Cause of worst mass extinction ever found

A new study reveals what caused most life on Earth to die out during the end-Permian extinction, also known as the Great Dying.

https://bigthink.com/surprising-science/cause-of-worst-mass-extinction-ever-found

PAUL RATNER26 June, 2021

Cause of worst mass extinction ever found

Illustration showing the beginning of the Permian-Triassic mass extinction. 2020.Credit: PaleoFactory, Sapienza University of Rome for Jurikova et al., Nature Geoscience 2020.

  • A new paper claims to identify the cause of the Great Dying that occured nearly 252 million years ago.
  • During the worst mass extinction event ever, most of Earth’s life perished.
  • The study suggests a volcanic eruption in Siberia spread aerosolized nickel particles that harmed organisms on the planet.

Dinosaurs are the most infamous victims of a mass extinction event 66 million years ago. But an even worse extinction happened 251.9 million years ago.

Called the end-Permian mass extinction or the Great Dying, this most severe of extinction events wiped out about 90 percent of the planet’s marine species and 75 percent of terrestrial species. While scientists long have suspected it was initiated by volcanic eruptions in what is now Siberia, until now they haven’t been able to explain exactly how so many species died out.

A new paper published in Nature Communications lays out the case that nickel particles that became aerosolized as a result of eruptions in the Siberian Traps region became dispersed through the air and water and were the cause of the ensuing environmental catastrophe. The paper pinpoints huge Norilsk nickel sulfide ore deposits in the Tunguska Basin that “may have released voluminous nickel-rich volcanic gas and aerosols into the atmosphere” as the start of the chain of events that led to the mass extinction.


The study is based on analysis of nickel isotopes that came from late Permian sedimentary rocks gathered from the Buchanan Lake section in the Sverdrup Basin in the Canadian High Arctic. What’s notable about the rock samples is that they featured the lightest nickel isotope ratios ever measured, leading the scientists to conclude that the nickel came in the form of aerosolized particles from a volcano.

As the paper outlines, the only comparable nickel isotope values would be those from volcanic nickel sulfide deposits. The scientists write that of all the mechanisms that could result in such values, “the most convincing” explanation is that they got there as “voluminous Ni-rich aerosols” from the Siberian Traps large igneous province (STLIP).

The deadly effect of nickel particles

When the nickel got into the water, it wreaked havoc on the underwater ecosystem.

Co-author of the study, associate professor Laura Wasylenki of Northern Arizona University, explained that “nickel is an essential trace metal for many organisms, but an increase in nickel abundance would have driven an unusual surge in productivity of methanogens, microorganisms that produce methane gas. Increased methane would have been tremendously harmful to all oxygen-dependent life.” This would have affected living creatures in and out of the water. The professor believes their data offers direct evidence that links nickel-rich aerosols, changes to the ocean, and the mass extinction that followed. “Now we have evidence of a specific kill mechanism,” she added.https://f1bb792bf57395a28b571c77451c94cd.safeframe.googlesyndication.com/safeframe/1-0-38/html/container.html

NAU associate professor Laura Wasylenki.Credit: Northern Arizona University.

Other theories on the Great Dying

Previous studies have pointed to other effects of the Siberian volcanic eruptions that likely contributed to the extinction event, including an overall warming of the planet, release of toxic metals, and acidification of the oceans, which likely killed off a number of species quickly. Others died out as a result of the depleted oxygen levels in the water.

“This domino-like collapse of the inter-connected life-sustaining cycles and processes ultimately led to the observed catastrophic extent of mass extinction at the Permian-Triassic boundary,” said marine biogeochemist Hana Jurikova of the University of St. Andrews in the UK, who carried out a 2020 study on the end-Permian extinction. Her study looked at fossil shells from brachiopods in what is now the Southern Alps in Italy.

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Geochemical study confirms cause of end-Permian mass extinction event

https://phys.org/news/2021-06-geochemical-end-permian-mass-extinction-event.html

UNE 21, 2021

by Heather Tate, Northern Arizona University

volcano
Plinian column of the eruption of Sarychev (Russia) on 12 June 2009. Credit: NASA

The most severe mass extinction event in the past 540 million years eliminated more than 90 percent of Earth’s marine species and 75 percent of terrestrial species. Although scientists had previously hypothesized that the end-Permian mass extinction, which took place 251 million years ago, was triggered by voluminous volcanic eruptions in a region of what is now Siberia, they were not able to explain the mechanism by which the eruptions resulted in the extinction of so many different species, both in the oceans and on land.

Associate professor Laura Wasylenki of Northern Arizona University’s School of Earth and Sustainability and Department of Chemistry and Biochemistry is co-author on a new paper in Nature Communications entitled, “Nickel isotopes link Siberian Traps aerosol particles to the end-Permian mass extinction,” in collaboration with Chinese, Canadian and Swiss scientists. The paper presents the results of nickel isotope analyses performed in Wasylenki’s lab on Late Permian sedimentary rocks collected in Arctic Canada. The samples have the lightest nickel isotope ratios ever measured in sedimentary rocks, and the only plausible explanation is that the nickel was sourced from the volcanic terrain, very likely carried by aerosol particles and deposited in the ocean, where it dramatically changed the chemistry of seawater and severely disrupted the marine ecosystem.

“The study results provide strong evidence that nickel-rich particles were aerosolized and dispersed widely, both through the atmosphere and into the ocean,” Wasylenki said. “Nickel is an essential trace metal for many organisms, but an increase in nickel abundance would have driven an unusual surge in productivity of methanogens, microorganisms that produce methane gas. Increased methane would have been tremendously harmful to all oxygen-dependent life.”

New geochemical study confirms cause of end-Permian mass extinction event
NAU associate professor Laura Wasylenki is co-author on a new paper in Nature Communications entitled, “Nickel isotopes link Siberian Traps aerosol particles to the end-Permian mass extinction,” in collaboration with Chinese, Canadian and Swiss scientists. Credit: Northern Arizona University

“Our data provide a direct link between global dispersion of Ni-rich aerosols, ocean chemistry changes and the mass extinction event,” Wasylenki said. “The data also demonstrate that environmental degradation likely began well before the extinction event—perhaps starting as early as 300,000 years before then. Prior to this study, the connection between Siberian Traps flood basalt volcanism, marine anoxia and mass extinction was rather vague, but now we have evidence of a specific kill mechanism. This finding demonstrates the power of nickel isotope analyses, which are relatively new, to solve long-standing problems in the geosciences.”

