What Is: Extinction Level Events

A Chronicle of Earth's Biotic Crises and an Assessment of Future Threats
Image Credit: Scientific Frontline

Defining Biotic Catastrophe

The history of life on Earth is a story of breathtaking diversification and innovation, but it is punctuated by chapters of profound crisis. These are the extinction level events—catastrophes of such magnitude that they fundamentally reset the planet's biological clock. Popular imagination often pictures a single, sudden event, like the asteroid that sealed the fate of the dinosaurs. The geological reality, however, is more complex and, in many ways, more instructive for our current era. Understanding these events requires a rigorous scientific framework that moves beyond simple notions of species loss to appreciate the systemic collapse of entire global ecosystems.

Did Lead Limit Brain and Language Development in Neanderthals and Other Extinct Hominids?

UC San Diego researchers have found high levels of lead in the teeth of both Neanderthals (left) and modern humans (right). However, a gene mutation may have protected modern human brains, allowing language to flourish.
Photo Credit: Kyle Dykes/UC San Diego Health Sciences

Ancient human relatives were exposed to lead up to two million years ago, according to a new study. However, a gene mutation may have protected modern human brains, allowing language to flourish.

What set the modern human brain apart from our now extinct relatives like Neanderthals? A new study by University of California San Diego School of Medicine and an international team of researchers reveals that ancient hominids — including early humans and great apes — were exposed to lead earlier than previously thought, up to two million years before modern humans began mining the metal. This exposure may have shaped the evolution of hominid brains, limiting language and social development in all but modern humans due to a protective genetic variant that only we carry. The study was published in Science Advances.

The researchers analyzed fossilized teeth from 51 hominids across Africa, Asia and Europe, including modern and archaic humans such as Neanderthals, ancient human ancestors like Australopithecus africanus, and extinct great apes such as Gigantopithecus blacki.

The Red Sea Went Completely Dry Before Being Flooded by the Indian Ocean

 KAUST scientists have determined a rapid flood more than 6 million years ago radically changed the Red Sea and all its marine life.
Photo Credit: Francesco Ungaro

KAUST researchers find the Red Sea experienced a massive disruption 6.2 million years ago completely changing its marine life 

Scientists at King Abdullah University of Science and Technology (KAUST) have provided conclusive evidence that the Red Sea completely dried out about 6.2 million years ago, before being suddenly refilled by a catastrophic flood from the Indian Ocean. The findings, published in Communications Earth & Environment, put a definitive time on a dramatic event that changed the Red Sea. 

Using seismic imaging, microfossil evidence, and geochemical dating techniques, the KAUST researchers showed that a massive change happened in about 100 000 years – a blink of an eye for a major geological event. The Red Sea went from connecting with the Mediterranean Sea to an empty, salt-filled basin. Then, a massive flood burst through volcanic barriers to open the Bab el-Mandab strait and reconnect the Red Sea with the world’s oceans. 

“Our findings show that the Red Sea basin records one of the most extreme environmental events on Earth, when it dried out completely and was then suddenly reflooded about 6.2 million years ago,” said lead author Dr. Tihana Pensa of KAUST. “The flood transformed the basin, restored marine conditions, and established the Red Sea’s lasting connection to the Indian Ocean.” 

Stem Cell Technique Could Preserve Endangered Bird Species

Avian stem cells in culture (blue, left) that be efficiently converted in large numbers into germ cells (green, right).
Image Credit: C. Lois

Birds are a critical part of the global ecosystem; they enable our food production through consumption of agricultural pests like aphids and rodents, and control the spread of diseases by eating insects like mosquitos and ticks. However, around 15 percent of all bird species now face risk of extinction—in Hawaii alone, 33 of the state's 45 native species are critically endangered.

Caltech researchers have now developed technology to freeze and preserve stem cells from birds that can then be reconstituted to help propagate populations.

The work was conducted by Caltech postdoctoral scholar Xi Chen as a collaboration between the USC laboratory of Qi-Long Ying and the Caltech laboratory of Carlos Lois, research professor of biology. The study is described in a paper in the journal Nature Biotechnology.

Captivity makes salmon less symmetrical

Photo Credit: Courtesy of Cardiff University

The stress of captivity is likely to be causing reared salmon to be less symmetrical in appearance, according to a new study.

Research by the University of Eastern Finland, Natural Resources Institute Finland, and Cardiff University has found that salmon reared in captivity are more asymmetrical in appearance compared to wild salmon, suggesting that captive fish are more stressed, and their appearance might have impacts on salmon in the wild.

