Name: 古生物学者だけど「絶滅」について質問ある？| Tech Support | WIRED Japan
Uploaded: 2025-02-11T09:26:31.000Z
Duration: 21 min 33 s
Description: VoiceTubeの動画で発音を聞きながら英語表現を覚えよう！学べる英語：

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. ["Extinction Support"] Lindsay Kinselle 2 asks, how do we know an asteroid killed the dinosaurs?

Well, dinosaurs dominated Earth's terrestrial ecosystems for 165 million years.

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.

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 died 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.

TheRealLemming asks, where is the asteroid that killed the dinosaurs?

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 70s, and they didn't tell anyone because 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.

Sunpay Tarku 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, it 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 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 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 shot.

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.

Noman Densele 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, a lot of birds, frogs, other amphibians, small mammals.

If you want to precipitate an extinction event, if you want to wipe out big animals, kill off the insects.

Ambre Del Queso, or Cheese Man, how many animals have humans hunted to extinction?

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 wearily 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.

Base Shivers states, invasive species are bad, they out-compete native ones.

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 biosphere.

Death by Kool-Aid Man 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 70s, 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.

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 the one was dredged up off the coast of South Africa in the 1930s.

There's a pine tree called the wallamy 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.

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 supervolcano Yellowstone erupts?

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.

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 Chicxulub 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?

Brutja writes, how strong is the evidence for an alternative hypothesis for the dinosaur extinction?

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 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.

Smudgy90 asks, what stopped dinosaurs reemerging as the dominant species after the meteor event?

Death is hard to come back from, but birds tried.

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, fossil found in Africa that we call Nyasasaurus. 100% of that species' descendants, that's the group that we call dinosaur.

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.

Swen Roeschla 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?

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古生物学者だけど「絶滅」について質問ある？| Tech Support | WIRED Japan

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