Let's start with the oldest of the five and work our way towards the most recent mass extinction. Number five, the End-Ordovician extinction. 444 million years ago, the world looked very different.
The planet didn't have trees, plants, or animals on land, and Earth looked something like this, which is clearly wrong and not where they were supposed to be. But inside the ocean, it was a different story. It was packed with species and thriving.
During this time, most of the marine life lived in warm, shallow seas. Here are some of the animals you could expect to see during this time period: trilobites, brachiopods, bryozoans, crinoids, and nautilus, just to name a few. And don't bother double-checking my pronunciation.
I can tell you now, I easily nailed over half of them. But just when these animals began to get comfortable, everything changed. The coastlines where the majority of life existed slowly began to retreat year after year.
The winters began to get longer and harsher, and the ice that formed took longer to melt. But eventually, the winters got so severe that the ice stopped melting altogether. The planet went into a severe ice age that lasted anywhere from 200,000 to 400,000 years.
You see, the giant continent of Gondwana had drifted over the South Pole, and when snow fell onto the land, combined with the Earth's cooling, the snow didn't melt. Then year after year, the snow compressed into large glaciers, which would otherwise have flowed into the ocean, lowering sea levels. The very few life forms that survived the ice age eventually adapted to the new climate and began to thrive once again.
But just when they began to get comfortable, you guessed it, everything changed. Temperatures began to rise, ice melted, sea levels rose, and the oceans became low in oxygen, leading to another mass extinction of life that was not adapted to the increasing warming climate and changing environment. In the end, around 85% of all marine species on Earth died, making this event the second largest mass extinction in our planet's history.
Number four, the late Devonian extinction. 360 million years ago, Earth had another massive extinction that changed the planet forever. During the Devonian period, Earth was going through many changes.
The first true forest appeared and were quickly spreading. Plants were diversifying and soil formation was increasing like never before thanks to deep root systems. At this time, Earth looks something like this.
Sea levels had risen once again, allowing life to thrive in shallow waters. Let's take a look at some of the strange animals that inhabited the seas. Now, obviously, I could just show you the fossilized remains of these animals and move on.
But don't forget, I'm one of the most historically accurate artist of the 21st century. So, I might as well show you what these animals really look like. Dunkleosteus was a large armored fish that was among the top predators.
Titanictis was one of the first filter-feeding fish. The Cladoselache was regarded as one of the first true sharks. Eurypterid, also known as sea scorpions.
I don't have a fact for that one, but I just thought they were really cool. Then, of course, there were the boring animals like brachiopods and trilobites among many others. But perhaps the more interesting animals were those that were briefly exiting the ocean and waddling onto land.
Animals like the Tiktaalik, Acanthostega, and Ichthyostega. But the good times couldn't last forever. As forests spread across the land, trees began to pull large amounts of CO2 out of the air, cooling the planet.
The trees' deep and intricate root systems expanded, breaking down rock and soil. Rain carried those nutrients into rivers and finally into the ocean. The extra nutrients caused massive algae blooms, using up the oxygen in the water and creating large dead zones where animals can no longer survive, essentially suffocating them.
Around 75% of all species went extinct. Number three, the Permian-Triassic extinction. 250 million years ago, Earth finally became interesting.
Gone were the times of ocean bugs and silly-looking fish, and we finally got something that is actually fun to draw. The Permian period was awesome. The oceans were teeming with life, and the long-awaited land expansion was finally released, allowing hundreds of animals to roam across it.
This is what the planet looked like during this time period. Nearly all land joined forces to create Pangaea, a supercontinent. The weather was hot, dry, and got more unbearable the further you went into the continent.
The oceans were full of life and contained all the usual suspects: brachiopods, ammonoids, crinoids, reefs, trilobites, cartilaginous fish, ray-finned fish, and lobe-finned fish, just to name a few. Land was now completely different from the last time we saw it. It was covered in trees, plants, and moss, and full of large and dangerous animals.
Animals like the Dimetrodon, a large apex predator. Gorgonopsians, a saber-toothed apex predator. Dicynodonts, a tank build that was just funny to look at.
Then there were the first early therapsids, reptiles, and insects. It seemed like the circle of life was getting back on track, but just as the competition was heating up, so would the planet. Well, even more than it already was.
Volcanoes in the Siberian region began to erupt, releasing large amounts of CO2, methane, and toxic gases. These eruptions continued for hundreds of thousands of years. This enormous amount of CO2 trapped heat in the atmosphere, heating the entire planet another 5 to 10° C.
The planet became much drier. Oxygen levels dropped in the oceans once again, and entire ecosystems collapsed, turning the planet into a hellish oven. Around 90 to 96% of all marine life, and around 70% of all land vertebrae went extinct, making this the largest mass extinction in our planet's history.
