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0:00
I'm Dr. Kenneth LaCava, paleontologist and executive director of the Edelman Fossil Park Museum of Rowan University.
0:04
I'm here to answer your questions from the internet.
0:08
This is Extinction Support.
0:20
Lindsey Kinel 2 asks, "How do we know an asteroid killed the dinosaurs?"
0:20
Well, dinosaurs dominated Earth's terrestrial ecosystems for 165 million years.
0:25
They were cosmopolitan; you find them on every continent.
0:31
And then we see this impact back layer, this ash, the fallout from the asteroid, and nowhere on Earth has anyone found a single in-place dinosaur fossil 1 cm above this layer.
0:27
We can see that there was a day in history when, poof, they were gone.
0:40
Where is Brandon writes, "If asteroids killed the dinosaurs, how come every other animal that was alive at the same time as them that's still alive now survived?"
0:52
The biggest killer that day when the asteroid struck was the heat.
0:53
So if you were on the surface of the Earth and had no place to hide, you died that day.
1:01
If you could get underground, like a little shrew-like mammal or a lizard or crocodiles, or good burrowers, or even birds—there were birds at the end of the Cretaceous period—if you could get under the ground that day, you had a chance of surviving.
1:06
The real Ling S, "Where is the asteroid that killed the dinosaurs?"
1:13
"Has it ever been found?"
1:15
It has been found actually, and there's a crater off the Yucatan Peninsula, that's the East Coast of Mexico, that's about 110 miles across and 12 miles deep.
1:29
It was published in 1991; that's when scientists knew about it, but actually, petroleum companies knew about it since the 70s, and they didn't tell anyone because they're petroleum companies.
1:29
The asteroid that wiped out the dinosaurs was about 18 km across, traveling at about 45 times the speed of a bullet, and it probably landed in the springtime because there are some fish in North Dakota, some fossil fish that have spring pollen trapped in their gills.
1:29
Sunp Taru asks a good question: "Which animal species came the closest to going extinct and then successfully recovered?"
1:29
Well, the best example I know of is the California condor.
1:29
In 1972, it was down to about 22 individuals.
1:29
The chemical DDT was causing their eggshells to be soft and to break, and so they couldn't reproduce.
1:29
Plus, they're scavengers, so they would eat a dead deer that had been shot by a hunter with lead shot, and they were getting lead poisoning.
2:20
And so, through an amazing effort, zoos and other conservation organizations, they captured every single remaining condor, all 22.
2:27
They had an intensive breeding program, and then they started to release them back into the wild.
2:35
They are not out of danger; they are still a critically endangered species, but right now there are about 550 California condors in the world.
2:44
Some of them have actually made their way from California to Zion National Park, and there's now a small breeding population of California condors there.
2:49
So they seem to be moving in the right direction because we took action, because we banned DDT, because California banned lead shot.
2:57
So it's not like we're helpless in these cases.
2:59
There are things that we can do to help pull these organisms back from the brink, but the time to act is now.
3:05
Nandi S, "What's the worst that could happen if mosquitoes and flies were to be extinct?"
3:15
Well, although they are pests, small insects like that are really down pretty close to the base of the food chain, and you think about all the things that eat mosquitoes and flies: a lot of birds, frogs, other amphibians, small mammals.
3:17
And so, you know, what if you want to precipitate an extinction event, if you want to wipe out big animals, kill off the insects.
3:29
That's the best way to do it.
3:31
Ombre del Queso or Cheeseman, "How many animals have humans hunted to extinction?"
3:37
Certainly we have examples.
3:39
When the government of Australia put a bounty on the Tasmanian Tiger, people went out and shot every single one of them.
3:45
There's a heartbreaking film of the last Tasmanian tiger circling wearily in this cage, and that was the last of its species.
3:53
Passenger pigeons, we killed all of them just for sport.
3:56
They used to block out the sun for hours with flocks of billions.
4:01
Dodos, Dutch sailors would club them to death.
4:04
They wouldn't eat them, they would just stack them up and use them for firewood.
4:10
The same thing happened to the Great Auk, which was sort of the penguin of the North Atlantic.
