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Einstein’s theory of general relativity unveiled a dynamic and bizarre cosmos
Albert Einstein’s mind reinvented space and time, foretelling a universe so bizarre and grand that it has challenged the limits of human imagination. An idea born in a Swiss patent office that evolved into a mature theory in Berlin set forth a radical new picture of the cosmos, rooted in a new, deeper understanding of gravity.
Out was Newton’s idea, which had reigned for nearly two centuries, of masses that appeared to tug on one another. Instead, Einstein presented space and time as a unified fabric distorted by mass and energy. Objects warp the fabric of spacetime like a weight resting on a trampoline, and the fabric’s curvature guides their movements. With this insight, gravity was explained.
Einstein presented his general theory of relativity at the end of 1915 in a series of lectures in Berlin. But it wasn’t until a solar eclipse in 1919 that everyone took notice. His theory predicted that a massive object — say, the sun — could distort spacetime nearby enough to bend light from its straight-line course. Distant stars would thus appear not exactly where expected. Photographs taken during the eclipse verified that the position shift matched Einstein’s prediction. “Lights all askew in the heavens; men of science more or less agog,” declared a New York Times headline.
Even a decade later, a story in Science News Letter, the predecessor of Science News, wrote of “Riots to understand Einstein theory” (SN: 2/1/30, p. 79). Apparently extra police had to be called in to control a crowd of 4,500 who “broke down iron gates and mauled each other” at the American Museum of Natural History in New York City to hear an explanation of general relativity.
This article is an excerpt from a series celebrating some of the biggest advances in science over the last century. For an expanded version of the story of the universe, visit Century of Science: Our wild universe.
By 1931, physicist Albert A. Michelson, the first American to win a Nobel Prize in the sciences, called the theory “a revolution in scientific thought unprecedented in the history of science.”
But for all the powers of divination we credit to Einstein today, he was a reluctant soothsayer. We now know that general relativity offered much more than Einstein was willing or able to see. “It was a profoundly different way of looking at the universe,” says astrophysicist David Spergel of the Simons Foundation’s Flatiron Institute in New York City, “and it had some wild implications that Einstein himself didn’t want to accept.” What’s more, says Spergel (a member of the Honorary Board of the Society for Science, publisher of Science News), “the wildest aspects of general relativity have all turned out to be true.”
What had been masquerading as a quiet, static, finite place is instead a dynamic, ever-expanding arena filled with its own riot of space-bending beasts. Galaxies congregate in superclusters on scales vastly greater than anything experts had considered before the 20th century. Within those galaxies reside not only stars and planets, but also a zoo of exotic objects illustrating general relativity’s propensity for weirdness, including neutron stars, which pack a fat star’s worth of mass into the size of a city, and black holes, which pervert spacetime so strongly that no light can escape. And when these behemoths collide, they shake spacetime, blasting out ginormous amounts of energy. Our cosmos is violent, evolving and filled with science fiction–like possibilities that actually come straight out of general relativity.
“General relativity opened up a huge stage of stuff for us to look at and try out and play with,” says astrophysicist Saul Perlmutter of the University of California, Berkeley. He points to the idea that the universe changes dramatically over its lifetime — “the idea of a lifetime of a universe at all is a bizarre concept” — and the idea that the cosmos is expanding, plus the thought that it could collapse and come to an end, and even that there might be other universes. “You get to realize that the world could be much more interesting even than we already ever imagined it could possibly be.”
An expanding picture
Einstein’s equations of general relativity were a wellspring from which our current view of the cosmos has flowed. That the theory continues to supply so many rich questions is part of what makes it “just incredible,” says David Spergel, an astrophysicist at the Simons Foundation’s Flatiron Institute in New York City. Over the last century, we’ve detected cosmic beasts that defy the imagination. We’ve also learned some crucial facts about our cosmos: The universe is expanding, and at an accelerating rate. The universe began with a bang 13.8 billion years ago. And mysterious forms of matter and energy are shaping the cosmos in unexpected and largely unknown ways. Read about some of the milestones in our expanding picture, including Vera Rubin’s contributions.