Currently, hatcheries are used in some countries to help boost wild populations with captive reared salmon. Global sales of aquatic species reared in captivity for food are also worth over $300 billion annually, with the Atlantic salmon being the most valuable of these species.

Global ‘Noahʻs Ark’ to safeguard coral reefs, led by UH scientists

Acropora muricata, Heron Island, Australia.
Photo Credit: Claire Lager, Smithsonian

In a landmark effort to combat the devastating effects of climate change, a new global alliance with key leadership from the University of Hawaiʻi at Mānoa has been established to create a “Noahʻs Ark” for coral reefs. The initiative, detailed in a publication in BioScience, focuses on building a worldwide network of coral biorepositories to safeguard the genetic diversity of these vital ecosystems.

The research, led by Mary Hagedorn of the UH Mānoa Hawaiʻi Institute of Marine Biology and Smithsonian’s National Zoo and Conservation Biology Institute, highlights the critical need for a proactive conservation strategy. With global carbon emissions continuing to rise, the alliance aims to provide a critical safeguard against extinction by preserving coral genetic material in biosecure facilities.

Clownfish and Anemones Are Disappearing Because of Climate Change

A Red Sea clownfish (Amphiprion bicinctus) peers out of a bleached sea anemone (Radianthus magnifica) during a record-breaking heat wave in 2023.
Photo Credit: © Morgan Bennett-Smith

A new study led by Boston University marine biologists reveals that heat waves are threatening the future of the fish made famous by Finding Nemo

The Red Sea, circled by desert landscapes, is home to marine life accustomed to the water’s bathtub-like temperatures—often reaching 85 to 90 degrees Fahrenheit in the summer. But in the past three years, marine heat waves have made the Red Sea even hotter. Rising ocean temperatures, there and around the world, have been devastating for many sea creatures, including an iconic ocean duo: clownfish and anemones. 

A new paper from a Boston University–led research team finds that this extreme heat has caused a breakdown in the mutualistic relationship of clownfish—also called anemonefish— and anemones and has resulted in a population collapse in the central Red Sea.

Wolf protection downgrade highlights need for adaptive conservation frameworks

The protected category means greater flexibility in managing wolf populations
Photo Credit: Marcel Langthim

Following the European Parliament’s historic vote to move wolves from the strictly protected to protected category, experts are calling on policymakers to ensure the change becomes a catalyst for fairer, more adaptive and transparent wildlife management to meet the challenges of successful species recovery.

The protected category means greater flexibility in managing wolf populations

The reclassification reflects a remarkable recovery of the wolf population, having increased by 58% in a decade, with populations of brown bears, lynxes and wolverines also on the rise. 

The protected category affords member states greater flexibility in managing expanding wolf populations, but although protections remain in place, the move has raised fears among conservation groups of widespread culling. 

At the same time, farming and hunting communities and landowner associations see it as necessary to regulate the population and enable management that is adapted to local conditions. 

Whale poop contains iron that may have helped fertilize past oceans

A blue whale photographed in September 2010.
Photo Credit: NOAA

The blue whale is the largest animal on the planet. It consumes enormous quantities of tiny, shrimp-like animals known as krill to support a body of up to 100 feet (30 meters) long. Blue whales and other baleen whales, which filter seawater through their mouths to feed on small marine life, once teemed in Earth’s oceans. Then over the past century they were hunted almost to extinction for their energy-dense blubber.

As whales were decimated, some thought the krill would proliferate in predator-free waters. But that’s not what happened. Krill populations dropped, too, and neither population has yet recovered.

A recent theory proposes that whales weren’t just predators in the ocean environment. Nutrients that whales excreted may have provided a key fertilizer to these marine ecosystems.

Research led by University of Washington oceanographers supports that theory. It finds that whale excrement contains significant amounts of iron, a vital element that is often scarce in ocean ecosystems, and nontoxic forms of copper, another essential nutrient that in some forms can harm life.

The open-access study, the first to look at the forms of these trace metals in what’s commonly known as whale poop, was published in January in Communications Earth & Environment.

