Relocated beavers helped mitigate some effects of climate change

In the upper reaches of the Skykomish River in Washington state, a pioneering team of civil engineers is keeping things cool. Relocated beavers boosted water storage and lowered stream temperatures, indicating such schemes could be an effective tool to mitigate some of the effects of climate change.

In just one year after their arrival, the new recruits brought average water temperatures down by about 2 degrees Celsius and raised water tables as much as about 30 centimeters, researchers report in the July Ecosphere. While researchers have discussed beaver dams as a means to restore streams and bulk up groundwater, the effects following a large, targeted relocation had been relatively unknown (SN: 3/26/21).
“That water storage is so critical during the drier periods, because that’s what can keep the ecosystem resilient to droughts and fires,” says Emily Fairfax, an ecohydrologist at California State University Channel Islands in Camarillo who was not involved with the study.

The Skykomish River flows down the west side of Washington’s Cascade Mountains. Climate change is already transforming the region’s hydrology: The snowpack is shrinking, and snowfall is turning to rain, which drains quickly. Waters are also warming, which is bad news for salmon populations that struggle to survive in hot water.

Beavers are known to tinker with hydrology too (SN: 7/27/18). They build dams, ponds and wetlands, deepening streams for their burrows and lodges (complete with underwater entrances). The dams slow the water, storing it upstream for longer, and cool it as it flows through the ground underneath.

From 2014 to 2016, aquatic ecologist Benjamin Dittbrenner and colleagues relocated 69 beavers (Castor canadensis) from lowland areas of the state to 13 upstream sites in the Skykomish River basin, some with relic beaver ponds and others untouched. As beavers are family-oriented, the team moved whole clans to increase the chances that they would stay put.

The researchers also matched singletons up with potential mates, which seemed to work well: “They were not picky at all,” says Dittbrenner, of Northeastern University in Boston. Fresh logs and wood cuttings got the beavers started in their new neighborhoods.

At the five sites that saw long-term construction, beavers built 14 dams. Thanks to those dams, the volume of surface water — streams, ponds, wetlands — increased to about 20 times that of streams with no new beaver activity. Meanwhile below ground, wells at three sites showed that after dam construction the amount of groundwater grew to more than twice that was stored on the surface in ponds. Stream temperatures downstream of the dams fell by 2.3 degrees C on average, while streams not subject to the beavers’ tinkering warmed by 0.8 degrees C. These changes all came within the first year after relocation.

“We’re achieving restoration objectives almost instantly, which is really cool,” Dittbrenner says.

Crucially, the dams lowered temperatures enough to almost completely take the streams out of the harmful range for salmon during a particularly hot summer. “These fish are also experiencing heat waves within the water system, and the beavers are protecting them from it,” Fairfax says. “That to me was huge.”

The study also found that small, shallow abandoned beaver ponds were actually warming streams, perhaps because the cooling system had broken down over time. Targeting these ponds as potential relocation sites could be the most effective way to bring temperatures down, the researchers say. When relocated populations establish and breed, young beavers leaving their homes could seek those abandoned spots out first, Dittbrenner says, as it uses less energy than starting from scratch. “If they find a relic pond, it’s game on.”

Oldest known avian relative of today’s birds found in China

Two partial skeletons unearthed in northeastern China have dashed the record for the oldest avian relatives of today’s birds.

The remains belonged to a species, Archaeornithura meemannae, that lived 130.7 million years ago — about 6 million years earlier than the previous record holders. Fossil hunters discovered bones of the hummingbird-sized creatures embedded in siltstone slabs in what may have once been a lake. Stubby feathers stipple the ancient birds’ bodies, except for some spots on the legs. These bald patches hint that the animals once waded through watery homes, suggest Chinese Academy of Sciences paleontologist Min Wang and colleagues May 5 in Nature Communications.

How did Earth get its water?

Earth — a planet of oceans, rivers and rainforests — grew up in an interplanetary desert.

When the solar system formed about 4.6 billion years ago, shards of calcium- and aluminum-rich minerals stuck together, building ever-larger pebbles and boulders that smashed together and assembled the rocky planets, including Earth.

But Earth’s signature ingredient was nowhere to be found. Heat from the young sun vaporized any ice that dared to come near the inner planets. Earth’s relatively feeble gravity couldn’t grab on to the water vapor, or any other gas for that matter. And yet, today, Earth is a planet that runs on H2O. Water regulates the climate, shapes and reshapes the landscape and is essential to life. At birth, humans are about 78 percent water — basically a sack of the wet stuff.
To get water, Earth had to have help from somewhere else.

