The idea comes from lemurs, biologist did investigate how those primates reached the Madagascar island and the plausibility of the hypothesis of a free ride on a drifting log across the ocean which would require several weeks if not months, obviously without food or drink.
They found the answer in the mouse lemur, one of the several species of lemurs living in Madagascar.
The mouse lemur has the peculiar ability to drop in lethargy when deprived of food, in the dry season it can stay in lethargy without eating and drinking for up to 4-5 months.
This ability explains how it is possible an ocean crossing lasting a considerable amount of time without any food or drink.
The idea is that eventually this kind of ability is exceptionally marked in lemurs but at a certain level common to most living creatures, not really a proper lethargy in most cases but a slow down of all physiological processes which of course will lead to a slow down of senescence as well.
We do know, for example, that calories restriction leads to HGH increase and we do know that HGH increase leads to kind of lethargic behavior....
As far as I know this hypothesis has never been investigated but to me sounds reasonable, not the only mechanism involved, of course, but possibly a concurring one.