Why Do So Many Animals in the Deep Sea Not Die?

There’s a very famous saying that goes, “There’s only one thing guaranteed in life, death.” And this would be true if you completely decided to ignore all the horrors of the deep ocean. Down here, you’ll encounter a select few creatures that for some reason seem to have somehow managed to cheat the rules of death. They will not die.

 It doesn’t make sense because this is the one universal rule of literally everything that has ever been alive. Everything is supposed to die. People die, dogs die, all the insects and trees and cows and even your little pet Timmy the turtle will die. So, how are these animals actually pulling this off? And what exactly do you have to sacrifice to live forever? Well, to understand how insane the deep ocean’s lifespans actually are, we first have to look at what we usually consider to be a long life.

 When most people think of an animal that lives a ridiculously long time, the first thing that comes to mind is the giant land tortoise. And to be fair, they do live a really long time. Some of these guys have been recorded living up to 150 or even close to 200 years old. That means there are tortoises alive today that were literally walking around before the lightbulb was even invented.

 To a human, that sounds like an eternity. But in the context of the deep ocean, 200 years old is basically just finishing puberty. The tortoise is actually a perfect example of how limited land animals really are. Down on the surface, you have to deal with gravity. You have to deal with changing seasons, and you have to deal with the sun constantly bombarding yourselves with radiation.

 All of these things slowly chip away at your DNA until your body just gives out. But once you strip all of these things away and plunge into the freezing depths of the ocean, the timer slows down. And the first real proof of this comes from an animal that absolutely shouldn’t be able to live as long as it does, the bowhead whale.

 These whales live in the freezing Arctic and deep subarctic waters, and they routinely live over 200 years, although we still aren’t fully sure of the maximum. We only figured this out because scientists found 19th century harpoon tips buried in the blubber of living whales. They had been swimming around with antique weapons stuck in them for over a century, seemingly unbothered, which is a pretty massive flex, honestly.

 But realistically, this shouldn’t even be possible for any whale to do. See, being a 60-ft, 100,000-lb mammal that lives for two centuries comes with a pretty glaring flaw, and that flaw is cancer. Cancer is basically just a numbers game. Every time your cells divide, there’s a microscopic chance that the cell makes a typo in its DNA.

 If that typo happens in the wrong spot, the cell starts multiplying out of control. So, logically, the more cells you have and the longer you live, the higher your chances of getting cancer. A bowhead whale has thousands of times more cells than a human, and it lives twice as long. By all standard logic, every single bowhead whale should be absolutely riddled with tumors by the time they hit 50, but they aren’t.

 This is known as Peto’s paradox. The whale somehow completely bypasses rule, and the way they do this is actually kind of insane. Their bodies have evolved advanced DNA repair mechanisms. Their genetics actively hunt down and fix the damaged DNA before ever becomes a problem. They’re constantly repairing their own DNA in real time.

 Their bodies actively fight off the exact diseases that kill everything else. But even with perfect DNA repair, 200 years isn’t actually that crazy, because if you want to push past the two-century mark, you have to stop relying on just having good genetics while still being a normal animal. You have to make some sacrifices.

 If you want to live for 500 years, you have to become this guy. This is the Greenland shark, and yes, you heard that right. These sharks can live for over 500 years. There are Greenland sharks swimming in the ocean right now that were born during the Renaissance. They were alive before Shakespeare wrote a single play.

 They were swimming around when the Aztec Empire was still a thing. So, how do you actually survive half a millennium? Well, you just stop doing things. Seriously, you just do absolutely nothing. The Greenland [music] shark has essentially stretched a normal lifespan out over 500 years by doing everything as slowly as physically possible.

 They live in waters that are barely above freezing, which basically drops their metabolism to zero. To put that in perspective, a normal human heart beats about 60 to 100 times a minute. A Greenland shark’s heart beats exactly one time every 10 to 12 seconds. They move at a maximum cruising speed of about 0.7 mph. That’s slower than a human walking casually through a grocery store.