Wasylenki, who joined NAU in 2018, was formerly an igneous petrologist and then a specialist in calcite crystal growth and biomineralization. She now focuses on the use of metal stable isotope geochemistry to address geological, environmental and biological questions. Many of her recent and current projects have investigated metal isotope effects at solid-fluid interfaces, in particular during metal adsorption to oxyhydroxide mineral particles. This work has implications for ancient and modern geochemical cycles and environmental metal transport. Wasylenki’s lab group, named Systematic Experimental Study and Analysis of Metals in the Environment (SESAME Lab), focuses on two main research themes, the cycling of transition metals in modern and ancient oceans and the environmental transport of toxic heavy metals.


Explore furtherNew evidence that Siberian volcanic eruptions caused extinction 250 million yrs ago


More information: Menghan Li et al, Nickel isotopes link Siberian Traps aerosol particles to the end-Permian mass extinction, Nature Communications (2021). DOI: 10.1038/s41467-021-22066-7

NASA aims for 2 new missions to Venus to learn more about ‘lost habitable’ world

https://www.foxnews.com/science/nasa-aims-for-2-new-missions-to-venus-to-learn-more-about-lost-habitable-world

13 hours ago

In 1989, NASA used a space shuttle to send its Magellan spacecraft into orbit around Venus

By Edmund DeMarche | Fox News

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Fox News Flash top headlines for June 2

For the past few years, Mars has been having its moment. 

The planet has captured the fascination of Hollywood, the U.S. and China both landed rovers on its surface and Elon Musk, the head of SpaceX, recently announced that his company hopes to launch its next-generation rocket in 2022 from a platform in the Gulf of Mexico. His sights are set on Mars.

Other planets have become something of an afterthought. When was the last time you caught yourself thinking about Neptune? Pluto had the worst fate of all and in 2006 was downgraded to dwarf planet.

(NASA/JPL-Caltech)

But NASA on Wednesday announced its intention to bring more attention to Venus, the second planet from the sun. The planet–which is one of the brightest objects in the night sky–  is considered an “inferno-like world” but may have been “the first habitable world in the solar system, complete with an ocean and Earth-like climate.”

NASA said in a statement that the two missions to the planet will be part of its Discovery Program and will award about $500 million per mission for development. The voyages are expected to take place at the end of the decade.

One will study the planet’s atmosphere, which could shed light on whether the planet once had an ocean. The other mission will study the planet’s surface in hopes to learn “why it developed so differently than Earth.”

The U.S. and the former Soviet Union sent multiple spacecraft to Venus in the early days of space exploration. NASA’s Mariner 2 performed the first successful flyby in 1962, and the Soviets’ Venera 7 made the first successful landing in 1970.

In 1989, NASA used a space shuttle to send its Magellan spacecraft into orbit around Venus.

ASTROPHYSICIST EXPLAINS WHY UFO VIDEOS FAIL TO IMPRESS HIM

The European Space Agency put a spacecraft around Venus in 2006.

“It is astounding how little we know about Venus, but the combined results of these missions will tell us about the planet from the clouds in its sky through the volcanoes on its surface all the way down to its very core,” Tom Wagner, NASA’s Discovery Program scientist, said in the statement. “It will be as if we have rediscovered the planet.”

The Associated Press contributed to this report

An Exploding Star 65 Light-Years Away From Earth May Have Triggered a Mass Extinction

https://www.sciencealert.com/an-exploding-star-65-light-years-away-from-earth-may-have-triggered-a-mass-extinction

Composite image of supernova 1987A. (NASA, ESA et al.)SPACE

PETER DOCKRILL3 APRIL 2021

Life was trying, but it wasn’t working out. As the Late Devonian period dragged on, more and more living things died out, culminating in one of the greatest mass extinction events our planet has ever witnessed, approximately 359 million years ago.

The culprit responsible for so much death may not have been local, scientists say. In fact, it might not have even come from our Solar System.

Rather, a study published in August last year, led by astrophysicist Brian Fields from the University of Illinois Urbana-Champaign, suggests this great extinguisher of life on Earth could have been a distant and completely foreign phenomenon – a dying star, exploding far across the galaxy, many light-years away from our own remote planet.

Sometimes, mass die-offs like the Late Devonian extinction are thought to be triggered by exclusively terrestrial causes: a devastating volcanic eruption, for instance, which chokes the planet into lifelessness.

Or, it could be a deadly visitor barging in from out of town – an asteroid collision, like the kind that took out the dinosaurs. Death from space, however, could ultimately come from far more remote places.

“The overarching message of our study is that life on Earth does not exist in isolation,” Fields said back in 2020.

“We are citizens of a larger cosmos, and the cosmos intervenes in our lives – often imperceptibly, but sometimes ferociously.”

In their new work, Fields and his team explore the possibility that the dramatic decline in ozone levels coinciding with the Late Devonian extinction might not have been a result of volcanism or an episode of global warming.

Instead, they suggest it’s possible the biodiversity crisis exposed in the geological record could have been caused by astrophysical sources, speculating that the radiation effects from a supernova (or multiple) approximately 65 light-years from Earth may have been what depleted our planet’s ozone to such disastrous effect.

It may be the first time such an explanation has been put forward for the Late Devonian extinction, but scientists have long considered the potentially deadly repercussions of near-Earth supernovas in this kind of context.

Speculation that supernovas could trigger mass extinctions dates back to the 1950s. In more recent times, researchers have debated the estimated ‘kill distance’ of these explosive events (with estimates ranging between 25 to 50 light-years).

In their recent estimates, though, Fields and his co-authors propose that exploding stars from even farther away could have harmful effects on life on Earth, through a possible combination of both instantaneous and long-lived effects.https://6237f23f4b1e522ac14ce2b179dd377d.safeframe.googlesyndication.com/safeframe/1-0-38/html/container.html

“Supernovae (SNe) are prompt sources of ionizing photons: extreme UV, X-rays, and gamma rays,” the researchers explain in their paper.