Researchers recently found traces of Earth’s aquatic starter kit locked away inside several meteorites, chunks of rock that fell to the planet’s surface. Those meteorites were a gift from Vesta, the second largest body in the asteroid belt between Mars and Jupiter. Vesta is thought to have formed earlier than Earth, roughly 8 million to 20 million years after the start of the solar system. (Earth needed 30 million to 100 million years to pull itself together.)

Well before the rocky planets formed, recent research suggests, ice-infused asteroids were forged beyond Jupiter and subsequently swarmed the inner solar system. These space rocks delivered water to Vesta and to Earth after being hurled at our planet by the gravity of Jupiter and Saturn. Whether the giant planets were a help or a hindrance is anybody’s guess. But if what happened here can happen anywhere, then water might be prevalent on other worlds, giving life a good chance of thriving throughout the galaxy.

Comets vs. asteroids
For decades, researchers have debated whether comets or asteroids delivered Earth’s water. At first glance, comets seemed a likely source. Originating beyond the orbit of Neptune, comets are the deep-freeze storage units of the solar system. They hold a lot of ice that has been locked away within their interiors since the formation of the solar system. Some comets are occasionally thrown inward after a close brush with a planet or passing star. It makes sense that, during the chaos of the early solar system, Earth would have been pummeled with comets, bringing plenty of water to fill the oceans.

In recent years, however, the comet hypothesis has lost favor. “It looks like comets are pretty much out,” says cosmochemist Conel Alexander of the Carnegie Institution for Science in Washington, D.C. Most of the comet water tested so far doesn’t match that of Earth’s oceans. Plus, it’s incredibly difficult to bring a comet toward Earth, much less a whole slew of them. “It just shouldn’t be part of the discussion anymore,” he says.

Part of the problem lies in a subtle chemical difference between water on Earth and water in most comets. Water is a simple molecule resembling a pair of Mickey Mouse ears: two hydrogen atoms grab a single oxygen atom. But sometimes deuterium, a slightly heavier version of hydrogen, weasels its way into the mix. The nucleus of a deuterium atom contains one proton and one neutron; in hydrogen, the proton stands alone. On Earth, only about 156 out of every 1 million water molecules contain deuterium.
Researchers have long used the relative amount of deuterium compared with hydrogen — known as the D/H ratio — to trace water back to where it originated. At colder temperatures, deuterium starts to show up in ice more frequently. So bodies that formed in the frigid backwaters of the solar system, such as comets, should be enriched in deuterium, whereas the water vapor that swirled around the infant Earth should have little to none.
Most comets appear to follow that logic; their D/H ratio is typically about twice what has been measured on Earth.

Two comets, however, threw a curveball at scientists who had counted out comets as the source of Earth’s water. In 2010, researchers used the Herschel space telescope to measure the D/H ratio of comet 103P/Hartley 2. They reported that 103P’s water nearly matched that found on Earth. Observations of comet 45P/Honda-Mrkos-Pajdušáková three years later also found abnormally low D/H ratios. Suddenly one, possibly two, comets were carrying Earthlike water.

Jupiter’s pull
Both of these comets are part of a community known as Jupiter family comets. They originated in the Kuiper belt, the ring of icy debris beyond Neptune where Pluto lives. The gravity of first Neptune and then Jupiter gradually nudged these comets into relatively short orbits that bring them closer to the sun. All previous D/H measurements were of comets that hail from the far more distant Oort cloud, a shell of ice fragments that envelops the solar system. Comets 103P and 45P suggested that researchers may have been hasty in dismissing all comets as Earth’s water source. Perhaps just the Jupiter family comets were responsible.

But then in 2014, the European Space Agency’s Rosetta probe arrived at Comet 67P/Churyumov–Gerasimenko, another Jupiter family comet. As the spacecraft sidled up to the comet, it sampled the water streaming from the comet body and found 67P’s D/H ratio to be staggeringly high — more than three times that of Earth’s oceans (SN: 1/10/15, p. 8).

“Each new comet measurement is giving us a different picture,” says Karen Meech, a planetary scientist at the University of Hawaii in Honolulu. The Rosetta results show that even among a single family of comets, there is incredible diversity in water composition. “Comets formed over a huge range of distances, so it’s no surprise that there’s a huge range in D/H,” she says.

