- 2 days ago
There’s an invisible line running through Indonesia that animals refuse to cross, and it splits the wildlife of Asia and Australia like two different worlds.
This boundary, known as the Wallace Line, marks where species suddenly change — tigers, elephants, and monkeys on one side, and kangaroos, cockatoos, and marsupials on the other.
Scientists discovered that deep ocean trenches and ancient sea levels kept these animal groups separated for millions of years, even when humans could cross freely by boat.
The line still affects evolution today, shaping ecosystems and creating one of the most dramatic natural divides on Earth.
And in this video, you’ll find out why this invisible barrier exists, how it formed, and what it reveals about the wild history of our planet. Animation is created by Bright Side.
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This video is made for entertainment purposes. We do not make any warranties about the completeness, safety and reliability. Any action you take upon the information in this video is strictly at your own risk, and we will not be liable for any damages or losses. It is the viewer's responsibility to use judgement, care and precaution if you plan to replicate.
This boundary, known as the Wallace Line, marks where species suddenly change — tigers, elephants, and monkeys on one side, and kangaroos, cockatoos, and marsupials on the other.
Scientists discovered that deep ocean trenches and ancient sea levels kept these animal groups separated for millions of years, even when humans could cross freely by boat.
The line still affects evolution today, shaping ecosystems and creating one of the most dramatic natural divides on Earth.
And in this video, you’ll find out why this invisible barrier exists, how it formed, and what it reveals about the wild history of our planet. Animation is created by Bright Side.
----------------------------------------------------------------------------------------
Music from TheSoul Sound: https://thesoul-sound.com/
Check our Bright Side podcast on Spotify and leave a positive review! https://open.spotify.com/show/0hUkPxD34jRLrMrJux4VxV
Subscribe to Bright Side: https://goo.gl/rQTJZz
----------------------------------------------------------------------------------------
Our Social Media:
Facebook: https://www.facebook.com/brightplanet/
Instagram: https://www.instagram.com/brightside.official
TikTok: https://www.tiktok.com/@brightside.official?lang=en
Stock materials (photos, footages and other):
https://www.depositphotos.com
https://www.shutterstock.com
https://www.eastnews.ru
----------------------------------------------------------------------------------------
For more videos and articles visit: http://www.brightside.me
----------------------------------------------------------------------------------------
This video is made for entertainment purposes. We do not make any warranties about the completeness, safety and reliability. Any action you take upon the information in this video is strictly at your own risk, and we will not be liable for any damages or losses. It is the viewer's responsibility to use judgement, care and precaution if you plan to replicate.
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FunTranscript
00:00This invisible line divides the world into two parts, and most animals, fish, and birds, for some reason, can't cross it.
00:09The line is called the Wallace Line, and it runs between Australia and Asia.
00:15It has its name after Alfred Russell Wallace, a British scientist and explorer who discovered it in 1859.
00:22He traveled to Asia to explore a group of islands called the Malay Archipelago.
00:28As Wallace walked through the jungles, climbed hills, and sailed on boats, he noticed something like an invisible wall.
00:38On its west side, in places like Borneo and Sumatra, he saw animals you might find in Asia.
00:45There were big rhinos munching on leaves and monkeys swinging from tree to tree.
00:50The forests were full of life, with all kinds of animals you'd expect to see in a jungle.
00:56But in places like Sulawesi and Lombok, just across the imaginary line he came up with, Wallace found animals more like the ones in Australia, and colorful birds like cockatoos.
01:09The behaviors of animals differ on different sides of the Wallace Line.
01:15Some creatures are great at traveling across tough barriers, like water, but others are not.
01:21For example, bats can fly across open water, but they sometimes cross the Wallace Line.
01:27On the other hand, big animals that live on land, like elephants, usually stay on just one side of the line.
01:35Some birds are shy and like to stay hidden in thick bushes and trees to avoid predators.
01:40They wouldn't feel safe flying over wide stretches of water with no place to hide.
01:44Plants don't stick to the Wallace Line as strictly as animals do, because they spread in their own unique ways, like with seeds carried by the wind, water, or animals.
01:57One plant genus, the eucalyptus, mostly stays on the Australian side.