“Over longer timescales, the blast collides with surrounding gas, forming a shock that drives particle acceleration. In this way, SNe produce cosmic rays, that is, atomic nuclei accelerated to high energies. These charged particles are magnetically confined inside the SN remnant, and are expected to bathe Earth for ~100 ky [approximately 100,000 years].”

These cosmic rays, the researchers argue, could be strong enough to deplete the ozone layer and cause long-lasting radiation damage to life-forms inside Earth’s biosphere – which roughly parallels evidence of both loss of diversity and deformations in ancient plant spores found in the deep rock of the Devonian–Carboniferous boundary, laid approximately 359 million years ago.

Of course, it’s just a hypothesis for now. At present, we don’t have any evidence that can confirm a distant supernova (or supernovae) was the cause of the Late Devonian extinction. But we might be able to find something almost as good as proof.

In recent years, scientists examining the prospect of near-Earth supernovas as a basis for mass extinctions have been looking for traces of ancient radioactive isotopes that could only have been deposited on Earth via exploding stars.

One isotope in particular, iron-60, has been the focus of much research and has been found in numerous locations on Earth.

In the context of the Late Devonian extinction, though, other isotopes would be strongly indicative of the extinction-by-supernova hypothesis put forward by Fields and his team: plutonium-244 and samarium-146.

“Neither of these isotopes occurs naturally on Earth today, and the only way they can get here is via cosmic explosions,” explained co-author and astronomy student Zhenghai Liu from the University of Illinois Urbana-Champaign.

In other words, if plutonium-244 and samarium-146 and can be found buried in the Devonian–Carboniferous boundary, the researchers say we’ll basically have our smoking gun: interstellar evidence that firmly implicates a dying star as the trigger behind one of Earth’s worst-ever die-offs.

And we’ll never look up at the skies in quite the same way again.

The findings were reported in PNAS.

A version of this article was first published in August 2020.

Earth’s oxygen will be gone in 1 billion years

Posted by Kelly Kizer Whitt in EARTH | March 7, 2021

A billion years from now, as the sun heats up, the warmer atmosphere will break down carbon dioxide, killing off plant life, which in turn will shut off Earth’s source of oxygen.Sharing is caring!

Partial view of Earth from orbit with clouds and fuzzy atmosphere visible aganist black space.

The oxygen currently in Earth’s atmosphere will be gone in a billion years, say scientists. This image of Earth’s atmosphere was taken from the International Space Station on February 26, 2021. Image via NASA.https://8505ac7d1ccf4966634f1f008ed6ceef.safeframe.googlesyndication.com/safeframe/1-0-37/html/container.html

Take a deep breath. The air expanding your chest is mostly nitrogen and oxygen, the chief components of our atmosphere. Oxygen exists in our atmosphere thanks to the exhalation of plants, through the process of photosynthesis. A study released in March 2021 shows that – a billion years from now, as the sun heats up – plants will die off, taking with them the oxygen in our atmosphere that humans and animals need to breathe.

Kazumi Ozaki of the University of Tokyo and Chris Reinhard of Georgia Tech modeled Earth’s climatic, biological and geological systems to fine-tune scientists’ understanding of future atmospheric conditions on Earth. They undertook the research as part of a NASA program called NExSS to explore and assess the habitability of exoplanets. Their study was published March 1, 2021, in the peer-reviewed journal Nature Geoscience.

Earth’s present atmosphere is made up of 78% nitrogen, 21% oxygen, 0.9% argon, and 0.1% other gases, including carbon dioxide, methane, water vapor and neon. Earth hasn’t always had such a high percentage of oxygen in its atmosphere. For Earth’s first 2 billion years, no oxygen existed in the atmosphere. Low levels of oxygen first appeared when cyanobacteria, also called blue-green algae, began releasing oxygen as a byproduct of photosynthesis. Then, about 2.4 billion years ago, Earth underwent the Great Oxidation Event. At this point, whether through a slackening in the outgassing of volcanoes or an evolutionary innovation that made cyanobacteria more successful, oxygen began to accumulate in larger amounts in the atmosphere, killing off some bacteria but allowing more complex life (us!) to evolve.

This oxygen utopia in which we currently live – where plants produce oxygen for humans and animals to breathe – is only a temporary condition on Earth. As Ozaki said:

We find that the Earth’s oxygenated atmosphere will not be a permanent feature.

Man with black hair and thin mustache wearing blue zip-up jacket.

Kazumi Ozaki of the University of Tokyo, lead author on the paper investigating the future of oxygen on Earth. Image via NASA.https://8505ac7d1ccf4966634f1f008ed6ceef.safeframe.googlesyndication.com/safeframe/1-0-37/html/container.html

As the solar system continues its life cycle, the aging sun will begin to heat up. The increased solar output will further warm the atmosphere, and the carbon dioxide will react to the increase in temperature by breaking down. Carbon dioxide levels will lower until photosynthesizing organisms – which rely on taking in carbon dioxide to live, just as we rely on oxygen to live – can no longer survive, removing the source of oxygen from Earth. (Read about how scientists believe that phytoplankton contribute between 50 to 85% of the oxygen in Earth’s atmosphere.) So when plants die from the lack of carbon dioxide, it’s not just a loss in the food chain but, crucially, a loss in the air they produce and the air we breathe.Skip Ad

While the end of oxygen is still a billion years away, when the depletion begins to take hold, it will occur rather rapidly, in about 10,000 years. Reinhard explained the severity of the change:

The drop in oxygen is very, very extreme; we’re talking around a million times less oxygen than there is today.

Man facing camera standing under a tree.

Chris Reinhard of Georgia Tech, one of the lead authors who researched the future amount of oxygen in Earth’s atmosphere. Image via NExSS.

The future deoxygenation event will coincide with a rise in methane, until methane levels are about 10,000 times more than exist in the atmosphere today. These shifts will occur too fast for adaptation in the biosphere. The ozone layer, made of oxygen, will vanish, and ultraviolet light and heat will aid in extinguishing both terrestrial and aquatic life. All but microbes will face extermination. Reinhard said:

A world where many of the anaerobic and primitive bacteria are currently hiding in the shadows will, again, take over.

Just as in the beginning, when life on Earth was in a microbial form before flourishing into the variety we see today, so too will the future look much like the past, as if the clock is running backward, and complex life forms will go extinct except for tiny colonies of cells.Dry ground and dead trees with wind-blown sand.