 They grow at a rate of about one single centimeter per year. Everything about this animal is operating in extreme slow motion. They don’t burn energy. They don’t rush. They just exist, barely ticking over, conserving every single ounce of energy they have. But obviously, living your entire life in slow motion comes with a pretty severe catch.

 Being a Greenland shark is honestly completely miserable. You’d think that a 500-year-old apex predator would be some kind of majestic killing machine, but the reality is that they’re basically just floating garbage cans that happen to be toxic. First of all, almost every single adult Greenland shark is completely blind. They have a specific parasite that attaches itself directly to the shark’s eye, which looks like, well, yeah, you can see it’s pretty disgusting.

 The parasite literally eats the shark’s eye tissue, leaving them with completely useless eyes with little worms dangling out of them, which, you know, sounds like an absolute nightmare. But, the shark doesn’t even care. It’s so dark and cold down there that vision is basically useless anyway. They just slowly drift around in the pitch-black water, relying entirely on their sense of smell to find dead things floating in the water.

 And if you’re wondering why nothing else in the ocean just eats them, since they’re blind and incredibly slow, well, they’re heavily toxic. Greenland sharks don’t have a normal urinary tract. They don’t filter urea out of their bodies like a normal animal. They just shove it directly into their tissues.

 Their flesh is packed with urea and a chemical called TMAO, which acts as an antifreeze to keep their blood from turning into ice. If you try to eat raw Greenland shark meat, the toxins will make you violently drunk, incredibly sick, and then you’ll probably die. So, yeah, they’re basically just swimming biohazards.

 They only live 500 years because they’re too toxic to be eaten, too slow to burn out, and live in a frozen wasteland where nothing else even wants to bother them. So, how does a blind, toxic shark actually stack up against a real predator? Let’s put the Greenland shark up against the great white shark. The great white is easily one of the most dangerous things in the coastal waters.

 It’s fast, it’s aggressive, and it has a bite that can do that, which means anything caught in front of it is getting shredded. The Greenland shark is the exact opposite. It’s a blind scavenger that barely has the energy to swim. If these two actually fought, the great white would obviously win. It wouldn’t even be close.

 The great white would easily outmaneuver the Greenland shark and tear it to pieces before the Greenland shark even registered what was happening. But, here’s the thing. The Greenland shark wins the waiting game. A great white shark lives for about 70 years. That means a single Greenland shark will literally outlive the great white.

 And then it will outlive the great white’s children, and its grandchildren, and its great-grandchildren. The great white will go through seven entire generations of life, death, hunting, and reproducing, and the Greenland shark will still just be slowly drifting in the exact same spot, completely unbothered.

 It just has to go deep enough to avoid the shark for 70 years. These species don’t really ever interact in real life. So, why does this extreme patience only seem to work in the deep, freezing ocean? Well, look at the one thing almost all of these freakishly long animals have in common, their environment. The deep ocean and the polar waters are so brutally cold that they basically put biology on pause.

When you drop the temperature of water to near freezing, everything on a chemical level slows down. Chemical reactions take longer to happen. Cells take longer to divide. The cold just slows everything down. On top of that, cold water holds significantly more oxygen than warm water. So, these animals are getting a massive supply of oxygen while simultaneously burning almost zero energy.

 But, the biggest advantage of the deep sea is the absolute stability. Up on the surface, animals have to deal with summer heat waves, winter freezes, droughts, storms, and unpredictable food shortages. Your body has to constantly adapt and stress itself out just to survive the year. In the deep ocean, nothing changes, ever.

It’s pitch black, freezing cold, and highly pressurized today, and it will be pitch black, freezing cold, and highly pressurized a thousand years from now. This stability means animals don’t have to waste any energy adapting to new conditions. They can just lock into one highly efficient state and stay there indefinitely.

 And when you apply this exact same logic to something that doesn’t even [music] need to swim, the lifespan stop being measured in centuries and stopped being measured in millennia. When you descend even further into the abyss, you start finding creatures that make the Greenland shark look like a mayfly. This is black coral. Now, I know what you’re thinking.

