When we talk about mass extinctions, most people think of the same thing, the extinction of the dinosaurs. But that was just the most recent episode in a series of moments when life was virtually exterminated from the face of the Earth. I don't want to scare anyone, but extinctions are relatively common.
Of every 50 species that once inhabited our planet, 49 no longer exist. See? You're a lucky person.
Many of these extinctions happen very slowly, little by little. Certain species are unable to adapt and gradually cease to exist, while at the same time at the same time other species are slowly emerging and gaining a foothold on Earth. And that's just the natural cycle of life.
But every once in a while, a catastrophe sweeps away all the species that live around here. Practically all forms of life, many of which took millions of years to emerge, adapt and thrive, are simply BAM! Deleted.
In short, there is no single, definitive meaning of what an extinction is mass extinction. The concept may vary in the opinion of each researcher, but in this video we will adopt the criterion used by the Natural History Museum of the United Kingdom. Their definition says that a mass extinction is when species disappear a lot faster than they are replaced.
In numbers, this is when at least 75% of species die out in a short period of time. I just need to make it clear that when we say short here, we're referring to to geological periods of time, and they can last literally anything between 800,000 and 2,000 years. million years.
And that time scale makes sense. The Earth is 4. 5 billion years old.
A period like that is equivalent to less than 0. 001% of all that time, which is basically a geological finger snap. So now that we have a good definition of what a mass extinction is, we can review the entire history of our planet.
And in doing so, we can find five major episodes in which the existence of the life on Earth literally hung by a thread. So sit down, now I'm going to tell you the story of all the times that life was almost extinguished from the Earth. Just before I go on, I've recently started venturing into the world of intelligences generative artificial intelligences, and I even made a picture of how I imagined the Earth a few billion years ago.
It turns out that in order to use these tools well, you need to improve your prompting skills, which is the command you give when generating an image. And lucky for me, Allura, who made this video in partnership with me, is fully trained in artificial intelligence. If you want to improve your technique and really master these new technologies that are changing the market every day, go to allura.
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And now, back to the video, let me tell you the story of all the times when life was almost extinguished from the Earth. First mass extinction, Ordovician-Cilurian, 450 million years ago. The first great extinction was in the Ordovician period.
. . Ordo.
. . Ordov.
. . The first great extinction was 450 million years ago.
Back then it was all sea, literally. Plants dominated the terrestrial environment, animals only existed underwater, animals marine invertebrates spread throughout the oceans. Still small beings, but they represented the beginning of the diversity of the animal kingdom.
The miracle of life was finally taking shape. But along with life also came its inseparable companion, death. And she had a lot of work to do at that time.
The first mass extinction was caused by the movement of the continents. As you no doubt learned in geography lessons at school, the map of the world doesn't always had the format we're used to today. At that time the great tectonic plates of the Earth were arranged in this other way.
The mega continent called Gondwana, which today corresponds to South America, Africa and Oceania and Antarctica, was moving towards the south pole of the planet. And this led to a cooling of the Earth's temperature. Glaciers formed and, as a result, sea levels began to fall.
Quite a problem since it was home to all the animals of that time. The result? Around 85% of the species that used to inhabit our planet have simply ceased to exist.
And that was just the first time the Earth underwent a general clean-up. The second great extinction took place a few tens of millions of years later, in a period a little easier to talk about, the Devonian. It was also easier to live in back then.
It's just that life was no longer so restricted to water. In other words, it was at this time that an unoccupied fish decided to go to Earth and because of him you have to work Monday morning. At this stage in the history of life on Earth, the first insects and terrestrial vertebrates walked across the continents for the first time.
And with the new forms of life came new forms of death. And there were many. Scientists in general attribute this extinction to not just one, but a number of reasons.
The movement of the continents continued, and caused further changes in the level of the oceans. The planet's temperature also underwent changes, warming and cooling. There has also been a reduction in the concentration of oxygen in the atmosphere.
And the result of this sum of factors was the massive subtraction of life here. For every four living beings that existed until then, three could not survive the that time. And that's a frightening number, but nowhere near the biggest extinction of all that have happened to date on planet Earth.
Permian, 250 million years ago. 95% of all beings that lived at that time became extinct. It's not for nothing that this period is known by the unsavory name of The Great Dying.
Once again, one of the causes was the movement of the continents. But they don't rest either. It was at this time that the continents came together in this virtually single block.
The famous Pangea. A period marked by mega catastrophes on a global scale. Volcanic activity was extremely intense.
Constant eruptions spread ash and lava across the planet. In addition to releasing a gigantic amount of carbon dioxide into the atmosphere. And then the acid rain made the oceans toxic.
In other words, a combination of factors formed a perfect storm. It was a period of so much dust blocking the sunlight that some researchers did not rule out the possibility that an asteroid also hit the Earth at that time. The fact is that the planet has become practically uninhabitable.
Large vertebrate species that could give rise to animals we have no idea about today ended up falling by the wayside. Life had to start again practically from scratch. Until it was impacted by yet another great extinction.
Fourth mass extinction. Triassic. 200 million years ago.
50 million years later. And guess who kept moving back and forth and messed up all life on Earth again? once?
That's right. Pangea split apart and the continents went one way. Gradually moving towards the positions they occupy today.
And again it was a dramatic moment for life around here. New active volcanoes, more carbon dioxide in the atmosphere and other storms of acid rain have wreaked real havoc on Earth. Many of the first mammals that lived here died out at this time.
