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Discover what life might have been like in the Devonian, and how humanity nearly vanished during a catastrophic event. These two stories reveal the fragility and resilience of life on our ever-changing planet.
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00:00Now, we as human beings have faced all sorts of challenges.
00:04Ice ages, tough diseases, squabbles over real estate, and so on.
00:08But let's try to go way, way back to 400 million years ago,
00:13to the times when our oceans were ruled by sea creatures
00:16and the lands barely had any animals on them.
00:19Do you think you'd be able to survive there?
00:22We're talking about the Devonian period.
00:25It started around 400 million years ago and lasted really long, about 60 million years.
00:32It's named after Devon, England, where scientists first studied rocks from this time.
00:37The world was quite different then.
00:39Our planet featured three continents, a gigantic supercontinent, Gondwana, down south,
00:45a smaller one called Siberia up north, and another medium-sized one called La Russia to the east.
00:51These landmasses were moving around and crashing into each other, making big mountains.
00:57Now, imagine if your time machine broke down and you ended up in this ancient world.
01:02You're now in a world where the land is pretty much a barren wasteland.
01:07You are surrounded by basic plants like mosses and ferns.
01:11This is the early Devonian period.
01:13There were no trees yet, but moss was everywhere.
01:17And wow, that's a lot of water.
01:18Around 85% of the Earth was covered by oceans during the Devonia.
01:23So, you see many warm, shallow, oxygen-depleted lakes around you.
01:28The first thing you notice is that breathing seems a little harder.
01:32Well, don't panic.
01:33It's all because of lower oxygen levels, around 19%.
01:37It's still enough to ignite fire, and trust me, you'll need one.
01:41But prepare to feel a bit dizzy.
01:44Luckily, there are no huge predators to run away from, but you'll probably have to do a lot of swimming.
01:50All right, at least the weather seems pretty nice, warm and steady.
01:54If you keep traveling, you'll notice that the land seems almost limitless.
01:59That's because we're on Gondwana, the biggest supercontinent of them all.
02:03Since the tectonic plates don't move around much, there are barely any mountains around, and the Earth actually feels flat.
02:11Well, not totally flat.
02:13Gondwana boasted a gigantic mountain range, akin to the Himalayas.
02:18This range was gradually breaking down, sending sediments into the ocean.
02:22Those sediments would provide nutrients that help marine life thrive.
02:27In any case, it really feels like a whole different planet.
02:30The landscape around you looks like something out of Mars, if it had water.
02:35The only question is, where is all the life?
02:39Underwater, of course.
02:41There's a reason why Devonian is called the Age of Fishes.
02:45Now, to be fair, it wasn't all fish.
02:48The conditions were perfect for certain early marine life to develop important things, like lungs.
02:54Some even gained the ability to crawl out of the water and onto land for short periods.
02:58So, if you spot a tiny lizard-like creature around the coast, don't step on it.
03:04It's your great-great-great-great-great-grandparent.
03:07Well, it's not like you'd be able to really step on it.
03:10Remember the guy from the evolution meme with a funny crocodile-like head?
03:15His name is Tiktawik.
03:17As you can guess, it was one of the first creatures linking fish to land.
03:21And although it might look friendly, it actually has a 9-foot-long body and very sharp teeth.
03:28And yes, it can crawl.
03:30So, if you notice a huge lizard, better find a hiding spot.
03:35You'll start seeing more of those Tiktawiks and four-legged animals in general by the middle Devonian.
03:43But let's risk our lives for a moment and dive underwater.
03:47What do we have here?
03:48Welcome to Subnautica, Earth Virgin.
03:52While the land looks very primitive, marine life is incredibly diverse.
03:57We have corals, sponge-like creatures, sea lilies, shellfish that resemble clams, and more.
04:03The oceans are filled with various critters that look fascinating and potentially dangerous.
04:09Here are some tough armored plachoderms.
04:11And yes, all of them are bigger than you.
04:14These formidable fish had powerful jaws with blade-like plates as teeth.
04:19They started as tiny guys who munched on mollusks.
04:22But as time went on, some turned into massive fish-slicing monsters, reaching up to 33 feet in length.
04:29The biggest of them was Heterosteus with their scary-looking eyes.
04:33This other guy, who's named Titanicthus, with its mouth always ready to swallow you.
04:40And the largest one, Dunkley Osteus.
04:43Oh, those are $5 names, huh?
04:45And here are some smaller guys.
04:47These are the shark ancestors, the cartilaginous fish.
04:51They had small, rough scales, fixed fins, and sharp, replaceable teeth.
04:56And finally, there are tiny ancestors of our normal modern sea creatures, bony fish.
05:03They're nice and pretty harmless.
05:05They were covered in scales and equipped with maneuverable fins.
05:08You know what?
05:09I think you can cook this one.
05:12So the question is, how do you cook it?
05:14There are no trees for fuel around.
05:16Not until the Middle Devonian, at least.
