00:00For millions of years, something has been lurking in the depths of the ocean.
00:05You can't see it, touch it, or map with sonar.
00:08Yet it keeps entire species trapped where they are.
00:12Recently, scientists uncovered its victims.
00:15Strange jellyfish cousins that look almost identical, except for one odd detail.
00:21One travels the world's oceans.
00:23The other is stuck in the Arctic, unable to escape.
00:27What blocks its way?
00:29It's not ice, not land, not even depth.
00:32Something far stranger.
00:34Let's take a look at this mystery.
00:37The jellyfish in question belong to a subspecies with a pretty complicated and hard-to-pronounce name.
00:42So I won't. See?
00:45Anyway, they live very deep in the ocean, about 3,300 to 6,600 feet down.
00:51That's so deep that sunlight doesn't even bother showing up there.
00:54The strange thing is that some of these jellyfish have a little bump or knob on top of their umbrella-shaped body, and others don't.
01:03And this tiny difference decides their entire life story.
01:07Jellyfish with a knob are world travelers found across all oceans.
01:13Jellyfish without a knob are stuck in the Arctic, like they're grounded for life.
01:19To figure out what was going on, scientist Javier Montenegro and his team looked back at more than 120 years of jellyfish photos and sightings.
01:27Then, they added in modern DNA testing.
01:32The results were curious.
01:33Genetically, the knobless and knob jellyfish in the Arctic were identical to knob species in the western Atlantic.
01:41In any case, this bizarre similarity aside, only the knobless jellyfish are trapped in the north.
01:48So, what's keeping them from leaving?
01:51It's not a giant underwater wall or a rocky barrier.
01:56Instead, scientists think the wall is biological or linked to geography.
02:02Just like something called the Wallace Line, nature's invisible border.
02:06So, imagine sailing on a boat in Indonesia, crossing from the island of Bali to the island of Lombok.
02:15It's only about 22 miles, not even enough for a long nap on deck.
02:20Once you're there, the beaches look the same, the weather feels the same, and the palm trees all sway the same way.
02:27But when you look at the animals, it feels like stepping into a different universe.
02:32Birds, mammals, even reptiles suddenly don't match what you just saw a short distance away.
02:40That invisible line dividing the two worlds is the very Wallace Line.
02:45The story began in 1859.
02:48Alfred Russell Wallace, a British naturalist, traveled through the East Indies.
02:54While hopping between islands, he noticed something that didn't make sense.
02:58On the western islands, like Borneo and Bali, the animals all looked like they belonged to Asia.
03:04Monkeys, tigers, woodpeckers, the usual.
03:07But East, the animals seemed to have come straight out of Australia.
03:12Marsupials, cockatoos, even kangaroo cousins.
03:15The two sides weren't blending at all.
03:18Wallace realized that a narrow stretch of water could act like a massive biological border.
03:23How could two islands close enough to sea across the water pose such different wildlife?
03:30The line is not just some quirk of nature, but the result of powerful geological forces.
03:36Between the islands, there are underwater trenches that have never dried up, even when ancient sea levels rose and fell.
03:44To the west, you can find the Sunda Shelf.
03:47That's an enormous sunken platform that once connected Asia to nearby islands.
03:51That's why Borneo, Sumatra, and Java are packed with Asian-style wildlife.
03:57To the east is the Sahal Shelf.
04:00It once linked Australia and New Guinea, helping Australian species spread.
04:05The Wallace line slices right between these shelves.
04:09This part of the world, the Indo-Australian Archipelago, is where four massive tectonic plates slam into each other.
04:17As the seas rose, animals became trapped on islands.
04:22When seas fell, some species made it across, but not so many.
04:26That's why two islands, separated by just a short boat ride, ended up with completely different ecosystems.
04:33The Wallace line isn't some recent discovery.
04:36This invisible border has been messing with animals for millions of years.
04:40Back in the Pleistocene, when giant mammoths roamed our planet and the oceans were up to 400 feet lower, many of the islands in Indonesia were actually connected.
