Seeking a Break in a 252 Million-Year-Old Mass Killing
A Geologist Investigates a Mass Extinction at the End of the Permian Period
by Carl Zimmer
Sam Bowring is officially a geologist at M.I.T. Unofficially, he’s a homicide detective trying to solve the ultimate cold case. Dr. Bowring wants to understand how an estimated 96 percent of all species on Earth became extinct at the end of the Permian Period 252 million years ago. It was the biggest of the five mass extinctions recorded in the fossil record. But because this killing happened so long ago, the culprit has evaded discovery for decades.
Dr. Bowring and his colleagues have now gotten an important break in the case. They’ve made the most precise measurement yet of how long it took for all those species to become extinct. Writing in the Proceedings of the National Academy of Sciences, they report that the extinction took less than about 60,000 years. That’s a geological blink of an eye — a fact that will help scientists evaluate different hypotheses for what triggered the mass extinction.
For now, however, the new result has Dr. Bowring puzzled. “I just think there’s probably something really fundamental that we don’t understand,” he said…
A project to reintroduce these little brown birds helps protect them from extinction.
by Emma Bryce
In 2011 a rescue mission more than 30 years in the making began to unfold in the Pacific Islands. Scientists were embarking on an expedition to reintroduce the Millerbird to a northwest Hawaiian atoll called Laysan Island. The nondescript little brown bird was last seen there in 1923, after having its habitat destroyed by introduced rabbits and livestock.
The biologists planned to capture birds from a nearby rocky outcrop called Nihoa Island—the Millers’ last stronghold—and transport them nearly 650 miles by boat to Laysan’s shore. The stakes were high: There were only about 800 Millers left, and moving even a small number of them seemed risky. But it was worth it, they decided.
"We believed that if the birds survived the trip, they would flourish," says Sheldon Plentovich, a U.S. Fish and Wildlife Service restoration ecologist, who planned the translocation.
The expedition made the three-day voyage twice, carrying a total of 50 birds, which appeared “unflappable,” says Plentovich. “Even in the boat, they were eating the whole time.” In the end, they all survived, and Laysan now supports more than 125 individuals…
End-Permian extinction happened in 60,000 years—much faster than earlier estimates, MIT study says
The largest mass extinction in the history of animal life occurred some 252 million years ago, wiping out more than 96 percent of marine species and 70 percent of life on land—including the largest insects known to have inhabited the Earth. Multiple theories have aimed to explain the cause of what’s now known as the end-Permian extinction, including an asteroid impact, massive volcanic eruptions, or a cataclysmic cascade of environmental events. But pinpointing the cause of the extinction requires better measurements of how long the extinction period lasted.
Now researchers at MIT have determined that the end-Permian extinction occurred over 60,000 years, give or take 48,000 years—practically instantaneous, from a geologic perspective. The new timescale is based on more precise dating techniques, and indicates that the most severe extinction in history may have happened more than 10 times faster than scientists had previously thought…
Excerpt from The Sixth Extinction: An Unnatural History
Writer Elizabeth Kolbert travels the globe investigating evidence that a mass extinction is underway.
The Icelandic Institute of Natural History occupies a new building on a lonely hillside outside Reykjavik. The building has a tilted roof and tilted glass walls and looks a bit like the prow of a ship. It was designed as a research facility, with no public access, which means that a special appointment is needed to see any of the specimens in the institute’s collection. These specimens, as I learned on the day of my own appointment, include: a stuffed tiger, a stuffed kangaroo, and a cabinet full of stuffed birds of paradise.
The reason I’d arranged to visit the institute was to see its great auk. Iceland enjoys the dubious distinction of being the bird’s last known home, and the specimen I’d come to look at was killed somewhere in the country—no one is sure of the exact spot—in the summer of 1821…
Tundra and steppe turning to less-nutritious grasses may have contributed to extinction of ancient Arctic beasts.
by Dan Vergano
Grasslands suddenly spreading across the Arctic about 10,000 years ago helped killed off the woolly mammoth and other prehistoric mammals, suggests a study of ancient Arctic vegetation.