4:10
And then if you go back a little further in time to Stone Age humans, the woolly mammoth and the woolly rhino and the giant ground sloth and all those amazing Pliocene creatures that all of a sudden died when humans showed up.
4:10
B Shiver states, "Invasive species are bad, they outcompete native ones."
4:10
Yes.
4:10
So it's called the free market.
4:28
It's true, and that there's natural selection that is occurring, but invasive species for the most part are able to invade those places because of us, because of our transportation systems, or sometimes intentionally humans releasing them into the environment.
4:46
And the result of that is that native species go extinct, native species that are important in the ecosystem or important to us as maybe a food crop.
4:55
And so, you know, I don't think we want to really be playing planetary engineer with the Earth's biosphere.
5:03
Death by Kool-Aid Man writes, "What extinct animals do you think are really just hidden away from humans?"
5:35
I would be surprised if us paleontologists have discovered 1% of the species that have ever lived.
5:35
And if you look at just the group that we call dinosaurs, if you go back to the early part of the last century, there was a new dinosaur species published about once every year.
5:35
By the '70s, it was about a half a dozen a year, and now it's about one a week.
5:35
Now, there are some animals that were at one point believed to have gone extinct that are later found alive.
5:35
It's very, very rare; they're actually called Lazarus species.
5:39
And a good example of that would be the coelacanth, which is a very ancient fish.
5:43
It lived alongside of the dinosaurs, and it was believed to be extinct until one was dredged up off the coast of South Africa in the 1930s.
5:43
There's a pine tree called the Wollemi Pine that was thought to have been extinct since the Cretaceous Period, and in the '90s it was discovered alive in a valley in Australia.
5:43
So this can happen, but it's very, very rare.
5:43
Most things that we determine are extinct in the fossil record, we never see again.
6:06
Great Blue Panda asks, "What if super volcano Yellowstone erupts?"
6:11
"What happens to all species?"
6:11
Well, probably bad things.
6:12
Yellowstone is a giant super volcano.
6:15
In fact, it wasn't discovered until just a few decades ago because it's so big, geologists didn't know they were inside a volcano.
6:21
It was when satellite imagery started to become available that we saw Yellowstone as this huge, huge volcanic caldera.
7:03
The last time it had a really huge eruption was about 600,000 years ago, and parts of the West were covered with 600 feet of ash.
7:03
600 feet!
7:03
If that were to ever happen again, it would take out a lot of the United States.
7:03
Even here in New York, a couple thousand miles away, there would be terrible effects.
7:03
The ash would reach New York.
7:03
Aviation here and probably globally would shut down.
7:03
Probably not going to erupt tomorrow, but there is going to be a tomorrow someday.
7:03
Maverick 8358 writes, "Would we as humans be extinct if another Chicxulub asteroid hit Earth?"
7:00
Probably not, not at least initially.
7:03
And when an asteroid hits, the most deadly moment is when the fallout comes in.
7:08
The rock and the dust that's blasted from the impact zone goes into space and then resettles back through the atmosphere.
7:14
You can imagine the energy released by the impact.
7:18
In the case of the asteroid that wiped out the dinosaurs, a body of rock the size of Massachusetts, times 12 miles deep, was blasted into space.
7:26
So that day when the dinosaurs died, global temperatures got up to probably somewhere between toaster oven and pizza oven, and that means if you were on the surface of the Earth that day, you were dead.
7:26
Now if that happened in today's world, it would surely be calamitous, but a lot of humans are underground.
7:26
They work underground, there's tunnels underground, there's subways, there are defense facilities underground, so certainly some humans would survive that day.
7:26
We'd probably be in a Mad Max situation for some time, whether we pull out of that or not, who knows.
7:26
Britt J writes, "How strong is the evidence for an alternative hypothesis for the dinosaur extinction?"
7:26
Well, I would say weak at this point.
7:26
There are other hypotheses that have been out there for decades.
7:26
For example, maybe volcanoes wiped out the dinosaurs.
8:10
Well, that sort of thing takes hundreds of thousands or millions of years, and it would unfold gradually around the planet and doesn't look like the instantaneous extinction that we see in the fossil record.
8:21
Some people have said, well, the dinosaurs weren't doing so well leading up to the extinction, so they really died of multiple causes.