It has even been referred to as the great dying. Number two, the Triassic-Jurassic extinction. Finally, we get to the time periods we all care about.
After the end-Permian extinction came the Triassic period, a time of recovery and new beginnings that would completely reshape the planet forever. Earth's land still consisted of the single large continent Pangea and was surrounded by Panthalassa, a mega ocean. The planet was still very warm and the majority of the land was covered in large deserts.
Out in and near the oceans is where life thrived. Large trees and plants emerged near river valleys and dry climate plants spread across harsher, hotter lands. Many apex predators began to emerge and take over entire ecosystems.
Animals like the Lystrosaurus, a small pig-sized herbivore. Then there was one of the earliest known dinosaurs, Coelophysis, a medium-sized carnivore that grew to enormous numbers. And just by looking at them, you could just tell they were annoying.
One of the most terrifying animals to emerge was the Postosuchus, a large crocodile-like predator with enormous jaws. During this time was when the first true mammals began to appear. In the oceans, marine life was also diversifying and the first animals that somewhat resemble today's creatures began to emerge.
Animals like the Ichthyosaur, a marine reptile resembling dolphins. Just, you know, way more terrifying. Then there was also Nothosaurus, which was last spotted in 1933 in Scotland.
Then of course, towards the end of the Triassic period, thousands of other marine species had emerged. The Triassic period lasted over 50 million years, but eventually the continent of Pangea began to be torn apart. Enormous volcanic eruptions occurred that lasted up to a million years.
And just like the mass extinction before, these eruptions heated the planet, starved many parts of the ocean of oxygen, and led to the extinction around 75% of all species. But, even in this nightmare landscape, a small group managed to survive. A relatively small, non-dominant creature who witnessed its larger, stronger competition slowly die off and become extinct.
[music] And in this power vacuum, the once insignificant creature rose and went on to dominate the planet for the next 135 million years. It was now the time of the dinosaurs. Number one, Cretaceous-Paleogene extinction.
Soon after the end Triassic extinction, small dinosaurs like the Coelophysis, Dilophosaurus, and Plateosaurus began to take over the planet. Scientists believe these creatures survived thanks to their upright posture, efficient lungs, and their ability to withstand heat and droughts. During the Jurassic period, the dinosaurs solidified themselves as the most dominant animal on the planet.
With large amounts of food available, they quickly diversified. Many grew to enormous sizes and evolved. Some didn't.
Scientists estimate that there could have been as many as 10,000 species of dinosaurs roaming the planet. Here are some of the most notable ones just so you can get an idea of who the star players were. There were the apex predators like the Tyrannosaurus, Spinosaurus, and Allosaurus.
Then, of course, you had your giant herbivores like Brachiosaurus, Diplodocus, and Triceratops. Then, you had the dinosaurs that were just there for comedic relief like the Suchomimus and the Pegomastax. This is also when the first birds appeared.
Going into the Cretaceous period, dinosaurs had adapted and flourished in forest, plains, coastal environments, and oceans. New flowering plants also encouraged insects to heavily diversify. But, as we all know, these times wouldn't last and eventually everything would change in the blink of an eye.
One day, a day just like the millions of days before it, over what is now the Yucatán Peninsula in Mexico, what looked like a small glowing star appeared in the sky. Not a single animal on the planet knew of its existence or had any idea it was even there. A few moments later, that small glowing pin in the sky quickly grew and became brighter than any other star, and within [music] minutes it rivaled even the sun.
Birds scattered, dinosaurs lifted their heads and froze in place as they tracked the light that was traveling towards the Earth. The impact of the meteor is unimaginable. It's been described as billions of Hiroshima atomic bombs all exploding simultaneously.
All nearby animals were instantly vaporized. Not even their bones would be left behind. Entire [music] forests were flattened.
A massive wall of water over a mile high raced across the ocean and tore through the Earth as magnitude 11 earthquakes shook the land. An hour after impact, superheated debris began to rain down across the planet incinerating anything it touched. This, combined with the radiant heat pulses, ignited forests, grasslands, and anything flammable, quickly turning the planet into a burning inferno.
A few days after impact, the enormous cloud of vaporized debris, which traveled from the impact site, had covered the entire planet, turning some areas pitch black while the rest of the planet received minimal light. The fine dust could have remained in the stratosphere for up to 10 years. In that time, photosynthesis completely stopped.
With no vegetation growing, for most life on Earth was all but impossible. Around 75% of all life on Earth went extinct. In the end, it's pretty mind-boggling when you sit back and think that humans have only been on the planet for around 300,000 years.
Yet, dinosaurs walked and ruled the planet for over 164 million years.
