It seems that ever more people these days argue for aging to influence natural selection through effects on the group, or at least on offspring. The core argument made here, as I understand it, is that a sort of inverse Grandmother effect can allow a rapid pace of aging to reduce fitness in early life by reducing parental or grandparental contributions to survival. If the case, then this means that age-related diseases are not just side-effects of a relentless evolutionary focus on early life at the expense of later life, but are actively involved in selection in some way, perhaps as a buffer against more subtly harmful mutations. Like most of the more abstruse discussion of evolution, proof is hard to come by – most arguments at this level are a matter of model versus model and assumption versus assumption. The line between hypothesis and opinion is more blurred than it might be elsewhere in the life sciences.
During evolution, Muller’s ratchet permanently generates deleterious germline mutations that eventually must be defused by selection. It seems widely held that cancer and aging-related diseases (ARDs) cannot contribute to this germline gene selection because they