The Invisible Barrier Keeping Two Worlds Apart 

Imagine not knowing anything about plate tectonics and realizing that some birds being missing on a random island implied the existence of continents that went underwater millions of years ago. Incredible.

Wallace is well known in Indonesia, actually more famous than Darwin. We learn from child that he found the theory of natural selection almost at the same time as Darwin, but decided to let Darwin took the honor. Wallace was depicted as a humble man who prefer focusing on his research instead of fame or prestige. He spent the majority of his life going from one island to another island to pursue his study and interest. Truly a researcher at its core.

I remember my high school geography teacher (in around 1966) doing a little rant about how "the continents do *not* move!". We had no idea what he was talking about because the plate tectonic theory hadn’t trickled out to the general population yet. He never explained but that strange rant stuck with me and only cleared up when I learned about ‘continental drift’ 5 or so years later.

As a person who currently live in Sulawesi island, this explains why i found a lot of shell and mollusks fossil on the mountain regions, it even scattered everywhere everytime we dig gravels for construction.

I’m a Dutch biology teacher on holiday in Bali. Currently staying at the coastal village Amed, on the far east side of the island. Looking across the exact Wallace line described in this video, at the island of Lombok. All while watching this video while the sun rises on the horizon, quite close to my sight of Lombok. This was a delightful video with perfect timing.

Imagine trying to describe to describe to someone from 500 years ago that the movement of rocks creates an invisible line that decides what type of food is available

The Wallace Line also influenced the people living in Australia too. Aboriginal Australians and Torres Straight Islanders have lived here for 65-120 thousand years and they were isolated for most of that time and so that’s a big part of why the animal and plant biodiversity is so unique, why the people’s genetics are relatively unique and with big cultural differences too. It’s something I’m only just learning about, but I think it’s really interesting

Did you know the Wallace Line is also important culturally and historically? It marks the boundary between two regions that have had different influences over time, which has led to a diverse mix of languages and cultures in Indonesia. Along our trip with Pinisi boats, we learn about Indonesia's history and culture, including the significance of the Wallace Line in shaping the country's diversity.

The statement "I'm as old as plate tectonics," really drives home how quickly our understanding of science had grown, and just how recently too.

In Indonesia, we were taught about one other line: Weber's line. It's basically a line east of Wallace's line (between Sulawesi and Moluccas iirc) which separates the Australia + Papua plate with the transitionary islands. So unlike Wallace's only 2 zones (Asia/Sunda - Australia/Sahul) it's now three zones (Asia - Transitionary - Australia)

I remember the controversy when plate tectonics was first suggested. Some people insisted that the idea of the continents moving was absurd, they're literally solid rock. A guy named Thor Heyerdahl sailed a primitive raft called "Kontiki" from Africa to South America to establish an explanation for people getting to the new world thousands of years ago. Then someone mentioned "Continental drift", and it was literally a whole new world. I was ten.

In this video, we use Alfred Russel Wallace’s term the ‘Malay Archipelago’. We recognize that Wallace's term perpetuates a Eurocentric viewpoint with harmful implications. In the future, we will do our best to include this important context and moving forward we will refer to the region as the Indonesian archipelago or Nusantara.

I was sitting in 9th grade science in 1960, looking at the world map and noticing how the coasts of Africa and South America seem to fit together. I pointed that out during discussion and wondered aloud if they'd ever been joined. The teacher ridiculed my remarks, declaring it an outlandish idea. Now, whenever plate tectonics is discussed, I think to myself: "Take that Mr. Lee."

My geology prof was doing her thesis defense in the late 60's. One people on the panel asked her a question about tectonics but one of the other members took issue with that. So two members of the panel that was convened to determine if my future professor should get her doctorate in geology... started arguing with each other, and my prof just stood their quietly, letting them run out the clock.

For my masters thesis (biology) i am working on tarsiers (small primates) on Sulawesi Indonesia, and my research is connected strongly to biogeography. Nice video, thanks :)

Apparently, the invisible barrier isn't so invisible underwater. The Balinese side is quite shallow, but as you move towards Lombok, the waters get deep. Very deep.

