Earth's mass extinctions | Peter Ward

314,446 views ・ 2009-01-28

TED


Please double-click on the English subtitles below to play the video.

00:18
So, I want to start out with
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this beautiful picture from my childhood.
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I love the science fiction movies.
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Here it is: "This Island Earth."
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And leave it to Hollywood to get it just right.
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Two-and-a-half years in the making.
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(Laughter)
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I mean, even the creationists give us 6,000,
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but Hollywood goes to the chase.
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And in this movie, we see what we think is out there:
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flying saucers and aliens.
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Every world has an alien, and every alien world has a flying saucer,
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and they move about with great speed. Aliens.
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Well, Don Brownlee, my friend, and I finally got to the point
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where we got tired of turning on the TV
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and seeing the spaceships and seeing the aliens every night,
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and tried to write a counter-argument to it,
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and put out what does it really take for an Earth to be habitable,
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for a planet to be an Earth, to have a place
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where you could probably get not just life, but complexity,
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which requires a huge amount of evolution,
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and therefore constancy of conditions.
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So, in 2000 we wrote "Rare Earth." In 2003, we then asked,
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let's not think about where Earths are in space, but how long has Earth been Earth?
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If you go back two billion years,
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you're not on an Earth-like planet any more.
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What we call an Earth-like planet is actually a very short interval of time.
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Well, "Rare Earth" actually
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taught me an awful lot about meeting the public.
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Right after, I got an invitation to go to a science fiction convention,
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and with all great earnestness walked in.
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David Brin was going to debate me on this,
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and as I walked in, the crowd of a hundred started booing lustily.
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I had a girl who came up who said, "My dad says you're the devil."
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You cannot take people's aliens away from them
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and expect to be anybody's friends.
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Well, the second part of that, soon after --
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and I was talking to Paul Allen; I saw him in the audience,
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and I handed him a copy of "Rare Earth."
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And Jill Tarter was there, and she turned to me,
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and she looked at me just like that girl in "The Exorcist."
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It was, "It burns! It burns!"
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Because SETI doesn't want to hear this.
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SETI wants there to be stuff out there.
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I really applaud the SETI efforts, but we have not heard anything yet.
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And I really do think we have to start thinking
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about what's a good planet and what isn't.
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Now, I throw this slide up because it indicates to me that,
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even if SETI does hear something, can we figure out what they said?
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Because this was a slide that was passed
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between the two major intelligences on Earth -- a Mac to a PC --
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and it can't even get the letters right --
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(Laughter)
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-- so how are we going to talk to the aliens?
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And if they're 50 light years away, and we call them up,
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and you blah, blah, blah, blah, blah,
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and then 50 years later it comes back and they say, Please repeat?
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I mean, there we are.
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Our planet is a good planet because it can keep water.
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Mars is a bad planet, but it's still good enough for us to go there
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and to live on its surface if we're protected.
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But Venus is a very bad -- the worst -- planet.
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Even though it's Earth-like, and even though early in its history
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it may very well have harbored Earth-like life,
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it soon succumbed to runaway greenhouse --
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that's an 800 degrees [Fahrenheit] surface --
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because of rampant carbon dioxide.
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Well, we know from astrobiology that we can really now predict
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what's going to happen to our particular planet.
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We are right now in the beautiful Oreo
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of existence -- of at least life on Planet Earth --
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following the first horrible microbial age.
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In the Cambrian explosion, life emerged from the swamps,
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complexity arose,
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and from what we can tell, we're halfway through.
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We have as much time for animals to exist on this planet
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as they have been here now,
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till we hit the second microbial age.
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And that will happen, paradoxically --
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everything you hear about global warming --
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when we hit CO2 down to 10 parts per million,
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we are no longer going to have to have plants
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that are allowed to have any photosynthesis, and there go animals.
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So, after that we probably have seven billion years.
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The Sun increases in its intensity, in its brightness,
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and finally, at about 12 billion years after it first started,
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the Earth is consumed by a large Sun,
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and this is what's left.
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So, a planet like us is going to have an age and an old age,
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and we are in its golden summer age right now.
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But there's two fates to everything, isn't there?
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Now, a lot of you are going to die of old age,
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but some of you, horribly enough, are going to die in an accident.
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And that's the fate of a planet, too.
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Earth, if we're lucky enough -- if it doesn't get hit by a Hale-Bopp,
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or gets blasted by some supernova nearby
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in the next seven billion years -- we'll find under your feet.
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But what about accidental death?