All plant and animal life on Earth needs oxygen to survive. A billion years from now, Earth’s oxygen will become depleted in a span of about 10,000 years, bringing about worldwide extinction for all except microbes. Image via Dikaseva/ Unsplash.

Studying the past and future of Earth is a gateway to understanding the conditions favorable to life on other planets. The presence of oxygen is an important factor in determining if life might exist on a planet. As we see with Earth, however, a planet that doesn’t have an oxygen signature may be capable of supporting life in the future or in the past.

Thus, while finding a planet with oxygen would be an exciting step toward finding life, not finding oxygen shouldn’t rule out the possibility that a planet ever had life.

Bottom line: A billion years from now, scientists say, as the sun heats up the warmer atmosphere will break down carbon dioxide, killing off plant life, which in turn will shut off Earth’s source of oxygen.

Source: The future lifespan of Earth’s oxygenated atmosphere

Dinosaur-Killing Impact Came From Edge Of Solar System, New Theory Suggests

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February 16, 20211:55 AM ET

https://www.npr.org/2021/02/16/968228310/new-theory-suggests-dinosaur-killing-impact-came-from-edge-of-solar-system

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A skeleton of an Allosaurus on display at Drouot auction house in Paris in October. A new theory says the dinosaurs were killed by a comet fragment that originally came from the edge of the solar system.Thibault Camus/AP

For decades, the prevailing theory about the extinction of the dinosaurs was that an asteroid from the belt between Mars and Jupiter slammed into the planet, causing cataclysmic devastation that wiped out most life on the planet.

But new research out of Harvard University theorizes that the Armageddon-causing object came from much farther out than originally believed.

According to this new theory, the devastation came not from a relatively nearby asteroid, but from a sort of long-distance comet that came from the edge of the solar system in an area known as the Oort cloud.

The gravity from Jupiter pulled the comet into the solar system. At that point, according to Amir Siraj, a Harvard student who co-authored the paper with Professor Avi Loeb, “Jupiter acts as a kind of pinball machine.”

The theory goes: Jupiter’s gravity shot this incoming comet into an orbit that brought it very close to the sun, whose tidal forces caused the comet to break apart. Some of the comet’s fragments entered Earth’s orbit, and one — 50 miles across, roughly the size of Boston — slammed into the coast of Mexico.Article continues after sponsor message

So long, dinosaurs.

The theory also posits that large-impact craters, such as the so-called Chicxulub crater caused by this impact, are more likely to be made of “carbonaceous chondrite” — a primitive material dating to the beginning of the solar system. Only about 10% of asteroids in the belt are made of carbonaceous chondrite, the researchers said.

“Our hypothesis explains the composition of the largest confirmed impact crater in Earth’s history as well as the largest one within the last million years,” the authors wrote.

Although Siraj and Loeb’s novel theory has raised eyebrows among the scientific community, it has also been criticized. “I believe their work has several intrinsic problems,” Bill Bottke, a planetary scientist at the Southwest Research Institute in Boulder, Colo., told The New York Times.

For instance, Bottke says, the proposed model overestimates how frequently long-period comets actually get pulled apart by the sun. “There’s still wiggle room if somebody really wants it to be a comet,” he said. “I just think making that case is really hard.”

The Devonian Extinction: A Slow Doom That Swept Our Planet

Over millions of years, most living organisms suffocated in oxygen-deprived oceans. In the aftermath, modern vertebrates conquered the world.

By Cody CottierJanuary 23, 2021 9:00 AM

ocean underwater

(Credit: Rich Carey/Shutterstock)

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We think of mass extinctions as brief moments of havoc — profoundly devastating but over within a geologic instant. The Devonian, the second of the so-called “Big Five,” defies this notion. If the other great die-offs are short stories of death and destruction, this one is an epic akin to War and Peace. Even that paradoxical title seems fitting: The Devonian extinction ravaged Earth on and off for 25 million years, and although it ultimately killed three-quarters of all species, it also cleared the way for a new balance of animal life that endures to this day.

The extinction began roughly 380 million years ago, midway through the segment of geologic time known as the Devonian period, or the age of fish. (Vertebrates hadn’t yet made the leap onto land.) The prehistoric waters teemed not with the likes of tuna, sardines and salmon, but with their bizarre, long-dead predecessors. At the top of the food chain sat the placoderms, a race of heavily-armored and sometimes massive fish. The most famous of these mean-mugging beasts, Dunkleosteus, may have grown as long as 30 feet, probably winning it the distinction of largest animal — until the dinosaurs.

Dunkleosteus - Shutterstock

An illustration of the enormous extinct prehistoric fish Dunkleosteus swimming in search of food within a Devonian Sea. (Credit: AuntSpray/Shutterstock)about:blankabout:blank

But for all their might, Dunkleosteus and its kin wouldn’t survive the age that bears their name. “A series of crises piled up to affect life on Earth,” says Michael Coates, a biologist at the University of Chicago. Annihilation crept in, and slowly swept away the dominant Devonian species. This opened ecological niches to a new cast of organisms — no less than, in Coates’ words, “the signature of modern vertebrate life on the planet.”

Gasping for Air

In terms of its time scale, “the Devonian extinction is quite different from the others,” says University of Cincinnati geologist Thomas Algeo. Over the course of millions of years, as many as 10 distinct events raised the loss of biodiversity above the normal background rate, or baseline. Two, however, stand out: the Kellwasser and Hangenberg events, which occurred in the middle of and at the end of the Devonian period, respectively.

Clear-cut answers are rare in the realm of extinction, but researchers broadly agree that both events were accompanied by widespread ocean anoxia, or low oxygen levels. Some of the best evidence is found in the layers of black shale — which form under anoxic conditions — that date to the time. It’s likely, then, that one of the major kill mechanisms throughout the Devonian period was asphyxiation. Along with the armored fish, reef-builders like corals and sponges died en masse, as did trilobites, nautilus-like goniatites and many more creatures.