"I'm as old as plate tectonics!" Really? You're in great shape, I'd never tell you have more than 220 million years!

I’m from Indonesia and we were taught this back in elementary school, this brings so many memories back! We had to remember the local species of both sides, haha

While this is part of our Geography lessons back in school since elementary school, I hope we can emphasize more like this video did on how unique the Wallace line is. We also know the Weber line but never understand the impact of species distribution. Thank you for telling us this story.

I think its so cool that you might find ancient artic species or pangea species that have now evolved to monitor lizards, cockatoos, kangaroos, etc, in Australia, New Guinea and West Indonesia.

I'm Indonesian. I remembered growing up we learned at school that every island and province has its local iconic fauna. Never knew why it was so diverse, tho. Each animal became sort of a local pride symbol. Ours from Northern Sulawesi is the Tarsius (tiniest primates) mentioned in the video. Curiously comparable to the neighboring island crossing the wallace line, in Kalimantan they have Orangutan which is one of the largest primates found only in Kalimantan and Sumatra but not in Sulawesi. Wonderful, isn't it? Thanks for sharing this video 😊

Mr Wallace doesn't get the credit he deserves. He's a giant.

Love the bloopers at the end :) It goes to show that recordings are seldom perfect on their 1st try and it takes a lot of time to create them. Thank you to the team!

The concept of Wallace's line and its effects on species evolution is fascinating. The explanation of how geography affects species distribution over time is clear and insightful. Thank you for broadening our understanding of the world. Looking forward to more discoveries!

been following your channel since 4 or 5 years ago. Seeing my country being discussed in this video is unbelievable. Anyway, here in Indonesia, the concept of Wallace Line had been introduced since elementary school. Most of us didn't even understand what Wallace Line is. I think Eons has done a great job explaining the Wallace Line.

I live in Lombok island just realising how contrast our animals are compared to animals in Java and Bali. If only my biology teacher can be this clear and fun, I would love biology more than ever

As an Indonesian, the way you explained Wallace line is so much more interesting than my geography teachers could ever did lol

I'm from Indonesia and when I was watching the video for the first time 9 days ago I really wished it would do well since well, I'm from Indonesia (especially coming from one the the "black slate" islands), I think Wallace should have gotten more recognition and I love Eons. Fast forward to today and 11 million views later, I'm smiling from ear to ear 😁

I think we Indonesians are the only ones who are taught about Wallace’s Line at school, as well Weber’s and Lydekker’s, but only in passing, as we mainly focus on species difference between Sunda (Asian animals like tigers and elephants), Sahul (Australian like kangaroos and emus), and Wallacean (including Indonesia’s endemic animals like Komodo dragons and babirusas). Looking back, this short video would have made it easier to understand how the differences came to be.

Blake being born in the late 60's is as much of a revelation to me as plate tectonics would be to Wallace.. I wouldn't have thought him a day older than 1975 at the oldest.

Wallace is the most studied westerner in Indonesian school

hii, indonesian here. in school we’ve been teached 2 line, wallace and weber. divide indonesia to 3 geological differences

While everyone is saying Wallace needs credit, we all know Gromit did all the work. Wallace just complained about his trousers while Gromit lay the railroad tracks.

i am sure many indonesians have expressed the good impression about how grateful we're that this channel covered one of the most memorable thing from our geography lesson that we received since we were in elementary school, so i just want to give a prop for using real our beach footages too :)

We (Indonesian) has learned this on elementary school, thanks for recalling my memory about this study

I just discovered this channel and I’m in love with the relaxed and educational vibes. I might rest here for a while!

Indonesia is easily one of the most biologically fascinating places on the planet, with such tectonic complexity, a dizzying number of islands, land on two continents and a myriad of microcontinents and large islands in the region of Wallacea. Not to mention all the volcanism and mountain ranges, including some impressive calderas and lots of cloud forest! It deserves so much more attention, especially compared to more mainstream rainforest like the Amazon or even the Congo. Such a shame that so much is getting deforested, especially on the side of the Sunda shelf. Someday I hope to visit what's left of the rainforest there.

