Do planeria not age? That’s surprising; even bacteria age! And it’s remarkably interesting for research if it’s true.
As for the splitting, that happens with humans as well, due to Everett branching. We can’t observe it directly like we can with the worm, but it seems to be the case.
There are a range of animals that do not seem to show increased likelihood of death as they age. Hydra, naked mole rats, sea urchins, Aldabra giant tortoises, aspen trees, Greenlank sharks, and planaria are examples. It may ultimately turn out that we’re just not looking hard enough for evidence of aging in these organisms.
It may seem surprising that complex organisms can show less aging than simple organisms, given that it seems harder to maintain all the parts of a complex organism in working order.
However, the complexity of multicellular life also permits higher-fidelity regeneration and maintenance mechanisms that are unavailable to simpler life forms. Also, multicellular life may derive a survival advantage from investing in structures that promote longer or indefinite individual life expectancies, while single-celled life may benefit from maximizing the rate of reproduction and genetic adaptation to changing conditions.
For bacteria, individual cells die easily, but colonies can live indefinitely as damaged macromolecules are diluted between daughter cells during cell division.
I’ve heard the claim about naked mole rats, but not the details: is it possible to have a naked mole rat that lives for an arbitrarily long time if you keep them in a sterile environment where it’s hard to get significantly injured? That would seem to be a straightforward implication of them not aging, but I’ve never heard that this has been done.
This isn’t quite what it means to not experience aging. Instead, “not aging” means that the likelihood of dying in a given year does not increase with age. So a naked mole rat kept in a cage for an indefinite period of time can still die, and yet not be aging.
Thanks! Do you know what tends to kill them then? I was under the impression that organisms usually die of disease, injury, cancer, transposon propagation or programmed aging. I notice I am confused, because keeping a naked mole rat in a safe environment should protect them from disease and injury, and transposons and programmed aging would do more damage over time. Do they die of cancer then, or am I missing something big about biology here?
Captive NMRs are kept in colonies, and can inflict injuries on each other.
They do get cancer at very low rates.
Animals that haven’t been specially reared to have had zero contact with pathogens can also harbor dormant diseases, and the current longest-lived NMR has not spent his whole life in a sterile environment.
Complex organisms may be at a constant low-level risk of deadly internal injuries (i.e. a random stroke).
Do planeria not age? That’s surprising; even bacteria age! And it’s remarkably interesting for research if it’s true.
As for the splitting, that happens with humans as well, due to Everett branching. We can’t observe it directly like we can with the worm, but it seems to be the case.
There are a range of animals that do not seem to show increased likelihood of death as they age. Hydra, naked mole rats, sea urchins, Aldabra giant tortoises, aspen trees, Greenlank sharks, and planaria are examples. It may ultimately turn out that we’re just not looking hard enough for evidence of aging in these organisms.
It may seem surprising that complex organisms can show less aging than simple organisms, given that it seems harder to maintain all the parts of a complex organism in working order.
However, the complexity of multicellular life also permits higher-fidelity regeneration and maintenance mechanisms that are unavailable to simpler life forms. Also, multicellular life may derive a survival advantage from investing in structures that promote longer or indefinite individual life expectancies, while single-celled life may benefit from maximizing the rate of reproduction and genetic adaptation to changing conditions.
For bacteria, individual cells die easily, but colonies can live indefinitely as damaged macromolecules are diluted between daughter cells during cell division.
I’ve heard the claim about naked mole rats, but not the details: is it possible to have a naked mole rat that lives for an arbitrarily long time if you keep them in a sterile environment where it’s hard to get significantly injured? That would seem to be a straightforward implication of them not aging, but I’ve never heard that this has been done.
This isn’t quite what it means to not experience aging. Instead, “not aging” means that the likelihood of dying in a given year does not increase with age. So a naked mole rat kept in a cage for an indefinite period of time can still die, and yet not be aging.
The oldest known naked mole rat in captivity is 40 years old, while most naked mole rats live 2-5 years in the wild.
Thanks! Do you know what tends to kill them then? I was under the impression that organisms usually die of disease, injury, cancer, transposon propagation or programmed aging. I notice I am confused, because keeping a naked mole rat in a safe environment should protect them from disease and injury, and transposons and programmed aging would do more damage over time. Do they die of cancer then, or am I missing something big about biology here?
Captive NMRs are kept in colonies, and can inflict injuries on each other.
They do get cancer at very low rates.
Animals that haven’t been specially reared to have had zero contact with pathogens can also harbor dormant diseases, and the current longest-lived NMR has not spent his whole life in a sterile environment.
Complex organisms may be at a constant low-level risk of deadly internal injuries (i.e. a random stroke).
Source
Very interesting; thank you!