I heard about these [immortal jellyfish](https://en.m.wikipedia.org/wiki/Turritopsis_dohrnii) that are ‘[biologically immortal](https://en.m.wikipedia.org/wiki/Biological_immortality)’. I have three questions that I would like to have eli5:
1. How can animals be biologically immortal?
2. What can we learn from it in terms of human aging science and biotechnology?
3. What would it take for humans to ‘achieve’ biological immortality?
In: 2
Our human dna is complex and difficult to replicate. We have a lot of it and while most mistakes won’t kill you, and some are good in fact, having so much complex dna means we have a lot of dna that just regulates dna… But jelly fish don’t even have brains and they have close to no neurons compared to other ocean life and humans. Their dna can replicate very simply with almost no errors. Their developmental stages of growth differ indefinitely so that there is less competition. They can live for a very very long time and they usually get killed by something else before they die naturally. Thing is they don’t have many natural predators so nothing is really killing them.
In summary, they’re not immortal. They have very simple dna. They have natural population control and little predators.
To evolve to be immortal like them we would have to evolve into some light weight floating creature that just orbits the earth at high altitude and does nothing else ever except occasionally sting a high flying bug or bird and take in a little carbon from them.
When creatures become too complex, like humans, the dna that regulates dna slowly breaks down. It’s difficult to evolve those genes because the complexities have inherent weaknesses. Places in the genome where many mutations occur which is good. But over time the dna ultimately begins to have too many errors and that species will go extinct. Who knows maybe we got our mutations in the the perfect spot of the chromosome and the mutations will fix themselves. Probably not though.
They are “theoretically” immortal.
What were you, what was I when we first became that sperm/egg merger. A bitty zygote. Pretty simple. I didn’t have my cancer mutations in 1981 because of my smoking habit. I hadn’t developed any mutations, particular traits, etc. What if I could shift back to that state? My mom probably would not like a pregnancy in her 70’s, but skipping over that, what if I could just restart from my birth genetics?
Some jellies seem to be able to do this. Just opt for their birth era genes, go back to being zygotes. Fetuses. Whatever particulars those are called.
We will never, ever be immortal in this way. If I was able to take your genes and replant them. You grow up anew with the same genes. Are you immortal? Well, strong argument that without any of the same history or experiences you would not be you at all. You would just be a new person in stolen genetics. I could become more “you” if I hacked your Instagram account.
Also, they can still die. Sea turtles have a thirst for eating them. And if you get eaten, no more immortality.
1.) The immortal jellyfish is functionally immortal because instead of dying they revert themselves to the beginning of their lifecycle. The thing is it’s more like a clone than a true continuation of life.
2.) From the jellyfish? Not much, humans are far too complex to revert back to a simpler form like a fertilized egg or fetus.
3.) There are plenty of theorized ways. The most practical is probably electronic immortality, ie uploading a copy of your brain into a machine. There are plenty of other ways but you can look them up pretty easily.
Edit: A cool sci-fi way of biological immortality was explored in one of my favorite games “The Turing Test”, essentially A microorganism would use the human as a host and implant itself in a human cells, then via a symbiotic relationship would regenerate the telomeres at the end of DNA. The deterioration of Telomeres is a big part of aging as Telomeres function as a buffer against DNA damage, but over time they get chipped away until your DNA starts getting damaged which leads to improper duplication and malfunctioning cells.
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