But even if some comets have an Earth-like D/H ratio, it’s still really hard to get comets to hit our planet in the first place. “Any comet that’s going to bash into Earth has to get past this really big linebacker of Jupiter,” says planetary scientist Sean Raymond of the Laboratoire d’Astrophysique de Bordeaux in France. Jupiter has a tendency to take comets that come too close and fling them out of the solar system. The few that do end up on Earth-crossing orbits don’t stay there for long.

“The comet only has a certain number of tries to get in close and either hit Earth or get scattered on to another orbit,” Raymond says.

So Jupiter’s gravity may be too big a hurdle for comets to overcome. But it may be just the ticket for flinging asteroids at the inner planets.

A more ‘tack’-ful approach
In 2011, a team of researchers including Raymond were tackling a different problem: Why is Mars so small? There should have been plenty of raw material available 4.6 billion years ago to turn Mars into a planet closer in size to Venus or Earth. But Mars is just about half Earth’s diameter and about one-tenth its mass. One possible explanation is that something prematurely robbed the nascent Red Planet of its building blocks.

One solution, known as the Grand Tack model, describes a solar system far less sedate than the one we inhabit today (SN Online: 3/23/15). In the Grand Tack scenario, Jupiter and Saturn stride back and forth across the solar system like schoolyard bullies, hurling rocks at and stealing food from the other planets. The gas that encircled the sun dragged Jupiter and then Saturn inward. Once Jupiter arrived at about the current orbit of Mars, a gravitational tug from Saturn flung both back out from where they came (the “tack” in “Grand Tack”).  Jupiter’s encroachment on the inner solar system carved a gap in the debris field from which the rocky planets were forming, depriving Mars of raw ingredients.
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Along with Earth, a couple of dwarf planets and several moons have shown evidence of water, in one form or another. Their potential to support life varies.
The same planetary tango that robbed Mars of resources might also explain how icy asteroids pummeled Earth. As Jupiter and Saturn wandered back out, their gravity latched on to asteroids that formed beyond the snow line — the boundary beyond which temperatures are low enough for ice to form — and flung them inward. About 1 percent of these ice-infused boulders, known as C-type asteroids, were dropped into the outer regions of the asteroid belt. But for every C-type asteroid relocated to the belt, at least 10 were sent careening into the region where the rocky planets were materializing.

This bombardment of asteroids a few million years after the start of the solar system could have easily delivered enough ice — locked inside the rocks, safe from the sun’s heat — to account for Earth’s oceans, computer simulations indicate. Water makes up to about 20 percent of the mass of some of these asteroids. On Earth, despite having more than 70 percent of its surface blanketed in blue, water accounts for only 0.023 percent of the planet’s mass. Compared with some asteroids, Earth is positively parched.

The Grand Tack nicely explains the formation of Mars, the layout of the asteroid belt and the delivery of water to Earth via icy asteroids. But Raymond stresses that it’s just one way to match all the data. “It’s an evolution of thinking,” he says. “It’s not meant to be a final solution.”

The same D/H ratio that exonerated comets is now pointing a finger at these asteroids. In 2012, Alexander and colleagues concluded in the journal Science that the bulk of Earth’s water arrived via bodies similar to a class of meteorites known as CI carbonaceous chondrites. Researchers think that these meteorites, which were knocked off asteroids that formed beyond Jupiter, are among the oldest objects in the solar system.

Alexander’s research, along with that of many others, builds a strong case for a chemical match between Earth’s water and chondrites’ water. But it doesn’t address when the water arrived. Brown University geologist Alberto Saal argues that part of the answer lies on the moon.

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The bounty of lunar samples brought to Earth by Apollo astronauts included volcanic glass hauled in during the Apollo 15 and 17 missions. The glass formed from rapidly cooling magma that was spat out from the moon’s interior long ago. In 2013, Saal and colleagues reported in Science that the D/H ratio of water trapped within the glass matched that measured in both Earth’s oceans and Alexander’s carbonaceous chondrites (SN: 6/29/13, p. 8). Saal’s findings suggest two things: Earth and the moon have a common source of water and the water was already here when the moon formed.