05:19So you'd have to scrounge up some super-dry moss and get to work rubbing rocks together.
05:25Fortunately, the warmth of the climate would save you from freezing at night.
05:29But since there's not much stuff to burn, you might be better off sticking to a raw diet
05:34of mollusks and other early arthropods.
05:37In this world of basic plant life on land and a huge ocean around, getting food and resources
05:43would be quite tough for you.
05:45Perhaps you could stick to fishing or collecting stuff from the sea.
05:49Overall, you'd have to be really clever to live off the small amount of plant life
05:54and maybe learn a thing or two from the sea creatures about navigating the oceans.
05:59In any case, you'd have to start from scratch.
06:03Surviving in the Devonian would be quite a challenge.
06:05Our bodies aren't built for living underwater or thriving in an environment dominated by early
06:11marine life.
06:12You need some shelter.
06:14Maybe you could try to build a basic house along the shores using dirt and moss, probably.
06:19You just need to create tools and shelters using whatever resources you can find.
06:24So, get creative.
06:26Also, get used to living without clothes.
06:29Unless you make up a way to create a dress out of moss, seashells and fish bones, all Little
06:35Mermaid style.
06:37Alright, alright.
06:39To make it more fair for you, let's say you ended up closer to the late Devonian period.
06:44Hey, now things are looking up.
06:46At the end of that era, the first forest started covering our earth.
06:50Now, we had plants with spores, leaves and roots, and even the first plants with seeds.
06:56The land is slowly getting some life.
06:59Hooray to normal breathing again!
07:01We've got some little bugs, four- and six-legged critters.
07:04The first land vertebrates, early tetrapods, started showing up.
07:09They're pretty cool.
07:10Very early ancestors of mammals and eventually us humans.
07:14But hold on, Houston, we've got a problem.
07:17As plants started taking over the land and breaking the rocks with roots, they released
07:22tons of nutrients in the water and caused a chain reaction.
07:26The sea got filled with algae, greedy bacteria thrived, and since there was almost no oxygen
07:32in the waters, around 70-80% of the species vanished.
07:37Whoops!
07:38But hey, good news for you!
07:40Less oxygen-hungry predators in the water.
07:43However, now you have to watch out for your new land neighbors.
07:47Most of them aren't harmful, but it's better to watch out.
07:50But still, with more trees and plants around, you could make useful tools like spears, fishing
07:56hooks, and rope.
07:58During the end of the Devonian, you might even build yourself a treehouse.
08:02Picture that, in a world with the first tree ever, reaching 90 feet tall with a super-wide
08:08trunk.
08:09So, it seems like you'd be able to survive without much trouble.
08:12You might even turn into a vegetarian with all these plant options.
08:16And hey, no more itchy clothes!
08:19You could fashion something much more comfortable.
08:22And remember that dinosaurs are on their way!
08:24Until then, enjoy your time!
08:30With more than 8 billion people in the world today, it's hard to imagine there was a time
08:36when there were so few human beings that they almost went extinct.
08:40It happened about 900,000 years ago, when our ancient ancestors faced a crisis.
08:46Recent studies tell us there were only about 1,280 of them left, which is an incredibly small
08:53number.
08:53However, it's like just one village, or a very, very small town, left alone on the
08:59whole planet.
09:00The human race got into a population bottleneck, where almost 98% of people disappeared.
09:06And things were tough for them for more than 100,000 years.
09:09We don't completely understand why this happened, but it was likely the result of tremendous changes
09:15in Earth's climate.
09:19It was a time when periods of cold weather lasted longer, the sea was colder, and there
09:24were more glaciers.
09:26Monsoons were immensely powerful, and yet there was less rain.
09:30These changes had an impact on wildlife species in Africa and Eurasia, and many plants and animals
09:36that were food sources for people disappeared.
09:38But at some point, our ancestors showed their strength and managed to bounce back despite
09:44tough times.
09:46The numbers started to go up again, because people learned how to handle fire better.
09:50Plus, temperatures got warmer too.
09:53But what would the world look like if nature had defeated us, and it all had really stopped
09:58for humanity back then?
10:00Let's take a trip to some parallel dimension where it really happened.
10:04In that universe, there wouldn't be empires, pyramids, and impressive achievements that
10:09some old civilizations left us.
10:13No neighborhoods, cities, your favorite park, or that bench where you like to sit and drink
10:18your coffee.
10:19No coffee?
10:20Ouch, that hurts.
10:22No pools, adventure parks, and no rush at the beaches.
10:25No creature would be able to go to another continent separated by the ocean.
10:30There would be no ships or planes that could carry it.
10:33Animals would have to wait for tectonic plates to move again to visit new territories.
10:39Wow, you've just realized how incredibly silent the world is.
10:43All because nature almost never produces as much noise as humans do.
10:47Our buildings are noisy, together with cars, motorcycles, and all other vehicles.
10:52If you live somewhere by the airport, you know how much noises planes can make, too.
10:58And here, no one's phone's ringing.
