About 100 million years ago, Earth looked completely different. With no humans, some scary animals were ruling over this planet: dinosaurs. Dinosaurs so big that they were taller than buildings. With jaws so strong that they could have crushed your bones within a second. They were so fast that they ran at around the speed of 90 km/hr. They were truly fear-arousing creatures. They ruled over Earth for more than 170 million years. But then one day, something happened that completely wiped them off the planet. What happened exactly?
“As it gets closer to the planet, Earth’s gravitational pull gets stronger.”
“They now can’t see what’s headed their way.”
Friends, the word ‘dinosaur’ originated from Greek, from the words *deinos* and *sauros*. *Deinos* means terrible, and *sauros* means lizard. A terrible lizard. This is the literal meaning of the word dinosaur. The word was used for the first time in 1841 when a dinosaur fossil was discovered. Richard Owen, a British scientist, used the word dinosaur. Back then, people did not know much about dinosaurs or their appearance. So the initial drawings of how dinosaurs might have looked are vastly different from what we know now.
Megalosaurus was one of the first fossils to be discovered. Today, more than 10,000 dinosaur fossils have been unearthed by paleontologists worldwide, and more than 900 distinct species have been identified. You might be excited by the prospect of discovering more fossils. But interestingly, from 2003 to 2022, on average, about 45 new species of dinosaurs have been identified each year. The work of paleontologists is far from over.
Of them, this is a bizarre dinosaur discovered in Chile, with a weapon that looks like a blade on its tail and a beak for a mouth. It was named Stegouros elengassen. Overall, we know a lot about dinosaurs today. But come, let’s start this story at the beginning. Let’s dive into the past, millions of years ago.
Scientists estimate that the first dinosaurs emerged about 230-240 million years ago. The oldest dinosaur fossils that we have found so far are from 231.4 million years ago in Africa. Back then, Earth was much different than it is today. The continents that you see now—Asia, Africa, Australia, Europe—all were joined together. There was only one supercontinent that we call Pangaea.
Scientists believe that Pangaea looked somewhat like this. You can even see the placement of the continents that we know. Back then, the climate of Earth was dry and arid with only a little rain. This time period has been named the Triassic Period, the era when dinosaurs started emerging. Dinosaurs were slowly populating the Earth due to evolution. The dinosaurs of this era weren’t anything like the ones you imagine; they were quite small in size. The common dinosaurs of the time were generally around 2 meters long. For example, Eoraptor was a dinosaur that existed in that period. In fact, this dinosaur is known as the ancestor of other dinosaurs. The dominant animals of the era were giant reptiles. Some of these reptiles looked cute, like this one, which is believed to be the ancestor of all turtles.
With time, Earth started changing. About 201 million years ago, the Triassic Period ended when Earth’s climate changed suddenly. The Pangaea started breaking apart. Although I am using the word ‘suddenly,’ it didn’t happen in a day or two; it was relatively sudden in the time scale of millions of years. It happened gradually over thousands of years. Cracks appeared in the supercontinent, and large-scale volcanic explosions took place on and around the cracks. Due to the numerous volcanic eruptions, a large amount of carbon dioxide and sulfur dioxide was released into the atmosphere. This caused intense global warming. When the sulfur dioxides and aerosols entered the atmosphere, they blocked the sunlight and caused some cooling. Acidification of the oceans started when the carbon dioxide and sulfur dioxide mixed with the water. The acidity of the ocean water increased.
The climate was changing rapidly, and survival became difficult for the animals that existed. Most reptiles and other species back then were cold-blooded animals, and they couldn’t withstand the temperature changes. But the dinosaurs were warm-blooded like humans, so it was easier for them to tolerate the temperature changes. The volcanic eruptions and climate change continued for about 600,000 years. Due to this, almost all the other species became extinct. The only animals remaining on Earth were the dinosaurs, crocodiles, turtles, and early mammals. This event is known as the Triassic-Jurassic Extinction Event.