It’s more difficult to say why the oceans suddenly became unbreathable for them. Volcanic activity is a perennial suspect in extinction investigations, and scientists have duly scoured the rock record for traces of it in the Devonian extinction. “There’s been a lot of searching for a plausible candidate,” Algeo says. Nothing has been found yet to compare with the monstrous eruptions of the later Permian extinction, but some evidence does suggest that volcanism in a large igneous province called the Viluy Traps may have played a role, including, perhaps, via mercury poisoning. An asteroid also struck Earth during this period, leaving behind the 40-mile-wide Siljan crater.

One recent study concluded that the trigger for the Hangenberg event was ultraviolet radiation, penetrating the atmosphere through a break in the ozone layer. The researchers collected Devonian rock samples from mountains in Greenland and the Andes, and, after dissolving them, found malformed plant spores consistent with DNA damage from UV exposure.about:blankabout:blank

Life Turns on Itself

Algeo has his own, astounding theory: Death came not from geologic or climatic processes, but as a “natural consequence of the evolution of the whole biosphere.” In other words, the enemy of Devonian life was life itself. He believes that as vascular plants — basically everything except moss and lichen — first colonized dry ground, their deep roots broke up Earth’s surface rocks, releasing nutrients and minerals that fueled algal blooms. This left the oceans riddled with dead zones devoid of oxygen. While the plants thrived, the rest died.

Plants also absorb carbon dioxide, or CO2, the atmosphere-warming greenhouse gas. As they spread, they could have chilled the planet, bringing on an ice age that would have made life even less sustainable. (Indeed, some research suggests global cooling was involved in the Devonian extinction, disproportionately affecting tropical species.) Over the long term, though, the greatest legacy of this newfangled vegetation may lie in the extinction’s rebound.

Whether or not the vascular plants were to blame for the extinction, they were undoubtedly pervasive by the end of it, with trees and ferns forming the first modern forests. The above-water world had finally grown complex enough to support a menagerie of animal life, and sea-faring species took notice. “Everyone’s looking at that, and there’s stuff to exploit,” Coates says. “They’ve suddenly got this golden opportunity.”

New World Order

The tetrapods, our oldest terrestrial ancestors, abandoned the ocean for this new environment. Every single vertebrate that has walked the Earth since is a descendent of these primitive, four-legged landlubbers: “grotesque amphibians slumping around in swamps,” Coates calls them, half-jokingly. 

Elginerpeton BW - wikimedia commons cc by 3.0

A drawing of Elginerpeton pancheni, an early tetrapod from the Late Devonian period. (Credit: Nobu Tamura/CC by 3.0/Wikimedia Commons)

After the Devonian extinction ended, around 360 million years ago, Romer’s gap began. This void in the fossil record, named for Harvard professor Alfred Sherwood Romer, puzzled scientists for decades. Most significantly, it thwarted attempts to piece together the improbable history of the first land animals whose lineage eventually leads to us. For the most part, tetrapods were bit players before the extinction: a few weird, lungfish hybrids like acanthostega, sprouting half-hearted limbs where they should have had fins. They certainly didn’t look like they were only an evolutionary hop, skip and jump from world domination. about:blankabout:blank

But after Romer’s gap, “when you pick them up again,” Coates says, “they’re diverse and doing all sorts of exciting things.” Lumbering amphibians are suddenly walking on land, and steadily improving at it. One of the most famous specimens is ichthyostegaa meter-long creature that’s a bit reminiscent of the Chinese giant salamander. In another few million years, the amphibians diverge from the shelled-egg-laying reptiles, which themselves later give rise to the dinosaurs and mammals.

The Devonian extinction ushered in not only the land-bound tetrapods, but also the animals that command the marine vertebrate world to this day: ray-finned (or bony) fish, and cartilaginous fish, like sharks, rays and chimeras. Though we see ourselves in the tetrapods, the progeny of post-Devonian fish is, in its own way, even more impressive — today’s marine vertebrates (including the bristlemouth, likely the most abundant vertebrate on Earth) far outweigh their dry-ground cousins. If a Martian biologist were to select one vertebrate at random from our planet, Coates says, “chances are it would be something like a herring.” 

It’s not clear to what extent the Devonian extinction actually altered the flow of evolution. Maybe the tetrapods, sharks and bony fish would have outcompeted their rivals anyway. According to Algeo, the extinction “probably served mostly to finish off these groups that were already not doing well.” Still, it was the extinction that finished them off, yielding the ecological floor decisively to the forms of life we see today. As Coates put it, “the modern vertebrate biota is the product of this big editing event.” In no small sense, we may have the Devonian extinction to thank for our existence.


Read more: The Ordovician Extinction: Our Planet’s First Brush With Death

RELATED CONTENTThe Ordovician Extinction: Our Planet’s 

https://www.discovermagazine.com/planet-earth/the-devonian-extinction-a-slow-doom-that-swept-our-planet

Artificial Intelligence Discovers Surprising Patterns in Earth’s Biological Mass Extinctions

TOPICS:Artificial IntelligenceBiodiversityBioinformaticsEvolutionExtinction EventMachine LearningPaleontologyTokyo Institute Of Technology

By TOKYO INSTITUTE OF TECHNOLOGY DECEMBER 13, 2020

A new study applies machine learning to the fossil record to visualize life’s history, showing the impacts of major evolutionary events. This shows the long-term evolutionary and ecological impacts of major events of extinction and speciation. Colors represent the geological periods from the Tonian, starting 1 billion years ago, in yellow, to the current Quaternary Period, shown in green. The red to blue color transition marks the end-Permian mass extinction, one of the most disruptive events in the fossil record. Credit: J. Hoyal Cuthill and N. Guttenberg

The idea that mass extinctions allow many new types of species to evolve is a central concept in evolution, but a new study using artificial intelligence to examine the fossil record finds this is rarely true, and there must be another explanation.

Charles Darwin’s landmark opus, On the Origin of the Species, ends with a beautiful summary of his theory of evolution, “There is a grandeur in this view of life, with its several powers, having been originally breathed into a few forms or into one; and that, whilst this planet has gone cycling on according to the fixed law of gravity, from so simple a beginning endless forms most beautiful and most wonderful have been, and are being, evolved.”