11:00You don't hear music coming from bars or gyms.
11:03Wow, look how incredibly blue the sky is.
11:07You've never seen a sky like that in your world.
11:11The rain and wind scrub the surface of our planet clean.
11:15Although there's not much work to be done, since there's no dust and smog humans produce.
11:20I mean, there is dust, but a different kind.
11:23One that nature creates.
11:25We don't really notice it, since we have so many heaters and air conditioning systems
11:29that blow air and all that dust around.
11:32The only drinking water you see is in lakes and rivers,
11:35and lots of different animals get together in these areas.
11:38It takes a while to get used to it.
11:40Wherever you go, there are wild animals passing by.
11:43There are no dogs, cats, or other pets you're used to.
11:47There's no electricity, either.
11:49In case you've brought your phone, take pictures as fast as possible,
11:52because you won't be able to charge your gadget when it runs out of battery.
11:56There's no internet valve, so you'll be the only one who will see the photos.
12:01It's so weird to see grass so tall and wild.
12:04No one mows it, so it's hard to walk, especially considering there are no roads.
12:09And you don't have a scythe or any other tool that could help you clear your way,
12:14because human civilization hasn't reached that level of progress.
12:20Wow, there are plants you've never seen before.
12:23Every time a tree drops a seed, something new might grow.
12:27And there are no humans to select which plants they like and which they don't.
12:32You suddenly feel nostalgic, thinking of carrots, broccoli, potatoes,
12:36and all other vegetables people once started growing on their farms.
12:40You can hear tons of bugs buzzing around.
12:44We usually do everything to get rid of them.
12:46And now, without humans, you get to see how annoying they really are.
12:51Hey, the sun is going down.
12:54Without electric lights, all creatures just follow the rhythm of nature.
12:57So, if you're up for a late-night walk, wait for the moon and stars to lighten your path.
13:03But be aware of night predators.
13:05You may face creatures that didn't survive in the world where humans rule.
13:11Fire.
13:12Luckily, there's a river nearby, so you jump into the water to get to the other side.
13:17Fires happen more frequently in the world without humans.
13:20For instance, lightning can strike a tree or set a brush on fire.
13:24No one is there to put the flames out.
13:26So, fires just keep spreading until, at some point, they burn themselves out.
13:31It's hard to see the world like this.
13:33But it's even harder to accept that Earth is fine without us.
13:37Just like it's doing well without dinosaurs, megalodons, woolly mammoths, dodos,
13:42and other ancient creatures that went extinct.
13:45Back to the research.
13:46Some scientists don't think our ancient ancestors were really that close to extinction.
13:51To get these results, researchers used FITCOL,
13:55a special tool that helps study changes in ancient human populations
13:59by looking at the genetic information of modern people.
14:02They examined DNA from over 3,000 individuals in Africa and other places for this study.
14:10Some believe that the actual population numbers might have been bigger.
14:14The method used focuses on a small group of breeding individuals and may not exactly represent the whole population.
14:22There may be many archaeological sites in Euroasia and Africa that date back to the time when this population decline
14:29might have happened.
14:30So, it may have affected just some groups of people in certain areas.
14:34Either way, not only wasn't it the end, but it was a new beginning.
14:39Two ancestral chromosomes combined to create a structure known as chromosome 2 in modern humans.
14:46This might have been the start of a new species because there was a split between our ancestors and other
14:52ancient humans,
14:53such as Neanderthals and Denosovans, our ancient cousins.
14:57Some evidence tells us this idea is plausible because our common ancestor lived about 500,000 to 700,000 years
15:05ago.
15:07Well, humans did survive all those devastating moments in history.
15:12But scientists believe that the extinction of our species is a matter of when, not if.
15:17Our fields will overgrow, cities will end up in ruins, and bridges will fail.
15:23Nature quickly reclaims the landscape where humans don't go.
15:26Check out how these roots and trees have taken over the temple in Cambodia.
15:30Roman ruins still defied time for over 1,500 years now.
15:36Some of the buildings and things we create in the modern world will do it too.
15:40Nature will break everything down at some point.
15:43And if humans were to go extinct, who would replace us?
15:47It took 200 million years for our kind to evolve from the first mammals.
15:51Who can repeat this entire process again?
15:54The last common ancestor of chimps and humans lived 8 million years ago.
15:59Knowing this, it seems possible that if Homo sapiens went extinct,
16:03a new species capable of using technologies would evolve from chimps.
16:08But hold on.
16:11There's something called the Fermi paradox.
16:14Even though there are hundreds of millions of rocky planets that could host life in our galaxy,
16:19we don't see any evidence of its existence.
16:22Our galaxy is 13.5 billion years old.
16:26So you can't say life hasn't had time to develop.
16:29One possible explanation is that certain crucial steps in the evolution of intelligent life
16:34are so rare they hardly ever happen.
16:37So, Earth would get along fine without us.
16:41The only ones who would care are us.
16:43And right now, we need to care a lot.
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