There are many different theories as to why we age. In truth, it is a complicated process. There isn’t one theory out there that can adequately explain all the factors. Indeed, even logical sounding theories have been proven false, or simply don’t apply.
The first theory I’d like to talk at is the ‘Good of the Species’ theory. It states that aging occurs as a renewal, to get rid of the elderly in a population to make room for the new generation. The theory explains it as a group advantage. Although not really getting into the technical processes behind aging, this theory backs itself up using evolution. However, evolution dictates that advantageous characteristics of individuals will be carried on through their genes. This runs contradictory to a group advantage. Assuming this, we would expect to see an increase in longevity in individuals: the increased life span of the species creating more genes of their type, since they would be able to reproduce more often. The genes controlling for an increase in longevity would prosper. This would be worse for the group, but favors the individual, which is what evolution is all about: survival of the fittest. The ‘Good of the Species’ theory just doesn’t hold up.
The ‘Rate of Living’ theory explains aging like a ticking clock. There are a lot of different explanations within the theory. Some pin aging on metabolism, some on cellular division, and even some outdated versions on number of breathes! The theory speculates that a higher metabolic activity accelerates aging. There is a lot of support for this as a general rule, although there is still a lot of variation. It’s based around the idea that all organisms are born with a certain amount of energy. Larger organisms, or more active ones, will use it up faster and therefore age quicker. A kind of sub-theory of this is the idea that the eventual inability for cells to reproduce will eventually cause aging. Once again, we can find examples for and against. The strongest proof runs counter to the theory of a cell division limit. As we age, the muscles in our body become weaker. This isn’t due to the cell’s inability to reproduce, but rather the cells losing their ability to contract. Though The ‘Rate of Living’ theory cannot explain the entire process, it does help us understand many factors.
A theory that I believe holds up relatively well, and also accurately describes biological and mathematical models, is the ‘Reliability’ theory of aging. What it essentially says is that system failure causes an increased mortality rate in organisms, based on flaws and defects.
-A site which explains the metabolic factor in the ‘Rate of Living’ theory: http://courses.cit.cornell.edu/psych527_nbb420-720/student2005/nrb26/Page_2.htm
-Paper written on the Reliability Theory, by Leonid and Natalia Gavrilova: http://longevity-science.org/JTB-01.pdf
-I also used Wikipedia as a basis for my research, as well as the assigned reading “Why We Age.”