As I said, after this, the Triassic Period ended, and the Jurassic Period began. If this sounds like a familiar name, this is the inspiration for the name of the Jurassic Park films. The word Jurassic refers to this Jurassic Period. The Jurassic Period lasted from 201 million years ago to 145 million years ago. During this time, dinosaurs emerged as the most dominant species on the planet. Due to evolution, some of them became quite large in size, like some of the earliest Titanosaurus. They lived around 160 million years ago. Each of them weighed up to 15,000 kg and could be up to 15 meters long.
Some other iconic dinosaurs of the time were... During the Jurassic Period, some dinosaurs evolved to fly. One of the first feathered dinosaurs was Archaeopteryx. It looked somewhat like this. At this time, the Pangaea supercontinent was divided into two smaller supercontinents. We named them Laurasia and Gondwanaland. Friends, due to the Jurassic Park films, the Jurassic Period is the most widely known. But it was the next period when dinosaurs truly flourished—the Cretaceous Period. During this time, we saw an explosion in the diversity of dinosaurs. Several new species of dinosaurs evolved. T-Rex, perhaps the most famous dinosaur to be shown in films, existed in the Cretaceous Period. It reached peak dominance only at the end of the Cretaceous Period, around 65-68 million years ago. Though this is debated among researchers, most scientists believe that T-Rex didn’t exist in the Jurassic Period. It’s quite ironic that in the film *Jurassic Park*, T-Rex is used for their logo.
The Cretaceous Period was the longest time in the era of dinosaurs. Starting around 145 million years ago, it lasted till 65 million years ago. The two supercontinents, Laurasia and Gondwanaland, started breaking up, and the structure of the continents looked similar to what we see today. Several flowering plants evolved around this time, and the average temperature of the Earth was warmer than it was in the past. Sea levels were quite high, and almost all kinds of dinosaurs that you can imagine existed during this period: raptors, armored dinosaurs, giant herbivorous dinosaurs, and dangerous carnivorous dinosaurs. Titanosaurus, one of the largest land animals, and Argentinosaurus, which could weigh up to 77 tonnes, lived during this period. T-Rex, which could be up to 40 feet long, is believed to be the apex predator of its time. It had the strongest and most powerful jaws compared to any other animal.
A fun fact: the evolution of grass began only 70 million years ago. In the story that I have been telling you, don’t imagine a grass-filled Earth; there were other kinds of plants. T-Rex and Triceratops evolved 68 million years ago. Do you know what this means? We are closer to the dinosaur T-Rex than it was to the Jurassic Period. Since there’s 80 million years between the Jurassic Period and the T-Rex evolution, but only 68 million years between us and T-Rex.
Another interesting dinosaur that existed then were the Ornithomimids. They looked like ostriches and were among the fastest dinosaurs. They could run at a speed of 80 km/hr. And in terms of flying, instead of running, the largest flying dinosaur was Quetzalcoatlus, which had a wingspan of 10-11 meters. As you can see, this was the most prosperous period for dinosaurs. The climate was favoring them, new species were evolving, and there were no other animal species to compete with them. They were simply ruling over Earth.
Everything was going well until one day, something happened that completely wiped off dinosaurs from Earth forever. A large asteroid, with a diameter of roughly 10-15 km, came hurling towards Earth and crashed into it. This happened 66 million years ago, and this asteroid strike ended the Cretaceous Period. The speed of the asteroid was 30 km per second, 150 times faster than a jet airliner. Specifically speaking, it hit the Yucatán Peninsula in Mexico, the same place where millions of years later, the Mayan tribe emerged and built historical wonders like Chichen Itza. I explored the Yucatán Peninsula in my vlogs as well. You can watch the vlogs of this place if you want to; the link will be in the description.
When the asteroid hit Earth, it created a large crater.
With a diameter of 180 km, the impact released energy at a speed equivalent to 100 teratonnes of TNT [100 trillion tonnes or 100,000 trillion kg]. If you compare this with the atomic bombs dropped on Hiroshima and Nagasaki, the asteroid produced 1 billion times their energy. This was such a big impact that everything around it disintegrated in the blink of an eye.