04:51Tigers and elephants could stroll from place to place without ever touching water.
04:57But even when sea levels dropped that much, Asia and Australia never linked up.
05:02There was always a stretch of really deep water between them, and that watery gap acted like an uncrossable wall.
05:10For more than 50 million years, it's been stopping animals from mixing, keeping Asia's lineup on one side and Australia's weird crew on the other.
05:20That middle zone of islands, the ones stranded between the two continents, is called Wallacea.
05:26Only animals that could swim, fly, or somehow make it across the open ocean managed to live there.
05:32Everyone else was stuck at home, no exceptions.
05:36As you see, there can be a logical scientific explanation for almost any phenomenon on Earth.
05:43Maybe we could find one of those poor trapped jellyfish.
05:46Apparently, the problem lies in the North Atlantic drift.
05:50It's a warm current that flows up from the Gulf Stream.
05:53Scientists don't know exactly why, but something about this area blocks the knobless jellyfish.
05:58One theory claims that predators beyond the drift are too dangerous for these creatures.
06:04Another idea is that the knob itself somehow gives jellyfish an edge in survival.
06:09But no one really knows.
06:12For now, it's like an invisible border.
06:15Knob jellyfish pass, knobless jellyfish stay put.
06:19On the Pacific side of the Arctic, there's no need for a mysterious barrier.
06:23The Bering Strait already does the job.
06:26On average, it's only 165 feet deep, which is way too shallow for deep-sea creatures to get through.
06:32So, these jellyfish, knob or no knob, can't escape south.
06:38And since we're back at the topic of animal life, let's speak a bit more about the weird fauna quirks of the Wallace Line.
06:45Because animals are the easiest way to see this barrier in action.
06:48Birds, for example, often refuse to cross even the tiniest gaps of open water.
06:55So, their species stop right at the line.
06:58Mammals are even stricter.
07:00Bats can cross because they fly, but larger land animals never made the jump.
07:06On the Australian side, it's all about marsupials, like kangaroos and possums.
07:12You'll also find native rodents that settled there more recently.
07:15On the Asian side, you get a different cast.
07:19Apes, elephants, tigers, cats, monkeys, rhinos.
07:24Sure, there are some oddball exceptions.
07:26Siloessi, right in the middle of the divide, has macaques, pigs, and big-eyed little tarsiers.
07:33But overall, the split is obvious.
07:36Step off the boat, and the animal world changes completely.
07:40But then, what about plants?
07:42Well, they don't always follow the rules as neatly.
07:45Seeds can hitch rides on birds, float on water, or get blown by the wind.
07:50But even here, the Wallace line shows up.
07:53Take eucalyptus trees, for example.
07:56They're as Australian as kangaroos.
07:58Almost no species make it across to Asia.
08:01There's just one exception, which somehow popped up on Siloessi and the Philippines.
08:06That's the magic of the Wallace line.
08:09Two islands can look the same.
08:11Same climate, same forests.
08:13Sometimes even close enough that you can see across the strait.
08:16But their animals are like night and day.
08:19And it's all because of an invisible border in the sea that's been in place for millions of years.
08:25Such discoveries might sound small, but they're important.
08:29They show us that there are still hidden boundaries in the ocean that humans don't understand.
08:34These invisible fences could explain how marine animals spread, evolve, and survive.
08:40As scientists put it, finding two different body shapes inside a single genetic family shows how little we know about jellyfish and other gelatinous creatures.
08:51As for the Wallace line, even today, it stands as one of the most fascinating mysteries in biogeography.
08:58It reminds us that life doesn't always spread evenly.
09:01Sometimes, a short stretch of water can act like an uncrossable wall.
09:07There's a lot more mystery in the deep sea than we thought.
09:15That's it for today.
09:16So hey, if you pacified your curiosity, then give the video a like and share it with your friends.
09:21Or if you want more, just click on these videos and stay on the bright side!
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