Hi phil, Another thing to keep in mind is there is intense selection for an individual to reproduce. But once you have reproduced or have gotten beyond the age of reproduction, there is no selection...you will not pass on any genes or you already have. There is no selection pressure to get older. However, age varies tremendously in the population and among organisms and so far, most of the genes underlying this variation seem to be related to development or reproduction. Though some are related to cell maintenance such as DNA damage repair.
Metabolism. 2003 Oct;52(10 Suppl):5-9. Related Articles, Links
Genes of aging.
Hamet P, Tremblay J.
According to developmental genetics theories, aging is a genetically programmed and controlled continuum of development and maturation. Being dynamic and malleable processes, development and aging are controlled not only by genes but also by environmental and epigenetic influences that predominate in the second half of life. Genetic mutations affect many phenotypes in flies, worms, rodents, and humans which share several diseases or their equivalents, including cancer, neurodegeneration, and infectious disorders as well as their susceptibility to them. Life span and stress resistance are closely linked. Oxidative stress actually constitutes a defined hypothesis of aging in that macromolecule oxidative damage accumulates with age and tends to be associated with life expectancy. DNA methylation, a force in the regulation of gene expression, is also one of the biomarkers of genetic damage. The mitotic clock of aging is marked, if not guided, by telomeres, essential genetic elements stabilizing natural chromosomic ends. The dream of humans to live longer, healthy lives is being tested by attempts to modify longevity in animal models, frequently by dietary manipulation. The quest continues to understand the mechanisms of healthy aging, one of the most compelling areas of research in the 21st century