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00:00Does the animal kingdom hold the key to immortality?
00:03It's regrowing a whole complex system.
00:06It's almost like magic, but it's nature just trying to survive.
00:09Humans have the benefit of medicine,
00:10but these skills pale in comparison to nature's super healers.
00:15We require probably hundreds of people
00:17to be able to begin to approximate what they do.
00:19In the animal world, some have evolved to replace parts.
00:23Regeneration is an amazing evolutionary advantage.
00:26It is an extremely elegant process.
00:28Some use their bodies as the ultimate weapon,
00:31while others grow features to display dominance.
00:34Imagine if we could unlock that power and use it ourselves.
00:37It just takes your brain to, like, limits.
01:01Imagine if we could regenerate limbs or organs or teeth.
01:05Imagine what it would mean to recovery from disease or injury.
01:09These six remarkable creatures can literally regrow parts of themselves
01:14in the ultimate power-up move.
01:16They can activate and change cells to repair their own damage.
01:20This is the story of the regenerators.
01:24Sharks, one of nature's most deadly predators,
01:28just happens to be one of its most powerful regenerators.
01:32Sharks lie at the top of the food chain, making them apex predators.
01:35Sharks are found in every ocean on the planet,
01:38come in all sizes and many different shapes.
01:41They are the oldest and least changed of the living backboned creatures.
01:45When nature gets things right, it tends to keep it.
01:50Sharks are a marvel of evolutionary engineering,
01:54famous for their massive jaws, rows of razor-sharp teeth,
01:58and their ability to strike swiftly and silently.
02:02What does a shark need to do?
02:03A shark needs to be able to attack prey and kill it.
02:06To get the job done, they have some extremely effective weapons
02:10that have been perfected through hundreds of millions of years of evolution.
02:14Their sense of smell is really good.
02:16They can detect if there's an injury in an animal by smelling their blood.
02:20Their eyesight, maybe not so great,
02:22but they can detect electromagnetic fields in the muscles as their prey move.
02:27That would come from muscle contractions,
02:30nerve pathway signalings that occur in their body and even their heartbeats.
02:34They can actually detect if fish is about to die,
02:36and that's how they are able to target those fish and maximize that opportunity.
02:41All this goes into building the ultimate predator.
02:44Their razor-sharp teeth are designed not to chew, but to cut through flesh and bone.
02:50Some sharks can have, on average, about five rows in each jaw.
02:54The bull shark can actually have about 50 rows.
02:57Their teeth face backwards a little bit, meaning that once they bite down,
03:00it's very difficult to kind of escape.
03:02They have no arms. You know, they have nothing to say,
03:05oh, I've got you. It's, boom, I've got you.
03:09Sharks' teeth are such a vital part of their arsenal that they are born with a full set.
03:14And their teeth take a beating, in part because they're cartilaginous,
03:18meaning sharks have no bones.
03:20Their skeletons are made of flexible cartilage similar to the human nose or ear.
03:25Their teeth sit in that soft, soft tissue instead of hard bone.
03:29Some great whites have been shown to have more than 1,000 pounds of pressure on that bite.
03:34That's a huge amount of pressure.
03:36If a great white's attacking a seal, the shark, as it comes out of the water,
03:39often thrashes, trying to serrate and tear.
03:44The forces of that action are transmitted through those teeth.
03:47When they eat their food, there's a very high chance of them losing their teeth.
03:51They can lose up to 100 teeth per day.
03:54Which leads to their most stunning superpower,
03:56the ability to grow new teeth to replace their lost ones.
04:00This is something that sharks have evolved over millennia.
04:04Those teeth are your front-line mechanism of attack.
04:07If you don't have those, you're not going to be able to eat
04:10and you're not going to be around particularly long.
04:13New teeth will form in the mouth, and then when they are ready,
04:16they kind of flip out to be available onto the biting surface
04:19and the old teeth fall out.
04:21It's a conveyor belt of teeth.
04:23Some can lose and replace up to 40,000 teeth over a lifetime.
04:28The conveyor belt rows of razor-sharp teeth are designed to work seamlessly
04:33with the shark's incredible jaw.
04:35Their jaw can unhinge, and that allows them to open their mouth exceptionally wide,
04:40push their jaw forward so that they can get up around the backside,
04:44so they can actually grab onto something.
04:47So it's more of a grappling-type effect than just a biting.
04:50That jaw has a huge number of muscles on it that clamp closed
04:54to give you that crushing power that hold onto the object
04:57and shake and tear it up so that you can actually kill it.
05:00A shark's jaw is not attached to the skull
05:02and even has a joint in the middle for increased flexibility.
05:06The jaw has also evolved to hold the key to tooth regeneration.
05:11In their mouth, there's a larger concentration of stem cells,
05:14which are cells that don't have an assigned role yet.
05:18Stem cells are the building blocks of life.
05:21Every creature on Earth that is made up of two or more cells
05:24has stem cells lying in wait.
05:26Because you need constant teeth regeneration,
05:29these stem cells are then assigned to regrow its teeth
05:32again and again and again throughout their life.
05:36When you think about the predator-prey relationship,
05:38it's live or die.