In fact, scientists now know that most species that have ever existed are extinct. This extinction of species has on the whole been roughly balanced by the origination of new ones over Earth’s history, with a few major temporary imbalances scientists call mass extinction events. Scientists have long believed that mass extinctions create productive periods of species evolution, or “radiations,” a model called “creative destruction.” A new study led by scientists affiliated with the Earth-Life Science Institute (ELSI) at Tokyo Institute of Technology used machine learning to examine the co-occurrence of fossil species and found that radiations and extinctions are rarely connected, and thus mass extinctions likely rarely cause radiations of a comparable scale.

Creative destruction is central to classic concepts of evolution. It seems clear that there are periods in which suddenly many species suddenly disappear, and many new species suddenly appear. However, radiations of a comparable scale to the mass extinctions, which this study, therefore, calls the mass radiations, have received far less analysis than extinction events.

This study compared the impacts of both extinction and radiation across the period for which fossils are available, the so-called Phanerozoic Eon. The Phanerozoic (from the Greek meaning “apparent life”), represents the most recent ~ 550-million-year period of Earth’s total ~4.5 billion-year history, and is significant to paleontologists: before this period most of the organisms that existed were microbes that didn’t easily form fossils, so the prior evolutionary record is hard to observe.

The new study suggests creative destruction isn’t a good description of how species originated or went extinct during the Phanerozoic, and suggests that many of the most remarkable times of evolutionary radiation occurred when life entered new evolutionary and ecological arenas, such as during the Cambrian explosion of animal diversity and the Carboniferous expansion of forest biomes. Whether this is true for the previous ~ 3 billion years dominated by microbes is not known, as the scarcity of recorded information on such ancient diversity did not allow a similar analysis.

Paleontologists have identified a handful of the most severe, mass extinction events in the Phanerozoic fossil record. These principally include the big five mass extinctions, such as the end-Permian mass extinction in which more than 70% of species are estimated to have gone extinct. Biologists have now suggested that we may now be entering a “Sixth Mass Extinction,” which they think is mainly caused by human activity including hunting and land-use changes caused by the expansion of agriculture. A commonly noted example of the previous “Big Five” mass extinctions is the Cretaceous-Tertiary one (usually abbreviated as “K-T,” using the German spelling of Cretaceous) which appears to have been caused when a meteor hit Earth ~65 million years ago, wiping out the non-avian dinosaurs.

Observing the fossil record, scientists came to believe that mass extinction events create especially productive radiations. For example, in the K-T dinosaur-exterminating event, it has conventionally been supposed that a wasteland was created, which allowed organisms like mammals to recolonize and “radiate,” allowing for the evolution of all manner of new mammal species, ultimately laying the foundation for the emergence of humans. In other words, if the K-T event of “creative destruction” had not occurred, perhaps we would not be here to discuss this question.

The new study started with a casual discussion in ELSI’s “Agora,” a large common room where ELSI scientists and visitors often eat lunch and strike up new conversations. Two of the paper’s authors, evolutionary biologist Jennifer Hoyal Cuthill (now a research fellow at Essex University in the UK) and physicist/machine learning expert Nicholas Guttenberg (now a research scientist at Cross Labs working in collaboration with GoodAI in the Czech Republic), who were both post-doctoral scholars at ELSI when the work began, were kicking around the question of whether machine learning could be used to visualize and understand the fossil record.

During a visit to ELSI, just before the COVID-19 pandemic began to restrict international travel, they worked feverishly to extend their analysis to examine the correlation between extinction and radiation events. These discussions allowed them to relate their new data to the breadth of existing ideas on mass extinctions and radiations. They quickly found that the evolutionary patterns identified with the help of machine learning differed in key ways from traditional interpretations.

The team used a novel application of machine learning to examine the temporal co-occurrence of species in the Phanerozoic fossil record, examining over a million entries in a massive curated, public database including almost two hundred thousand species.

Lead author Dr. Hoyal Cuthill said, “Some of the most challenging aspects of understanding the history of life are the enormous timescales and numbers of species involved. New applications of machine learning can help by allowing us to visualize this information in a human-readable form. This means we can, so to speak, hold half a billion years of evolution in the palms of our hands, and gain new insights from what we see.”

Using their objective methods, they found that the “big five” mass extinction events previously identified by paleontologists were picked up by the machine learning methods as being among the top 5% of significant disruptions in which extinction outpaced radiation or vice versa, as were seven additional mass extinctions, two combined mass extinction-radiation events and fifteen mass radiations. Surprisingly, in contrast to previous narratives emphasizing the importance of post-extinction radiations, this work found that the most comparable mass radiations and extinctions were only rarely coupled in time, refuting the idea of a causal relationship between them.

Co-author Dr. Nicholas Guttenberg said, “the ecosystem is dynamic, you don’t necessarily have to chip an existing piece off to allow something new to appear.”

The team further found that radiations may in fact cause major changes to existing ecosystems, an idea the authors call “destructive creation.” They found that, during the Phanerozoic Eon, on average, the species that made up an ecosystem at any one time are almost all gone by 19 million years later. But when mass extinctions or radiations occur, this rate of turnover is much higher.

This gives a new perspective on how the modern “Sixth Extinction” is occurring. The Quaternary period, which began 2.5 million years ago, had witnessed repeated climate upheavals, including dramatic alternations of glaciation, times when high latitude locations on Earth, were ice-covered. This means that the present “Sixth Extinction” is eroding biodiversity that was already disrupted, and the authors suggest it will take at least 8 million years for it to revert to the long term average of 19 million years. Dr. Hoyal Cuthill comments that “each extinction that happens on our watch erases a species, which may have existed for millions of years up to now, making it harder for the normal process of ‘new species origination’ to replace what is being lost.”