 Coral looks like a plant or maybe a weird underwater rock. And I mean, you wouldn’t be wrong for thinking that. But coral is actually an animal. It’s made up of thousands of genetically identified polyps that build a skeleton to protect themselves. And in the deep ocean, black coral can live for over 4,000 years.

 There are individual coral colonies sitting at the bottom of the ocean right now that started growing when the ancient Egyptians were building the pyramids. They have just been sitting there, silently existing, for the entirety of recorded human history. So, how do you survive 4,000 years without accidentally getting destroyed by the ocean? Well, the biggest threat to something anchored to the seafloor is the ocean current.

 If you build a hard skeleton, a strong deep-sea current will eventually just snap you in half. But black coral evolved a completely different strategy. Their skeletons are made of a unique protein that basically turns them into rubber. They don’t try to fight the current, but just kind of bend with it. They sit in the pitch black, bending slightly in the water, catching microscopic bits of food that happen to drift by.

 They grow at a microscopic rate, adding maybe a fraction of a millimeter to their skeleton every year, even less than the Greenland shark. They have mastered the art of doing the absolute bare minimum required to stay alive. But realistically, 4,000 years is still amateur numbers. If you want to find the oldest living things on the planet, you have to travel to the bottom of the Antarctic Ocean.

 Down here, you’ll find the Antarctic glass sponge. These sponges are made of silica, the exact same material used to make actual glass. They look like pale vases just sitting on the ocean floor, and they can live for up to 15,000 years. [music] These sponges were already thousands of years old before humans even invented agriculture.

 They’re the oldest living animals on the entire planet. But, this raises a really interesting point. Is a 15,000-year life even impressive if you’re essentially just a living rock? Glass sponges have no brain. They have no heart. They have no nervous system. They don’t have muscles, and they definitely don’t move. They just sit there pumping freezing water through their glass bodies, filtering out tiny bacteria and dissolved organic matter.

Their metabolism is so unbelievably slow that scientists struggle to even measure it. They barely even count as living animals at this point. They’re basically just a part of the ocean floor. They traded every single aspect of actually experiencing life just for the ability to never turn off. But, sitting perfectly still for 10,000 years also comes with a pretty fatal catch.

 Living for 10,000 years sounds like you’re basically invincible. But, just because you can’t die of old age doesn’t mean you can’t be killed. These corals and sponges have completely beaten the aging process. Their cells don’t degrade, their DNA doesn’t break down, and they don’t die of old age. But, they’re actually unbelievably fragile.

 Because they have spent 10,000 years doing absolutely nothing, they have absolutely no way to defend themselves if something changes. If a predator decides to take a bite out of them, they can’t swim away. If the water temperature suddenly spikes, their metabolism completely collapses. And worst of all, human fishing nets.

 A deep-sea trawler dragging a heavy net across the ocean floor can instantly crush a 15,000-year-old glass sponge in a fraction of a second. An animal that survived the entirety of human civilization completely wiped out by a random piece of rope and metal. It’s a little anticlimactic. They might have beaten time, but they have absolutely zero defense against just getting crushed.

 So, surviving forever by being a fragile rock isn’t exactly a perfect strategy. But, what if an animal figured out how to beat time and physical damage? Every animal we’ve talked about so far has used the exact same strategy. They just age really, really slowly. But, Turritopsis dohrnii, better known as the immortal jellyfish, actually ages backwards.

 Or really, it just completely ignores the concept of aging altogether. This jellyfish is tiny, usually only about the size of your pinky nail, and it completely ignores how life is actually supposed to work. When the immortal jellyfish gets old, it just hits the reset button. It reverts from a fully grown adult back into a baby, and then starts its entire life cycle completely over again.

 And it can do this an infinite number of times. It’s the only known animal on Earth that’s biologically immortal. But, how is that actually biologically possible? Well, take a look at what triggers the reset in the first place. The jellyfish doesn’t just age backwards for fun. It only does this when it’s highly stressed.