05:39When an animal loses a limb or gets really injured,
05:44Mother Nature is completely ruthless.
05:47So the ability to have those stem cells to just say,
05:50Oh, you need another tooth?
05:51Boom. We got another tooth.
05:53And it just keeps going.
05:54You've got rows of teeth waiting to be used.
05:56It's ultimate survival.
05:58As humans, we get two sets of teeth.
06:01Baby teeth are replaced by adult teeth around the age of 12.
06:05And that's it.
06:06If you lose one, the only way to replace it is with an implant.
06:09It would be so much easier if, you know,
06:12we get a cavity in the tooth and it just falls out
06:14and a new tooth pops in behind it.
06:15But what if we could regrow our teeth like sharks do?
06:19To do that, we would have to harness the power of our own stem cells.
06:23We can grow things and heal things.
06:26You know, if you have a burn that heals,
06:27you're growing new skin cells.
06:28However, we can't create undifferentiated material
06:32and choose what it becomes
06:34and make it create a whole variety of different things.
06:37We know what stem cells are capable of.
06:39If we can harness that biology,
06:42we should be able to regrow limbs, et cetera,
06:45because we know what these progenitor cells are.
06:47Now we have to figure out how to program them
06:49to do what we need them to do.
06:51Human beings lose our limbs and parts of our bodies all the time.
06:54Often it kills us.
06:55Often it changes our lives dramatically.
06:58If we could untap that potential, yeah, I mean,
07:01I think that it would make a huge difference
07:03in the quality of life of a lot of people.
07:05While we are a long way off from harnessing the power of stem cells
07:09to regenerate human replacement parts,
07:12scientists and engineers are already using other knowledge
07:15gained from the shark's super physiology.
07:18To understand this better,
07:20we need to take a deep dive into their engineering.
07:24First and foremost, sharks are adapted to their environment, the ocean.
07:29When you watch them swim,
07:30and they just look like they're just going along,
07:34it's beautiful.
07:35You talk about a machine that can just be so fluid in the water,
07:39and when it hunts it can move faster,
07:41it can slow down, it can spin on a pinpoint.
07:44It's just phenomenal to me.
07:45That lethal agility comes from the shark's remarkable bone structure,
07:50or rather, lack of one.
07:52That same cartilage that gives the shark its flexible jaw
07:55extends to their entire skeleton.
07:59Sharks are speed demons.
08:01It almost looks like a torpedo going through a water.
08:03The cartilage in the shark allows them to have less mass,
08:07and force equals mass times acceleration.
08:09So if you want to go faster,
08:12having a lower mass really, really helps with that.
08:15It also has a hydrodynamic body shape that slices through the water.
08:19One of the things we try to do as engineers when we're designing objects
08:23that sit in the water is reduce the wake,
08:25because that wake is wasted energy.
08:27The shark's biology has developed so that they're minimizing that wake.
08:31So rather than energy going into displacing the water,
08:35the energy goes into them moving forward.
08:37You see that they're tapered at the front,
08:39they get larger in the middle, and then narrower at the back.
08:41That's going to try and keep that water hugging the surface of their body,
08:45reducing that amount of energy that's transmitted.
08:48Animals that live in water, they adapt their external surfaces,
08:53their skin or their shell, to that environment.
08:57So where you want to get really high speeds in water,
08:59you don't want that little drag of the water molecules on the surface.
09:03You have a surface that's hydrophobic, and that's what the sharks have,
09:06is they've developed a surface that doesn't stay quite in contact with the water.
09:10Evolutionary engineering gave sharks a skin that is both tough and fast.
09:15And the secret?
09:16Thousands of microscopic, hard-ridged scales, made of dentin.
09:21Basically, teeth.
09:22They were created like teeth, but they're called denticles.
09:25Denticles are an ingenious bit of engineering.
09:28They repel water by creating tiny vortices around the shark's body,
09:32not only reducing drag from the water, but helping to create thrust to propel the shark forward.
09:38They are curved backwards to reduce that friction drag to allow them to swim faster.
09:42But unlike a shark's teeth, denticles don't regenerate.
09:45It's believed that there are certain genes that control the regeneration,
09:49because they are similar properties, they're both found in the same animal,
09:53but yet it's only the teeth that regenerate.
09:55The shark evolved their unique design system over 450 million years ago,
10:00and not much has changed since.
10:03Evolution said, hey, this works, and it's worked for millions and millions and millions of years.
10:08It's clear the shark's design has a very distinct advantage
10:12that their competitors haven't been able to catch up to.
10:15To survive extinctions, to go through different changes in climate
10:20that the Earth has gone through,
10:21these species are probably some of the toughest species that we've ever seen.
10:25They are the ultimate apex predator.
10:26As we begin to unlock the secrets
10:28to the shark's incredible bioengineering and power to regenerate,
10:32maybe one day we will swim faster and even grow new teeth.
10:36It's something that we don't totally understand, but it's unbelievable.
10:40And it kind of begs the question, what other potential is there
10:43within the genes of all of these creatures?
10:46What could come next?