02:02But one eucalyptus tree has made its way to the Philippines on the Asian side.
02:07Underwater, the Wallace Line doesn't matter as much.
02:12The area between the Wallace Line and Australia is called the Coral Triangle, and it's bursting with light.
02:20Now, after more than 150 years, scientists think they finally have an explanation of the Wallace Line mystery.
02:26They believe it all started about 35 million years ago, when Australia broke away from Antarctica and slowly moved up to crash into Asia.
02:38When this happened, the crash created a chain of islands called the Malay Archipelago between Asia and Australia.
02:45This caused extreme changes in the weather, which made the area very different and affected which animals could live there.
02:52Researchers used a computer model that looked at how more than 20,000 species of animals from both sides of the Wallace Line would have behaved millions of years ago.
03:04When Australia started to drift away from Antarctica, it opened up a huge new era of deep ocean around Antarctica.
03:12This is where the biggest ocean current on Earth, called the Antarctic Circumpolar Current, began to flow.
03:18This swirling current made the planet's climate much cooler and completely changed how animals could live in different places.
03:26But not all animals were affected in the same way.
03:30Indonesia stayed warm and rainy, which was perfect for animals from Asia.
03:34These creatures could hop from island to island like stepping stones and make their way toward Australia.
03:41But animals from Australia had a harder time.
03:43Over millions of years, they had gotten used to living in cooler, drier places.
03:48So the tropical islands didn't suit them as well.
03:53Scientists believe if we can see how animals adapted to big changes in weather patterns millions of years ago,
03:59we might be able to predict how today's animals will cope with a similar situation.
04:03Other scientists after Wallace also tried to describe and explain the invisible natural border between Asia and Australia and came up with their lines.
04:17The Weber Line, for example, is in a slightly different location than the Wallace Line,
04:22between the Oriental and the Australasian faunal regions within Wallasea.
04:26It's a group of mainly Indonesian islands that are separated by deep-water straits from the Asian and Australian continental shelves.
04:35They were never connected to the big continents by land,
04:38so animals that could swim, fly, or float across the water made it to these islands.
04:44That's why the creatures living there are so unique and come from both Asia and Australia.
04:50Weber's Line is where the balance tips.
04:53If you go one way, most of the animals are from Asia.
04:56If you go the other way, most of the animals are from Australia.
05:01Another important migration event in the history of our planet happened in the Americas.
05:07Around 30 million years ago, South America became a separate landmass as tectonic plates moved and pulled it away from Antarctica and Africa.
05:16Once it was on its own, the animals living there started to evolve in unique ways
05:21and turned into creatures you couldn't find anywhere else in the world.
05:26There were animals we still see today, like opossums, giant rodents like capybaras and chinchillas,
05:33armadillos, anteaters, and sloths.
05:38Some of the animals from those times are now extinct.
05:41There were giant ground sloths, bigger than cars, roaming around.
05:45There were glyptodonts, which were like giant armadillos with super-tough, bony shells.
05:52There were also huge, scary birds that couldn't fly but could chase down their prey.
05:58Up in North America, animals could still travel to other parts of the world through the Bering Strait.
06:04So North America was full of different animals like deer, bison, horses, camels, and even mammoths and mastodons.
06:14They all lived alongside predators like big cats, wolves, and bears.
06:24About 3 million years ago, the continents of North and South America got connected by a strip of land called the Isthmus of Panama.
06:33It formed because the tectonic plates shifted again.
06:36Some major volcanic activity between 25 million years ago also contributed to the process.
06:44Animals started to move between North and South America,
06:47and this long process went down in history as the Great American Interchange.
06:53During the Ice Age, huge glaciers in the North grew and shrank over tens of thousands of years.
07:00When the glaciers were at their biggest, they held so much water that the sea levels dropped,
07:06and forests probably turned into wide, grassy plains.
07:10So animals had the perfect conditions to cross over.
07:15Giant ground sloths were among the animals that went up north from South America, all the way to Alaska.
07:23One special kind even roamed the chilly tundras alongside woolly mammoths and caribou.
07:30Lots of North American predators decided to explore the South.
07:35There were cats like cougars, jaguars, and saber-toothed tigers with their giant teeth.
07:41Wolves, foxes, otters, raccoons, and bears also joined the migration.