The impact threw a lot of soil into the air, heating the land, and the hot dust rained over the other areas. Global temperatures rose by several degrees for hours. All animals within thousands of kilometers were cooked alive by the sheer heat. It’s believed that only small animals could survive the impact of this initial blast because they found underground shelter or hid underwater, in caves, or in large tree trunks.
But this was only the initial impact. This was followed by shock waves, heat pulses, wildfires in forests for thousands of kilometers, and massive tsunamis. It’s speculated that there would have been an immediate tsunami with a 2 km tall wave. Can you even imagine a 2 km tall tsunami wave? Volcanic eruptions started once again, acid rain fell, and earthquakes occurred.
The short-term effects were quite deadly, but you would think that on the other side of the Earth, which wasn’t hit, animals could have perhaps survived. However, the long-term consequences were even deadlier. The dust particles in the air blocked sunlight for the next year all around the planet. The planet went into a nuclear winter. The temperature dropped drastically. It’s estimated that for the next 3 years, the Earth experienced freezing temperatures, killing many plants and animals.
Since the sunlight was blocked for a year, it was impossible for plants to use photosynthesis. The plants died, and with them, the herbivorous animals had nothing to eat and died out. Even the carnivorous animals were left with nothing to eat, and they too died out, causing a chain reaction. The only animals safe from these consequences were small omnivorous animals such as mammals, lizards, turtles, and some birds. These animals could survive because they could scavenge on dead dinosaurs, fungus, and decaying plant matter.
The impact of the asteroid destroyed carbonate rocks too, releasing carbon and sulfur into the atmosphere once again. For the next several thousand years, sunlight was significantly reduced and was not at normal levels. Acid rain continued for thousands of years. When the nuclear winter ended and the dust in the atmosphere settled down, sunlight reached the planet once again. But the problem was that a large quantity of carbon dioxide was already released into the atmosphere, causing intense global warming.
Think about this, friends: one asteroid changed Earth’s history for the next thousands of years. If we ignore a few exceptions, no four-legged creature weighing more than 25 kg could survive this event. All terrestrial dinosaurs went extinct, and with them, more than 75% of the plant and animal species once thriving on Earth went extinct.
At this point, the Cretaceous period ended, and the next era began—the Paleogene period. It wasn’t as if everything had ended. This event was like an opportunity for the rest of the animal species. With the dinosaurs gone, other animals had the opportunity to rise and rule. Humans should be thankful for this asteroid because it provided a good opportunity for the evolution of mammals after the extinction of dinosaurs. The gap in the food chain left by the dinosaurs was filled by several mammals. It was during this period that we saw the evolution of horses, whales, bats, and primates. Several snakes and smaller lizards started emerging in this period.
The only group of dinosaurs that survived were the flying dinosaurs. Gradually, they evolved and became the birds that we now know. Yes, you read that right. The birds you see flying around today have flying dinosaurs as their ancestors. Most studies have confirmed that birds belong to the same family as dinosaurs. Specifically, ancestry is shared most closely by chickens and ostriches. This is why people might say that the closest living relative of T-Rex, a dangerous dinosaur, is a chicken.
You might have a question about the asteroid. How did we find out the spot where the asteroid crashed and that it crashed 66 million years ago? How did we figure out the date? This is evidenced by a rare mineral: iridium. Scientists found that at a few places on Earth, we have a high concentration of iridium on the ground. But when the geologists analyzed Earth, they found that it is a very rare mineral on Earth. Despite that, it is so abundant on our ground. How could this be? This could happen because comets and asteroids have a high concentration of iridium. When scientists put the iridium into carbon dating, they found that the iridium layer is 66 million years old. This could happen only when the asteroid hit the planet, and in the ensuing blast, this mineral spread all around.