10:51Harnessing the power of stem cells so that we could program them
10:54to build new teeth, limbs, or organs, or any part,
10:58is still more science fiction than fact.
11:02Unless you're a salamander, one of this planet's tiniest creatures,
11:07but a true giant when it comes to regeneration.
11:11Salamanders are a really cool species.
11:14They move quickly.
11:14They come in a variety of different colors.
11:17A lot of people think they're cute.
11:20You think of salamanders, you think of something that's just like gooey,
11:23something that looks like a cross between a frog and a lizard.
11:25But they're so cool and they're regenerative abilities.
11:29They can regrow limbs, even organs, like their heart.
11:33They are an amphibian, meaning that they're with toads and frogs.
11:38They have a cylindrical trunk and usually four limbs,
11:42but some may have two and a tail.
11:43They even come in a range of sizes.
11:45There's like tiny salamanders and there's giant salamanders
11:48that are just like this big.
11:52Salamanders are found pretty much everywhere,
11:55but the greatest diversity is found north of the equator.
11:58They are found in a wide variety of habitats.
12:00Some are a little more dry areas, some are more humid,
12:02but they do need to have access to water
12:04since their life cycle requires them to be in an aquatic phase
12:08for a part of their life.
12:10Some of them have gills, some of them have lungs,
12:13and some of them breathe through their skin.
12:15So they have a lot of abilities that allow them to survive
12:18and thrive in those environments.
12:21Just about every kid knows
12:23that salamanders can easily lose their tails.
12:26As a kid, being inquisitive as I am,
12:28I think I turned over every rock and nook and cranny
12:31for a kilometer around that cottage.
12:34And periodically I'd flip over a rock and I'd find a salamander.
12:39Invariably once in a while we'd smack it by the tail
12:41and the tail would fall off.
12:43But what isn't as well known
12:44is that sometimes the salamander loses its tail on purpose.
12:48when faced with a predator.
12:49The tail is a really incredible example
12:51of this kind of defense mechanism.
12:53So it's kind of a deliberate self-amputation
12:55when a bird swoops down and grabs that tail.
12:57You know, it's not going to let itself be held back by that.
12:59It just cut the whole tail off and it gets to go on its way.
13:02Hopefully it buys itself enough time.
13:04This perfect piece of bioengineering
13:06is designed to help the small amphibian gain the upper hand.
13:10And if this super defense mechanism wasn't amazing enough,
13:13when the salamander loses a tail or even one of its limbs,
13:17they just grow a new one.
13:19They actually can regrow it to the very same state
13:22that it was before and not a lower version of it.
13:25There is no blood or scarring.
13:27Within the first few hours, a salamander's skin cells
13:30actually migrate to the wound site to close off the wound.
13:33They have kind of the whole road map of what this limb should look like.
13:37And so over the course of a few weeks usually,
13:39it will slowly kind of get to work and construct the new limb.
13:42And so it will produce the blood vessels that go through.
13:44It will produce the bones that need to be there as the scaffold.
13:47It will produce the ligaments and the muscles.
13:49Imagine being able to grow a new arm or leg,
13:52complete with new bone, muscles, nerves and veins.
13:56It's incredible, you know, when you look around
13:58what we humans can do, you know, in terms of reattaching limbs,
14:00returning functionality to fingers or, you know,
14:03other parts of our bodies that have been cut off.
14:05But it's even more incredible when you think that salamanders
14:07have had this for millions of years
14:09and they don't even bother with the reattaching.
14:11They just grow a whole new one.
14:12It's, you know, absolutely mind-blowing.
14:14We're only just starting to unlock the secret of salamander regeneration.
14:19And much of the study is focused on this astonishing creature.
14:23The axolotl is kind of the king regenerator.
14:26And it's the model organism that we use.
14:28And a lot of research on regeneration.
14:31Nicknamed the Mexican walking fish, it's not a fish at all,
14:35but a salamander that lives in the water full time.
14:38Axolotl are related to the tiger salamander,
14:41but are much bigger, sometimes as big as 32 centimeters long.
14:45Still small compared to others in the animal kingdom.
14:49But that little body contains the most colossal genome ever sequenced.
14:53By some reports almost 10 times the size of our own genome,
14:58the axolotl has an almost supernatural ability to regrow not just tail and limbs,
15:03but internal organs as well.
15:05You can cut off pieces of their heart, of their spine.
15:07You can cut out pieces of their brain and they will grow it back.
15:11The fact that these cells even know where to go,
15:13it's almost as if they have a positional memory of where to direct themselves is amazing.
15:18What gets activated when a body part goes missing is stem cells.
15:23Stem cells are undifferentiated cells.
15:25They have the potential to become any cell in the body.
15:27In humans, we lose these cells in most of our bodies by the time we're born.
15:31Salamanders keep these their entire life.
15:33And so when they lose a limb, these stem cells are able to flood into the wound,
15:37and they form these blastemas.
15:38The blastema is a bunch of stem cells,
15:41but also some differentiated cells that can become undifferentiated.
15:46So these cells may previously have had a role, let's say they were a muscle cell,
15:51but then they can be assigned a new role.
15:53We probably don't know the full capability of the stem cells that we have.