And large amphibians didn't survive either. The estimate is that around 76% of the beings that inhabited the planet have disappeared. But, as in all the great extinctions that we've shown so far, part of the beings were able to survive.
And in this case, some of the animals that escaped alive were dinosaurs. The extinction of so many other species marked the beginning of the dinosaurs' lasting reign. A crown that has always belonged to them for more than 60 million years.
And here it's worth pausing for a moment to reflect on the duration of events on a geological scale. We often don't realize how frightening this duration is. To give you an idea, our species, Homo Sapiens, has existed for around 160,000 years.
And that means you'd have to take absolutely everything that our ancestors did, lived and built from leaving the caves to stepping on the moon and then multiplying all that by a thousand. Only then can we grasp the scale of the period in which dinosaurs dominated our planet. It was an extremely long-lasting era, but it changed drastically from one day to the next 65 million years ago.
Fifth mass extinction. Cretaceous. 65 million years ago.
An asteroid about 14 kilometers wide crossed space, passed through the Earth's atmosphere and fell into the sea where it meets the Yucatán peninsula, which belongs to the territory of Mexico. And this was perhaps the biggest butterfly effect in the history of the universe. Because if the meteor's route had been just a few kilometers different, none of us would be here today.
Life on Earth would be absolutely different. But luckily for us, and unluckily for the dinosaurs, that's not what happened. The asteroid's colossal impact gave rise to a series of catastrophes.
It's as if what caused the other extinctions happened again, only all at the same time. Right after the shock, the first consequence was a super tsunami. Earthquakes also shook the continent, as the meteor fell right on top of Terra Fílm.
Volcanoes erupted, fires spread everywhere and a cloud of millions and millions of tons of dust blocked out the sunlight. Not for a few hours or days, as many people might think. All that dust was in the air for years.
Rinnite was the main cause of the extinction of the dinosaurs. That was obviously a joke, don't take it seriously. Without sunlight for so long, the plants' photosynthesis was interrupted.
And this caused a domino effect throughout the food chain. One species was wiped out, causing its predator to be wiped out too, and then the predator of that other species was also wiped out, and so on. It turns out that life doesn't happen in isolation, everyone depends on everyone else.
The estimate is that 80% of species disappeared as a direct or indirect consequence of the asteroid strike, and among them, almost all of our beloved dinosaurs. Only the lineage of birds survived, leaving descendants who are still with us today. A study by the American Harvard University in 2008, for example, showed that chickens are descended from tyrannosaurs.
And this shows that even in such an adverse scenario, living beings have managed to find a way to survive. And here I quote another important scientific paper on the life of dinosaurs, called Jurassic Park. Okay, just kidding, that's Steven Spielberg's movie.
But one of the most famous lines in the movie says that life finds a way, and that's exactly what I mean. Despite so many obstacles that have threatened to take life, it persists in existing and resisting. It's like that flower that grows on the asphalt, a symbol of the hope that springs up in the midst of chaos.
Although asphalt isn't very chaotic. But that's exactly what happened in the five great extinctions that have taken place to date. And well, that could be the end of the video.
It would end quite poetically, quite inspiringly, and then I could say thank you, thank you very much and see you next time, and everything would be fine, but the little red bar at the bottom of YouTube shows that, well, there's more to come, isn't there? So I apologize for cutting the mood, but we need to talk seriously. Sit down.
Unfortunately, the extinction of the dinosaurs may not have been the last mass extinction. Sixth mass extinction? Anthropocene?
Currently? You didn't think I was going to cause an existential crisis today, did you? But in this case, it's literally an existential crisis, because it's our existence that's at stake.
Many experts point out that yes, the sixth mass extinction is happening now, and it's being caused by us. Calculations show that the extinction of species has accelerated between 100 and 1000 times since the emergence of human beings. In other words, a single species is being able to decimate several other species.
Extinction, this thing that nature has taken millions of years to do on other occasions, and needed earthquakes, hurricanes, tsunamis and even a meteor, humanity is kind of managing to do it on its own. Let's hear it for us. And that happens in many ways.
The unbridled exploitation of natural resources, the cutting down of forests, the pollution of rivers, the degradation of the soil, as well as the unprecedented emission of tons of carbon dioxide into the atmosphere every day. All this is contributing to the real risk of the sixth great extinction. And remember that domino effect I mentioned just now?
The end of one species, which leads to the end of another species, which leads to the end of another species. It is foolish for humans to think that they can escape all this destruction of the environment. Humanity does not exist apart from the ecosystem; we are part of it.
That is why it is urgent to take action to change this reality while there is still time. I often feel that a pessimistic and conformist atmosphere is taking hold of some of us. Some people make comments like, we have nothing to do, when in fact the story is different.
Our future does not seem promising if we continue as we are now, but we still have a chance to rewrite the next pages of the history book of our planet if our next actions are taken wisely. And even if we one day manage to, I don't know, migrate to another planet, like terraforming Mars, it is more likely that we would just transport our destruction there. Especially because if Earth itself, with so many natural resources, is being devastated in this relentless way by humans, we have no reason to believe that much harsher environments can be the salvation of a species capable of causing another mass extinction on its own.
And that was our existential crisis for today. So now, thank you very much and until next time. I hope there will be a next time.
Please don't ruin everything.
