How Did Anything Survive the Mass Extinction? | Stops | Prehistoric Road Trip

How Did Anything Survive the Mass Extinction?

Hell Creek Formation, Jordan, Montana

Cretaceous-Paleogene Extinction Event, 66 million years ago

You might call it “a bad day.”

Roughly 66 million years ago, a miles-wide asteroid slammed into Earth, somewhere near the present-day Yucatán Peninsula. The impact itself killed many living creatures, and it set off a series of events that led to the extinction of most life on the planet.

This event, known as the Cretaceous-Paleogene extinction event (K-Pg, for short), has been widely covered in popular articles, books, and TV shows, partly because the effects were so catastrophic.

According to some estimates, 75 percent of life on the planet was wiped out. So how on earth did anything survive, and what lessons can we learn for the future?

The Main Event

The K-Pg Extinction

Tracing the Day the Dinosaurs Died

Emily Graslie meets with experts in the Hell Creek Formation to learn more about the mass extinction that wiped out the dinosaurs.

First, let’s go back to that very bad day for the dinosaurs. Clint Boyd, senior paleontologist at the North Dakota Geological Survey, said it would have been a very quick event since the asteroid travelled at approximately 17,000 miles per hour. There would have been a bright flash and a release of energy that some experts say would have been the equivalent of millions of nuclear bombs going off simultaneously. The dinosaurs and other creatures living in North America would have been particularly hard-hit, said Boyd.

“The directionality of the impact blew all of the debris in this direction,” Boyd said. “It would not have been a great time to be around.”

In addition to the heat generated by the impact, things such as hot bits of glass and rock would have rained down on the dinosaurs in a matter of only a few minutes. Then fires would have broken out. 

Overall, the K-Pg extinction event was likely pretty quick, especially in North America, Boyd said. If the animals didn’t immediately die from the heat flash, falling debris, or fires, they still had a rapidly crumbling food chain to contend with. The fires would have wiped out the main course for plant eaters, so they would have starved. Once the plant eaters died out, the meat eaters would have run out of food. 

“In other areas that were farther away from the impact, it would have been a similar type of [process], except for there, they would have had to deal more with so much debris and soot being put into the air that it blacks out the skies,” Boyd said. The planet would have been jolted into climate change.

To make a long story short, it would not have been a fun time to be alive.

Though many scientists agree that an asteroid was, at the very least, a catalyst for the K-Pg extinction, paleontologists came up with just about every hypothesis a person could think of, because, hey, everyone is just trying to figure this thing out. Boyd said some other hypotheses included a virus, climate change, or even an influx in mammals that ate dinosaur eggs, so they eventually died out. But in recent years, the asteroid theory has been the one that has stuck due to more and more evidence, such as tsunami deposits near the Yucatán Peninsula and the presence of iridium – a metal that’s found in asteroids – that are around the same age as the extinction.

What Survived and How?

Believe it or not, some animals and other organisms survived the mass extinction. Crocodiles, small mammals, and even some tenacious plants, for example, managed to live on after the asteroid impact. So how did they do it?

“With some of it, we don’t know,” Boyd said. “It’s kind of an open question why some groups survived and some didn’t.”

Boyd offered crocodiles as an example. It’s hard to know the exact reason why they survived, but it could be because their diet was a bit more diverse. 

“They’re meat eaters, but they’ll eat anything for meat, like fish and turtles. So it’s not like they have one food item they’ll only eat,” Boyd said. 

Emily Graslie meets with geochemist Tom Tobin

The Clam's Testimony

Emily Graslie meets with geochemist Tom Tobin to search for clams – which could hold important clues about the mass extinction.

Compare crocodiles to herbivores, such as one of the sauropods or a Triceratops, who might eat only a specific type of tree or shrub. Some paleontologists thought that because crocodiles lived in the water, they were safer from the fallout, but then that doesn’t explain why the marine-dwelling mosasaur died out.

Similarly, many small mammals survived, but the exact reason why isn’t clear, either. Was it because of their body size, which didn’t require a lot of food? Or was it because many of them burrowed and were able to camp out underground, away from the chaos above?

“Some of it may just be based on luck,” Boyd said. “You might have had small pockets in certain parts of the world where certain types of animals had the right conditions for them to survive. Maybe all their other representatives around the planet went extinct, but because that one small pocket survived, then they could eventually repopulate over again.”

There is also a fossil record of many plants coming back relatively quickly, especially ferns. Boyd said even today, ferns tend to do well after a disaster and, for example, are often the first plants that come back after a forest fire. The fossil record shows that ferns spiked after the extinction and thrived.

All of this happened relatively quickly, at least in terms of geologic time. Boyd pointed to one recent study out of Colorado led by Tyler Lyson that revealed it may have taken thousands of years, rather than millions, for life on Earth to repopulate and diversify again. 

Boyd said there’s evidence in the soil that earthworms started doing what they do best, kicking off the recycling of organic matter.

“The generalist plants and animals do really well, and then that creates the right conditions and enough biomass for other animals to survive off of those animals and push their way back in again,” Boyd said.

Lessons for the Future of Our Planet

There are plenty of lessons we can learn from the K-Pg extinction.

“The [K-Pg] extinction helps us understand just how we got the world that we live in today,” Boyd said.

Of course, it’s hard for human beings to plan for a similar event. It’s probably hard to stop a miles-wide asteroid.

“We can look at…how both the flora and the fauna react and readapt afterwards,” Boyd said. “That can tell us a lot about how animals and plants today are going to react to ongoing climate change.”

Obviously, today’s climate change is not as abrupt as the climate change during the K-Pg extinction event. But there are some parallels, particularly the wildfires that are more common as the planet warms. Boyd said we can look at evidence about what happened to the animals who were affected by the forest fires brought on by the asteroid to see what creatures came back first and which struggled the most.

“Which of those types of animals and plants have the most trouble and are therefore the most likely to go extinct and likely need our protection the most to help them survive these times?” Boyd said.

If you couldn’t tell, the short answer to a lot of the questions surrounding the K-Pg event is: we simply don’t know the reason why. Paleontologists are still studying it. But knowing what happens during the dinosaur extinction, or any other time in geologic history, for that matter, depends on paleontologists finding and preserving the right rocks.

“Obviously there [are] an untold number of questions that we’ll never be able to ask about the history of life on Earth because there’s just not a record preserved of it anymore for that specific question,” Boyd said.

“One of the important things for us to do is to make sure that those resources remain around for everybody in the future,” Boyd said. “We’ve answered some questions now, but we don’t understand what methods and techniques are going to be available in the future to answer questions we haven’t even thought of yet.”