15:57That comes with looking at sort of mitochondrial RNA
16:00and looking at the process of what triggers those stem cells,
16:04maybe in manipulation or putting in something that allows us to trigger regeneration of spinal fluid
16:11or, you know, cells that could replace other cells.
16:15And I think if we can actually figure out those triggers, we can go pretty far.
16:21We have stem cells in a few key areas, like bone marrow, blood vessels, skin.
16:27But taking differentiated cells, that is cells that are assigned a role,
16:31and turning them into undifferentiated cells to be used where needed, like the salamander,
16:36that is a long way off.
16:38Adapting biology to our own needs is something that we're trying to achieve.
16:42Looking at a salamander that can regrow a severed limb, I mean, it's just not even a fair comparison.
16:48We are not even starting down the road that biology has been going down for millions of years.
16:53But there's one tiny creature that can regenerate an entire skeleton.
16:59Meet the spider.
17:02The Iron Man of the animal kingdom.
17:05Spiders are one of the world's most fascinating creatures.
17:08But they have a bit of a reputation.
17:11Mostly because, well, people find them a bit creepy.
17:14Humans are interesting in that we're often scared of heights.
17:19We're often scared of water.
17:21We're scared of spiders.
17:22In fact, fear of spiders is one of the most common phobias.
17:26They seem creepy and crawly because media has portrayed them that way.
17:30When you take a closer look, they are one of nature's most successful attempts at bioengineering.
17:35We have this image of spider.
17:38But when you look at spiders going from tarantulas, the little tiny spiders, their morphology is remarkably different.
17:45They do very different things ecologically.
17:48So, you know, you're built for what you do.
17:53Spiders are an incredibly successful species.
17:57Forged over hundreds of millions of years of evolution,
18:0148,200 species of spider are found on every continent except Antarctica and live in every kind of habitat.
18:09Just like they're in every corner of your house, the spiders are in every corner of the world.
18:13I love spiders.
18:15They look so simple and they're so small that you might not think they're capable of such amazing abilities.
18:20When people look at a spider on the wall, they're just like, ew, gross, kill it.
18:24When I look at it, I see mechanics.
18:27A lot of people mistake spiders for bugs or insects, but they're actually arachnids.
18:33Spiders are arthropods, which literally means joint-footed.
18:37They do have joints that are located on their arms.
18:40They actually have seven as opposed to us.
18:42We just only have one in each extremity.
18:44Arthropods includes any invertebrate with a segmented body, articulated legs, and an exoskeleton.
18:50That exoskeleton is a phenomenal bit of evolutionary engineering, guarding spiders from predators.
18:56The spider is involved essentially with a plastic casing.
19:02But even though that light armor gives the spider a real advantage, it can't grow with it.
19:08If you're going to get bigger, there's no mechanism for that plastic chitin shell to expand.
19:13What happens when the exoskeleton gets too tight for the creature inside?
19:17It grows a new one, of course.
19:20Spiders are master regenerators.
19:22That exoskeleton needs to be shed. It's a process called molting.
19:26Also fancily known as ectasis, which is the shedding of their outer exoskeleton and growing a larger new one.
19:32Imagine you're wearing a pair of shoes. You have to change them as your feet get bigger.
19:37Unlike other super regenerators in the animal kingdom, the spider does not use stem cells to build a new exoskeleton.
19:45That chitin shell is a polymer. It's a polysaccharide, which means it's a sugar molecule that's been added onto and
19:51added onto and added onto.
19:53Polymers built by biology are still polymers. They're still plastics. And they have the same kind of properties.
20:00That light protein and polysaccharide casing is created entirely inside the spider.
20:06They would actually grow a new exoskeleton underneath their existing skeleton, but this one's much more pliable.
20:14It's softer. Think of it as a very snug sweater under shirt that you're wearing.
20:21Once the new exoskeleton is ready, the body releases hormones that dissolve a thin layer attaching the old exoskeleton
20:29to the new exoskeleton.
20:31It's almost like it's trying to take off a wetsuit. Imagine being able to just be like,
20:35I'm just going to melt this thing off so it just sheds.
20:37On the old skin, although it looks like it's one piece, there are areas where there are what are called
20:42sutures,
20:43where segments come together, and they're fault lines almost.
20:47Those fault lines spread to ease in shedding the old exoskeleton.
20:52But they do double duty, acting as joints in the spider's articulated legs.
20:57When the spider emerges, the exoskeleton has not yet hardened.
21:02So what they would do during this time is expand their muscles to extend the shape of the new exoskeleton.
21:09And in this process, they also release this hormone called bursicon that is a tanning hormone
21:14that allows the hardening process of that new exoskeleton, which could take anywhere from a day to a few days.
21:22As it's exposed and with the light, it gets harder. It's a bit like if you pour glue, you know,
21:27and then it goes hard.
21:28It's a series of chemical, biological reactions that are progressing to make this change.
21:34So it's not just a simple, I'm casting off a shell. There's a lot going on in behind there.
21:39It is an extremely elegant process.
21:43It is at this point that the spider is exceptionally vulnerable to attack.
21:48A lot of these spiders during molting, they actually become reclusive. They hide in tunnels.
