Why do we age?

The chapter "Why does aging happen?" disproved two theories behind aging. The theories disproved included the good-of the species theory and limited cell division theory. At first, each of these theories seemed to make some logical sense but after further reading, the explanations given by the authors also provided a logical argument against the validity of such theories. All of the ideas and research brought up in the reading caused me to start pondering exactly what the cause of our aging could be.

I do agree that the limited cell division theory can be associated with aging without being a causal theory. While reading about the cell division theory, I thought about the large number of other scientific discoveries that have been made in the field of cancer research over the last decade. Mutations in the Ras family (genes involved in cell signaling) have been found in approximately 90% of patients with pancreatic cancer (http://www.cancerquest.org/ras-oncogene). This subject was not touched upon in the reading but it certainly adds significance to the limited cell division theory.

Life expectancy has increased throughout the last century due to discoveries in the field of modern medicine (e.g. vaccines that have almost completely eradicated certain diseases). With increased technology, fewer persons die at a young age due to infection or simple illnesses such as the common cold. This medical revolution has led to a new phenomenon which was not known of 50 to 100 years ago. Following reproduction, there are often illnesses and conditions that set in that can expedite the aging process. While Cancer is not the cause of aging, it (and other illnesses) seem to be the one cause behind senescence for those who have aged. In my mind, this gives an answer to the question of why do we ultimately die but it does not exactly answer why we age prior to senescence. At this point, I believed that aging and senescence could be connected somehow.

While looking around online, I stumbled upon the evolutionary senescence theory of aging (http://www.afar.org/pdfs/AFAR-Guide-to-Theories-of-Aging.pdf - page 3). Natural selection was touched upon in the reading with disproving the good-of-the-species theory of aging, and it plays a role in the senescence theory. The key to natural selection is reproduction. Following reproduction, natural selection does not necessarily prevent the aging that every person experiences because the goal of natural selection has already been met. I feel that the evolutionary senescence theory can especially be applied to women because following menopause (the natural loss of reproductive capabilities) there are many other health issues such as osteoporosis, cancer and arthritis that set in. The onset of these medical conditions often age a sign of aging because mobility or physical ability is lost within ones body.

There is no final answer on whether the evolutionary senescence theory of aging is right or wrong, however, it has yet to be disproved. The theory ties in cellular life to the life of an organism while explaining the one phenomena science has yet to prevent, senescence.

In time, there will be an answer to the question "Why do we age?", but until that time, it is anyone's best guess as to why we really age.