General relativity has become the foundation for today’s understanding of the cosmos. But the current picture is far from complete. Plenty of questions remain about mysterious matter and forces, about the beginnings and the end of the universe, about how the science of the big meshes with quantum mechanics, the science of the very small. Some astronomers believe a promising route to answering some of those unknowns is another of general relativity’s initially underappreciated features — the power of bent light to magnify features of the cosmos.
Today’s scientists continue to poke and prod at general relativity to find clues to what they might be missing. General relativity is now being tested to a level of precision previously impossible, says astrophysicist Priyamvada Natarajan of Yale University. “General relativity expanded our cosmic view, then gave us sharper focus on the cosmos, and then turned the tables on it and said, ‘now we can test it much more strongly.’ ” It’s this testing that will perhaps uncover problems with the theory that might point the way to a fuller picture.
And so, more than a century after general relativity debuted, there’s plenty left to foretell. The universe may turn out to be even wilder yet.
Ravenous beasts
Just over a century after Einstein unveiled general relativity, scientists obtained visual confirmation of one of its most impressive beasts. In 2019, a global network of telescopes revealed a mass warping spacetime with such fervor that nothing, not even light, could escape its snare. The Event Horizon Telescope released the first image of a black hole, at the center of galaxy M87 (SN: 4/27/19, p. 6).
“The power of an image is strong,” says Kazunori Akiyama, an astrophysicist at the MIT Haystack Observatory in Westford, Mass., who led one of the teams that created the image. “I somewhat expected that we might see something exotic,” Akiyama says. But after looking at the first image, “Oh my God,” he recalls thinking, “it’s just perfectly matching with our expectation of general relativity.”
For a long time, black holes were mere mathematical curiosities. Evidence that they actually reside out in space didn’t start coming in until the second half of the 20th century. It’s a common story in the annals of physics. An oddity in some theorist’s equation points to a previously unknown phenomenon, which kicks off a search for evidence. Once the data are attainable, and if physicists get a little lucky, the search gives way to discovery.
In the case of black holes, German physicist Karl Schwarzschild came up with a solution to Einstein’s equations near a single spherical mass, such as a planet or a star, in 1916, shortly after Einstein proposed general relativity. Schwarzschild’s math revealed how the curvature of spacetime would differ around stars of the same mass but increasingly smaller sizes — in other words, stars that were more and more compact. Out of the math came a limit to how small a mass could be squeezed. Then in the 1930s, J. Robert Oppenheimer and Hartland Snyder described what would happen if a massive star collapsing under the weight of its own gravity shrank past that critical size — today known as the “Schwarzschild radius” — reaching a point from which its light could never reach us. Still, Einstein — and most others — doubted that what we now call black holes were plausible in reality.
The term “black hole” first appeared in print in Science News Letter. It was in a 1964 story by Ann Ewing, who was covering a meeting in Cleveland of the American Association for the Advancement of Science (SN: 1/18/64, p. 39). That’s also about the time that hints in favor of the reality of black holes started coming in.
Just a few months later, Ewing reported the discovery of quasars — describing them in Science News Letter as “the most distant, brightest, most violent, heaviest and most puzzling sources of light and radio waves” (SN: 8/15/64, p. 106). Though not linked to black holes at the time, quasars hinted at some cosmic powerhouses needed to provide such energy. The use of X-ray astronomy in the 1960s revealed new features of the cosmos, including bright beacons that could come from a black hole scarfing down a companion star. And the motions of stars and gas clouds near the centers of galaxies pointed to something exceedingly dense lurking within.
Black holes stand out among other cosmic beasts for how extreme they are. The largest are many billion times the mass of the sun, and when they rip a star apart, they can spit out particles with 200 trillion electron volts of energy. That’s some 30 times the energy of the protons that race around the world’s largest and most powerful particle accelerator, the Large Hadron Collider.
As evidence built into the 1990s and up to today, scientists realized these great beasts not only exist, but also help shape the cosmos. “These objects that general relativity predicted, that were mathematical curiosities, became real, then they were marginal. Now they’ve become central,” says Natarajan.