8:26
And A, we have no evidence that they weren't doing well.
8:31
We don't have that kind of resolution in the fossil record, and actually, it looks more like they were doing great and their biodiversity was flourishing.
8:37
But to say that they died of multiple causes would be something like saying Bob had a cold and he got shot by a bazooka, so he died of multiple causes.
8:49
Smudgy 90 asks, "What stopped dinosaurs re-emerging as the dominant species after the meteor event?"
8:51
Well, death.
8:51
Death is hard to come back from, but birds tried.
8:57
We call birds avian dinosaurs.
9:02
A flamingo or a hummingbird is a dinosaur to the same degree that a stegosaurus or a triceratops is.
9:02
We have certain anatomical features that you have to have to be considered a dinosaur, and if we go back to the very first creature that satisfies those criteria 237 million years ago, a fossil found in Africa that we call Nyasasaurus, 100% of that species' descendants, that's the group that we call dinosaurs.
9:24
So when I say the dinosaurs went extinct 66 million years ago, what I'm really talking about is the non-avian dinosaurs, but some avian dinosaurs survive until today.
9:36
Swen Rosla asks, "Would human evolution, the evolution of higher intelligence, ever been possible without this mass extinction event, or would it have taken a different course?"
9:36
I think it would have almost certainly taken a different course.
9:36
Earth history is so contingent.
9:36
If you run the movie of life on Earth back, it never turns out the same way twice.
9:36
If you can imagine that asteroid that wiped out the dinosaurs, well that formed the same time the solar system did, 4 and a half billion years ago.
9:36
Go out to the asteroid belt at that time and hit that asteroid with a piece of popcorn, and then 66 million years ago, it doesn't hit the Earth.
9:36
And our mammalian ancestors, during the entire reign of the dinosaurs, were little tiny nocturnal shrew-like creatures living in the hidden and forgotten recesses of the dinosaur world.
10:19
They could never really get anywhere until the dinosaurs went extinct.
10:22
And then the dinosaurs went extinct and almost immediately early primates evolved, some mammals returned to the sea, they become whales, some mammals become big predators, big herbivores.
10:32
None of that happens, I think, including intelligent species such as us, without the extinction of the dinosaurs.
10:40
A Reddit user asks, "99% of all living things that ever lived on Earth are now extinct, fact or fiction?"
10:45
It's fact-ish.
10:51
We don't know the exact percentage, but certainly the vast, vast majority of creatures that ever lived, something approaching 99%, they evolve, they persist for some amount of time, and then they went extinct.
11:01
Extinction is a natural process, but it generally happens gradually over geological time, not in rapid succession as is happening today.
11:10
San Cancel Guru opines, "Pandas are so bloody useless, they deserve to go extinct."
11:15
Well, that's pretty judgy there, Guru.
11:19
Pandas have a place in this world just like we do, and they fulfill a role in their ecosystem.
11:29
And pandas, like every creature, have an unbroken chain of ancestry stretching back 3.8 billion years to their microbial forebears.
11:34
This is a lineage that survived all five mass extinctions, including the one that wiped out the dinosaurs.
11:39
But they're having trouble surviving us, so what does that tell you?
11:43
Lynn Irwin wants to know, "How did cockroaches survive the dino-killing asteroid strike?"
11:49
Well, have you ever tried to kill a cockroach?
11:49
It's not that easy.
11:49
Cockroaches are small, their needs are meager, and they can get underground, and that is a formula for success.
11:49
Our Dot 12 writes, "What will cause the extinction of life on the planet next time?"
11:49
"Volcanoes erupting, asteroid impacts, sunspots, or developing fatal diseases in a lab?"
11:49
Well, here's what we know from history.
12:10
There have been five past mass extinctions, and every one was caused by a climate crisis.
12:17
The last, a climate crisis caused by an asteroid impact.
12:17
We are experiencing a sixth extinction right now.
12:17
We're not quite at the levels obviously that happened when the dinosaurs were wiped out, but the rate of extinction that's happening right now, if it persists, will cause Earth's sixth extinction.
12:17
Your boy asks, "What if there was a mass extinction so big it wiped away all evidence of anything being there?"
