There are some reasons for optimism, although nothing that conclusively rules out a large number of mechanisms.
First, humans only have ~tens of thousands of genes, so thousands of independent mechanisms would mean that a substantial portion of all the molecular species in the organism are involved. On top of that, the vast majority of components—from molecules to organelles to cells—turn over on timescales many orders of magnitude faster than aging, which severely limits the number of possible root mechanisms. Just based on that, I’d be very surprised to see even hundreds of independent mechanisms. Tens of mechanisms would be plausible, but single-digits seems most likely. It’s just extremely rare for biological systems to operate on timescales that slow.
Another direction: there are animals which display negligible senescence (i.e. no aging). Most of them are not very close to humans on the evolutionary tree, but even distant animals have reasonably similar core mechanics, so there’s only so much room for divergence.
There are some reasons for optimism, although nothing that conclusively rules out a large number of mechanisms.
First, humans only have ~tens of thousands of genes, so thousands of independent mechanisms would mean that a substantial portion of all the molecular species in the organism are involved. On top of that, the vast majority of components—from molecules to organelles to cells—turn over on timescales many orders of magnitude faster than aging, which severely limits the number of possible root mechanisms. Just based on that, I’d be very surprised to see even hundreds of independent mechanisms. Tens of mechanisms would be plausible, but single-digits seems most likely. It’s just extremely rare for biological systems to operate on timescales that slow.
Another direction: there are animals which display negligible senescence (i.e. no aging). Most of them are not very close to humans on the evolutionary tree, but even distant animals have reasonably similar core mechanics, so there’s only so much room for divergence.
which animals?
See Highlights of Comparative and Evolutionary Aging.