We now know supermassive black holes reside at the centers of most if not all galaxies, where they generate outflows of energy that affect how and where stars form. “At the center of the galaxy, they define everything,” she says.
Though visual confirmation is recent, it feels as though black holes have long been familiar. They are a go-to metaphor for any unknowable space, any deep abyss, any endeavor that consumes all our efforts while giving little in return.
Real black holes, of course, have given plenty back: answers about our cosmos plus new questions to ponder, wonder and entertainment for space fanatics, a lost album from Weezer, numerous episodes of Doctor Who, the Hollywood blockbuster Interstellar.
For physicist Nicolas Yunes of the University of Illinois at Urbana-Champaign, black holes and other cosmic behemoths continue to amaze. “Just thinking about the dimensions of these objects, how large they are, how heavy they are, how dense they are,” he says, “it’s really breathtaking.”
Spacetime waves
When general relativity’s behemoths collide, they disrupt the cosmic fabric. Ripples in spacetime called gravitational waves emanate outward, a calling card of a tumultuous and most energetic tango.
Einstein’s math predicted such waves could be created, not only by gigantic collisions but also by explosions and other accelerating bodies. But for a long time, spotting any kind of spacetime ripple was a dream beyond measure. Only the most dramatic cosmic doings would create signals that were large enough for direct detection. Einstein, who called the waves gravitationswellen, was unaware that any such big events existed in the cosmos.
Beginning in the 1950s, when others were still arguing whether gravitational waves existed in reality, physicist Joseph Weber sunk his career into trying to detect them. After a decade-plus effort, he claimed detection in 1969, identifying an apparent signal perhaps from a supernova or from a newly discovered type of rapidly spinning star called a pulsar. In the few years after reporting the initial find, Science News published more than a dozen stories on what it began calling the “Weber problem” (SN: 6/21/69, p. 593). Study after study could not confirm the results. What’s more, no sources of the waves could be found. A 1973 headline read, “The deepening doubt about Weber’s waves” (SN: 5/26/73, p. 338).
Weber stuck by his claim until his death in 2000, but his waves were never verified. Nonetheless, scientists increasingly believed gravitational waves would be found. In 1974, radio astronomers Russell Hulse and Joseph Taylor spotted a neutron star orbiting a dense companion. Over the following years, the neutron star and its companion appeared to be getting closer together by the distance that would be expected if they were losing energy to gravitational waves. Scientists soon spoke not of the Weber problem, but of what equipment could possibly pick up the waves. “Now, although they have not yet seen, physicists believe,” Dietrick E. Thomsen wrote in Science News in 1984 (SN: 8/4/84, p. 76).
It was a different detection strategy, decades in the making, that would provide the needed sensitivity. The Advanced Laser Interferometry Gravitational-wave Observatory, or LIGO, which reported the first confirmed gravitational waves in 2016, relies on two detectors, one in Hanford, Wash., and one in Livingston, La. Each detector splits the beam of a powerful laser in two, with each beam traveling down one of the detector’s two arms. In the absence of gravitational waves, the two beams recombine and cancel each other out. But if gravitational waves stretch one arm of the detector while squeezing the other, the laser light no longer matches up.
The machines are an incredible feat of engineering. Even spacetime ripples detected from colliding black holes might stretch an arm of the LIGO detector by as little as one ten-thousandth of the width of a proton.
When the first detection, from two colliding black holes, was announced, the discovery was heralded as the beginning of a new era in astronomy. It was Science News’ story of the year in 2016, and such a big hit that the pioneers of the LIGO detector won the Nobel Prize in physics the following year.
Scientists with LIGO and another gravitational wave detector, Virgo, based in Italy, have by now logged dozens more detections (SN: 1/30/21, p. 30). Most of the waves have emanated from mergers of black holes, though a few events have featured neutron stars. Smashups so far have revealed the previously unknown birthplaces of some heavy elements and pointed to a bright jet of charged subatomic particles that could offer clues to mysterious flashes of high-energy light known as gamma-ray bursts. The waves also have revealed that midsize black holes, between 100 and 100,000 times the sun’s mass, do in fact exist — along with reconfirming that Einstein was right, at least so far.