The moon started with a literal bang. A planet the size of Mars is thought to have smashed into Earth toward the end of our planet’s formation. The collision blasted part of Earth, as well as the unfortunate interloper, into a ring of vaporized rock that encircled Earth before sticking together to build the moon (SN: 7/12/14, p. 14). Water must have been present at the time of impact for it to be sealed into the moon, Saal notes, or it at least arrived before the moon’s surface had time to cool and solidify. This puts water near Earth about 150 million years after the start of the solar system. But based on the moon data alone, we can’t say how much earlier, says Sune Nielsen, a geologist at the Woods Hole Oceanographic Institution in Massachusetts.
To narrow in on a more precise time for water’s arrival, researchers have turned to the asteroid Vesta. Or, more specifically, meteorites nicked off Vesta after the asteroid got whacked by another space rock. Woods Hole geologist Adam Sarafian, Nielsen and colleagues analyzed small amounts of water trapped within minerals of apatite locked inside a sample of Vesta meteorites. The team reported last fall in Science that the D/H ratio of the meteorites’ water matched Earth’s. That discovery implies that whatever delivered Vesta’s water brought along Earth’s as well and that this water had to have arrived before Vesta finished forming (SN Online: 11/1/14).

That finding pushes the influx of water back, possibly as early as 8 million years after the start of the solar system. This is the oldest stockpile of water ever dated in the solar system, Nielsen says. These observations place water in the inner solar system well after Jupiter and Saturn were on the prowl, lobbing asteroids around the solar system.

Nailing down how and when water arrived at Earth is about more than just understanding how our planet was built. “If you have to have some sort of external delivery mechanism for getting water to terrestrial planets,” says Alexander, “it becomes harder to make a habitable planet.” Rocky planets forming around other stars will face the same problem that Earth faced. These planets in the habitable zones of their stars, while able to support liquid water on their surfaces, develop in dry environments and need to have ice sent in from farther out. Did Earth get lucky by having Jupiter and Saturn as neighbors, or are there other ways to move water around?

Just because Earth formed one way doesn’t mean all habitable planets must follow the same path. “I would be cautious,” Nielsen says, about saying that gas giants are the only way to bring water to rocky planets.

In fact, gas giants may even be a hindrance. “Jupiter and Saturn just screw things up,” says Raymond. Their gravity is strong enough that they tend to kick asteroids and comets right out of the solar system. If Jupiter and Saturn didn’t exist, he notes, Earth’s gravity could have stolen 10 times as much water from the outer edge of the asteroid belt. In the absence of giant planets, water delivery could happen naturally as planets pull in debris from different parts of the solar system. Recent observations from the Kepler space telescope suggest that planets the size of Jupiter are relatively uncommon around other stars. Perhaps most habitable planets do just fine on their own.

If that’s the case, then maybe the galaxy is teeming with ocean worlds waiting to be discovered. “From my point of view,” Raymond says, “having water on a planet like Earth is an everyday occurrence.”

WET AND WILD Earth may have Jupiter and Saturn to thank for sending it water way back when. The two gas giant planets did a gravitational dance with the sun and each other that sent them hurling in then back out to the outer solar system. In reaction, a bunch of icy asteroids shot into the inner solar system, pummeling early Earth and bringing it water, as shown in this animation. Credit: Drawings by Helen Thompson; Images courtesy of NASA; Narrated and produced by Helen Thompson and Ashley Yeager

This article appears in the May 16, 2015, issue with the headline, “Water, water everywhere: Every bit of Earth’s H2O was delivered by space rocks, but which ones?”

Editor’s note: This story was corrected on May 18, 2015. A caption incorrectly referred to hydrogen molecules, instead of hydrogen atoms. The Water Here and There slideshow was corrected and updated on May 20.

Wandering planets, the smell of rain and more reader feedback

Free-range planets
Astronomers are puzzling over some space oddities: planets that don’t orbit stars. In “Wandering worlds” (SN: 4/4/15, p. 22), Ashley Yeager explored how these lonely rogues may alter the definition of a planet.

Tim Geho wanted to know more about how scientists locate homeless worlds. “Where does the light come from that allows rogue planets to be seen, either directly or via gravitational lensing?” he asked. “Is there some sort of fluorescence or luminescence involved or is [light] reflected from distant suns?”
Some rogues can be imaged directly because big planets can emit their own heat, Yeager says. Telescopes detect this heat as infrared light. Identifying a planet with gravitational lensing is also possible. In this case, astronomers use light from a distant star to infer the existence of a planet. First they track the movement of the star. From the viewpoint of Earth, when the star passes behind some unseen object, the hidden object’s gravity will bend the star’s light. How much the object bends the light reveals the object’s mass. If the mass is similar to the mass of a planet, then astronomers assume that the unseen object is a planet.