Climate warming after the Ice Age, prehistoric hunters, and even a comet impact have been proposed as reasons for the extinction of the mammoth, woolly rhinoceros, and other oversized “megafauna” that once inhabited Siberia and North America’s far northern plains.
The new DNA analysis of Arctic vegetation over the past 50,000 years, published in Nature by a team led by Eske Willerslev of the University of Copenhagen, offers a new wrinkle on the climate-warming theory: The great beasts vanished because they weren’t getting enough of the right food…
Studies show that Australia’s “favorite scapegoat” most likely didn’t kill the Tasmanian tiger
By Helen Thompson
ingoes are Australian icons for all the wrong reasons. Maligned as baby snatchers and sheep killers, the outback’s free-ranging dogs are viewed by many as pests. Until recently, they have also taken the blame for the extinction of two of the Australian mainland’s former inhabitants: the Tasmanian tiger and its relative, the Tasmanian devil.
Bert Roberts, a field ecologist at the University of Wollongong in Australia, argues for “a pardon for the dingo” in last week’s issue of Scienceand points to recent evidence placing the blame for those extinctions squarely on humans, instead.
For thousands of years, the Tasmanian tiger (Thylacinus cynocephalus), a wolf-like marsupial with tiger-esque stripes, dominated mainland Australia’s food chain, along with the Tasmanian devil (Sarcophilus harrisii). Hitching a ride with humans from Asia, the wild dogs showed up about 4600 years ago, and tigers and devils disappeared from the Australian mainland roughly 2000 years ago…
Reversing local extinction: scientists bring the northern bald ibis back to Europe after 300 years
by Federica Di Leonardo
The northern bald ibis (Geronticus eremita), also called the hermit ibis or waldrapp, is a migratory bird. Once, the bald ibis lived in the Middle East, northern Africa and southern and central Europe, but due to hunting, loss of habitat and pesticide-use, the birds disappeared from most of these areas and is currently considered Critically Endangered.
It became extinct in Europe 300 years ago; the bird is almost gone in Syria, with only a single individual recorded at the country’s lone breeding site in 2013; and the only stronghold left is a small population of around 500 birds in Morocco. But now, a team of scientists from Austria is working to reestablish a self-sustaining, migratory population of bald ibis in Europe.
In 2002 Johannes Fritz, who had been a doctoral student in biology at the Konrad Lorenz Research Station in Austria, came up with the idea of taking northern bald ibises from zoos and imprinting them, in effect becoming their foster parent to teach them a new migratory route to Italy…
Research groups around the world are attempting to resurrect extinct species.
by Abby Olena
The only ever successful de-extinction was the birth of a baby bucardo (Capra pyrenaica pyrenaica)—a type of ibex specifically adapted to the Pyrenees Mountains in Europe—in 2003, though the young animal died soon after birth because its lungs did not function properly, according to BBC News. The clone was generated using frozen cells harvested in 1999 from the last bucardo, an old female that died in 2000. Now, the BBC reports that the Centre for Research and Food Technology of Aragon (CITA) in Zaragoza, Spain, will begin a new project to examine the burcado frozen cells to determine whether de-extinction efforts ought to be resurrected.
“At this moment, we are not initiating a bucardo recovery plan,” Alberto Fernandez-Arias, the head of the Service of Hunting, Fishing and Wetlands in the Aragon government, told the BBC. “We only want to know if Celia’s cells are still alive after having been maintained frozen during 14 years in liquid nitrogen.” Fernandez-Arias told the story of the 2003 bucardo de-extinction experiment in one of 25 talks at the TEDxDeExtinction meeting held this spring (March 15) in Washington, D.C…
Strange mouth-brooding frog driven to extinction by disease
by MongaBay staff
An unusual species of mouth-brooding frog was likely driven to extinction by the fungus Batrachochytrium dendrobatidis (Bd), making an unusual example of ‘extinction by infection’, argue scientists writing in the open-access journal PLOS ONE.
A team of researchers led by Claudio Soto-Azat of the Universidad Andres Bello in Santiago and the Zoological Society of London (ZSL) took samples from hundreds of preserved specimens of Darwin’s frogs (the northern Darwin’s frogRhinoderma rufum and the southern Darwin’s frogRhinoderma darwinii) that were collected from the wild between 1835 and 1989 and looked for the presence of Bd, a fungus that causes the disease chytridiomycosis. They also collected samples from surviving wild populations of Rhinoderma darwinii from Chile and Argentina.