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Well, paleontologists for the last 200 years
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have been charting death. It's strange --
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extinction as a concept wasn't even thought about
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until Baron Cuvier in France found this first mastodon.
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He couldn't match it up to any bones on the planet,
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and he said, Aha! It's extinct.
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And very soon after, the fossil record started yielding
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a very good idea of how many plants and animals there have been
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since complex life really began to leave
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a very interesting fossil record.
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In that complex record of fossils,
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there were times when lots of stuff
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seemed to be dying out very quickly,
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and the father/mother geologists
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called these "mass extinctions."
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All along it was thought to be either an act of God
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or perhaps long, slow climate change,
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and that really changed in 1980,
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in this rocky outcrop near Gubbio,
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where Walter Alvarez, trying to figure out
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what was the time difference between these white rocks,
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which held creatures of the Cretaceous period,
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and the pink rocks above, which held Tertiary fossils.
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How long did it take to go from one system to the next?
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And what they found was something unexpected.
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They found in this gap, in between, a very thin clay layer,
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and that clay layer -- this very thin red layer here --
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is filled with iridium.
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And not just iridium; it's filled with glassy spherules,
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and it's filled with quartz grains
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that have been subjected to enormous pressure: shock quartz.
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Now, in this slide the white is chalk,
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and this chalk was deposited in a warm ocean.
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The chalk itself's composed by plankton
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which has fallen down from the sea surface onto the sea floor,
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so that 90 percent of the sediment here is skeleton of living stuff,
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and then you have that millimeter-thick red layer,
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and then you have black rock.
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And the black rock is the sediment on the sea bottom
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in the absence of plankton.
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And that's what happens in an asteroid catastrophe,
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because that's what this was, of course. This is the famous K-T.
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A 10-kilometer body hit the planet.
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The effects of it spread this very thin impact layer all over the planet,
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and we had very quickly the death of the dinosaurs,
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the death of these beautiful ammonites,
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Leconteiceras here, and Celaeceras over here,
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and so much else.
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I mean, it must be true,
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because we've had two Hollywood blockbusters since that time,
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and this paradigm, from 1980 to about 2000,
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totally changed how we geologists thought about catastrophes.
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Prior to that, uniformitarianism was the dominant paradigm:
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the fact that if anything happens on the planet in the past,
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there are present-day processes that will explain it.
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But we haven't witnessed a big asteroid impact,
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so this is a type of neo-catastrophism,
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and it took about 20 years for the scientific establishment
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to finally come to grips: yes, we were hit;
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and yes, the effects of that hit caused a major mass extinction.
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Well, there are five major mass extinctions
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over the last 500 million years, called the Big Five.
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They range from 450 million years ago
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to the last, the K-T, number four,
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but the biggest of all was the P, or the Permian extinction,
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sometimes called the mother of all mass extinctions.
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And every one of these has been subsequently blamed
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on large-body impact.
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But is this true?
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The most recent, the Permian, was thought to have been an impact
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because of this beautiful structure on the right.
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This is a Buckminsterfullerene, a carbon-60.
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Because it looks like those terrible geodesic domes
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of my late beloved '60s,
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they're called "buckyballs."
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This evidence was used to suggest
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that at the end of the Permian, 250 million years ago, a comet hit us.
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And when the comet hits, the pressure produces the buckyballs,
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and it captures bits of the comet.
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Helium-3: very rare on the surface of the Earth, very common in space.
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But is this true?
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In 1990, working on the K-T extinction for 10 years,
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I moved to South Africa to begin work twice a year
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in the great Karoo desert.
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I was so lucky to watch the change of that South Africa
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into the new South Africa as I went year by year.
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And I worked on this Permian extinction,
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camping by this Boer graveyard for months at a time.
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And the fossils are extraordinary.
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You know, you're gazing upon your very distant ancestors.
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These are mammal-like reptiles.
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They are culturally invisible. We do not make movies about these.
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This is a Gorgonopsian, or a Gorgon.
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That's an 18-inch long skull of an animal
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that was probably seven or eight feet, sprawled like a lizard,
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probably had a head like a lion.
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This is the top carnivore, the T-Rex of its time.
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But there's lots of stuff.
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This is my poor son, Patrick.
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(Laughter)
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This is called paleontological child abuse.
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Hold still, you're the scale.
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(Laughter)
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There was big stuff back then.
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Fifty-five species of mammal-like reptiles.
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The age of mammals had well and truly started
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250 million years ago ...
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... and then a catastrophe happened.
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And what happens next is the age of dinosaurs.
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It was all a mistake; it should have never happened. But it did.