21:53The ones hanging up from trees might drag a silk line down so they're not in view of predators.
21:58During this time as well, they don't eat because their entire exoskeleton is being molted, which does include their fangs.
22:05Building, shedding, and hardening a new exoskeleton is an incredible feat of regeneration.
22:10The chitin shell is extremely tough, extremely durable, and protects them extremely well.
22:16And this is incredibly helpful because inside their body, they're essentially goo.
22:22It's a soft tissue body that cannot function without that exoskeleton.
22:26But that's not all the spider has to offer when it comes to superpowers.
22:30A remarkable fluid circulates through the spider's body.
22:34They use the hemolymph, which is the blood, because they have an open system. It's not like ours with blood
22:40vessels.
22:41Because the spider doesn't have veins or arteries, it makes use of hemolymph by building pressure.
22:47In molting, that fluid pressure helps the spider push out of the exoskeleton.
22:52That buildup of fluid is key to how a spider moves.
22:56They don't really have muscles the way we think of them. They can pull their legs in with their muscles,
23:00but they can't push them back out.
23:02Hydraulics is the application of pressure to fluid inside a closed system that will transmit that pressure in the direction
23:08it's needed.
23:09So the bulldozer that lifts the blade up and down, those cylinders that are pistons with a ram inside,
23:16when we put hydraulic oil at high pressure in, it pushes the ram in and out of the cylinder.
23:22Well, essentially, the spider's doing the same thing. It's using the hydraulic pressure it generates in the fluid inside its
23:28body,
23:29putting it into the arm to push it back out. And then it uses the muscle to pull it back
23:35in.
23:35And while it's pulling it back in, that fluid flows back out.
23:38And then when it needs to re-extend the limb, it lets the fluid back in.
23:42So it's doing this almost hydraulic action in moving those limbs.
23:47It's an amazing adaptation because it allows them to use less weight to achieve the same thing,
23:54because they're just using that pressure to re-establish the limb position without having any muscle weight to do it.
24:02And just like a machine that uses hydraulic pressure, there is no movement without fluid.
24:07Having a hard casing is important to enclose that liquid system because it's in transport system, nutrient system,
24:13and also prevents desiccation, basically drying out of the animal.
24:18You put a pinhole in that exoskeleton and that fluid comes out, that spider dies, it can't move, it can't
24:23survive.
24:24And so that exoskeleton is crucial to the survival of the spider.
24:28Imagine if humans could take the spider's chitin, a sort of biological polymer, and use it in biomedical applications.
24:36I think the fact that they're able to transfer nerves and blood vessels from their old exoskeleton to the new
24:41exoskeleton
24:42can be helpful in transplant surgeries.
24:45We are already experimenting with the concept of exoskeletons,
24:49which augment human motion and add strength when lifting objects.
24:53But we can't create them biologically yet.
24:56Those kind of technologies are something that we strive for as engineers and scientists,
25:00but they're still out of our grasp.
25:03Biology, over millennia, has come up with so many creative ways to solve problems,
25:09to address issues, and to become the best it can be, to fill niches, to protect itself.
25:14It's been so creative, and as scientists and engineers, we look to that to see how we can use that
25:20to better technologies.
25:23The spider's exoskeleton is a true miracle of regeneration.
25:28But there are even bigger and more impressive examples to be examined.
25:34Every autumn, males in the deer family engage in an annual courtship ritual.
25:39They do battle with their weapon of choice, their antlers.
25:45They would use them almost like swords.
25:47They use it to show dominance in establishing their territories,
25:50and that will allow them access to females in the area.
25:55It's head-to-head.
25:56They're maximizing their force when they hit each other.
25:59Now, those antlers are also there to sort of take away the force from the head.
26:03So it's not as if they're getting concussions every time they're hitting.
26:07Those antlers sort of take the brunt of the force, so it's not damaging the animal.
26:15Antlers are made entirely of bone.
26:17They come in different sizes.
26:19The older the deer, the bigger the rag, and the higher the status.
26:23Sometimes an impressive set of antlers is enough to win the female deer,
26:27and scare off any challenges.
26:29You kind of have this antler arms race where the deer with the larger antlers,
26:34the stronger antlers are able to pass their genes on to the next generation,
26:37and the next generation also has bigger, stronger antlers, et cetera, et cetera.
26:41Some of the antlers can weigh up to 40 pounds,
26:44and it's definitely challenging because there's risks that come into play,
26:48especially when they, let's say, get entangled with another buck's antlers
26:52or even getting tangled in wires.
26:55Because those antlers are so heavy,
26:58it's understandable that when mating season is over,
27:01male deer discard their antlers,
27:03tossing away those powerful and elaborate structures
27:06as if they were a pair of old shoes.
27:08A lot of people are actually shocked when they see antlers being shed.
27:12Oh, my God, a deer passed away.
27:13But they actually just dropped these antlers.
27:16And then they grow them back.
27:18The antlers usually grow at around late April, peaking May, June.
27:24The mating season usually happens in the late fall.
27:26And then they fall off around December.
27:29And then they restart the whole process once they do fall after just three weeks.
