From the start, we need to think about how to think about growing old””and, in particular, how to think not simply of aging but of human aging. This will require that we learn from but also move beyond what has become the standard way to think about aging. Scholars study both why we age and how we age. The first seems to invite talk about a purpose, the second a mechanism. The first is more germane to my inquiry here.
Why do we age? The dominant answer today is that of evolutionary biology. We age because nature has relatively little stake in keeping us alive beyond our reproductive years. Insofar as we may speak of our lives having a point, it is to be carriers of DNA. Having passed that on to the next generation, we are dispensable. Any genetic trait harmful enough to cause death before the reproductive years will have difficulty surviving the filter of natural selection. Those who have such traits are less likely to reproduce, less likely to be effective carriers and transmitters of DNA. And, by contrast, natural selection will have relatively little effect on harmful genes if those harms appear only in the post-reproductive years.