I'm Dr. Kenneth Lacovara,

Paleontologist and Executive Director

of the Edelman Fossil Park Museum of Rowan University.

I'm here to answer your questions from the internet.

This is Extinction Support.

[upbeat music]

@LindseyKinsell2 asked,

How do we know an asteroid killed the dinosaurs?

Well, dinosaurs dominated Earth's terrestrial ecosystems

for 165 million years.

They were cosmopolitan. You'd find them on every continent.

And then we see this impact layer,

this ash, the fallout from the asteroid,

and nowhere on Earth has anyone found

a single in-place dinosaur fossil

one centimeter above this layer.

We can see that there was a day in history when, poof,

they were gone.

@Whereisbrandon 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?

The biggest killer that day, when the asteroid struck,

was the heat.

So if you were on the surface of the Earth

and had no place to hide, you'd die that day.

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 at surviving.

@DaRealLemm1ng asks, Where is the asteroid

that killed the dinosaurs? Has it ever been found?

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.

It was published in 1991,

that's when scientists knew about it.

But, actually, petroleum companies knew about it

since the seventies and they didn't tell anyone

'cause they're petroleum companies.

The asteroid that wiped out the dinosaurs

was about 18 kilometers 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.

@SunpaiTarku asks a good question,

Which animal species came the closest to going extinct

and then successfully recovered?

Well, the best example I know of is the California condor,

in 1972, was down to about 22 individuals.

The chemical DDT was causing their eggshells

to be soft and to break, and so they couldn't reproduce.

Plus, they're scavengers,

so they would eat a dead deer that had been shot by a hunter

with a lead shot, and they were getting lead poisoning.

And so through an amazing effort,

zoos and other conservation organizations,

they captured every single remaining condor, all 22.

They had an intensive breeding program

and then they started to release them back into the wild.

They are not outta danger,

they are still a critically endangered species,

but right now there are about

550 California condors in the world.

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.

So they seem to be moving in the right direction

because we took action, because we banned DDT,

because California banned lead shots.

So it's not like we're helpless in these cases,

there are things that we can do

to help pull these organisms back from the brink,

but the time to act is now.

@Nomondensele asks, What's the worst that could happen

if mosquitoes and flies were to be extinct?

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,

there are a lot of birds, frogs,

other amphibians, small mammals.

And so you know what?

If you wanna precipitate an extinction event,

if you wanna wipe out the big animals, kill off the insects,

that's the best way to do it.

@Hombre_del_queso, or Cheese Man,

How many animals have humans hunted to extinction?

Certainly we have examples.

When the government of Australia

put a bounty on the Tasmanian tiger,

people went out and shot every single one of them.

There's a heartbreaking film of the last Tasmanian tiger

circling rearly in this cage,

and that was the last of its species.

Passenger pigeons, we killed all of them just for sport.

They used to block out the sun for hours

with flocks of billions.

Dodos, Dutch sailors would club them to death.

They wouldn't eat them, they would just stack them up

and use them for firewood.

The same thing happened to the great auk,

which was sort of the penguin of the North Atlantic.

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 Pleistocene creatures

that all of a sudden died when humans showed up.

@Based_shiver states, 'Invasive species are bad.

They outcompete native ones!'

Yeah, so? It's called the free market.

It's true, in 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.

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,

and so, you know, I don't think we wanna really be playing

planetary engineer with the Earth's biosesphere.

@Deathbykoolaidman writes,

What extinct animals do you think

is really just hidden away from humans?

I would be surprised if us paleontologists

have discovered 1% of the species that have ever lived.

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.

By the seventies, it was about a half a dozen a year.

And now, it's about one a week.

Now there are some animals that were at one point

believed to have gone extinct, that are later found alive.

It's very, very rare,

they're actually called Lazarus species,

and a good example of that would be the coelacanth,

which is a very ancient fish.

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.

There's a pine tree called the Wollemia pine

that was thought to have been extinct

since the Cretaceous period,

and in the nineties, it was discovered alive

in a valley in Australia.

So this can happen, but it's very, very rare.

Most things that we determine

are extinct in the fossil record, we never see again.

@GreatBluePanda asks,

What if super-volcano 'Yellowstone' erupts?

What happens to all species?

Well, probably bad things.

Yellowstone is a giant super-volcano.

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.

It was when satellite imagery started to become available

that we saw Yellowstone as this huge, huge volcanic caldera.

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.

600 feet.

If that were to ever happen again,

it would take out a lot of the United States.

Even here in New York, a couple thousand miles away,

there would be terrible effects.

