Aurelia Butler

The demise of most of Australia’s kangaroo species by 40,000 years ago may have had less to do with climate-caused dietary pressures and more to do with human hunters.

Dental analyses of ancient kangaroos reveal they weren’t such picky eaters as once thought, researchers report in the Jan. 10 Science. Instead, when it came to climate-related changes in food availability, the animals might have rolled with the punches, the scientists suggest.

Between 65,000 and 40,000 years ago, more than 90 percent of Australia’s large animal species went extinct. Over half were kangaroos. The primary suspects behind these extinctions were thought to be human hunters, who had arrived sometime between 70,000 and 50,000 years ago, and rapid changes in the climate, which may have dramatically reduced the animals’ dietary options. More

Unusually dry conditions and hurricane-force seasonal winds are fueling multiple fast-moving and destructive wildfires in Los Angeles County. Gusts that reached over 145 kilometers per hour (90 miles per hour) quickly drove the blazes into urban areas, forcing more than 100,000 people to evacuate from their homes and killing at least two people as of January 8.

The largest of the blazes, known as the Palisades fire, erupted the morning of January 7 on the west side of Los Angeles and has since burned more than 6,400 hectares (15,800 acres) and destroyed around 1,000 structures. The second largest, called the Eaton fire, ignited near Pasadena that night and had burned more than 4,290 hectares by the next morning. A third blaze, the Hurst fire near Sylmar, has burned more than 200 hectares. More

Landscapes in Southeast Asia once thought to stifle biological evolution may instead stoke its fires.

Karst ecosystems have been referred to as arks of biodiversity, a term that highlights their biological richness but also implies they merely preserve ancient lineages. These landscapes, with their isolated caves, cliffs and sinkholes, were thought to shelter species from extinction without contributing much to evolution.

But the discovery over the past several years of nearly 200 gecko species in such regions reveals that karsts are far from stagnant. “They’re not museums, but centers of speciation,” says evolutionary biologist Lee Grismer of La Sierra University in Riverside, Calif.

Some geckos from the Cyrtodactylus genus, like this newfound one from Cambodia, are uniquely adapted to thrive in the karst landscapes in Southeast Asia. Their specialized bodies allow them to cling to sheer rock faces.L. Lee Grismer

When Grismer first explored Myanmar’s karst landscapes in 2017, the richness of life hidden within the limestone towers and caves left him stunned. During a 19-day expedition, these ancient rock formations, rising abruptly from the surrounding farmland, revealed geckos so distinct and unexpected that his team identified 12 new species.

Since then, Grismer and his colleagues have ventured into similar formations across Southeast Asia, delving into the evolutionary secrets they harbor. In early 2024, an expedition to western Cambodia uncovered three new species of bent-toed geckos and a slender gecko — all detailed in upcoming papers — bringing the number of gecko species he has described to around 185. “The biodiversity in these landscapes is just off the charts,” Grismer says.

The gecko discoveries highlight this dynamism. Many karst-dwelling geckos belong to Cyrtodactylus, the third largest vertebrate genus in the world with close to 400 species described so far. Geckos of this genus discovered by Grismer and his team are among the most recently evolved members of their groups. They exhibit unique adaptations, such as elongated limbs, larger eyes and flatter heads, that enable them to cling to sheer rock faces, much like expert climbers.

Researchers discovered the Sanpel Cave bent-toed gecko, Cyrtodactylus sanpelensis, in a limestone cave in Myanmar. It was hiding under water running down a stalactite, says evolutionary biologist Lee Grismer. “This has never been observed before,” he says.
L. Lee Grismer

Grismer likens the karst formations to islands in an archipelago. Each formation, he says, serves as an evolutionary microcosm, producing species entirely distinct from neighboring karsts. “Species are coming from completely different species groups and different times throughout history.”

The true extent of gecko diversity in the karsts remains unknown. Grismer and his colleagues have surveyed only about 20 percent of the formations in western Cambodia, and he plans to return there and to Myanmar in 2025. “It wouldn’t surprise me if there are another 200 species out there.” More

“Forever chemicals” are pervasive, and researchers have in recent years been ringing the alarms about the negative impacts on human health. But humans aren’t the only animals to be concerned about.