 If the jellyfish is starving, if the water gets too cold, or if it gets physically injured, its body just hits the panic button. The jellyfish simply absorbs its own tentacles. Its bell shrinks down, and it drops to the bottom of the ocean floor, turning into a tiny blob of tissue. Through a process called transdifferentiation, the jellyfish literally rewrites its own cells.

 An adult muscle cell can completely change its identity and become a nerve cell. A skin cell can turn into a stomach cell. It essentially melts itself down and rebuilds its body from scratch. It turns back into a polyp, which is the baby stage of a jellyfish. It’s exactly like if a butterfly got injured and just folded its wings up to turn back into a caterpillar, which biologically speaking is completely insane.

 The polyp then grows back into a brand new adult jellyfish with the exact same DNA as before. Extreme stress, the very thing that kills most animals, is exactly what triggers this jellyfish to become young again. It literally uses getting hurt to stay alive forever. So, if it can just reset whenever it gets hurt, how does it ever actually die? If the immortal jellyfish can just hit the reset button every time it starves or gets injured, you’d think that the ocean would just be completely overrun with trillions of immortal jellyfish. But, it’s not.

Resetting your entire body takes time. When the jellyfish gets hurt, it needs to drop down to the seafloor and spend a few days reorganizing its cells into a polyp, which means to kill the immortal jellyfish, you just have to kill it instantly. If a sea turtle swims by and swallows the jellyfish whole, it’s dead.

It doesn’t get a chance to reset its cells if it’s currently being digested in its turtle stomach. Because, well, you can’t really hit the reset button when you’re actively being dissolved. If a larger fish chomps it in half, it’s dead. It might not die of old age, but it’s still just a squishy piece of protein sitting at the absolute bottom of the food chain.

 It’s a slightly dark realization. The only animal on the planet capable of living forever is completely defenseless against just being eaten as a light snack. But, this brings up the most important question of all. If immortality is physically possible, why didn’t evolution make us immortal? If a tiny jellyfish can figure out how to reset its cells and a shark can figure out how to live for 500 years, why does everything else on Earth have to die at all? Why isn’t extreme lifespan just a standard for all animals? Well, the brutal truth is that

if you want evolution to actually work, things have to die. If a new species never dies, it never replaces its population with new offspring. [music] And if it never creates new offspring, its DNA never changes. Evolution relies entirely on parents passing down [music] upgraded DNA to their children. Those children adapt to the changing environment, survive, and pass those upgrades on again.

 If you’re a 10,000-year-old glass sponge, your DNA hasn’t changed in 10,000 years. That works perfectly fine in the deep ocean because the deep ocean never changes. But up on the surface, the environment is constantly shifting. Diseases mutate, predators get faster, the climate changes. If a land animal lived for 10,000 years without reproducing and adapting, a new virus would just come along and wipe out the entire species overnight because their immune systems would be 10,000 years out of date.

 The virus would basically just walk in and go, “Wait, you guys still don’t have defenses for this?” Animals have to die so that the next generation can adapt and survive. Death is exactly what forces biology to keep working. It’s a good thing for species. So, what does this mean for us? Scientists are currently spending millions of dollars studying these deep-sea creatures.

They’re sequencing the bowhead whale’s DNA to understand cancer resistance. And they’re studying the immortal jellyfish to try and unlock anti-aging treatments for humans. And theoretically, we could eventually engineer biology that lets humans live for 500 years. But when you look at all the animals that actually hold this off naturally, you realize that extreme lifespans always come with a massive tax.

 You can live for 500 years, but you have to live in the freezing dark, move in slow motion, and let parasites eat your eyes. You can live for 15,000 years, but you have to become a literal glass rock that doesn’t have a brain. We burn through our lives in about 80 years because we’re warm-blooded and fast. Our bodies consume massive amounts of energy just to keep our brains running at a high level so that we actually experience the world.

 We burn hot and because of that, we burn out fast. Our short lifespans are simply the tax we pay for actually getting to do things. Honestly, I’d rather have 80 years of experiencing life than 10,000 years of sitting in the pitch black waiting for a piece of marine snow to fall in my mouth. But anyways, I’m definitely not trading my brain to become a deep sea sponge anytime soon.