The ash would reach New York,

aviation here, and probably globally, would shut down.

It's probably not going to erupt tomorrow,

but there is going to be a tomorrow someday.

@Maverick8358 writes,

Would we as humans be extinct

if another Chixilub asteroid hit Earth?

Probably not. Not at least initially.

And when an asteroid hits, the most deadly moment

is when the fallout comes in,

the rock and the dust that's blasted from the impact zone

goes into space

and then resettles back through the atmosphere.

You can imagine the energy released

by the impact 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.

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.

Now if that happened in today's world,

it would surely be calamitous.

But a lot of humans are underground, they work underground,

there's tunnels underground, there's subways,

there are defense facilities underground,

so, certainly, some humans would survive that day.

We'd probably be in a Mad Max situation for some time.

Whether we pull out of that or not, who knows?

@Brrrtje writes, How strong is the evidence

for an alternative hypothesis for the dinosaur extinction?

Well, I would say, weak at this point.

There are other hypotheses

that have been out there for decades.

For example, maybe volcanoes wiped out the dinosaurs.

Well, that sort of thing

takes hundreds of thousands or millions of years,

and it would unfold gradually around the planet,

and it doesn't look like the instantaneous extinction

that we see in the fossil record.

Some people have said,

Well, the dinosaurs weren't doing so well

leading up to the extinction,

so they really died of multiple causes.

And, A, we have no evidence that they weren't doing well.

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.

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.

@Smudgey90 90 asks, What stopped dinosaurs

reemerging as the dominant species after the meteor event?

Well, death. Death is hard to come back from.

But, birds tried. We call birds avian dinosaurs.

A flamingo or a hummingbird is a dinosaur to the same degree

that a stegosaurus or a triceratops is.

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.

So when I say that 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.

@SwenRoschlau 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?

I think it would've almost certainly

taken a different course.

Earth history is so contingent.

If you run the the movie of life on Earth back,

it never turns out the same way twice.

If you can imagine

that asteroid that wiped out the dinosaurs,

well, that formed the same time the solar system did

four and a half billion years ago.

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.

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.

They could never really get anywhere

until the dinosaurs went extinct.

And then the dinosaurs went extinct and almost immediately,

early primates evolve,

some mammals return to the sea, they become whales,

some mammals become big predators, big herbivores.

None of that happens,

I think including intelligent species such as us,

without the extinction of the dinosaurs.

A Reddit user asks, 99% of all living things

that ever lived on Earth are now extinct.

Fact or fiction?

It's fact-ish.

We don't know the exact percentage,

but certainly the vast, vast majority

of creatures that ever lived,

something approaching 99% have evolved,

they've persisted for some amount of time,

and then they went extinct.

Extinction is a natural process,

but it generally happens gradually over geological time,

not in rapid succession, as is happening today.

@Sangkancilguru opines,

Pandas are so bloody useless, they deserve to go extinct.

Well, that's pretty judgy there, Guru.

Pandas have a place in this world just like we do,

and they fulfill a role in their ecosystem.

And pandas, like every creatures,

have an unbroken chain of ancestry

stretching back 3.8 billion years

to their microbial forebearers.

This is a lineage that's survived all five mass extinctions,

including the one that wiped out the dinosaurs,

but they're having trouble surviving us.

So what does that tell you?

Lynne Irwin wants to know,

How did cockroaches survive

the dino-killing asteroid strike?

Well, have you ever tried to kill a cockroach?

It's not that easy.

Cockroaches are small,

their needs are meager, and they can get underground,

and that is a formula for success.

@Rnadeau12 writes, What will cause the extinction

of life on the planet next time?

Volcanoes erupting, asteroid impact, sunspots,

or developing fatal diseases in a lab?

Well, here's what we know from history.

There have been five past mass extinctions,

and every one was caused by a climate crisis.

The last, a climate crisis caused by an asteroid impact.

We are experiencing a sixth extinction right now.

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.

@Yaboy asked, What if there was a mass extinction

so big it wiped away all evidence of anything being there?

Well, there was actually a time in early Earth history

called the Age of Bombardment

four 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.

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.

@Stigmatronic writes, The whole concept

of the sixth mass extinction is bogus for the most part.

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.

The background extinction rate of vertebrate animals

over the last 2 million years

is to lose about nine species per century.

Well, just in the last century,

we have lost 615 species of vertebrate animals.

Some people think the rate might be

as much as 100 times higher than the normal background rate.

If you look at not species,

but populations of wild animals today, this is shocking.

Since 1970, there are 69% fewer wild animals on the land.

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.

