Hey there, humans! You don’t see me, because I’m not born yet. Yeah, I’m an official
representative of life on Earth, and we’re at the beginning of everything. The very beginning.
Yes, we can do that here. Fun huh? Today, I’ll guide you through the life cycle of
our planet, so fasten your seat belts and get ready for some time travel!
What you see before you is Earth, 4.6 billion years ago. Not the fancy blue and green ball
you’re used to, huh? Yeah, it’s more like a giant rock covered in molten lava and constantly
bombarded by comets and asteroids. You see, planets form because clouds of cosmic dust
clump together, thanks to gravity, until they take a ball-like shape. Of course, there’s
no sign of life here yet — nothing could survive in such an environment. That’s probably
why this first period of existence is called the Hadean Eon — from the Greek for Hades,
or hell. Well, quite fitting. Okay, moving on. I’m itching to be born
already! Not yet, though, it’s still too early. The hellish eon lasted for roughly
600 million years, and its main milestone was the forming of the Moon. Well, those human
know-it-alls who you call scientists have several hypotheses on how it happened. Perhaps
the most popular one is that some humongous astral body grazed the Earth in the late Hadean
Eon, became caught in its gravity field, and has stayed in its orbit ever since. Now just
think about what could’ve happened if that thing hit our planet! I, for one, wouldn’t
have appeared, and that’s a tragedy, you know.
Anyway, soon after the Moon started orbiting the Earth, the planet’s rotation slowed
down to a comfortable 24 hours per day. The impact also tilted the Earth, and it now had
seasons. That’s how the Archean Eon began. No, no life yet, but wait for it. Soon!
The climate became softer and more stable, and the planet began to cool down. Now here’s
where it all starts. Water vapor condenses, forming the oceans and, of course, continents.
Well, one supercontinent, to be more precise. And finally, after millions of years… Yes,
you guessed it: life appears on Earth! Here I am, the first ever living being on the planet.
Right now, I’m a single cell called a cyanobacterium. My buddies and I convert sunlight to energy
and release oxygen into the shallow waters of the ocean.
Now, you humans are clever, so you probably know that oxygen makes iron rust, right? As
there was a lot of iron in the water, we made it rust first. Then, as the iron ran out,
the oxygen we released had nowhere to go but into the atmosphere. You see? We, the simplest
life form ever, made the air of our planet breathable! You even gave it a posh name:
the Great Oxygenation Event. Thanks to us, the new eon began: the Proterozoic
Eon. It started 2.5 billion years ago, so it’s not hard to calculate that it took
us, the cyanobacteria, about 1.5 billion years to fill the atmosphere with oxygen. Anyhow,
it was our waste product, so it was toxic for us. Unfortunately, when there was too
much oxygen, we died out. But fear not, I’m not leaving you! Instead of disappearing,
I evolve to become an aerobic life form! Woo-hoo! And now I’m gonna stay for good, you’ll
see. Life began diversifying, and even multi-celled
organisms started appearing. Alas, it wasn’t for long: oxygen in the atmosphere mixed with
methane, which had been abundant there for a long time already, and created large amounts
of CO2. The greenhouse effect weakened, the temperature on Earth rapidly plummeted, and
the planet fell into its first ever Ice Age for a whopping 300 million years. You can’t
imagine how cold it was! But we persevered, and when the ice melted away, life began anew,
and at full force. The ozone layer appeared thanks to the richness in oxygen and shielded
the Earth from the Sun’s harmful radiation. My peers started timidly crawling from the
water, and when they realized it was safe, life flourished on land as well. We were the
pioneers, and we were victorious! Don’t get me wrong, though, everything I
described in the last minute or so took 2 billion years. So now we’re at the most
beautiful period of Earth’s development, and that’s the Paleozoic Era. It began 541
million years ago with an explosion of life called the Cambrian period. Waters started
swarming, first with invertebrates, then with fish, and finally with vertebrate animals,
which, in their turn, hopped ashore and thought it nice enough to settle. Me? Ha-ha! Thanks
for remembering about me, because… Poof! I’m the first wingless insect now! Soon
you’ll see my true face, but you may already know who I am. Any guesses? Leave them in
the comments below! So, in the Devonian period of the Paleozoic
era, about 415 million years ago, the Earth completely transformed. Lush rainforests grew
all over, fish and other sea life swarmed the oceans, vertebrates roamed the land, and
insects like yours truly crawled in their dens. A paradise! Unfortunately, it wasn’t
too long (well, at least on the planetary scale) before two big extinctions occurred.