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Now, luckily,
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this Thrinaxodon, the size of a robin egg here:
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this is a skull I've discovered just before taking this picture --
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there's a pen for scale; it's really tiny --
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this is in the Lower Triassic, after the mass extinction has finished.
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You can see the eye socket and you can see the little teeth in the front.
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If that does not survive, I'm not the thing giving this talk.
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Something else is, because if that doesn't survive, we are not here;
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there are no mammals. It's that close; one species ekes through.
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Well, can we say anything about the pattern of who survives and who doesn't?
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Here's sort of the end of that 10 years of work.
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The ranges of stuff -- the red line is the mass extinction.
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But we've got survivors and things that get through,
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and it turns out the things that get through preferentially are cold bloods.
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Warm-blooded animals take a huge hit at this time.
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The survivors that do get through
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produce this world of crocodile-like creatures.
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There's no dinosaurs yet; just this slow, saurian, scaly, nasty,
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swampy place with a couple of tiny mammals hiding in the fringes.
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And there they would hide for 160 million years,
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until liberated by that K-T asteroid.
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So, if not impact, what?
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And the what, I think, is that we returned, over and over again,
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to the Pre-Cambrian world, that first microbial age,
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and the microbes are still out there.
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They hate we animals.
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They really want their world back.
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And they've tried over and over and over again.
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This suggests to me that life causing these mass extinctions
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because it did is inherently anti-Gaian.
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This whole Gaia idea, that life makes the world better for itself --
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anybody been on a freeway on a Friday afternoon in Los Angeles
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believing in the Gaia theory? No.
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So, I really suspect there's an alternative,
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and that life does actually try to do itself in --
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not consciously, but just because it does.
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And here's the weapon, it seems, that it did so over the last 500 million years.
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There are microbes which, through their metabolism,
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produce hydrogen sulfide,
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and they do so in large amounts.
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Hydrogen sulfide is very fatal to we humans.
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As small as 200 parts per million will kill you.
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You only have to go to the Black Sea and a few other places -- some lakes --
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and get down, and you'll find that the water itself turns purple.
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It turns purple from the presence of numerous microbes
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which have to have sunlight and have to have hydrogen sulfide,
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and we can detect their presence today -- we can see them --
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but we can also detect their presence in the past.
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And the last three years have seen
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an enormous breakthrough in a brand-new field.
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I am almost extinct --
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I'm a paleontologist who collects fossils.
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But the new wave of paleontologists -- my graduate students --
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collect biomarkers.
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They take the sediment itself, they extract the oil from it,
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and from that they can produce compounds
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which turn out to be very specific to particular microbial groups.
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It's because lipids are so tough, they can get preserved in sediment
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and last the hundreds of millions of years necessary,
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and be extracted and tell us who was there.
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And we know who was there. At the end of the Permian,
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at many of these mass extinction boundaries,
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this is what we find: isorenieratene. It's very specific.
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It can only occur if the surface of the ocean has no oxygen,
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and is totally saturated with hydrogen sulfide --
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enough, for instance, to come out of solution.
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This led Lee Kump, and others from Penn State and my group,
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to propose what I call the Kump Hypothesis:
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many of the mass extinctions were caused by lowering oxygen,
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by high CO2. And the worst effect of global warming, it turns out:
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hydrogen sulfide being produced out of the oceans.
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Well, what's the source of this?
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In this particular case, the source over and over has been flood basalts.
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This is a view of the Earth now, if we extract a lot of it.
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And each of these looks like a hydrogen bomb;
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actually, the effects are even worse.
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This is when deep-Earth material comes to the surface,
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spreads out over the surface of the planet.
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Well, it's not the lava that kills anything,
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it's the carbon dioxide that comes out with it.
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This isn't Volvos; this is volcanoes.
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But carbon dioxide is carbon dioxide.
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So, these are new data Rob Berner and I -- from Yale -- put together,
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and what we try to do now is
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track the amount of carbon dioxide in the entire rock record --
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and we can do this from a variety of means --
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and put all the red lines here,
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when these -- what I call greenhouse mass extinctions -- took place.
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And there's two things that are really evident here to me,
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is that these extinctions take place when CO2 is going up.
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But the second thing that's not shown on here:
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the Earth has never had any ice on it
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when we've had 1,000 parts per million CO2.
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We are at 380 and climbing.
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We should be up to a thousand in three centuries at the most,
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but my friend David Battisti in Seattle says he thinks a 100 years.
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So, there goes the ice caps,
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and there comes 240 feet of sea level rise.
