of senescence.
The huge variability of lifespans is also unexplained. Within mammals for example, average lifespan vaires by a factor of 100 across different species. Shrews live about 2 years and some whales can live to over 200. (Source : Wikipedia )
There are many species which appear to have quite minimal or even no increase in mortality after maturity - so-called 'Negligible Senescence' - e.g. in fish (sturgeon) , plants (aspen), arthropods (lobsters) etc etc.
Ideas for new topics, and suggested additions / corrections for old ones, are always welcome.
If you have skills or interests in a particular field, and have suggestions for Wikenigma, get in touch !
Or, if you'd like to become a regular contributor . . . request a login password. Registered users can edit the entire content of the site, and also create new pages.
( The 'Notes for contributors' section in the main menu has further information and guidelines etc.)