It's crazy to me how much people take for granted the advancements of knowledge in the last 100 years, or even fight against it. I find the information amazing and humbling, and always want to hear more. I appreciate PBS and the impact they've had in my less than 35 years of life so far, especially when everyone around me was screaming pseudoscience and telling me the Earth was 6,000 years old.

one of the best episodes ever. I visited Bali as a kid and I heard about Lombok. I had no idea this lineation existed.

Incredible! Excellent job on this video. Educational, and very easy to understand. Thank you PBS!

The Wallace Line is fascinating! IMO, the most surprising aspect of the Wallace Line isn't just that it divides animals and plants from Asia and Australia, but that it also divides the animals found in the Indian and Pacific Oceans. Being the Line is water, some aquatic animals do swim across it, but interestingly, when a species can be found on both sides, they still show signs of being separated. For instance, the openwater Thompsons Surgeonfish(Acanthurus thompsonii) can be found on both sides, the Indian form has a dark gray tail(can be black depending on mood) whereas the Pacific form has a bright white tail. The Wallace Line divides these forms. Similar changes can be seen in many others as well. If you're familar with marine or reef aquariums, you may have noticed there is a significant and costly difference between "Indian" forms and Australian/Pacific forms, like the harlequin tuskfish or the regal angel. For many of these species, as reef dwellers, they are not able to effectively cross the deep waters found here, but remember, the Thompsons Surgeonfish is an openwater, pelagic species and even it does not effectively cross, allowing the different forms to evolve.

As Indonesian, we learn about Wallace Line since elementary school. But it never occurred to us how important that subject is

I just have to say the script for this video is so well-written and easy to follow! I have never heard of the Wallace Line, and I learned something new today, was super interesting! ☺️

lived in indonesia all my life and just now realized the distinct difference of animal habitats. That wallace guy got to be really smart and observant to realize that.

It's so interesting to see how an invisible barrier allows two different worlds to exist so close to each other. On the other hand, we have to create barriers that are not that invisible to save species and to build two words apart on purposes. Our crew recently filmed a project that aims to create a jaguar corridor through South and Central America to save the species. Jaguars lost 50% of their natural habitat, making it harder to find each other and reproduce. Travelling would be fine for them, but the territory they have to cross to reach protected areas are roads and croplands, making everything extremely dangerous for them. On the positive side, the project is already showing promising results.

As an Indonesian I feel happy to have this covered and shown to everyone, especially when you did a great explanation of the Wallace's line. We actually learned this in school! But I was a bit confused, why don't you include the 2nd biogeographical line in Indonesia, the Weber's line, as well? I know you touched upon it a bit by talking about the mostly-middle islands having different faunal composition than its left or right parts (in the Wallacea part of the video), which implies the Weber's line, but you did not explicitly talk about Weber's line here.

Never even thought of looking for PBS content on RU-vid. This was an excellent informative video.

Excellent video, thank you. I'd heard of Wallace and the Wallace line before, but never understood what it was 'all about' until THIS VIDEO! Now subscribed!

There’s also the Weber line between the Maluku Islands and New Guinea. As an Indonesian, I was taught in school that Indonesia is divided into three ecological boundaries, almost similar to the three time zones. West Indonesia, which is west of the Wallace Line has Asian fauna, while East Indonesia, mostly Irian Jaya, east of the Weber line has Australasian fauna. Wallacea, which comprises of Sulawesi and the Lesser Sunda Islands east of Bali has endemic fauna.

Oh, we learned about this in around elementary or middle school in Indonesia. Of course, we didn't learn about it too deeply (like, why did the Wallace line exist, that was for the high school-university level) But, we do categorize Indonesia's fauna into 3 categories. The West type animals (mostly Asian types, with animals that don't have pockets, many types of monkeys, Mammals with large bodies, various types of reptiles and they have many types of freshwater fish) The Middle/Switch type animals (they are a mixed fauna between Asian and Australian types. They're endemic, only found in one area. And consist of fauna that are endangered and very rare.) The last one is East Type animals (mostly animals that are also found in Australia. The mammals have a relatively small body, bird species have a colorful coat color, apes are not found in the forest, There are many marsupials, the Fresh water fish are relatively few, and there are many animals with horns.) Hope this helps!

