a popular theory of aging is the mitochrondial theory of aging.
There are several variants of this theory some of which are definitely false, while some are plausibly in sorta-the-direction. It’s a big controversy and I’m not an expert yada yada yada. Let me assume something like the following is true: aging is a metabolic phenomena where mitochrondia degrade overtime and at some point start to leak damaging byproducts which is substantially responsible for aging. Mitochrondial DNA have less repair mechanism than nuclear DNA. Over time they accrue mutations that are bad (much quicker than nuclear dna).
Species that reproduce fast & many may select less on (mitochrondial) mutational load since its matter less. On the other hand, species that have more selection on mitochrondial mutational load for whatever reason are less fecund. E.g. fetuses may be spontaneously aborted if the mitochrondia have too many mutations.
Some pieces of evidence: eggs contain the mitochrondia and are ‘kept on ice’, i.e. they do not metabolize. Birds have a much stronger selection pressure for high-functioning metabolism (because of flight)[1] and plausibly ‘better mitochrondia’.
[there are also variant-hypotheses possible that have a similar mutation meltdown story but don’t go through mitochrondia per se. There is some evidence and counterevidence for epigenetic and non-mitochrondial mutational meltdown theories of againg too. So not implausible]
I like this.
Another explanation I have heard:
a popular theory of aging is the mitochrondial theory of aging.
There are several variants of this theory some of which are definitely false, while some are plausibly in sorta-the-direction. It’s a big controversy and I’m not an expert yada yada yada. Let me assume something like the following is true: aging is a metabolic phenomena where mitochrondia degrade overtime and at some point start to leak damaging byproducts which is substantially responsible for aging. Mitochrondial DNA have less repair mechanism than nuclear DNA. Over time they accrue mutations that are bad (much quicker than nuclear dna).
Species that reproduce fast & many may select less on (mitochrondial) mutational load since its matter less. On the other hand, species that have more selection on mitochrondial mutational load for whatever reason are less fecund. E.g. fetuses may be spontaneously aborted if the mitochrondia have too many mutations.
Some pieces of evidence: eggs contain the mitochrondia and are ‘kept on ice’, i.e. they do not metabolize. Birds have a much stronger selection pressure for high-functioning metabolism (because of flight)[1] and plausibly ‘better mitochrondia’.
[there are also variant-hypotheses possible that have a similar mutation meltdown story but don’t go through mitochrondia per se. There is some evidence and counterevidence for epigenetic and non-mitochrondial mutational meltdown theories of againg too. So not implausible]
compare bats? what about their lifespans?