27:33They're not just these stale sticks that are on top of their head.
27:38They have a vascular system.
27:40There is blood that goes into the system.
27:42And so you have that constant regenerative ability.
27:46There's a lot of theories as to why they have to regrow antlers every year.
27:50Why not just keep the same antlers that they already have?
27:53It's a lot of weight to carry.
27:54So it's quite beneficial to just have them during the breeding season.
27:58There's also some theories that they need to be growing continuously
28:02because the antlers themselves don't grow once they're done forming.
28:05So that way they are able to grow in size as the buck matures.
28:12Deer are found in just about every environment, from tundras to tropical rainforests.
28:18The largest concentration of deer species is in temperate North America in the Rocky Mountains
28:23and the region between Alberta and British Columbia.
28:27Reindeer, elk, moose, and different varieties of deer all share this magical process of regeneration.
28:34Looking at antlers, they seem relatively inanimate.
28:37They don't seem like an important part of that animal.
28:40But when you actually look at what's happening biologically and their actual use
28:44and the forces that get transmitted through them, they're absolutely astounding.
28:49On the top of the head, they have these pedicles,
28:51which is essentially the feature that allows the stem cells to sort of turn on and be like, time to
28:57grow.
28:58And it sort of dictates what needs to grow.
29:01From these small pedicles, mighty antlers grow.
29:04Being able to regenerate living tissue on top of your head every year
29:08would be an impressive enough feat on its own.
29:11But antlers are also the fastest growing structures in the animal kingdom.
29:15Antlers will grow two centimeters per day. That's how fast they grow.
29:19You're looking at a lot of energy expended at the top of your head.
29:23Plus, the muscles that go into supporting that head as those antlers grow and branch out.
29:28At the outset, it just looks like a piece of bone, but it's an organ.
29:31There's a lot of other biology going there to make something grow at that rate.
29:36You can't just pop bone at the top of your head and make it just spontaneously grow.
29:41You need a support system. You need blood vessels.
29:44You need a way to get the oxygen and nutrients there to grow these structures.
29:48The budding structures are covered in a fuzzy skin called velvet
29:52that contains all the blood vessels and nerves to feed the bone growing within.
29:57It all happens at an amazing speed.
30:00The nerves in velvet grow ten times as fast as human nerves.
30:04The most that we could probably regenerate is like an inch more of our nerve,
30:08but we don't regenerate in the sense where we are able to replenish or restore to its original function.
30:15They do need to grow these antlers at a short amount of time and they're such big structures.
30:20The innervation in the velvet is so impressive because they need to direct so much energy into this growth.
30:27In spring, the velvet covering starts to itch and deer scrape their new head ornaments against trees to reveal the
30:35brand new antlers underneath.
30:37What's left is essentially a bony structure and that bony structure has no nerves in it.
30:42So when they actually do start fighting, they're not feeling any pain in their antlers.
30:48It's just a dead structure that's left on the top of their head.
30:51And then after the rut, those cells that are below the antlers basically say disconnect these and they drop off
30:59and start growing another set the next year.
31:01So it's really quite amazing. Not only is it regenerative, but it rejects at some point and says,
31:08Hey, I don't need this anymore. Let's not keep it on top of our head for the next seven months
31:13while I regrow all the fat that I needed to grow this.
31:16Let's not carry it. Let's build up our energy stores and then we'll start again next year.
31:22Perhaps the most magical aspect of antler growth is the bio memory they hold, almost as if there was some
31:28sort of internal blueprint.
31:30These antlers are absolutely amazing for a lot of different reasons.
31:34And maybe the one that's most fantastic to me is if in a given year a deer or a moose
31:41loses part of their antlers,
31:43there's a genetic memory that that piece has been lost.
31:46And in the subsequent year, the antler regrows with that same defect that happened in the prior year.
31:53It's just absolutely amazing that biology can have this memory.
31:59Regeneration is crazy on its own, but to have a memory of an injury and regrow it, it's just mind
32:05boggling.
32:06We have a lot to learn from deer antler regeneration.
32:09The ability to turn cells on and off, to grow antlers and then just drop them, could be the key
32:15in nerve, skin and limb regeneration.
32:18And could play a life saving role in diseases like cancer.
32:22What's happening in cancer is that we have a cell where something's gone haywire and it's reproducing far too quickly.
32:29Antler growth is similar to bone cancer growth, but deer can turn off the rampant cell growth, while humans cannot.
32:37So if we understand those molecular switches so that we can turn things off, like the antler growth turns on
32:45and off,
32:45then maybe we'll be able to attack those cancers and send the molecular signals to those cells to say,
32:52hey stop, we don't need you, stop growing.
32:55We're starting to understand those chemical signals and build the proteins that turn on and off signals in the body
33:02so that we can start to control individual cells and that technology is coming.
33:07Unlocking the secret to antler regeneration is still a long way off.
33:11At the moment, all we can do is marvel at this beautiful and mysterious process of bioengineering.
33:19Stem cells play a role in another species that is a master regenerator,
33:24although one that seems more like seaweed than sea creature.