Mount Rainier White-Tailed Ptarmigan Finally Receives a ‘Threatened’ Species Designation

An adult Mount Rainier white-tailed ptarmigan in brown summer plumage. Its feathers change seasonally—white in the winter, white and brown in the spring. Its tail remains white year-round.
Photo Credit: Pete Plage/USFWS

In July, the Mount Rainier white-tailed ptarmigan was officially listed as threatened by the U.S. Fish and Wildlife Service (FWS) under the Endangered Species Act (ESA), 14 years after the Center for Biological Diversity first petitioned for its listing. This designation is meant to help preserve the bird, whose survival depends on the glaciers of the Cascade Mountains of Washington State and British Columbia. It also reflects the complex challenges that alpine-adapted birds face in a warming world.

With its feathered, snowshoe-like feet that allow it to walk on high mountain terrain and its seasonal plumage that provides camouflage year-round, Mount Rainier white-tailed ptarmigans are adapted to high elevation regions above the treeline. They are frequently spotted in areas with mixed rock, snow and alpine plants. Their diet consists of twigs, leaves, buds and seeds of alpine tundra vegetation that only grow in treeless, cold and dry mountainous regions that receive critical moisture from spring snowmelt and summer glacier runoff.

Warming temperatures are accelerating glacier retreat and endangering the bird’s habitat: glaciers in the North Cascades shrunk 56 percent between 1900 and 2009. Mauri Pelto, director of the North Cascade Glacier Climate Project, told GlacierHub that ptarmigans are often spotted along the Shuksan and Ptarmigan Ridges near Mount Baker. In a study, Pelto found that seven of the 13 glaciers along those ridges have disappeared since the mid-1980s. Retreating glaciers risk reduced soil water availability for tundra vegetation and long-term habitat loss associated with warming temperatures.

Conservation paradox: Invasive species are often threatened in their native range

The wild rabbit is endangered in its native Europe. In other parts of the world, such as Australia, this species has been introduced and has large populations.
Photo Credit: ©Alexis Lours

Non-native animals are a threat to biodiversity, yet many are themselves threatened with extinction in their areas of origin

Non-native species introduced by humans are among the main causes of global species decline – they were partly responsible for 60 percent of the species that have become extinct worldwide in recent decades. In Central Europe, non-native mammals include species such as the Norway rat, the mouflon and the mink. Now a study led by biologists from the University of Vienna and La Sapienza University in Rome shows that some of these species introduced by humans are themselves endangered in their native range. The study has been published in the current issue of the journal Conservation Letters.

The globalization of the earth is contributing to the introduction of many animal and plant species into new parts of the world. Invasive species can displace native species through competition or transmit new diseases. At the same time, however, some of these non-native species are threatened with extinction in their native ranges. This creates a conservation paradox – because the question now is, should non-native occurrences of species that are endangered in their native range be protected or controlled? However, it was previously unknown how many non-native mammal species this paradox actually applies to. In the new study, the scientists have now quantified this in order to come one step closer to an answer to this paradox.

How mites have survived for millions of years

oribatid mite Platynothrus peltifer
Image Credit: Gemini (AI)

An international research team has discovered various mechanisms in asexual mites that generate genetic diversity and thus ensure survival

In collaboration with colleagues from international partner institutions, researchers at the University of Cologne have investigated the asexual reproduction of oribatid mites using genome sequencing techniques. They show that the key to evolution without sex in oribatid mites may lie in the independent evolution of their two chromosome copies – a phenomenon known as the ‘Meselson effect’. The research team identified various mechanisms that may contribute to the genetic diversity of the chromosome sets, potentially enabling the long-term persistence of the mite.

Like humans, oribatid mites possess two sets of chromosomes. However, the asexual oribatid mite Platynothrus peltifer reproduces parthenogenetically: Mothers produce daughters from unfertilized eggs, resulting in a population consisting entirely of females. Using single-individual sequencing, the researchers analysed the accumulated differences between the chromosome copies for the first time and evaluated their significance for the mite’s survival. The study titled ‘Chromosome-scale genome dynamics reveal signatures of independent haplotype evolution in the ancient asexual mite Platynothrus peltifer’, funded by the German Research Foundation (DFG), was published in Science Advances.

Polygamy is (not) for the birds

Rafael S. Marcondes, a faculty fellow in ecology and evolutionary biology at Rice
Photo Credit: Alex Becker/Rice University

Researchers at Rice University have uncovered new insights into the evolution of bird behavior, revealing why certain mating systems persist while others disappear over time. In a recent paper published in the journal Evolution, Rafael S. Marcondes and Nicolette Douvas reveal that lekking — a mating system where males display for females without forming lasting bonds — is an evolutionarily stable strategy. In contrast, resource-defense polygamy, where one sex — usually but not always the male — guards territories to attract mates, is highly unstable and often reverts to monogamy.