Freshwater turtles in Australia exposed to per- and polyfluoroalkyl substances, or PFAS, experienced changes to their metabolic functions, environmental biochemist David Beale and colleagues report in the Dec. 15 Science of the Total Environment. “We found a whole range of biomarkers that are indicative of cancer and other health problems within reptiles,” says Beale, of the Commonwealth Scientific and Industrial Research Organisation in Dutton Park, Australia. More

2024 was studded with record-setting scientific discoveries. From tracing the origins of glow-in-the-dark animals to developing the world’s fastest microscope, these superlative feats captured our imagination.

Ancient Airburst

Some 2.5 million years ago, an asteroid combusted in Earth’s atmosphere before it could hit the ground and leave a crater, making the event the oldest known midair explosion. That conclusion is based on a chemical analysis of nearly 120 microscopic rocks buried deep underneath Antarctic ice. The ancient pebbles are rich in olivine and spinel minerals, which suggests the specimens are the asteroid’s remnants, scientists say.

Chemical analysis of microscopic bits of rock collected in Antarctica (three shown) suggests they are consistent with a type of asteroid known as an ordinary chondrite that broke up in the atmosphere.  Courtesy of Matthias van Ginneken

The dawn of photosynthesis

Microfossils in Australia harbor the oldest evidence of photosynthesis. Fossilized bacteria dating to about 1.75 billion years ago preserve structures that resemble thylakoid membranes, which help modern cyanobacteria convert sunlight into oxygen. Scientists had previously suspected that cyanobacteria were photosynthesizing way back then, but the new finding is the first direct evidence.

Researchers found microscopic fossils of cyanobacteria dubbed Navifusa majensis (left) in 1.73 billion- to 1.78 billion-year-old shale from Australia). A peek inside the fossils revealed black horizontal lines indicating the bacterium contained stacks of membranes known as thylakoids (right) like those in modern bacteria and plants where oxygen-producing photosynthesis takes place.C.F. Demoulin, et al./Nature 2024

Fastest backflip

Dicyrtomina minuta springtails can launch themselves up to 60 millimeters in the air and spin at a rate of up to 368 times per second, making the arthropods the fastest known backflippers (SN: 10/5/24, p. 4). An appendage on the underbelly helps the miniature gymnasts lift off while another helps them stick the landing.

Backflipping arthropods called globular springtails can vault themselves up to 60 millimeters high and spin up to 29 times in the blink of an eye. Two springtails jump off a platform in a lab in this high-speed camera footage.A. Smith

Wee-est frog

At just 6.5 millimeters long, a Brazilian flea toad (Brachycephalus pulex) has been crowned the world’s smallest known frog (SN: 3/23/24, p. 4). Petite enough to sit on a pinkie fingernail, the amphibian beat the previous champion by about a millimeter.

The Brazilian flea toad has nabbed the title of world’s smallest known amphibian and smallest known vertebrate. At just 7 millimeters long on average, the frogs are a fraction the size of a 27-millimeter-wide $1 Brazilian real coin.W.H. Bolaños, I.R. Dias and M. Solé/Zoologica Scripta 2024

Large genome, small package

The largest known genetic instruction manual belongs to a tiny fern (SN: 6/29/24, p. 4). Tmesipteris oblanceolata is 15 centimeters long but possesses a genome that is 50 times as large as humans’. If unraveled, the fern’s spool of DNA would stretch 100 meters long, scientists say.

The yellow balls on this New Caledonian fork fern are synangia, the spore-producing structures in this group of ferns. Oriane Hidalgo

Oldest bioluminescence

Bioluminescence has a new birthday. Ancestors of a group of deep-sea corals glowed in the dark 540 million years ago, scientists say. Scientists had thought that animal bioluminescence began about 267 million years ago in an ancestor of sea fireflies — tiny, seed-shaped crustaceans.

Colonial false gold coral (Savalia) demonstrates its bioluminescence on a Bahamian reef. This form of bioluminescence in octocorals is the oldest yet dated.Sönke Johnsen

Supersmall knot

Knots come in all shapes and sizes. Small figure-eight knots hold people as they scale cliffs. Bigger bowlines secure ships to shore. This year, scientists designed the smallest and tightest knot yet (SN: 2/24/24, p. 4). This trefoil knot is made from a string of 54 gold, phosphorus, oxygen and carbon atoms that is pretzeled over itself three times.

In this simplified illustration of the smallest known molecular knot, a chain of 54 gold (red), phosphorus (purple), oxygen (mauve) and carbon (black) atoms crosses itself three times to form a pretzel-like shape.Z. Li et al/Nature Communications 2024 More