33:29Deep down at the bottom of the ocean lives this peculiar creature known as a sea cucumber,
33:36because, well, it looks like a cucumber.
33:39A lot of people just think it's a really soft log, you know, kind of looking squishy.
33:44People will have this, this looks gross kind of reaction to it.
33:49They're not complex organisms by any means.
33:51They take in food, they excrete it, they kind of crawl around the ground like a caterpillar.
33:56They come in different colors, but they're usually darker green, brown, black.
34:01They can be anywhere from, like, a few inches to three to five feet.
34:06If we didn't have sea cucumbers, there would be a tremendous amount of algal blooms
34:10caused by too much nutrients in the water.
34:14Sea cucumbers filter through the debris that's found in the ocean
34:17and pick up the organic matter, which is what they would eat.
34:20There's even a saying that all of the sand found in the ocean has gone through a sea cucumber's body.
34:26They are a simple creature made up of three main parts,
34:30digestive tract, respiratory tract, and reproductive system.
34:34They're an echinoderm. They're related to the starfish and sea urchins.
34:38Take away the hard part of an urchin and the spines,
34:42and take away the harder part of the starfish.
34:45Take all those other parts. You have a sea cucumber.
34:48They move on five rows of tiny feet by changing the water pressure in them,
34:53taking in water to stretch and expelling water to contract.
34:57They may be simple creatures, but as the saying goes,
35:01don't judge a book by its cover.
35:03They have a pretty remarkable trick when under attack.
35:06It has these collagen fibers called fibrils.
35:09There's an enzyme that binds these fibrils together
35:11and make them really strong and actually make the body completely stiff.
35:15You would not be able to easily bend it and flex it.
35:18These animals can be soft and be able to squeeze themselves in some nooks and crannies
35:22and then make themselves hard so that the predator can't pry them out of that hole.
35:27There aren't a lot of other analogies in the animal kingdom
35:30where something changes almost physical state from something that's relatively liquid and squishy
35:36to something that's really quite hard, almost like a piece of wood.
35:41But the sea cucumber can take it even one step further.
35:46But sea cucumbers are quite unique because they would expel their digestive tract
35:49and even their respiratory tubules called respiratory trees.
35:53Everything on the inside of the sea cucumber gets thrust outside,
35:57and they release a sticky substance that entangles their predators and paralyzes them.
36:02Most animals, the site of danger, they try to keep every part of their body intact
36:06and run away from it instead of throwing it right at their predator's face.
36:10You would think that turning itself inside out would be the last thing a sea cucumber ever did.
36:16So the sea cucumber superpower, they can regenerate after expelling all those items out into the ocean.
36:22If the sea cucumber releases the entire digestive tract except for the cloaca sac at the front,
36:28a new blind tube is formed from the remaining cloaca,
36:32and a mass of cells is formed at the other end that extends until the two meet.
36:37And if they release the intestines from behind, the wound at the end of the remaining esophagus is closed off,
36:44and the tubes grow and reform to create a continuous digestive tract.
36:48They can regenerate these body parts anywhere from a few days to a few weeks,
36:52and they have other abilities that can allow them to still function.
36:57For example, if they were to expel their respiratory trees,
37:01they can actually also still breathe by intaking water through their body and absorb oxygen that way.
37:07Like most regenerators, sea cucumbers use stem cells to rebuild themselves.
37:12But these strange creatures go a step further.
37:15Their cells can transform into whatever they need.
37:19A lot of stem cells have sort of these precursors of what they're supposed to regenerate.
37:24So in a shark it could be a tooth.
37:25Other animals might be a specific limb.
37:28But when you have a sea cucumber that, you know, has different body functions,
37:32it might lose different aspects of its body if it goes through an evisceration,
37:35these undifferentiated cells will actually regrow what is needed, what is necessary.
37:41Human stem cells are already programmed to perform various tasks like healing the skin and bone.
37:48Being able to take those cells and not just regrow parts of the body,
37:52but also reprogram them to use where needed would be an incredible step forward in medical science.
37:58But right now, it is still a far off dream.
38:02If you think about sort of the applications to that from a human aspect, this is amazing.
38:07How do you have a stem cell that could actually be able to regenerate whatever it needs to?
38:12What message is sent to say we need to regenerate a specific type of organ or a specific type of
38:18feature
38:18because this is what we lost? How is that message going across?
38:22That is the research that would be very interesting in hearing.
38:25It's hard to believe there could be any simpler marine life than the sea cucumber,
38:30but there is one with even more astonishing powers of regeneration.
38:37Jellyfish, one of the oldest marine species and one of the least complicated,
38:42yet one of the most unusual and mysterious in the ocean.
38:46If you think about a lot of sort of science fiction alien species that we've sort of conjured up,
38:52a lot of them have very similar features of jellyfish.
38:57The head and the tentacles, the flow-like features that we see.
39:01They're extremely beautiful, and they're very much an alien biology to us as humans
39:07in that they're translucent, they have these long tentacles.
39:11Their movements are hypnotic. They're nebulous.
39:14They don't seem to have a fixed form.
39:19Jellyfish aren't really fish at all. They're plankton, which in ancient Greek means wanderer.