Readers also had their own suggestions for what to call these rogues. Jeff Barry jokingly proposed naming them “nibirus,” after the mythical doomsday planet that is supposed to crash into Earth. John Turner commented, “Some sources refer to these nomadic bodies as ‘planemos.’ I notice we’re avoiding using that word in this article, though it’s been used in Science News pieces in the past. What gives?”
Planemo never became widely used in the astronomy community, according to Penn State astronomer Kevin Luhman . He suggests sticking with brown dwarf, while others, like Michael Liu at the University of Hawaii in Honolulu, prefer the term free-floating planet.
New thoughts on old tools
Developing new categories for types of stone tools could help anthropologists craft a more accurate view of hominid evolution, Bruce Bower reported in “Reading the stones” (SN: 4/4/15, p. 16).

Discussions on Facebook and Twitter centered on how difficult it would be to re-create some of the tools. Some readers, like Grink, declared confidently, “I can make that.” Others thought the process would be challenging. “It’s a very difficult technique,” wrote Shashank Ac. “Most modern humans would not last a day in the Stone Age.”

Mark S. took the idea a step further, suggesting a Paleolithic reenactment week: “Have the specialists get together and try to hunt, butcher and live as putative Stone Age peoples would. It would probably shed all sorts of light on what tools were really important and under what conditions. Anyone caught ordering pizza would lose their publication rights.”

The scent of rain
Andrew Grant explained how falling water drops can kick soil chemicals into the air, creating that well-known poststorm earthy aroma, in “Why rain smells like that” (SN: 4/4/15, p. 5).

The story confirmed what reader Bo Grimes had long suspected: “Ever since I first noticed the phenomenon as a child, I assumed chemicals were released from the soil, though I probably thought of it in terms of splashed dirt.” Commenter Zk10 wrote, “For whatever reason, the earthy, natural smell of raindrops on hot sand has a wonderful calming effect on me. These smells are so faint you do not even realize they are there. You just feel better. Nice to know the science behind it.”

In “An oil spill’s aftermath” (4/18/15, p. 22), U.S. District Judge Carl Barbier’s ruling about the amount of oil released in the 2010 Deepwater Horizon spill in the Gulf of Mexico was expressed incorrectly. The judge ruled that 4 million barrels of oil exited the reservoir but that, after accounting for oil collected at the site, 3.19 million barrels was discharged into the Gulf.

Cancerous clams and other sci-fi fodder

I blame my love for science fiction mostly on my mother, although my older brother Nathaniel probably should also take some of the heat. Both were voracious readers, leaving piles of books around the house, most of them sci-fi, that I couldn’t avoid escaping into.
Fans of science fiction will find a few items in this issue sure to trip the imagination. First, Tina Hesman Saey describes a discovery akin to something out of Alien: roving cancer cells that move from victim to victim, sneaking into others’ bodies to produce more of themselves. Saey, a lover of science fiction herself, calls it “cancer as parasite” or — as one researcher put it — extreme out-of-body metastasis.
Of course, this contagious cancer attacks clams, not people. But biologically, it’s pretty far-out. The leukemia-like disease is not, as was initially thought, caused by a virus. Jumping genes — bits of DNA that move around a chromosome, embedding themselves in places that can trigger cancers — may play some role. These genes revealed that clams from Maine to Maryland have the exact same malignancy — and that the cancer cells are genetically distinct from the clams’ own cells.

It’s the third example of contagious cancer in the animal world, but it’s the only one with no apparent direct contact between the carriers. What if there are other, similar types of cancers that we don’t know about? “That’s scarier to me than any virus,” says Saey. And good fodder for a thriller.

Also seemingly out of the pages of a novel: new drugs of abuse, designed by chemists to mimic illicit drugs but to evade legal restrictions, with some scary effects, as science writing intern Kate Baggaley describes. Or, see Christopher Crockett’s report about the effort to trace the origin of Earth’s water, which apparently was imported from some extraterrestrial source.

For a taste of actual sci-fi, see my brief review of the movie Ex Machina. It’s no Star Wars, but it does what some of the best science fiction does: uses futuristic technology to explore bigger, broader issues involving humans and society. It also offers a bit of an escape.

Ivory listings found on Craigslist as elephant poaching continues

Many of the world’s largest herbivores are threatened with extinction, scientists reported last week in Science Advances. Some of them, such as giraffes and zebras, are at risk because they are hunted for their meat. But elephants, which also make the threatened list, are prized not for their flesh but for their two large ivory tusks. For millennia, people have used ivory for everything from piano keys to false teeth to figurines. And despite plastic having long ago replaced ivory for commonplace items like buttons, trade in ivory has tripled since 1998 largely due to rising demand in Asia.