The first was the Carboniferous Rainforest Collapse in the — guess what? — Carboniferous
period. A major shift in global warming made life impossible for many animal and plant
species, so they were buried and cooked underground. Yep, that’s right. Those are the fossils
you dig out and the coal deposits you use for energy. Don’t be surprised now! You’re
actually using the remains of creatures that lived hundreds of millions of years ago.
But the rainforest collapse was just a trifle compared to the greatest mass extinction that
ever happened on Earth. At the end of the Paleozoic era, on the verge of the Permian
and Triassic periods, an asteroid hit the planet, wiping out roughly 96% of all life.
Boom! That was about 291 million years ago, and it took the Earth a long time to recover.
But still, life clung on, and the Mesozoic era began with the 4% that survived the asteroid
onslaught. The first 51 million years were marked by
the evolution of reptiles. The Triassic period was sort of a gateway to the famous era of
dinosaurs. Yes, we’ve finally arrived! But first, let me introduce myself properly. I
hope at least some of you guessed my personality correctly in the comments to this video, otherwise
I’ll be offended. Please meet the mighty, hardy, tenacious… cockroach! Yep, that’s
me, and I’m here to stay. You see, the first cockroaches appeared in just about the Jurassic
period and lived alongside those huge lizard-things you call dinosaurs. In fact, early dinosaurs
arrived in the Triassic period, but their real reign started closer to the Jurassic
one and lasted for roughly 160 million years. And all this time my creepy-crawly buddies
and I were somewhere nearby, making their life a nightmare, just like today. Mwahaha!
Ahem, anyway, I should add here that dinosaurs still lived on the single supercontinent of
Pangea, but closer to their dusk the tectonic movement began tearing it apart, forming the
smaller continents that we know today. Poor dinosaur families were separated by the implacable
movement of the Earth’s crust! Okay, just kidding. The movement was super slow, so no
families were actually separated. If anything, they could easily jump from one continent
to another in the early stages. Well, time passed, and the Cenozoic Era came,
and with it came the ultimate demise of the huge reptiles. A giant asteroid hit the Earth
once again (hey, what’s up with those asteroids?), and 66 million years ago, the dinosaurs went
extinct because of the rapid climate change. A moment of silence for the poor creatures,
please. You should’ve seen how happy the early mammals
were about that, though! Dinosaurs had dominated the land, so mammals had to stay low, but
now that the threat of being chomped by those giant sharp teeth was gone, they flourished.
And guess who was among those mammals? No, not me. I’m an insect, remember? I’ll
give you a hint: they only emerged about 3.9 million years ago and are still very, very
prominent on our planet. Yes, that was you! The first humans! Well, not really humans
back then, but hominids — primates that walked on two feet and tried to use their
environment to create tools. The epoch of Pliocene marked your ancestors’
arrival to the Earth, and on they went to evolve all through Pleistocene and finally
Holocene, which started just about 10,000 years ago. That was when your kind began clumping
into communities, and I was their perpetual friendly neighbor, but that’s a whole other
story. So, you there! Did I miss something, you think?
What other important events that shaped our planet would you like to add to my story?
What? When did the Flintstones appear? About 1960. Anyway, Let me know down in the comments!
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Stay on the Bright Side of life!