12:17
Well, there was actually a time in early Earth history called the Age of Bombardment, 4 and a half billion years ago to 3.8 billion years ago, when there was still a lot of debris in the solar system, and so planet-sterilizing impacts happened commonly.
12:52
It might well be possible that microbial Earth got started several times, but was wiped out by asteroid bombardment, and that wouldn't leave a record that we would ever find.
13:10
Stigmatronic writes, "The whole concept of the sixth mass extinction is bogus for the most part."
13:10
And you know what, Stigmatronic, I appreciate your skepticism, that's essentially the basis of science, but we have data for the assertion that a sixth extinction is underway right now.
13:05
The background extinction rate of vertebrate animals over the last 2 million years is to lose about nine species per century.
13:34
Well, just in the last century, we have lost 615 species of vertebrate animals.
13:34
Some people think the rate might be as much as 100 times higher than the normal background rate.
13:34
If you look at not species but populations of wild animals today, this is shocking.
13:34
Since 1970, there are 69% fewer wild animals on the land.
13:34
If that doesn't concern you, if that doesn't make you think that a sixth mass extinction is underway, I don't know what data you would need then.
13:59
Liz Way 34 asks, "Why are they attempting to bring back the woolly mammoth?"
14:05
"After six full Jurassic Park movies, my brain cannot fathom how anyone would possibly think this is a good idea."
14:11
My gosh, a lot of people conflate recent creatures like the woolly mammoth with dinosaurs.
14:19
Dinosaurs are truly ancient; their world is gone; that's 66 million years ago.
14:24
Mammoths were around only 3,300 years ago.
14:27
Mammoths lived in a world that had the Great Pyramids, that had written stories, that had beer; that's this world today.
14:34
And they had an important place in an ecosystem that still exists today.
14:37
And so if we could bring back creatures, particularly ones that are the keystone species in their ecosystems, meaning species that lots of other species depend upon, then that would be a good thing for our environment, for our ecology, and it also has carbon sequestration ramifications, so in some cases it could be a partial answer for the climate crisis as well.
14:58
I happen to be on the board of scientific advisers of Colossal Biosciences, endeavoring to de-extinct the woolly mammoth and the Tasmanian tiger and the dodo.
14:58
If there was a species that was on the brink today, if there were, say, only two of them left, let's say those two animals died and it's two days later, would you say, no, they're losers in Earth history, we're done with them?
14:58
Probably not, right?
14:58
Well, what if it was a week or 10 years or 100 years or a thousand years?
14:58
I kind of have a Pottery Barn philosophy on this, which is, you break it, you bought it.
14:58
I think if we're the agents of their demise, we have a moral and ethical responsibility to resurrect them and their ecosystems.
14:58
Dangerous Hotel 7839 writes, "Have there been animals that were hunted to extinction by other animals and not humans?"
14:58
There are lots of examples.
14:58
For example, in Hawaii today, exotic egg-eating snakes are wiping out many bird populations.
14:58
In New Zealand, house cats, which are not indigenous, are wiping out ground-nesting birds.
14:58
Rats are one of the things that pushed the dodo to extinction in Mauritius.
14:58
In the fossil record, when we see land masses connect, that often leads to extinction.
14:58
One of the things that caused the worst mass extinction ever, this happened about a quarter billion years ago, we call it the Great Dying, we think was caused by these giant volcanic fissures in Siberia, but it was exacerbated by the fact that all the continents just happened to bump into each other at that time, creating the supercontinent called Pangea.
14:58
When all the land masses are connected to each other, then all the animals have to compete with the other animals, and it's very hard on life.
14:58
When land masses are fragmentary, when you have lots of islands and little continents, then there's lots of little niches that different species can occupy, and that usually leads to an increase in biodiversity.
16:43
Bridget Hal writes, "Species of least concern, what does that mean?"
16:46
"It sounds so sad."
16:52
It means that they're not threatened, and threatened includes vulnerable, endangered, and critically endangered, which is the worst category to be in.
16:52
So least concern just means that the population is fairly stable.
16:58
An example of a species of least concern would be the laughing gull.