Reference: “Impacts of speciation and extinction measured by an evolutionary decay clock” by Jennifer F. Hoyal Cuthill, Nicholas Guttenberg and Graham E. Budd, 9 December 2020, Nature.
DOI: 10.1038/s41586-020-3003-4

What caused the ice ages? Tiny ocean fossils offer key evidence

DECEMBER 10, 2020

https://phys.org/news/2020-12-ice-ages-tiny-ocean-fossils.html?fbclid=IwAR3Yvv5PsX9bObsuEYXRS1eyffwir99o93K-yXW9g9mAfeZAoFZDAzbbpXw

by Liz Fuller-Wright, Princeton University

What caused the ice ages? Tiny ocean fossils offer key evidence
This diatom species, Fragilariopsis kerguelensis, is a floating algae that is abundant in the Antarctic Ocean and was the major species in the samples collected for the study by Princeton University and the Max Planck Institute for Chemistry. These microscopic organisms live near the sea surface, then die and sink to the sea floor. The nitrogen isotopes in their shells vary with the amount of unused nitrogen in the surface water. The researchers used that to trace nitrogen concentrations in Antarctic surface waters over the past 150,000 years, covering two ice ages and two warm interglacial periods. Credit: Philipp Assmy (Norwegian Polar Institute) and Marina Montresor (Stazione Zoologica Anton Dohrn)

The last million years of Earth history have been characterized by frequent “glacial-interglacial cycles,” large swings in climate that are linked to the growing and shrinking of massive, continent-spanning ice sheets. These cycles are triggered by subtle oscillations in Earth’s orbit and rotation, but the orbital oscillations are too subtle to explain the large changes in climate.https://8b4a283b4123076bbb082c6b0c4e1d40.safeframe.googlesyndication.com/safeframe/1-0-37/html/container.html

“The cause of the ice ages is one of the great unsolved problems in the geosciences,” said Daniel Sigman, the Dusenbury Professor of Geological and Geophysical Sciences. “Explaining this dominant climate phenomenon will improve our ability to predict future climate change.”

In the 1970s, scientists discovered that the concentration of the atmospheric greenhouse gas carbon dioxide (CO2) was about 30% lower during the ice ages. That prompted theories that the decrease in atmospheric CO2 levels is a key ingredient in the glacial cycles, but the causes of the CO2 change remained unknown. Some data suggested that, during ice ages, CO2 was trapped in the deep ocean, but the reason for this was debated.

Now, an international collaboration led by scientists from Princeton University and the Max Planck Institute for Chemistry (MPIC) have found evidence indicating that during ice ages, changes in the surface waters of the Antarctic Ocean worked to store more CO2 in the deep ocean. Using sediment cores from the Antarctic Ocean, the researchers generated detailed records of the chemical composition of organic matter trapped in the fossils of diatoms—floating algae that grew in the surface waters, then died and sank to the sea floor. Their measurements provide evidence for systematic reductions in wind-driven upwelling in the Antarctic Ocean during the ice ages. The research appears in the current issue of the journal Science.

For decades, researchers have known that the growth and sinking of marine algae pumps CO2 deep into the ocean, a process often referred to as the “biological pump.” The biological pump is driven mostly by the tropical, subtropical and temperate oceans and is inefficient closer to the poles, where CO2 is vented back to the atmosphere by the rapid exposure of deep waters to the surface. The worst offender is the Antarctic Ocean: the strong eastward winds encircling the Antarctic continent pull CO2-rich deep water up to the surface, “leaking” CO2 to the atmosphere.https://googleads.g.doubleclick.net/pagead/ads?guci=2.2.0.0.2.2.0.0&client=ca-pub-0536483524803400&output=html&h=280&slotname=5350699939&adk=3784993980&adf=780081655&pi=t.ma~as.5350699939&w=753&fwrn=4&fwrnh=100&lmt=1607891776&rafmt=1&psa=1&format=753×280&url=https%3A%2F%2Fphys.org%2Fnews%2F2020-12-ice-ages-tiny-ocean-fossils.html%3Ffbclid%3DIwAR3Yvv5PsX9bObsuEYXRS1eyffwir99o93K-yXW9g9mAfeZAoFZDAzbbpXw&flash=0&fwr=0&rpe=1&resp_fmts=3&wgl=1&tt_state=W3siaXNzdWVyT3JpZ2luIjoiaHR0cHM6Ly9hZHNlcnZpY2UuZ29vZ2xlLmNvbSIsInN0YXRlIjowfSx7Imlzc3Vlck9yaWdpbiI6Imh0dHBzOi8vYXR0ZXN0YXRpb24uYW5kcm9pZC5jb20iLCJzdGF0ZSI6MH1d&dt=1607891775727&bpp=226&bdt=1314&idt=999&shv=r20201203&cbv=r20190131&ptt=9&saldr=aa&abxe=1&cookie=ID%3D5d55f89f953c9743-22e6569e4cc5006c%3AT%3D1607721097%3ART%3D1607721097%3AS%3DALNI_MYEkuf_Iee2xDN3kq44UdtznCjh2Q&correlator=3168947984516&frm=20&pv=2&ga_vid=185394846.1565457508&ga_sid=1607891777&ga_hid=1178168891&ga_fc=0&u_tz=-480&u_his=1&u_java=0&u_h=640&u_w=1139&u_ah=607&u_aw=1139&u_cd=24&u_nplug=3&u_nmime=4&adx=263&ady=1965&biw=1123&bih=538&scr_x=0&scr_y=0&eid=42530671%2C21066435%2C21068084&oid=3&pvsid=2470879372500863&pem=466&ref=https%3A%2F%2Fl.facebook.com%2F&rx=0&eae=0&fc=896&brdim=0%2C0%2C0%2C0%2C1139%2C0%2C1139%2C607%2C1139%2C537&vis=1&rsz=%7C%7CpEebr%7C&abl=CS&pfx=0&fu=8320&bc=31&ifi=1&uci=a!1&btvi=1&fsb=1&xpc=O8lYBHvjyS&p=https%3A//phys.org&dtd=1090

The potential for a reduction in wind-driven upwelling to keep more CO2 in the ocean, and thus to explain the ice age atmospheric CO2 drawdown, has also been recognized for decades. Until now, however, scientists have lacked a way to unambiguously test for such a change.

The Princeton-MPIC collaboration has developed such an approach, using tiny diatoms. Diatoms are floating algae that grow abundantly in Antarctic surface waters, and their silica shells accumulate in deep sea sediment. The nitrogen isotopes in diatoms’ shells vary with the amount of unused nitrogen in the surface water. The Princeton-MPIC team measured the nitrogen isotope ratios of the trace organic matter trapped in the mineral walls of these fossils, which revealed the evolution of nitrogen concentrations in Antarctic surface waters over the past 150,000 years, covering two ice ages and two warm interglacial periods.

