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Claims of animal longevity are ridiculous.

Sorry, but nothing is immortal.

By Buck HardcastlePublished 3 years ago 5 min read
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Image from the American Museum of Natural History

We want stories about animals with a lifespan that’s way longer than humans or possibly even immortal. That’s exciting, almost magical. Of course you don’t have time to actually track an animal that long, so you’ll need to come up with some rationale for your declarations. Even if they don’t make sense.

I’m not a scientist. I don’t have the answers to how long these animals live. However, I have doubts that anyone else knows how long they live either.

“Immortal Jellyfish” keep ruining experiments by dying.

“The real paradox is they’re actually really hard to keep alive!” That’s the last line from a Science Focus article about turritopsis dohrnii, the so-called immortal jellyfish. It’s the kind of thing people might not notice before sharing the astounding claim that these jellyfish are immortal.

Normally jellyfish have a life cycle that goes: Fertilised egg - Planula - Polyp - Ephyra - Medusa. However, the turritopsis dohrnii can go from the medusa stage back to the polyp stage. In fact it can do this over and over again. This is why it’s been called immortal. Except they are “incredibly sensitive” and while they can overcome some challenges by reverting to polyp stage, in the end they still die when stressed too much. Attempts to find out how many times they can change form get interrupted when they die. Yet we call them immortal. This is basically what is happening:

Scientist: Everyone! I have discovered an immortal butterfly!

Public: Really? How is that possible?

Scientist: This butterfly can go back to being a caterpillar! It can do it repeatedly! Forever!

Public: Wow! Can we see these immortal butterflies?

Scientist: Well, I would show you but all of my specimens died.

Public: ...

Scientist: But hypothetically they could be immortal!

Public: Amazing!

Look, Turritopsis dohrnii is cool. We can appreciate what it does. But “Its life cycle is unexpected and weird” doesn’t mean the same thing as “It is immortal.”

The age of sponges is determined with useless data.

The giant barrel sponge, “the redwood of the reef” can live excess of 2,300 years, placing them among the longest-lived animals on earth. How do we know this? Are there giant barrel sponges that were mentioned in the bible that are still around today? Well, no, that age is an estimate. The age is estimated based on sponge growth. Except sponge growth can vary a lot, in a year a sponge can grow as little as 2% or as much as 404%. The same article notes in a splendid understatement “age extrapolations for very large sponges are subject to more error.” And that’s just the growth rate for the observed time. What if there’s some other factor that is causing sponges to grow differently now then they did 100 years ago?

From thefishsite.com

But hey, 2,300 years is only a tenth of the claim made about a supposedly 23,000 year old Scolymasfra joubini sponge. Except that scientist failed to account for fact when you’re going back that far you have to account for geological factors--the sponge he found would have had to survive for centuries on dry ground.

Greenland sharks can’t be aged like other sharks

Jellyfish and sponges maybe alive, but they’re not conscious beings with agency. An animal with character-and size at up to 18ft in length-is the Greenland shark. And they’re possibly the longest-living vertebrate on Earth with a lifespan of six centuries.

Like with the sponges though, there aren't any sharks that have actually been tracked for their entire lifespan. Generally to determine age in other sharks, biologists count the growth rings on their fin spines and vertebrae. But Greenland sharks have no hard tissues in their bodies; even their vertebrae are soft. So how do you age a Greenland shark?

The answer is carbon-14 dating. Carbon-14 dating isn’t like extrapolating age from growth, it’s a well established way of dating things. But it’s also an inexact way, and the older something is the more inexact it becomes. And sharks move around which affects how much radiation they receive. Hence the biggest shark studied was up to 512 years old but possibly only 272 years old.

Greenland sharks are almost certainly long lived, the estimate most often used is 400 years. But the fact that the shark that can’t be aged like other sharks is also by far the longest living vertebrate should make us suspicious of the high end conjecture about its age.

Lobster’s immortality is a fisherman’s myth.

There aren’t any scientists claiming that lobsters are immortal, but it’s such a widespread belief that it’s worth mentioning here. Some lobster’s are long lived, the American lobster can survive 100 years, but the Caribbean spiny lobster does not make it to 20. Lobsters continue to grow their entire life and can reproduce their entire life (well, actually that’s not that uncommon among animals. Only humans and some whales experience menopause.) Lobsters may not age like we do, but they eventually lose the ability to molt and grow new shells. Their aging shells get bacteria infection that can be fatal. This is known as shell disease and will end any lobsters that escape fisherman’s traps.

Steve Irwin didn’t own Darwin’s turtle.

One of the most famous non-ninja turtles was Harriet, who was the last surviving member of HMS Beagle’s famous trip that helped Charles Darwin form his theories of evolution. Harriet would go on to be transported to Australia where she would eventually come to live at a zoo owned by Steve "The Crocodile Hunter" Irwin until her death in 2006 at age 175.

Except that story is all bullshit. Harriet appears to have come from Santa Cruz, a Galapagos island not visited by the Beagle. Darwin’s turtle has been tracked to the Natural History Museum in London, where its remains were kept after it died at age 3.

Harriet’s story aside, turtles can definitely live a long time. Jonathan, a Seychelles giant tortoise, was born in 1832 making him the oldest known living land animal. He’s 189 years old...maybe…he’s... immortal!

Science
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About the Creator

Buck Hardcastle

Viscount of Hyrkania and private cartographer to the house of Beifong.

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