Thanks! That's really amazing. I was always wondering why the Kodomon dragon exist in certain islands of Indonesia, while Southeast Asia is known for many large mammals, they surely would compete for dominance with only one group wins, now I knew why. Thanks again for the wonderful video.

This is one of the most interesting videos I’ve watched in a while. Glad I found this video!

This like is so ecologically interesting. I feel like most people would ask "well what stops them from crossing that line and australian and south east asian animals from crossing into each others territory?" Rafting event are a thing after all. But its not many animals that get displaced by it at a time. So even if they do make it to the other side of the Wallace line, there's just not a big enough population to establish themselves, and they face trying to survive in, a full ecosystem not built up around their species.

Super interresting topic. And amazingly presented. Thanks for the Video

I love plate tectonics! So interesting how everything changed and the evolution of the animals was affected/catalyzed.

When I was in 4th grade (that would have been 1967) I remember looking at the world map on the wall and noticing that South America seemed to fit right into Africa. I pointed it out. My teacher laughed and blithely dismissed the idea that it was anything more than coincidence. 😏 By junior high school we were taking cutouts of the continents and fitting them together into Pangaea

Bali and Lombok have different landscape too! If you look at Bali Beaches have many cliff, rocky hillls but Lombok beaches are more greeny hills. Bali landscape have similarities with Java but Lombok more similarities to Flores (Komodo Islands).😊

Informative and vastly entertaining, especially the ending. Thank you so much!!! 😊

Recognized the islands... had a great time in Indonesia :) Thank you

Excellent video. Wallace is one of the giants of mid 1800's naturalists. Yet he rarely gets mentioned for his important contributions to science. Nice to see you giving him some of the credit that he truly deserves.

"The geological past shapes the biological present". Well-said, Mr. Wallace. Well-said. Cheers from Indonesia! Been following your channel for years. Bless you, Eons!

Wallace as the dividing line between Asian and Australian fauna in the Malay Archipelago. Weber's line is a line of supposed 'faunal balance' between the Oriental and the Australasian faunal regions within Wallacea.

This was a very well made video. Thank you

I crossed the line four times in my last trip to Indonesia without knowing it. And yes, it absolutely incredible how different is the flora and fauna. Nice video!!

I'm still perplexed at how dedicated scientists are/were. Doesn't matter if they're from the past or current time, all are commendable and deserve recognition.

This is fascinating! Thank you!

I wonder that information about separation of species is so uncommon considering the interest. I, for one, have had a passing curiosity about it for many years. Thank you!

I first crossed the Wallace Line on an Indonesian ferryboat across the Lombok Strait. I didn't notice different wildlife, though. I am nowhere near as observant as Wallace. There's a person who deserves more recognition.

Wow, I hadn’t realized Plate Tectonic science was so young! Much like the science, you also have influenced the way we see the world by working so hard to share awesome discoveries and ideas, Blake.

I'm glad I found this channel! So informative!

What a nice man ! Thank you for your performance

At school, we learn another line called weber line that separates papua island and surroundings from middle part of Indonesia like Sulawesi and Maluku where the animals are more endemic in this region, such as Anoa, Maleo bird, Babirusa and Komodo itself. These animals are not available both in Sunda and Sahul region

I had no idea that plate tectonics wasn't accepted until so late. It always seemed obvious to me growing up, but I was formally taught about it in the late 'eighties by an ageing geology teacher who must have been part of that debate. These things serve as a reminder of just how much we've taken on board as a society in, generationally speaking, an extremely short period of time.

I live in Timor, Wallacea. Nearby Flores Island is pretty similar, but very different from Java or Bali, indeed. Even in terms of anthropology and culture.

I actually crossed in between the two sides by BOAT, from Bali to a tiny island named Gili Air in the Lambok Archipelago province……. Wow. I myself can’t believe that!

This also helps with making sense of the really weird shape of Sulawesi.