“Analysis of the nitrogen isotopes trapped in fossils like diatoms reveals the surface nitrogen concentration in the past,” said Ellen Ai, first author of the study and a Princeton graduate student working with Sigman and with the groups of Alfredo Martínez-García and Gerald Haug at MPIC. “Deep water has high concentrations of the nitrogen that algae rely on. The more upwelling that occurs in the Antarctic, the higher the nitrogen concentration in the surface water. So our results also allowed us to reconstruct Antarctic upwelling changes.”

What caused the ice ages? Tiny ocean fossils offer key evidence
This diatom species, Fragilariopsis kerguelensis, is a floating algae that is abundant in the Antarctic Ocean and was the major species in the samples collected for the study by Princeton University and the Max Planck Institute for Chemistry. These microscopic organisms live near the sea surface, then die and sink to the sea floor. The nitrogen isotopes in their shells vary with the amount of unused nitrogen in the surface water. The researchers used that to trace nitrogen concentrations in Antarctic surface waters over the past 150,000 years, covering two ice ages and two warm interglacial periods. Credit: (c) Michael Kloster, Alfred-Wegener-Institute

The data were made more powerful by a new approach for dating the Antarctic sediments. Surface water temperature change was reconstructed in the sediment cores and compared with Antarctic ice core records of air temperature.

“This allowed us to connect many features in the diatom nitrogen record to coincident climate and ocean changes from across the globe,” said Martínez-García. “In particular, we are now able to pin down the timing of upwelling decline, when climate starts to cool, as well as to connect upwelling changes in the Antarctic with the fast climate oscillations during ice ages.”

This more precise timing allowed the researchers to home in on the winds as the key driver of the upwelling changes.

The new findings also allowed the researchers to disentangle how the changes in Antarctic upwelling and atmospheric CO2 are linked to the orbital triggers of the glacial cycles, bringing scientists a step closer to a complete theory for the origin of the ice ages.

“Our findings show that upwelling-driven atmospheric CO2 change was central to the cycles, but not always in the way that many of us had assumed,” said Sigman. “For example, rather than accelerating the descent into the ice ages, Antarctic upwelling caused CO2 changes that prolonged the warmest climates.”

Their findings also have implications for predicting how the ocean will respond to global warming. Computer models have yielded ambiguous results on the sensitivity of polar winds to climate change. The researchers’ observation of a major intensification in wind-driven upwelling in the Antarctic Ocean during warm periods of the past suggests that upwelling will also strengthen under global warming. Stronger Antarctic upwelling is likely to accelerate the ocean’s absorption of heat from ongoing global warming, while also impacting the biological conditions of the Antarctic Ocean and the ice on Antarctica.

“The new findings suggest that the atmosphere and ocean around Antarctica will change greatly in the coming century,” said Ai. “However, because the CO2 from fossil fuel burning is unique to the current times, more work is needed to understand how Antarctic Ocean changes will affect the rate at which the ocean absorbs this CO2.”

“Southern Ocean upwelling, Earth’s obliquity, and glacial-interglacial atmospheric CO2 change” by Xuyuan Ellen Ai, Anja S. Studer, Daniel M. Sigman, Alfredo Martínez-García, François Fripiat, Lena M. Thöle, Elisabeth Michel, Julia Gottschalk, Laura Arnold, Simone Moretti, Mareike Schmitt, Sergey Oleynik, Samuel L. Jaccard and Gerald H. Haug appears in the Dec. 11 issue of Science.


Explore furtherCarbon ‘leak’ may have warmed the planet for 11,000 years, encouraging human civilization

Two-fifths of plants at risk of extinction, says report

Amazon rainforest on fireImage copyrightGETTY IMAGES
Image captionOne of the main drivers of plant extinction is clearance of natural habitats

Scientists say they are racing against time to name and describe new plants, before species go extinct.

Plants and fungi hold promise as future medicines, fuels and foods, according to the Royal Botanic Gardens, Kew.

But opportunities are being lost to use this “treasure chest of incredible diversity” as species vanish due to habitat destruction and climate change.

New estimates suggest two-fifths of the world’s plants are at risk of extinction.

The assessment of the State of the World’s Plants and Fungi is based on research from more than 200 scientists in 42 countries.

The report was released on the day of a United Nations summit, which will press for action from world leaders to address biodiversity loss.

Gladiolus mariae in flower on GuineaImage copyrightRBG, KEW
Image captionThe increased figure is partly down to more rigorous assessments

We are living in an age of extinction, said director of science at Kew, Prof Alexandre Antonelli.

“It’s a very worrying picture of risk and urgent need for action,” he said.

“We’re losing the race against time because species are disappearing faster than we can find and name them. Many of them could hold important clues for solving some of the most pressing challenges of medicine and even perhaps of the emerging and current pandemics we are seeing today.”

The report revealed that only a small proportion of existing plant species are used as foods and biofuels.

More than 7,000 edible plants hold potential for future crops, yet only a handful are used to feed a growing world population.

And some 2,500 plants exist that could provide energy for millions worldwide, while only six crops – maize, sugarcane, soybean, palm oil, rapeseed and wheat – generate the vast majority of biofuels.

AkkoubImage copyrightRBG, KEW
Image captionThe thistle-like akkoub can be fried or pickled

Dr Colin Clubbe, head of conservation science at Kew, told BBC News: “We’re currently utilising such a small proportion of the world’s plant and fungi, be it for food or medicines or for fuel, ignoring the potential treasure chest of wild species which we now have increasing knowledge of and the techniques to investigate for the good of humanity.”

The scientists estimate that the extinction risk may be much higher than previously thought, with an estimated 140,000, or 39.4%, of vascular plants estimated to be threatened with extinction, compared with 21% in 2016.

They say the increased estimates are partly down to more sophisticated and accurate conservation assessments.

They are calling for risk assessments to be fast tracked, using technology such as artificial intelligence, and for more funding for plant conservation.

FonioImage copyrightRBG, KEW
Image captionFonio is a grass that grows across savannas of West Africa used as a cereal crop

The research found 723 plants used for medicine are at risk of extinction, with over-harvesting a problem in some parts of the world.

And 1,942 plants and 1,886 fungi were named as new to science in 2019, including species that might be valuable as foods, drinks, medicines or fibres.

The report contains a chapter on UK flora, which is better studied than in most parts of the world.

However, there is no single agreed list of the UK’s flowering plants and even more uncertainty over fungi, with estimates ranging from 12,000 to 20,000.