“This research not only examines how mating behaviors influence species survival but also sheds light on larger evolutionary questions,” said Marcondes, the corresponding author and a faculty fellow in ecology and evolutionary biology at Rice. “By studying birds, we’re uncovering principles that may resonate across other species too.”

The study analyzed data from more than 60% of the world’s bird species — approximately 6,620 species — making it one of the most comprehensive analyses of its kind.

‘Winners and losers’ as global warming forces plants uphill

Cerrado savanna in the Chapada dos Veadeiros National Park, Brazil.
Photo Credit Ana Christina

Some plant species will “win” and others will “lose” as global warming forces them to move uphill, new research shows.

Scientists examined the current range of more than 7,000 plant species in Brazil’s Cerrado savanna, and estimated shifts based on warming by 2040.

The fate of plant species will depend on where they live: lowland species can move uphill for cooler conditions, but mountain plants have nowhere to go.

The study was carried out by the universities of Exeter and Campinas, the Royal Botanic Garden Edinburgh and Trinity College Dublin.

“Every plant and animal species has a ‘geographical range’ – the area where conditions are suitable for it to live,” said Mateus Silva, from the University of Exeter.

“As the climate warms, plants’ ranges are shifting, with many species going uphill.

“This is the pattern we found in the Cerrado – suggesting lowland areas may become local extinction hotspots, while mountains will host new combinations of plant species.”

Bees need food up to a month earlier than provided by recommended pollinator plants

Buff-tailed bumblebee (Bombus terrestris).
Photo Credit Matthias Becher

New research from the Universities of Oxford and Exeter has revealed that plant species recommended as “pollinator friendly” * in Europe begin flowering up to a month too late in the spring to effectively contribute to bee conservation.

This “hungry gap” results in low colony survival and low production of queens for the following year.

The results showed that pollen and nectar availability during the early colony founding stage is a critical, and previously under-appreciated, factor in bee colony success. **

The study has been published in the journal Insect Conservation and Diversity. 

Senior author Dr Tonya Lander (Department of Biology, University of Oxford) said: “The results give us a simple and practical recommendation to help bees: to enhance hedgerows with early blooming species, especially ground ivy, red dead-nettle, maple, cherry, hawthorn, and willow, which improved colony success rate from 35% to 100%. This approach focuses on existing hedgerows in agricultural land and doesn’t reduce farm cropping area, so can appeal to land managers whilst also providing important conservation outcomes for pollinators.” 

These were assessed using the BEE-STEWARD model, which integrates data and runs simulations to predict how changes in different factors may impact bee populations over time.

Rays were more diverse 150 million years ago than previously thought

Aellopobatis bavarica: The newly discovered species, complete fossils are only known from Germany. This species is also the largest species of all and can grow up to 170 cm in size.
Photo Credit: Türtscher et al.

New fossil ray species discovered in Bavarica, Germany: Aellopobatis bavarica from the Late Jurassic

In a new study recently published in the journal Papers in Paleontology, an international team of scientists led by paleobiologist Julia Türtscher from the University of Vienna has explored the puzzling world of rays that lived 150 million years ago and discovered a previously hidden diversity – including a new ray species. This study significantly expands the understanding of these ancient cartilaginous fish and provides further insights into a past marine ecosystem.

In her new study, paleobiologist Julia Türtscher from the Institute of Paleontology at the University of Vienna examined 52 fossil rays from the Late Jurassic period. These rays are 150 million years old, from a time when Europe was largely covered by the sea, except for a few islands, comparable to today's Caribbean. The Late Jurassic specimens are particularly valuable to scientists because they are among the oldest known fully preserved ray specimens. As only the teeth of fossilized rays are usually preserved, such rare skeletal finds provide exciting insights into the early evolution of this group. Although the exceptionally well-preserved fossils (from Germany, France, and the UK) have been known for some time, they have been largely unexplored. Türtscher's study is the first comprehensive analysis of the variation in body shape in these rays.

Product that kills agricultural pests also deadly to native Pacific Northwest snail

Pacific sideband snail.
Photo Credit: William P. Leonard

A product used to control pest slugs on farms in multiple countries is deadly to least one type of native woodland snail endemic to the Pacific Northwest, according to scientists who say more study is needed before the product gains approval in the United States.

