Then why aren't children affected, each generation becoming more damaged than the last? Are reproductive cells special in some regard? If so, can we make normal cells more like that? (I know about older parents having a higher risk of giving their kid Down's and autism but that only happens for a small percentage and the rest of the kids are fine.)
Perhaps the (biological) choices are growth and decline. No steady state (stable equilibrium) is feasible. Just a stupid guess; I have no basis for this notion.
Human race is not destroying its DNA at current pace for long. Deterioration may be more pronounced in a few generations.
And as to why the child is not formed from bad copies of worn-off cells of a mature parent - it's been some time since I read the book but I think that there was some reset mentioned when a whole new person is formed inside another organism. Fetal stem cells are known to have superior properties.