Just five years in, some scientists are already eager for something even more exotic. In a Science News article about detecting black holes orbiting wormholes via gravitational waves, physicist Vítor Cardoso of Instituto Superior Técnico in Lisbon, Portugal, suggested a coming shift to more unusual phenomena: “We need to look for strange but exciting signals,” he said (SN: 8/29/20, p. 12).
Gravitational wave astronomy is truly only at its beginnings. Improved sensitivity at existing Earth-based detectors will turn up the volume on gravitational waves, allowing detections from less energetic and more distant sources. Future detectors, including the space-based LISA, planned for launch in the 2030s, will get around the troublesome noise that interferes when Earth’s surface shakes.
“Perhaps the most exciting thing would be to observe a small black hole falling into a big black hole, an extreme mass ratio inspiraling,” Yunes says. In such an event, the small black hole would zoom back and forth, back and forth, swirling in different directions as it followed wildly eccentric orbits, perhaps for years. That could offer the ultimate test of Einstein’s equations, revealing whether we truly understand how spacetime is warped in the extreme.
Top 10 science anniversaries to celebrate in 2021
Centuries from now, 2021 will be celebrated as an anniversary year most noted for getting rid of 2020. It will be less remembered as a year featuring a diverse roster of scientific anniversaries, ranging from the 1300th birthday of a prolific writer to the 25th birthday of a celebrity sheep.
Nevertheless, before too much of 2021 passes by, it’s time to name the Top 10 anniversaries worthy of celebration this year — some obscure, some fairly famous, and one that had an unfair advantage helping to make it No. 1.
10. Elizabeth Blackwell, 200th birthday
Born in England in 1821, Blackwell moved with her family to New York in 1832 and a few years later to Ohio, where she became a teacher in a boarding school. After the death of a close friend she began applying to medical schools, acquiring a bunch of rejections until Geneva College sent her an acceptance letter (apparently the faculty sought input from the school’s students, and they voted to accept her as a joke). But she showed up and the college honored its agreement; she became America’s first licensed woman medical doctor. She went to Europe for two years for advanced medical training and returned to the United States and opened a clinic in New York City to serve poor women and children. Eventually, she established a medical college specifically for women before returning to England to practice medicine there. She died in 1910.
9. Jabir Ibn Hayyan, 1,300th birthday
OK, this one is a little shaky, because 721 is just the internet’s best guess for Jabir’s birth year. Besides that, there is some question in the science history literature about whether this guy even actually existed. Nevertheless, he is pretty famous, supposedly having authored thousands of books, focusing on alchemy but also exploring astronomy and astrology, medicine, cosmology and a lot of other fields of early medieval science. He developed many chemical processes useful for metallurgy, dyes, glassmaking and medicine, among other applications.
Experts agree that Jabir could not have written all the books attributed to him; some in fact seem to have been written much later than the time of his death in about 815. It may even be that he was a collective group of authors choosing to write under one name. And his Latinized name, Geber, has been a source of some confusion since a 13th century writer chose that as a pseudonym for writing alchemical treatises.
In any case, the original Jabir, if he existed, was certainly one of his age’s brightest minds. He is considered by some to deserve the title of father of chemistry (at least in the Arabic-speaking world) and also a founder of modern pharmacy. Because one of his books was written in an incomprehensible code, some have thought the word gibberish was derived from Jabir. But modern language experts say that the idea that gibberish comes from Jabir is balderdash.
8. Rosalyn Yalow, 100th birthday
Yalow, born Rosalyn Sussman, described herself as a “stubborn, determined child” and an avid reader who developed an interest in math and chemistry. In college, she was captivated by physics, and she earned a Ph.D. in nuclear physics in 1945. After some time teaching, she turned her research —developing the use of radioactive isotopes for precise measurements of biological chemicals in the body — from hormones and enzymes to vitamins and viruses. That work won her a share of the 1977 Nobel Prize in physiology or medicine. The year before, she was awarded the Lasker Prize for medical research — the first nuclear physicist to receive that honor. She died in 2011.