That's why Indonesia considered to be one of the most diverse regions in the world. In terms of fauna, flora, even humans 😂

man, this really makes me nostalgic and takes me back to elementary school. I forgot there is this Wallace and weber line, I study this when I'm 3rd grader. I remember the first question teacher asked is "Why animals in Sumatra - Java - Malaysia is similar?" and I just answer it with "because it's close to each other" lmao. and then the teacher laughed. pretty embarrassing that I keep remembering it if this Wallace line is mentioned even after 15 years later. at that time I can't tell what is Borneo's and East java's animals so I think its kinda bigger gap to the middle of Indonesia such as Sulawesi and Nusa Tenggara, not to mention Papua who has kangaroo like Australia.

Those are some really cool plate tectonic visualizations!

I love how Blake just threatened Callie with HR over her puns!

Here I am, looking at the Lombok strait from the western coast of Lombok. Big thanks to you guys for giving me the insight of the natural beauty in this island where I lived.

Bali is blessed and iconic for a reason!

Great video! Maybe do another video about the WallaceLine with a focus on plants? ❤

4:50 existential crisis.

Plate tectonics are so fascinating. The more I learn, the more I want to learn. I recently moved from the Appalachians to the Ouachitas and find it incredibly comforting to know that both mountain ranges were created in the same collision between North America and Africa. In a very real sense, while I’ve moved from western NC to northern AL to central AR, I’ve never lived outside of the Appalachians.

Wonderful show!!! Thank you!! Have you done 1 on Devils Lake, WI?? Or some of the spring fed ponds , like 1 off of the County Y, out of Lodi, WI. It has a long history of never going dry or getting any major loss of water. I grew up there are we had easy findings of arrowheads.

Bring back memories from elementry school days 😭 thanks! Subscribed

I've been diving in that water between Bali and Lombok and sitting on the edge of an impossibly deep abyss waiting for deep water fish to pass by. I wish someone had told me I was looking at a continental shelf.

Not only did I learn something totally new, the Wallace line, I learned more about Alfred Wallace than I ever knew before. Please do an episode about Alfred Wallace's life and works; I'd like to learn more about him.

Great video! I’ll be looking for more of “Eons”. The producers of the show seem to be bucking the “dumbing down” trend that steered me away form PBS programming starting about 15 years ago. I love the way it seeks to engage me rather than lightly “washing over” me.

In the Philippines, Sardinella tawilis (Clupeiformes: Clupeidae) is the world's only freshwater sardine and is #endemic to #TaalLake, Batangas, Philippines. No other place in the Philippines can be found, Just on Taal lake itself. 🤔 very unique! Taal Lake is the third-largest lake in the Philippines and is located in the #caldera of an #ancientVolcano. . How Beautiful the Mother Nature is. Mother nature gives everyone of us distinguishing characteristics that others do not have. So, everyone of us is important to Mother Nature and the environment. Many species are endemic and only found on its unique area or place.

Brilliant video I’ve crossed the Lombok straits a few times to the Gili islands and it’s amazing because it’s one of the deepest sea trenches in the planet. Huge swells. Also the dumping ground for plastics that are compressed into giant blocks, loaded onto barges that are dumped into the trench. One of the most disturbing sights I’ve ever seen in my 60 years in this planet.

I just spent months learning about biogeography in University, and I must say you explained this super concisely. Awesome job!

Plate tectonics is probably one of the most fascinating topics in science. Geologic time is mind blowing.

Wow, fascinating! I had no idea about the Wallace line!

I'm Indonesian living in Bali, we did learn about this in elementary school. Thank you for reminding me of good times of late 80s til mid 90s.

Wallace and Weber line is my most favorite thing to learn in school!

I love this style of video! Great job! Funny tectonic joke too lol

omg the last lil joke part was a cherry on top of a great lil video. Legit made my day with the pun struggles and being unable to contain ur laughter 🤣i needed a good lil laugh / light hearted moment like that today!

hi, indonesian here, thanks for the video, it reminds me when we were kids (probably around elementary) we were thought, there were 2 actually imaginary lines (or rather two scholars) Wallas and Webber that separate 3 different areas which that almost the animals within the celebes islands and several little sundaes were endemic and couldn’t be found whether on the western sides (borneo, java, and sumatra), nor the eastern sides (moluccas and papua). please don’t bully me, my degree was only in chemical engineering. 😅