That trade thrives in some unlikely places. The International Fund for Animal Welfare, for instance, recently found hundreds of pieces of ivory worth millions of dollars being advertised on Craigslist within the United States — despite the site’s policy of prohibiting trade in animal parts. Craigslist responded to the report by adding ivory to its list of prohibited items, but IFAW notes that the list is pretty easy to ignore. IFAW recommends making those rules more visible and automatically alerting Craigslist staff when someone lists ivory or other elephant products on the site. But who knows how effective that will be. (And another recommendation to implement search filtering that would prevent people from searching for the term “ivory” is probably a non-starter — people selling ivory-colored products, such as wedding dresses, are sure to object.)
After IFAW discovered ivory objects for sale on eBay and Etsy, those companies began working with law enforcement to reduce the wildlife trade on those sites. And IFAW would like Craigslist to follow suit.

But the United States isn’t really the big problem — it’s Asia, and particularly China. Not only is ivory incredibly popular there, but there’s actually a subset of wealthy people who are stocking up on products made from elephants and other endangered species as investments, banking on extinction to make those products more valuable in the near future.

I was pleased to see last year that former NBA star Yao Ming has taken up the elephant cause and now campaigns against the ivory trade in China. His previous work with the group WildAid led to a decline in popularity of shark fin soup and a reduction in shark fin sales. Hopefully he will be as influential with ivory because as long as ivory is in demand, people will be willing to kill elephants so they can take home a tidy profit.

For the African elephant, there may be yet another problem: There is no “African elephant.” There are actually two species of African elephant, forest (Loxodonta cyclotis) and savannah (L. africana), and many conservation groups don’t differentiate, Alfred Roca of the University of Illinois at Urbana-Champaign and colleagues noted in the February Annual Reviews Animal Biosciences. Grouping all the African elephants together and assuming that all the populations are interchangeable puts both species at risk, the researchers warn. “It’s like saying, ‘We increased the lion population, which will more than make up for the fact that tigers are going extinct,’” Roca said in a statement.

Will there be any elephants left when I am old and gray? With the rate at which poachers are killing the animals for their ivory — 100,000 were killed in just three years — and inadequate plans for saving the creatures, I worry that the answer to my question increasingly looks like “no.”

Possible nearest living relatives to complex life found in seafloor mud

Cold mud from the seafloor has revealed signs of a new group of microbes that could be the nearest living relatives yet found to the domain of life that includes people and other creatures with fancy cell structures.

That mud carries DNA of a previously unknown and unusual phylum of one-celled microbes, researchers report online May 6 in Nature.

The microbes in this newly named Lokiarchaeota phylum carry the basic DNA of one-celled life called archaea, sisters to the domain of bacteria. Yet they possess roughly 100 genes that resemble those in eukaryotes, organisms with intricate structures in their cells.
“What was very surprising was the type of function of these genes,” says paper coauthor Thijs Ettema of Uppsala University in Sweden. What the genes do in Lokiarchaeota is still a matter of hypothesis. But in eukaryotes, many of these genes help with tasks not observed in archaea, such as changing cell shape and controlling internal compartments called vesicles.
The discovery of Lokiarchaeota could intensify debates about how living cells got complex. In recent decades, biologists largely embraced a broad view that divided living organisms into three vast domains: Two — archaea and bacteria — have single cells with no nuclei holding DNA or little structures tucked into membranes.

The third domain — eukaryotes — packages DNA inside cell nuclei and furnishes cells with internal nuggets such as mitochondria that specialize in handling energy. How such elaborate cells arose has puzzled biologists since they have not found clear-cut intermediate forms that suggest the evolutionary steps.

The new find has “genes that might provide a very good starting point to becoming eukaryote,” says James McInerney of the National University of Ireland Maynooth. It strengthens a hypothesis, called the ring of life, that eukaryotes arose not from a single ancient lineage but rather by mingling genes from two kinds of less-structured cells.

This hypothesis is especially promising in light of the discovery of Lokiarchaeota genes that might allow these organisms’ cell membranes to engulf other cells, says evolutionary biologist Mary O’Connell of Dublin City University. One objection to the ring-of-life idea has been the need to explain how genetic merging took place when neither archaea nor bacteria appear able to swallow other organisms. The new phylum, however, might have managed.