7. Wilhelm von Waldeyer-Hartz, centennial of death
Waldeyer–Hartz, born in 1836, was a German anatomist, famed in his day as an outstanding teacher and lecturer. He made numerous contributions to the understanding of human anatomy and the terminology for describing it (although some of his anatomical conclusions turned out to be erroneous).
His most noteworthy coinages were chromosome, for the structures containing DNA in the cell’s nucleus, and neuron for nerve cells. He named chromosomes in 1888, before their exact nature was well-known. Similarly, he introduced the term neuron before scientists had even reached agreement on whether such cells existed. Around the end of the 19th century, various studies on nerve tissue had provided clues to its structure; Waldeyer-Hartz summarized the evidence that its building blocks were in fact discrete, individual cells, the neurons.
6. Dolly the Sheep, 25th birthday
No sheep ever made bigger headlines than Dolly the Sheep, when scientists announced her existence in February 1997. (She had been born on July 5, 1996.) Before Dolly, most scientists doubted that a mammal could be cloned from an adult cell, although some cases of cloning from embryonic cells had been reported. But Dolly was cloned by scientists at the Roslin Institute in Edinburgh using a mammary cell from an adult sheep implanted in an egg from a black-faced sheep.
Dolly’s birth instantly made the film Jurassic Park seem more realistic and raised the specter of human cloning, boosting VHS rentals of The Boys from Brazil. Dolly seemed to be a perfectly typical sheep (although the telomeres capping the ends of her chromosomes were a tad shorter than usual) and had several offspring of her own. According to the Roslin Institute, she lived a normal life (except for the occasional media appearance) until infected with a cancer-causing virus during an outbreak in the lab, leading to her death at age 6 in 2003.
5. Ernest Rutherford, 150th birthday
Born in New Zealand in 1871, Rutherford attended the University of Cambridge and soon became the world’s premier experimental physicist (SN: 4/22/11). His early work at McGill University in Montreal established the basic principles of the newly discovered phenomenon of radioactivity. In 1911, at the University of Manchester in England, he deduced the existence of the atomic nucleus in analyzing results of experiments by his assistants Hans Geiger and Ernest Marsden. It was one of the most astounding and significant insights into the ultimate architecture of microscopic nature since the Greeks proposed the idea of atoms.
Later, Rutherford demonstrated the transmutation of one element to another and predicted the existence of a new subatomic particle, the neutron. When he died in 1937, the great atomic physicist Niels Bohr, who had studied under Rutherford at Manchester, remarked that, like Galileo, Rutherford had “left science in quite a different state from that in which he found it.”
4. DNA discovery published, 150th anniversary
Johann Friedrich Miescher, born in 1844 in Basel, Switzerland, went to medical school but chose a career in research rather than clinical practice. Biochemistry was a young science back then, as biologists were just beginning to understand the chemical contents of a living cell and how they interacted to drive cellular activity. A leader in the new field was Felix Hoppe-Seyler at the University of Tübingen in Germany, and Miescher went to work in his lab in 1868.
Miescher soon began to study white blood cells in pus from surgery patients in a nearby clinic. He found that the cell nucleus contained a substance that differed dramatically from the proteins and lipids in the rest of the cell. He called the new substance nuclein, later identified as DNA. Although Miescher made his discovery in 1869, Hoppe-Seyler wasn’t convinced and insisted on repeating the experiments himself, delaying publication until 1871.
Miescher believed that nuclein would turn out to be just as important as proteins. He did not realize that DNA was the carrier of heredity. But he did show that it was found in the sperm cells of many animals, a clue not fully appreciated until 1944, a century after his birth, when DNA was established to be the substance of genes. Miescher died in 1895.
3. Maxwell’s demon, 150th birthday
In 1871, in his book Theory of Heat, James Clerk Maxwell introduced the public to the idea of “a being whose faculties are so sharpened that he can follow every molecule in its course.” This hypothetical creature, later called “Maxwell’s demon” by the physicist William Thomson, was imagined by Maxwell to illustrate a quirk in the second law of thermodynamics.