The researchers found high prevalence of Bd at sites that had experienced Rhinoderma extinction or severe population declines, indicating a likely link between the disease and population collapse…
What Doomed the Stromatolites? - Scientists find key clue to an ancient enigma
by Cherie Winner
About a billion years before the dinosaurs became extinct, stromatolites roamed the Earth until they mysteriously disappeared. Well, not roamed exactly.
Stromatolites (“layered rocks”) are rocky structures made by photosynthetic cyanobacteria. The microbes secrete sticky compounds that bind together sediment grains, creating a mineral “microfabric” that accumulates in fine layers. Massive formations of stromatolites showed up along shorelines all over the world about 3.5 billion years ago. They were the earliest visible manifestation of life on Earth and dominated the scene for more than two billion years.
“They were one of the earliest examples of the intimate connection between biology—living things—and geology—the structure of the Earth itself,” said Joan Bernhard, a geobiologist at Woods Hole Oceanographic Institution (WHOI). “Then, around one billion years ago, their diversity and abundance begin to take a nosedive.” …
Old Stone Tools Add Twist to the Extinction of Madagascar’s Megafauna
by Brian Switek
Madagascar is an natural wonder, brimming with creatures that have evolved in the island’s “splendid isolation.” But Madagascar’s endemic fauna was even more spectacular in the not-too-distant past. The island is now devoid of the enormous elephant birds, giant lemurs, dwarfed hippos, and other unusual animals that lived there. They disappeared so recently, only about one thousand years ago, that their remains are referred to as “subfossils.”
How and why they were wiped out is a matter of contention, often seen as a catastrophic decline in the wake of human arrival, but a new archaeological find suggests that the downfall of Madagascar’s megafauna was a more protracted disaster.
Compared to our distant primate relatives, people haven’t occupied Madagascar for very long. The ancestors of today’s lemurs are thought to have arrived by rafting from mainland Africa around 50 to 60 million years ago, whereas the oldest known human villages only go back to around A.D. 500. Within a thousand years of these villages becoming established, every endemic species on the island over 10 kilograms was driven into extinction. Hunting, the use of fire, the spread of agriculture across the island, and other causes have been proposed without consensus, but the connection between humans and extinction is unmistakable…
Spiky-Headed Sharks Survived Mass Extinction, Surprising Scientists
An exotic, ancient shark thrived into the age of dinosaurs, study says.
by Dan Vergano
A family of small sharks—some of which had spiky heads—cruised the ancient seas for far longer than scientists had suspected, surviving to about 120 million years ago. Their surprising survival suggests that deep oceans sheltered predators during past mass extinctions.
Death by asexuality: IU biologists uncover new path for mutations to arise
"Contagious Asexuality" is Dominant in Sexual Genotypes
Univ. of Indiana media release
Ground-breaking new research from a team of evolutionary biologists at Indiana University shows for the first time how asexual lineages of a species are doomed not necessarily from a long, slow accumulation of new mutations, but rather from fast-paced gene conversion processes that simply unmask pre-existing deleterious recessive mutations.
Geneticists have long bet on the success of sexual reproduction over asexual reproduction based in a large part on the process known as Muller’s ratchet, the mechanism by which a genome accrues deleterious and irreversible mutations after the host organism has lost its ability to carry out the important gene-shuffling job of recombination.
The new work from the laboratory of IU Distinguished Professor of Biology Michael Lynch instead indicates that most deleterious DNA sequences contributing to the extinction process are actually present in the sexual ancestors, albeit in recessive form, and simply become exposed via fast-paced gene conversion and deletion processes that eliminate the fit genes from one of the parental chromosomes.
After sequencing the entire genomes of 11 sexual and 11 asexual genotypes of Daphnia pulex, a model organism for the study of reproduction that is more commonly known as the water flea, the team discovered that every asexual genotype shared common combinations of alleles for two different chromosomes transmitted by asexual males without recombination…