@Lizwei34 asks, Why, WHY,

are they attempting to bring back the woolly mammoth?

After six full 'Jurassic Park' movies,

my brain cannot fathom how anyone

would possibly think this is a good idea.

MY GOSH.

A lot of people conflate recent creatures,

like the woolly mammoth, with dinosaurs.

Dinosaurs are truly ancient. Their world is gone.

That's 66 million years ago.

Mammoths were around only 3,300 years ago.

Mammoths lived in a world that had the great pyramids,

that had written stories, that had beer.

That's this world today.

And they had an important place in an ecosystem

that still exists today.

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.

I happen to be on the Board of Scientific Advisors

of Colossal Biosesciences

endeavoring to de-extinct the woolly mammoth,

and the Tasmanian tiger, and the dodo.

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,?

Probably not, right?

Well, what if it was a week, or 10 years,

or 100 years, or 1,000 years?

I kind of have a Pottery Barn philosophy on this,

which is if you break it, you bought it.

I think if we're the agents of their demise,

we have a moral and ethical responsibility

to resurrect them and their ecosystems.

@Dangerous-Hotels-7839 writes,

Have there been animals that were hunted to extinction

by other animals and not humans?

There are lots of examples.

For example, in Hawaii today,

exotic egg-eating snakes

are wiping out many bird populations.

In New Zealand, house cats, which are not indigenous,

are wiping out ground nesting birds.

Rats are one of the things

that push the dodo to extinction in Mauritius.

In the fossil record, when we see land masses connect,

that often leads to extinction.

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 super continent called Pangaea.

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.

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.

@BridgetHowell writes, 'Species of least concern'?

What does that mean? It sounds so sad.

It means that they're not threatened,

and threatened includes vulnerable, endangered,

and critically endangered,

which is the worst category to be in.

So least concern just means

that the population is fairly stable.

An example of a species of least concern

would be the laughing gull.

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.

A critically endangered species

would be something like the northern right whale.

There's probably only about 25 of them alive in the world.

@SaintFiasco asks, What are the five mass extinctions?

The first one that happens is at the end of

the Ordovician period around 400 million years ago.

Life is confined to the oceans at this point,

and most of that is in the shallow seas.

Continents are drifting south.

It initiates a glacial period.

The 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.

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.

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.

And then the third mass extinction,

the worst of all, is called the Great Dying.

It happens at the end of the Permian period

about 250 million years ago.

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.

That in combination with Pangaea 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.

We lose these little guys. This is known as a trilobite.

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.

And then we go into the Triassic period,

a really hard time for life on Earth,

the world is recovering from this Great Dying event.

And then those volcanic fissures in Siberia,

they open up again, causing another mass extinction.

And then after the Triassic,

we really get into kind of the sweet spot

of the dinosaur age.

We're in the Jurassic period now. Things are going great.

Dinosaurs are getting big, they're getting biodiverse.

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,

they're are all kinds of sizes,

and then an asteroid hits and murders them,

and it's over that day.

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.

And now what's happening now, we are causing the beginnings

of the world's sixth mass extinction.

@Throwawaysimples writes the trolling question,

I think deforestation is a good thing. Change my view.

Well, Throw Away Simples, how do you like breathing?

Because most of your oxygen comes from plants.

The Earth has two great lungs,

one is the phytoplankton in the ocean,

the other is really the Amazon rainforest.

Rainforests such as the Amazon,

also have the highest biodiversity in the world.

And where do you think your medicines come from?

Well, they come from discoveries made from plants,

and animals, and microorganisms,

that mostly live in tropical rainforests.

So if you like not dying of horrible diseases,

you should be pro-forest.

@Realmfoster says,

I don't understand why sharks have to exist.

Well, there's really no why in evolution.

There's no forethought.

Animals exist because they happened,

and sharks happened a long time ago.

Sharks were around a couple hundred million years

before the dinosaurs.

They persisted through the entire reign of the dinosaurs.

They survived the mass extinction

that wiped out the dinosaurs.

And obviously, they exist today.

But you know what they're having trouble with? Us.

There's a lot of sharks

that are critically endangered right now

because they're being over-fished

and because their environments are being destroyed,

such as the great hammerhead shark, which is endangered.

And they are the apex predators

in many of the ecosystems in which they live,

and predators are important.

It keeps actually the prey populations healthy

because it winnows out the ones that are diseased,

that could spread those diseases through the population.

It causes natural selection, which causes the prey species

to become faster, stronger, quicker.

And so we really need sharks in this world.

Okay, that's it. That's all the questions.

I hope you learned something. Until next time.