These theories, based on the knowledge of their time, have, in 55 years, made considerable progress. That which was regarded, not that long ago, as alchemy, became molecular biology; and that which was magical became genetics.
Today, we know that aging is not due to a singular cause. Aging is the direct consequence of a sometimes complex series of events, which will change from year to year, depending on our interactions with our environment. These events will bring about changes in gene expression, that is, in the activation or deactivation of certain genes, and this will cause the production (or absence thereof) of certain specific proteins.
Today we recognize that the cellular control of aging is linked to our DNA, to its ability to duplicate, as well as to telomere integrity. These two elements will be essential to the preservation of a stock of quality stem cells. DNA is the essential element of life, as it is the basis for every molecule in our body. Damage inflicted to our DNA by our environment, as well as by an unhealthy lifestyle, will lead to the appearance of a series of age-related illnesses, such as cardiovascular disease, diabetes or cancer. This damage, accumulating in our 60 trillion cells, will be responsible for aging, whereas our longevity will depend on the manner in which we are able to repair this damage, as well as how fast we achieve it. Our DNA is constantly duplicating throughout our lives, and, in optimal conditions, these copies are perfect – especially in younger individuals. However, starting as young as 35 or 40 years of age, our DNA, which is continually bombarded by an excess of free radicals, by radiation and subjected to a toxic environment, can no longer be repaired sufficiently or fast enough. Copies will be of poorer quality and certain bits of genetic code will be damaged. Proteins essential to certain functions will be missing, and this will lead to premature aging and the appearance of chronic, age-related illnesses.
Today we know that chronological age has very little to do with aging. Statistical values officially defining the age at which we become old have gone out of the window. Certain scientists, like Aubrey de Grey, are convinced that aging is a disease and a curable one at that. According to him, human beings age in seven different ways, all of which can be prevented. Indeed, he claims that aging is optional and that we would have to be “crazy” to choose to. Others think he should apply that word to himself!
It is quite probable, in fact, that aging is a complex illness which affects not only our body, our thoughts and our emotions, but also our families and our societies. Aging and death remain the two greatest mysteries which humanity has yet to solve.