07:47The short-faced bear could stand up to 13 feet tall and weigh as much as a small car.
07:53South America also had some funny-looking animals called sanus, or South American native undulants.
08:01These were hoofed mammals that evolved into all kinds of weird shapes while South America was isolated.
08:08Big animals from North America, for example, relatives of elephants with strange tusks,
08:14came to the south and became some of the largest creatures around.
08:17The ancestors of today's llamas settled in the Andes Mountains,
08:23and deer, tapirs, and peccaries thrived in the forests.
08:28Animals kept moving back and forth between the continents for thousands of years.
08:32But as the Ice Age ended, many of the bigger animals, like the giant ground sloths,
08:38couldn't adapt and disappear.
08:39It seems North American animals were better at adapting to their new homes.
08:45You can find armadillos, porcupines, and opossums from South America in North America.
08:51But many of South America's most famous animals, like jaguars, llamas, and spectacled bears,
08:58left North America long ago.
09:01Scientists think South America's animals, after being isolated for millions of years,
09:05had a harder time dealing with new challenges when their ecosystems changed.
09:13Name a desert.
09:15Let me guess, Sahara?
09:16Well, actually, no matter which one you thought of, I'm sure of one thing.
09:21It's located somewhere below this line.
09:25See, when we hear the word deserts, we usually picture dry, sandy, blazing hot places.
09:31And there's not a single one of those above 45 degrees north latitude, or below 45 degrees south.
09:39In the south, that kind of makes sense.
09:42I mean, if you leave out Antarctica, there's not a whole lot of land down there.
09:47But things are different above 45 degrees north.
09:50There are tons of land.
09:52Countries like Canada, France, the United Kingdom, and a bunch of others.
09:56And still, not a single desert.
09:58Actually, not a hot desert.
10:01Most of the major hot deserts are up in the northern hemisphere, near the tropics of Cancer and Capricorn.
10:08And the hottest ones are usually found between 15 and 30 degrees north or south of the equator.
10:14Just like the Sahara, where average high temperatures can reach up to 104 degrees Fahrenheit.
10:21Together, hot deserts cover almost 15% of the Earth's land area.
10:25But if our planet is packed with them, why doesn't a single one appear above this line?
10:31I mean, the 45 degrees north latitude.
10:35I'll explain.
10:36Let's divide Earth into five main zones.
10:39The polar regions are located at both ends, north and south.
10:43Right here, we have the two temperate zones.
10:47And finally, right in the middle of the globe, is the tropical zone.
10:50Now, the line we're talking about sits in the temperate zone, in a colder area.
10:56Because the farther you go away from the equator, the colder it gets.
11:00Actually, the average annual temperature drops about 1.2 degrees Fahrenheit for every degree of latitude you move north in the northern hemisphere.
11:09And cold weather is the main reason hot deserts don't form above this line.
11:16It turns out that as you move farther north from the equator, the sun's rays hit the Earth at a more slanted angle.
11:23That spreads the solar energy over a larger area, which means less heat is concentrated in one spot.
11:29Basically, these regions just don't get as hot.
11:33And it's one of the reasons why countries like Finland are much colder than Colombia, for example.
11:38Another reason temperatures are lower in this zone has to do with something called albedo.
11:44Basically, this term refers to the amount of sunlight that a surface reflects back.
11:49Let me give you an example.
11:51Every surface on Earth both reflects and absorbs sunlight, but in different amounts.
11:57Take snow, for example.
11:59It can reflect up to 90% of the sunlight that hits it and only absorbs about 10%.
12:04That's what gives snow a high albedo.
12:07And it's totally different with sand, which has a lower albedo.
12:11In places like the Kalahari Desert, down in southern Africa, it's about a 50-50 situation.
12:18Most of the year, roughly 50% of the sunlight gets reflected around there.
12:22And the other 50% is absorbed.
12:25The heat absorbed by the sand is part of why it gets so hot in dry places like deserts.
12:31I mean, hot deserts.
12:33Simply put, sand soaks up more heat, while snow reflects most of it.
12:39This is one of the reasons why snowy areas stay much cooler.
12:43So the closer you get to the polar zones, the easier it is for sunlight to be reflected instead of absorbed.