39:26That's what a jellyfish does. It wanders and drifts, carried by ocean tides and currents,
39:32because it's not strong enough to swim against them.
39:34Their use of energy to move is so efficient.
39:38They're carried across the ocean, but they're still making sure that they're moving within that water mass
39:44so that they stumble upon their food sources.
39:48Just a really, really beautiful, kind of mysterious creature.
39:53Jellyfish have a simple anatomy.
39:56First of all, they're 98% water.
39:59The solid parts of them consist of the outer layer of the bell, called the epidermis.
40:05Inside is the mesoglia, a thick elastic jelly.
40:09And inside that, the gastrodermis.
40:12Tentacles hang from the bell like spokes in a wheel.
40:15They don't have brains, they don't have a heart, but they do have some sensory abilities
40:19that help them smell or detect light or detect the orientation of their body.
40:23They can still capture prey despite not having a centralized way of thinking.
40:27They just hunt based on their surroundings.
40:29It's not as differentiated cell-wise as a lot of other creatures.
40:33But there's still a lot of chemical biology going on there.
40:37There's still DNA.
40:38And this is unique in the animal kingdom.
40:41So there's something that makes this different from everything else.
40:45And what makes the jellyfish different is that some of them take regeneration one step further.
40:51Regeneration, I think, is an amazing evolutionary advantage
40:54because it allows these animals to increase their survival.
40:58Jellyfish can regenerate different parts when injured.
41:01But almost ten years ago, in a lab in China, a marine biology student found a polyp,
41:08the younger stage of a jellyfish's life, growing on the body of a deceased moon jellyfish.
41:14This moon jellyfish was literally regenerating itself from the dead.
41:18These particular jellyfish can essentially go back into that first part of their life history and regenerate.
41:25It's almost like I'm not going to die here, I'm going to go back and do my life cycle again.
41:30Is it cloning itself?
41:32Or is it the same animal with the same DNA strands it originally had?
41:37And then it just co-ops that original biology?
41:41The moon jellyfish could possibly live forever, an honor previously held by only one other species,
41:48Turritopsis dorni, the immortal jellyfish.
41:51Being an immortal jellyfish is almost like a character in a sci-fi movie.
41:55To give a better understanding on how the immortal jellyfish regenerates,
41:58you have to look at the actual life cycle of all jellyfish in general.
42:01In some ways, the life cycle of a jellyfish sounds more like a plant than a fish.
42:06It has this larva, it's called a planula.
42:08It floats around until it finds a suitable area to sort of secure to the ground,
42:14so the current can't take it away.
42:15Then a polyp forms, which is like a stationary creature on a rock somewhere.
42:20They look kind of like flipped over jellyfish with tentacles waving in the air.
42:23The polyps will start to butt off and become a free-swimming medusa again.
42:28And then that becomes what we know as a jellyfish.
42:31For most jellyfish, the medusa is their final stage of life.
42:35But if the immortal or the moon jellyfish can't find food or become stressed,
42:40or even if they become old and sick...
42:43They can just become polyps again.
42:45Essentially, it folds up in on itself, and then the polyps develop from there.
42:49The cycle repeats indefinitely.
42:51In theory, they are living forever until they are eaten.
42:55This is a way of actually reproducing itself.
42:57It's the same genetic material that goes and gets passed on,
43:00whereas sexual reproduction would be more of the exchange of genetic material.
43:05The process is known as trans-differentiation.
43:08Cells turn into different cells.
43:11For example, fully mature muscle cells can be turned back into stem cells,
43:16and used for another purpose, like nerve cells.
43:19That jellyfish biology is particularly amazing.
43:22This is essentially a perpetual jellyfish machine.
43:26I get old, I get injured.
43:28Oh, drop to the bottom, reset my DNA, reset all my cells,
43:32use all that existing energy, and I'm back.
43:35It's something never before seen in the animal kingdom.
43:38It's miraculous, and I can't think of anything like it, really,
43:44that takes something, breaks it down, and builds it up again
43:47into something totally different.
43:48Imagine if humans could turn back the clock.
43:51It's like the fountain of youth, you know, for humans.
43:53Everybody thinks, how do we get younger?
43:55How do we stay young?
43:56How do we stay active?
43:56That kind of stuff.
43:57Imagine going from, like, 45 to going back to your teenage years,
44:01you know, where everybody says,
44:03oh, college was so great.
44:04How about going back to your 20s and going back to college?
44:06For now, human application remains a far-off dream,
44:10because while we can watch an immortal jellyfish regrow,
44:13trans-differentiation remains a deep mystery to us.
44:17Humankind has spent a lot of time in the last 30, 50 years
44:22really starting to understand biology.
44:25We're starting to understand how those DNA building blocks
44:30come together to build a life form.
44:34And while the jellyfish is relatively a simple life form,
44:38a lot of those building blocks are still the same ones
44:41that are in you and me and every other human.
44:45So by understanding this jellyfish's biology
44:49and the way that it can reincarnate itself,
44:51essentially within its own body,
44:54may have really profound implications for humans
44:57and genetic engineering going forward.
44:59And extraordinary thinking to something that works near suck so the
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