You might also wonder, since the asteroid had such a big impact, we should be able to see the crater it left on Earth. Well, you are not wrong. But an event that occurred so long ago, 66 million years ago, might not look like you’d imagine it to be. Because since then, the continents have been relentlessly shifting. The crater of this asteroid is hidden in the Yucatan Peninsula. However, several digging expeditions were conducted that proved it actually happened and pinpointed the exact location. If you look at the map, this is the exact location. Half of it is submerged under the sea, and the other half is on land. A real-world impact that we can still see are the cenotes in this Mexican area. These beautiful sinkholes show a pattern. The cenotes can be found in a ring formation around the crater. Nowadays, they are famous tourist attractions. You can go swimming in these cenotes. Overall, these cenotes form the world’s largest underground cave system.
After hearing this astounding story of the asteroid strike, you might be thinking about what would happen if such an asteroid hit the planet now. Will humans go extinct? This is definitely a threat. The asteroids that might hit Earth in the foreseeable future are known as Near-Earth Asteroids. NASA and other space agencies are continuously tracking all near-Earth asteroids to compute their paths and predict if and when they will collide with Earth. As of April 2022, more than 28,000 near-Earth asteroids have been identified, with over 800 having a diameter of 1 km or more. This is a scary number, considering so many asteroids may potentially collide with Earth.
But today, you don’t need to be scared about this because scientific calculations are so advanced that we can clearly predict their path and calculate the exact location of the impact. We can even estimate the chances of it actually colliding with Earth. And if they are indeed on a path of collision, what can we do to stop it?
This was the idea behind NASA’s DART space mission launched in 2021—the Double Asteroid Redirection Test. They planned to have a spacecraft collide with an asteroid so that the path of the asteroid could be altered. If, in the future, there’s an asteroid about to collide with Earth, we can alter its path. This might sound like science fiction, but this idea was already successful.
In September 2022, a test was launched on an asteroid that was not on the path towards Earth. NASA sent a spacecraft to it, the spacecraft collided with the asteroid, and its path was altered. If they could successfully do it to that asteroid, it can be done to any asteroid on the way to Earth in the future. But that doesn’t mean that there’s no danger at all.
Humans are the danger here. The asteroid strike that killed the dinosaurs is known as the 5th extinction event in Earth’s history. After this, scientists believe that the 6th extinction event has already begun. This isn’t due to any volcano or asteroid—it is caused by humans. This is named the Holocene Extinction Event.
Over the last 100-200 years, we have seen the loss of biodiversity at an unprecedented scale. Animals and plant species are rapidly going extinct due to humans. Biologists agree that it is a mass extinction. Deforestation by humans and pollution in oceans and the atmosphere are driving this extinction. The normal rate is more than 100-1,000 times the current rate of extinction. Habitats of the animals that exist now are being destroyed. Thousands of mammals, birds, reptiles, and amphibians are now in the endangered category or have already gone extinct due to humans.
To stop this destruction, a United Nations Convention on Biological Diversity meeting was held in Japan in 2010. Twenty biodiversity targets were set to be achieved by 2020. Unfortunately, only six of those have been partially achieved. In January 2020, a new Paris-style plan was set to prevent biodiversity and ecosystem collapse, with a deadline set for 2030. Its purpose is to ensure that 30% of the land and oceans are given the status of being protected and to reduce pollution by at least 50%.
Scientists have proposed that the extinctions taking place need to be limited to 20 per year or fewer. We’ll have to see how many targets can be met. But one thing is certain: it is important to do these things because if plant and animal species go extinct now in the same way it happened in the previous extinction events, perhaps it wouldn’t be possible for humans to survive.
It’s interesting to note that humans originated merely 300,000 years ago in Africa, according to the data. Compared to the dinosaurs, who were the dominant species on Earth for 174 million years, we’ve been here for only 300,000 years, while they lived for 174 million years—600 times longer than humans.
What do you think? Can humans beat the record set by dinosaurs? Or will humans go extinct before they’re 1 million years old? Comment below with your opinion. Obviously, the right answer will depend on our collective efforts to save this planet.
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