It took extreme feats of computing to discover the new genetic mix, Ettema says. Researchers extracted DNA from promising bits of mud in a sediment core coaxed from the ocean floor more than two kilometers deep along the Arctic Mid-Ocean Ridge. The researchers censused the DNA fragments with a computer program that sorted bits into separate kinds of life.

The Lokiarchaeota showed up as a blend of genes, some distinctive to archaea and others resembling those from eukaryotes. The more eukaryote-like genes aren’t likely to be genetic material snitched from full-fledged eukaryotes, Ettema says. Microbes do snitch, but these genes were scattered among bona fide archaea DNA instead of appearing in chunks, as stolen goods do. And though similar, they were not entirely like eukaryote genes.

Since these conclusions are based on computer analysis of DNA, “we have huge gaps in our knowledge of what these beasts actually are,” McInerney says. “There is a lot of work to do to try to really understand if their relatives 2 billion years ago were important for formation of the eukaryotic cell.”

‘Black Hole’ traces 100 years of a transformative idea

Almost a century before Einstein was born, the English polymath John Michell speculated that a star of immense mass could exert enough gravitational force to imprison light. Michell’s insight marked the origin of an idea that was demonstrated in reality only in the 20th century, in the astrophysical offspring of Einstein’s general relativity known as the black hole.

In Black Hole, Marcia Bartusiak, an acclaimed science writer, tells the story of black holes as they emerged from studies of Einstein’s equations, focusing primarily on the period from the 1950s to the 1970s. Though first implied by the work of Karl Schwarzschild in 1916 — just months after Einstein had completed his theory — black holes weren’t seriously investigated until 1939, in a paper by J. Robert Oppenheimer and Hartland Snyder. The two showed that rather than just a heavy star that held light close, a black hole represented the disappearance of the star — its mass crushed to nothingness, leaving only the mass’s gravity behind.
World War II then stalled black hole research until the 1960s. During that decade various newly discovered astrophysical phenomena, such as quasars, forced physicists to revive general relativity, a theory that had been mostly neglected for decades. Gravitational collapse of matter to form a black hole, as implied by Einstein’s theory, turned out to be essential in explaining quasars. Although John Archibald Wheeler is given credit for coining the name black hole in 1967, Bartusiak points out that the term had already been in print journalistically in 1964, in Life magazine (January 24 issue) and a week earlier in this magazine, then called Science News Letter (1/18/64, p. 39).

Black Hole is engaging and lively, weaving in personal drama (tensions between Oppenheimer and Wheeler, for instance) with a clear account of the underlying science. Bartusiak also highlights the role black holes played in capturing the public imagination and fueling interest in the mysteries of the cosmos.

She does not extend the story through the explosion of black hole research from the 1980s onward. But she does briefly discuss black holes’ importance in many fundamental aspects of physical theory today, from their role in creating gravitational waves to their connections with the mysteries of quantum physics. Perhaps that story can be treated more fully later, after those mysteries have been solved and the offspring that their solutions imply are given clever names.

Here are experts’ answers to questions about COVID-19 vaccines for little kids

Four weeks ago, the U.S. Centers for Disease Control and Prevention signed off on COVID-19 vaccines for young children. Days later, doctors’ offices and clinics began rolling out shots for babies and toddlers.

In Portland, Ore., a clinic featuring bubbles, toys and a dance party delivered more than 1,100 shots in two days. In Arizona, more than 2,000 kids under 5 have received their first dose in about three weeks. Over the same time period in Fayetteville, Ga., one practice has given out roughly 100 doses to young kids.
As of July 14, nearly 400,000 kids under 5 have received at least one dose, the CDC reports. That’s about 2 percent of eligible children in this age group.

Pediatrician Eliza Hayes Bakken has seen an initial rush of parents who signed up for appointments as soon as the vaccines became available. “There’s a huge push of families that want to be in that first group that’s vaccinated,” says Bakken, who treats kids at Oregon Health & Sciences University Doernbecher Children’s Hospital in Portland. She suspects demand will soon taper off, following a pattern pediatricians have seen with vaccinations in older age groups.

Getting young kids vaccinated may be a long, slow haul, says Adrianne Hammershaimb, a pediatric infectious disease specialist at the University of Maryland School of Medicine in Baltimore. About half of U.S. parents with children under 4 said they were likely to get their kids the shot, her team reported last month in the Journal of the Pediatric and Infectious Diseases Society. That number is “lower than we’d like, but it’s not surprising,” she says.