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I live in a view house now;
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I'm going to have waterfront.
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All right, what's the consequence? The oceans probably turn purple.
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And we think this is the reason that complexity took so long
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to take place on planet Earth.
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We had these hydrogen sulfide oceans for a very great long period.
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They stop complex life from existing.
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We know hydrogen sulfide is erupting presently a few places on the planet.
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And I throw this slide in -- this is me, actually, two months ago --
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and I throw this slide in because here is my favorite animal, chambered nautilus.
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It's been on this planet since the animals first started -- 500 million years.
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This is a tracking experiment, and any of you scuba divers,
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if you want to get involved in one of the coolest projects ever,
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this is off the Great Barrier Reef.
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And as we speak now,
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these nautilus are tracking out their behaviors to us.
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But the thing about this is that every once in a while
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we divers can run into trouble,
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so I'm going to do a little thought experiment here.
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This is a Great White Shark that ate some of my traps.
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We pulled it up; up it comes. So, it's out there with me at night.
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So, I'm swimming along, and it takes off my leg.
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I'm 80 miles from shore, what's going to happen to me?
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Well now, I die.
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Five years from now, this is what I hope happens to me:
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I'm taken back to the boat, I'm given a gas mask:
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80 parts per million hydrogen sulfide.
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I'm then thrown in an ice pond, I'm cooled 15 degrees lower
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and I could be taken to a critical care hospital.
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And the reason I could do that is because we mammals
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have gone through a series of these hydrogen sulfide events,
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and our bodies have adapted.
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And we can now use this as what I think will be a major medical breakthrough.
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This is Mark Roth. He was funded by DARPA.
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Tried to figure out how to save Americans after battlefield injuries.
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He bleeds out pigs.
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He puts in 80 parts per million hydrogen sulfide --
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the same stuff that survived these past mass extinctions --
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and he turns a mammal into a reptile.
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"I believe we are seeing in this response the result of mammals and reptiles
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having undergone a series of exposures to H2S."
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I got this email from him two years ago;
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he said, "I think I've got an answer to some of your questions."
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So, he now has taken mice down
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for as many as four hours, sometimes six hours,
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and these are brand-new data he sent me on the way over here.
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On the top, now, that is a temperature record of a mouse who has gone through --
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the dotted line, the temperatures.
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So, the temperature starts at 25 centigrade,
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and down it goes, down it goes.
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Six hours later, up goes the temperature.
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Now, the same mouse is given 80 parts per million hydrogen sulfide
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in this solid graph,
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and look what happens to its temperature.
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Its temperature drops.
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It goes down to 15 degrees centigrade from 35,
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and comes out of this perfectly fine.
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Here is a way we can get people to critical care.
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Here's how we can bring people cold enough to last till we get critical care.
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Now, you're all thinking, yeah, what about the brain tissue?
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And so this is one of the great challenges that is going to happen.
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You're in an accident. You've got two choices:
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you're going to die, or you're going to take the hydrogen sulfide
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and, say, 75 percent of you is saved, mentally.
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What are you going to do?
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Do we all have to have a little button saying, Let me die?
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This is coming towards us,
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and I think this is going to be a revolution.
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We're going to save lives, but there's going to be a cost to it.
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The new view of mass extinctions is, yes, we were hit,
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and, yes, we have to think about the long term,
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because we will get hit again.
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But there's a far worse danger confronting us.
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We can easily go back to the hydrogen sulfide world.
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Give us a few millennia --
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and we humans should last those few millennia --
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will it happen again? If we continue, it'll happen again.
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How many of us flew here?
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How many of us have gone through
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our entire Kyoto quota
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just for flying this year?
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How many of you have exceeded it? Yeah, I've certainly exceeded it.
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We have a huge problem facing us as a species.
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We have to beat this.
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I want to be able to go back to this reef. Thank you.
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(Applause)
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Chris Anderson: I've just got one question for you, Peter.
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Am I understanding you right, that what you're saying here
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is that we have in our own bodies
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a biochemical response to hydrogen sulfide
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that in your mind proves that there have been past mass extinctions
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due to climate change?
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Peter Ward: Yeah, every single cell in us
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can produce minute quantities of hydrogen sulfide in great crises.
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This is what Roth has found out.
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So, what we're looking at now: does it leave a signal?
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Does it leave a signal in bone or in plant?
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And we go back to the fossil record and we could try to detect
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how many of these have happened in the past.
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CA: It's simultaneously
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an incredible medical technique, but also a terrifying ...
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PW: Blessing and curse.
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About this website

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