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The Permian/Triassic mass extinction seems to have been the turning point. The creatures that have not changed much since that earlier time are the creatures th
by lkrubner 4y ago
The Permian/Triassic mass extinction seems to have been the turning point. The creatures that have not changed much since that earlier time are the creatures that don't age. But when life revived at the end of the Triassic, the world was more competitive, eco-systems were more integrated, and specialization became more common. Aging allows specialization, we can see that most obviously with birds, which need to maintain a specific weight and body mass and ratio of wing span to body mass. A bird that simply grew and grew and grew, like a tortoise, would have a changing ratio of wingspan to body mass and therefore it would soon lose its ability to fly. The creatures that age are those that have a fixed adult body shape. By contrast, the tortoises and reptiles and fish that live forever also seem to grow and grow and grow -- their body mass to external ratio changes over time, therefore they are less specialized.
- jessermeyer 4y agoNone of this was mentioned in the article. Where to read more about this point of view?
- dalbasal 4y agoThis kind of happens to slow aging reptiles too. Massive snakes like anacondas, reticulated pythons and such are partly arboreal when small. When bigger, they can't really climb or hide in trees. Same thing for giant monitors. Komodo dragons are arboreal when small, and live a different lifestyle once large. They're kind of like different species, inhabiting different ecological niches.
- nofollow 4y agoI wonder how some snakes' ability to atrophy and regenerate internal organs (including the heart) is related to aging: https://www.tacc.utexas.edu/-/how-pythons-regenerate-their-organs-and-other-secrets-of-the-snake-genome https://www.tacc.utexas.edu/-/how-pythons-regenerate-their-o...
- bergenty 4y agoThat’s very interesting. Literally the dawn of aging. I’m skeptical though, do you have any sources you can point me to?
- pier25 4y agoSo you're saying that aging is basically growth control?
- ezconnect 4y agoGrowing means you're making new cell, aging is when you're cell seems tired and stop regenerating or being eaten by other cells.
- pier25 4y agoAren't cells replaced periodically?
- space_fountain 4y agoYes, but in a very controlled way, typically with a fixed number of total devisions. Understanding aging is a slow process, but as far as I know current thought is that it has a lot to do with that replacement slowing down for a variety of reasons. This slow down seems like it may somewhat be a tradeoff with cancer though. Cells that divide too robustly end up cancer, cells that sort of shutdown instead are known as senescent and seem to contribute to aging
- escapecharacter 4y agoif you were optimizing for success for a whole species, do you see how going for fast iterations and throwing out old code could appear as a strategy?
- hwillis 4y agoIt's the opposite. You don't have children when you die, and evolution occurs overwhelmingly due to genetic diversity rather than iteration. That is, mutations are not nearly as important as the number of parents with diverse code to recombine with. Excluding older individuals causes the gene pool to become more consistent, because mutations are easier to lose. If iteration was important, sexual maturity would occur drastically younger in birds and mammals, and you'd have tons of offspring to maximize iteration. Reptiles are the ones that have tons of children.
- tambourine_man 4y agoIt’s an interesting hypothesis, but why can’t growth slow or stall?
- svachalek 4y agoI think the idea is that evolution finds "good enough" solutions. If you can stop growth and it has the side effect of putting a time limit on an individual organism's lifespan, that may be an acceptable tradeoff in terms of genetic propagation. While halting growth without aging may be even better there may not have been enough pressure given how many animals in the wild don't die of old age. Not that I've ever heard this theory before. But logically it seems plausible.
- tambourine_man 4y agoRight, the question is why would stopping growth necessarily limit an organism's lifespan. I don't think that's a given. If you don't age and can stop growing at optimum size, then that's potentially a huge evolutionary advantage. And since even “marginally better” can often be selected given enough pressure, it's hard to imagine why growing older is so prevalent.
- fbanon 4y ago[citation needed]
- RosanaAnaDana 4y agoThis could also be a selection bias based on the nature of the selection events. Longer lived species for whatever reason (slower metabolism, ability to go dormant for long periods) may have had an edge for a period of time. Its important to not that there wasn't a sudden radiation based on these specific surviving species after these events either.
- FredPret 4y agoWhat are you talking about - I've been growing and growing as an adult!
- conradfr 4y agoNew Zealand has birds that don't fly due to the lack of predators and they don't get enormous and live very long life, IIRC. Although the ones that were big got extinct so maybe you have a point...
- outworlder 4y agoNot sure if aging is related to growing forever. Our ears never stop growing but they don't live forever :P It's more likely that those animals descended from an ancestor that didn't 'age' in the conventional sense _and_ had slow, unrestricted growth. Those two traits are not necessarily related. Not sure if I agree with the 'specialized' moniker. All creatures are specialized to their ecological niche. Humans are kind of an exception. What may have been selected for is fast and adaptable organisms. Why bother with 'aging' if you can tolerate damage over time, in exchange for more efficient organisms in the short term? You only need to repair enough to ensure the organism will reproduce (and maybe help care for the offspring for a while). Humans are actually pretty good in that aspect compared to many animals. Probably because it takes a while before we are able to reproduce.
- celrod 4y agoI think slow aging/longevity are "hard". You need excellent repair mechanisms, and for nothing to go wrong for a very long time. Random mutations can easily cause problems/chop some time off your lifespan. The question is, do individuals within the species benefit from longer life spans? To what extant are age related problems contributors to the deaths of individuals within a species? I would guess that a higher percentage of turtles at a reproductive age die of age related disease than reproductively mature rats. I would guess that turtles are much better at withstanding the passage of time, because time is a much more significant killer of turtles. Similarly, flying birds and bats tend to live longer than mammals of similar body mass, probably because predation is a less significant contributor to their mortality (and thus issues such as age, relatively more significant). Primates may be an exception, but they're also rather good at avoiding predators.