Only about 55 percent of U.S. adults surveyed say COVID-19 vaccination has been extremely or very effective at limiting the coronavirus’ spread, the Pew Research Center in Washington, D.C., reported on July 7. In Hammershaimb’s experience, the issue isn’t that most parents are anti-vaxxers or mistrust all vaccines. Rather, “parents are genuinely concerned about the unknown,” she says. There’s a lot of misinformation out there, she notes, and people are trying to figure out what’s best for their kids.

As BA.5 continues to spark cases (now accounting for some 65 percent of new infections in the United States), parents are talking to doctors about COVID-19 risks, vaccine safety and vaccination timing. Here, Hammershaimb and three other pediatricians answer some common questions they’ve been getting.

Is COVID-19 really a problem for kids?
“This is one big question we get a lot,” Hammershaimb says. Kids are just as likely to catch COVID-19 as adults, though cases tend to be milder. Half of kids infected may have no symptoms at all.

The disease also tends to be deadlier for adults than children. In people ages 55 and older, COVID-19 is the third leading cause of death in the United States, scientists reported July 5 in JAMA Internal Medicine. But COVID-19 can hit kids hard, too. It ranks as the eighth leading cause of death in people 19 and under in the United States.
“You hear on TV that COVID is not a big deal for kids,” says Sara Goza, a pediatrician in Fayetteville, Ga., who served as president of the American Academy of Pediatrics in 2020. “That’s a little bit shocking.” In her practice, she’s seen infected children develop long COVID and chronic fatigue. “This disease is not without its complications,” she says.

Bakken’s 9-year-old son caught COVID-19 in 2020, before the vaccine came out. His case wasn’t particularly serious, but he did have long-term effects. He had to take more medication to control his asthma and be extra cautious playing sports. That may seem minor, Bakken says, but it didn’t feel that way for her son. “It affected his daily life.”

What are the side effects of COVID-19 vaccines?
Parents taking their young kids to get the shot can expect to see side effects similar to those common in other childhood vaccines. Fatigue, fussiness, redness at the injection site ​​— those are signs the body is responding to the vaccine like it’s supposed to, Bakken says. Some kids may have no side effects, and that’s OK, too, she says.

Vaccine safety is another topic parents have questioned (something that also came up in a recent Science News Twitter poll). Clinical trials and real-world data suggest the vaccines are safe for kids and adults, Bakken says. “Adverse events are exceedingly rare — much more rare than complications from COVID itself.”
Take myocarditis, the rare heart inflammation condition sometimes seen after getting Pfizer’s or Moderna’s mRNA COVID-19 vaccines. In boys between the ages of 12 and 17, myocarditis crops up in roughly 1 out of 10,000 following vaccination, scientists reported July 13 in the BMJ.

But teen boys are up to six times more likely to experience heart complications after COVID-19 infection compared with after vaccination, CDC scientists reported in April. In younger boys, ages 5 to 11, heart complications following vaccination are even more rare. And in most people with myocarditis following vaccination, symptoms improve quickly and the heart fully recovers.

Hammershaimb is keeping an eye on CDC and U.S. Food and Drug Administration monitoring systems that track potential adverse events to the vaccine. If anything concerning comes up, she says, ”we can intervene, halt the vaccination program, and take a close look at any cases that are reported.” Ultimately, she says, parents need to weigh the hypothetical risk of a rare adverse reaction against the known risks of COVID-19 infection.

Should parents wait until the fall to vaccinate their kids?
No, Hammershaimb says. She encourages parents to sign their kids up for their shots this summer, so they’ll head into fall with some coronavirus protection already built up. It’s possible that COVID-19 boosters targeting the omicron variant may be available as the school year kicks off, but that doesn’t mean parents should wait, she says. “We want kids to be as protected as they can be when they go back to the classroom.”

Sophie Katz, a pediatric infectious disease doctor in Nashville, agrees. Though the current vaccines’ ability to prevent omicron infection in kids seems to wane rapidly, the shots continue to be effective against hospitalization, she wrote in a JAMA editorial in May. And a study of kids in Israel who had received the Pfizer vaccine found that two doses offered moderate protection against the original omicron variant, scientists reported in the New England Journal of Medicine on June 29.

Katz’s 13-month-old baby has already had COVID-19, but she says, “I am 100 percent going to get her vaccinated.” For Katz, it’s a matter of protecting her child from severe disease. “I will do anything to keep my daughter out of the hospital.”