12:49And that helps explain why there aren't any hot deserts around those parts.
12:53Then, we also have atmospheric patterns.
12:59Let's just say that the air patterns change a lot once you go above that 45-degree line.
13:04That's because this region is controlled by a wind belt known as the feral cell.
13:08Okay, so Earth has three main convection cells.
13:12You can think of them as big loops of moving air.
13:15Warm air rises, cools down, sinks, and then the cycle repeats.
13:20At the top and bottom of the planet, we have the polar cells.
13:24Right in the middle are the Hadley cells.
13:27And sandwiched between those two are the feral cells.
13:31Now, everything that happens between these three cells can get a little complicated.
13:35But for today, the main thing to know is this.
13:38In those middle zones, the warm air that comes from the tropics meets the cold air from the polar regions.
13:45So, feral cells play a big role in moving heat from the equator up toward the poles.
13:51This flow of warm air helps smooth out the temperature differences between the tropics and the polar regions.
13:57And that's what shapes the weather in places like North America, Europe, and parts of Asia.
14:02In the mid-latitudes, the feral cell keeps the air moving around so much
14:07that hot, dry air doesn't really get a chance to settle.
14:11So, those regions end up with more moisture, more clouds, and even storms,
14:15rather than dry, desert-like weather.
14:18That's why you don't usually see hot deserts around 45 degrees latitude.
14:23Basically, what I'm trying to say is that the feral cell makes the weather less stable.
14:27And that's very different from what happens in the Sahara Desert, for example.
14:32Over there, temperatures don't change all that much throughout the year.
14:35Just expect it to be hot.
14:38When you put all these factors together,
14:40it helps explain why hot deserts are mostly limited to the middle parts of the Earth,
14:44and why you'll never find a Sahara or Kalahari-style desert in places like Canada or Sweden.
14:49But that doesn't mean we don't have any deserts above the 45-degree line.
14:55Turns out, deserts don't always have to be hot and sandy.
14:59In fact, they can look like this.
15:02Yep, I'm talking about the Arctic.
15:05Because the actual definition of a desert isn't just some hot, dry, sandy place,
15:10it's really any area that gets very little precipitation.
15:14In other words, an area where it doesn't rain much.
15:16And it usually gets no more than 10 inches of precipitation per year.
15:21So, no matter if the weather is hot or cold,
15:24deserts are really dry places with hardly any vegetation around.
15:28That makes it pretty tough for animals and plants to live in those environments.
15:32If you think about it, that means the biggest desert on Earth is Antarctica.
15:37It covers about 5.5 million square miles,
15:40just endless ice flats as far as the eye can see.
15:44It's also the coldest desert on the planet,
15:46even colder than the Arctic, which is the other polar desert.
15:51Temperatures there can drop as low as minus 128.2 degrees Fahrenheit.
15:57If you look at the Earth, about 33% of its land is desert.
16:01Now, pay close attention to the ones located between 15 and 30 degrees latitude.
16:07These are called tropical deserts.
16:09But can you notice something curious about their locations?
16:14Most of them are found on the western edges of continents.
16:17And there's a reason for that.
16:19Actually, four main reasons.
16:21First, the winds that bring rain usually blow from the east.
16:25When they move across the land, they drop most of the rain early on.
16:29By the time these winds reach the west side, they're dry.
16:33So there's no rain left for those areas.
16:36That already makes things pretty dry.
16:39Second, in the western margins of continents, the air usually goes down instead of up.
16:44When air goes down, it gets warmer and can't form clouds.
16:47So again, no rain.
16:51Third, if there are mountains nearby, they can block the rain too.
16:56One side of the mountain gets all the moisture.
16:58And the other side, called the rain shadow, stays dry.
17:03And lastly, the ocean near these places often has cold water.
17:07Cold water cools the air above it and makes it calm.
17:10So clouds don't form easily.
17:12No clouds means no rain.
17:14So when you put all of that together, it helps explain why those tropical deserts
17:19seem to prefer one side of the continent more than the other.
17:25That's it for today.
17:26So hey, if you pacified your curiosity, then give the video a like and share it with your friends.
17:31Or if you want more, just click on these videos and stay on the bright side.
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