Dee Denver of the Oregon State University College of Science led a 10-week laboratory project that showed the effect of a biotool marketed as Nemaslug on the Pacific sideband snail. The study was published today in PLOS One.

Nemaslug is based on the organism Phasmarhabditis hermaphrodita, a species of tiny, parasitic worm known as a nematode.

The speed of the Pacific sidebands’ demise depended on the concentration of Nemaslug exposure and the size and maturity of the snails, but by the end of the study all 90 were dead, whereas all 30 snails in a control group were still alive.

“This finding is a big deal because there are strong efforts to bring this commercialized nematode to U.S. markets to control invasive pests, such as the gray field slug, that cause damage to a variety of agricultural crops,” said Denver, who heads OSU’s Department of Integrated Biology and directs the university’s School of Life Sciences.

All creatures great and small: Sequencing the blue whale and Etruscan shrew genomes

Prompts by Scientific Frontline
Image Credit: AI Generated by Copilot / Designer / DALL-E 3

The blue whale genome was published in the journal Molecular Biology and Evolution, and the Etruscan shrew genome was published in the journal Scientific Data.

Research models using animal cell cultures can help navigate big biological questions, but these tools are only useful when following the right map.

“The genome is a blueprint of an organism,” says Yury Bukhman, first author of the published research and a computational biologist in the Ron Stewart Computational Group at the Morgridge Institute, an independent research organization that works in affiliation with the University of Wisconsin–Madison in emerging fields such as regenerative biology, metabolism, virology and biomedical imaging. “In order to manipulate cell cultures or measure things like gene expression, you need to know the genome of the species — it makes more research possible.”

The Morgridge team’s interest in the blue whale and the Etruscan shrew began with research on the biological mechanisms behind the “developmental clock” from James Thomson, emeritus director of regenerative biology at Morgridge and longtime professor of cell and regenerative bBiology in the UW School of Medicine and Public Health.  It’s generally understood that larger organisms take longer to develop from a fertilized egg to a full-grown adult than smaller creatures, but the reason why remains unknown.

“It’s important just for fundamental biological knowledge from that perspective. How do you build such a large animal? How can it function?” says Bukhman.

What Makes Birds So Smart?

The avian brain is smaller than that of many mammals, but just as capable.
Photo Credit: Kevin Mueller

Researchers at Ruhr University Bochum explain how it is possible for the small brains of pigeons, parrots and corvids to perform equally well as those of mammals, despite their significant differences.

Since the late 19th century, it has been a common belief among researchers that high intelligence requires the high computing capacity of large brains. They also discovered that the cerebral cortex as typical of mammals, is necessary to analyze and link information in great detail. Avian brains, by contrast, are very small and lack any structure resembling a cortex. Nevertheless, scientists showed that parrots and corvids are capable of planning for the future, forging social strategies, recognizing themselves in the mirror and building tools. These and similar aptitudes put them on a par with chimpanzees. Even less gifted birds, such as pigeons, learn orthographic rules that enable them to recognize typos in short words or classify pictures according to categories such as “impressionism”, “water” or “man-made”. How do they do it with such small brains and without a cortex? With their article in Trends in Cognitive Science, Professor Onur Güntürkün, Dr. Roland Pusch and Professor Jonas Rose from Ruhr University Bochum come closer to solving this more than one hundred-year-old puzzle.

Study shows orchid family emerged in northern hemisphere and thrived alongside dinosaurs

Phallaenopsis orchid in bloom
Photo Credit: John Wiesenfeld

Scientists at the Royal Botanic Gardens in Kew and the University of Portsmouth, along with partners in Latin America, Asia and Australia, have presented an updated family tree of orchids, tracing their origins to the northern hemisphere some 85 million years ago.

The study, published in leading journal New Phytologist, sheds new light on their complex and fascinating evolutionary history, and the authors hope their findings will help inform future orchid conservation planning. 

The orchid family, Orchidaceae, is often lauded by scientists as one of the greatest evolutionary marvels within the plant world. Not only are these flowering plants found on every continent except the Antarctic and in virtually every habitat, including north of the Arctic Circle, but they are also incredibly diverse, with an estimated 29,500 species – nearly three times more than the recognized number of bird species globally.  

It is generally accepted that orchids originated as far back as around 90 million years or more ago, but they were previously thought to have emerged on the supercontinent Gondwana, in what is present-day Australia.

However, the new study indicates their common ancestor may have originated in the northern hemisphere, on the supercontinent Laurasia, before spreading out further into the world.