17:06
They're all over the country really, they're doing just great, they love being around humans, they love eating your hot dogs and your popcorn on the beach, and they're doing just fine.
17:11
A critically endangered species would be something like the Northern Right Whale.
17:15
There's probably only about 25 of them alive in the world.
17:21
St Fiasco asks, "What are the five mass extinctions?"
17:24
The first one that happens is at the end of the Ordovician period, around 400 million years ago.
17:30
Life is confined to the oceans at this point, and most of that is in the shallow seas.
17:30
Continents are drifting south, it initiates a glacial period, sea level drops, so it drops off of these shallow shelf areas, and it's just habitat loss, and so we have a mass extinction event.
17:30
Life recovers, and then we're in the Devonian period, after that, that seems to be a combination of climate change and bad ocean chemistry.
17:30
There's a lot of evidence of anoxic water, water that doesn't have enough oxygen in it because it produces these black shale deposits in the Devonian, and so we have that mass extinction.
18:01
And then the third mass extinction, the worst of all, was called the Great Dying.
18:10
It happens at the end of the Permian period, about 250 million years ago.
18:10
That is the result of these giant volcanic fissures in what is now Siberia, belching forth immense quantities of greenhouse gases, causing the planet to overheat, just like is happening today.
18:10
That in combination with Pangea forming, making all the animals have to compete with all the other animals, it was really tough on life, and we lose about 95% of species.
18:28
We lose these little guys, this is known as a trilobite.
18:36
They almost look like underwater bugs, but they evolved about a half a billion years ago, and they were super successful for about a quarter billion years, but then by the end of the Permian period, their immense run across deep time is over and they go extinct.
18:45
And then we go into the Triassic period, really hard time for life on Earth.
18:45
The world is recovering from this Great Dying event, and then those volcanic fissures in Siberia, they open up again, causing another mass extinction.
18:45
And then after the Triassic, we really get into kind of the sweet spot of the dinosaur age.
18:45
We're in the Jurassic period now, things are going great, dinosaurs are getting big, they're getting biodiverse.
18:45
We get into the Cretaceous Period, that's kind of the flower of the dinosaur world, and dinosaurs are cosmopolitan, they're in all kinds of niches, there are all kinds of sizes.
18:45
And then an asteroid hits and murders them, and it's over that day.
18:45
And then we get into the age that we are in now, the last 66 million years, that becomes the age of mammals, only because the playing field was cleared by that asteroid.
18:45
And now, what's happening now, we are causing the beginnings of the world's sixth mass extinction.
18:45
Throwaway Simples writes the trolley question: "I think deforestation is a good thing, change my view."
18:45
Well, Throwaway Simples, how do you like breathing?
18:45
Because most of your oxygen comes from plants.
18:45
The Earth has two great lungs, one is the phytoplankton in the ocean, the other is really the Amazon rainforest.
18:45
Rainforests such as the Amazon also have the highest biodiversity in the world.
18:45
And where do you think your medicines come from?
20:06
Well, they come from discoveries made from plants and animals and microorganisms that mostly live in tropical rainforests.
20:17
So if you like not dying of horrible diseases, you should be pro-forest.
20:17
Real M Foster says, "I don't understand why sharks have to exist."
20:17
Well, there's really no why in evolution.
20:17
There's no forethought.
20:17
Animals exist because they happened, and sharks happened a long time ago.
20:17
Sharks were around a couple hundred million years before the dinosaurs.
20:17
They persisted through the entire reign of the dinosaurs, they survived the mass extinction that wiped out the dinosaurs, and obviously they exist today.
20:17
But you know what, they're having trouble with us.
20:48
There's a lot of sharks that are critically endangered right now because they're being overfished and because their environments are being destroyed, such as the Great Hammerhead Shark, which is endangered.
20:58
And they are the apex predators in many of the ecosystems in which they live, and predators are important.
21:11
It keeps actually the prey populations healthy because it winnows out the ones that are diseased that could spread those diseases through the population.
21:05
It causes natural selection, which causes the prey species to become faster, stronger, quicker.
21:20
And so we really need sharks in this world.
21:23
Okay, that's it.
21:25
That's all the questions.
21:25
I hope you'll learn something.
21:27
Until next time.