In one popular version of the second law, hot (fast) and cold (slow) molecules always mix to reach an intermediate temperature. But a demon capable of tracking molecular velocities could sort the fast ones from the slow ones and reverse the normal equalizing of temperature. Such a demon would soon be very wealthy from providing free air conditioning in the summer and free heating in the winter. Maxwell’s point was not that the demon was a lawbreaker, but that the second law was statistical. Its validity depended on the impossibility of keeping track of trillions and trillions of molecules, something no real demon, or human, could manage.
Nevertheless, the demon haunted physicists for decades. In 1929, Leo Szilard claimed that the demon could not break the second law because it needed more energy to make its measurements than it could recover by sorting the molecules. But decades later, IBM physicist Charles Bennett, drawing on work by his IBM colleague Rolf Landauer, showed that the demon could track molecular velocities with as little energy as it wanted; the payback came when the demon had to erase data in its memory to make room for new observations. Erasure of information, Landauer had shown, always requires a minimum amount of energy, putting the second law securely back in the physics lawbook.
2. Hermann von Helmholtz, 200th birthday
Born in Potsdam (in the kingdom of Prussia) in 1821, Helmholtz was one of the 19th century’s most versatile scientists; his name turns up in the histories of multiple scientific fields and specialties. As a youngster, he had an interest in physics, but as that seemed a financially unwise career choice, he went to medical school and studied physiology instead. He was drawn to others who promoted the view that physiology should be based on the principles of chemistry and physics, not the “vital forces” that had been popularly emphasized previously.
After earning his medical degree, Helmholtz served as an army surgeon before becoming professor of physiology at the University of Königsberg. During that time, he composed a groundbreaking paper on the conservation of energy. While at Königsberg, he studied the nervous system, optics and acoustics, especially with regard to the physiology of the senses. He moved on to the University of Bonn as professor of anatomy and physiology, although he wasn’t very good at anatomy and shifted his attention to the physics of whirlpools in fluids.
After some time at the University of Heidelberg, where he became interested in philosophy, epistemology and the foundations of geometry, in 1871 he was awarded the physics chair at the University of Berlin. At last he could focus on physics, emphasizing the importance of the principle of least action for explaining physical phenomena. He also explored the ramifications of Maxwell’s new theory of electromagnetism, as well as dabbling in chemical thermodynamics and meteorology. By this time, he was recognized as one of Germany’s premier scientists, until his death in 1894.
1. Founding of Science Service, centennial
A century ago, newspaper publisher E.W. Scripps and biologist William Emerson Ritter perceived the need for better science journalism to serve the American public. They joined forces to create Science Service, which began syndicating articles about the frontiers of science to newspapers around the country.
The first week packet of such stories, labeled Science News Bulletin, was dispatched on April 2, 1921. Soon science enthusiasts sought personal subscriptions to Science Service’s weekly news, leading to the birth of Science News-Letter (on March 13, 1922) — a new weekly magazine available by subscription for $5 per year.
Today Science News-Letter is Science News, and Science Service is the Society for Science, but the philosophy is the same: to provide the public with the important news from the world of science in an understandable, yet accurate and authoritative form. Celebrating anniversaries, not part of the original mission, is a bonus.
This ancient sea reptile had a slicing bite like no other
Shortly before a mass extinction ended the Age of Dinosaurs, a reptilian, barracuda-like carnivore with a mouth like a box cutter patrolled the warm seas that once covered swaths of what is now North Africa. A recently described fossil of the ocean-dwelling beast reveals that its bite was unlike that of any of its relatives, in the water or onshore.
The animal was a mosasaur, an extinct, marine reptile related to snakes and monitor lizards. Mosasaurs commonly had piercing, conical teeth for gripping slippery prey or flat, crushing teeth for smashing hard-shelled animals. But this new variety had short, serrated, squarish blades, packed tightly in series to form a knife’s cutting edge. This mouth of razors is unique among mosasaurs, and even within the entirety of the tetrapod lineage, mostly landlubbing vertebrates that include amphibians, reptiles, birds and mammals.
The discovery, described January 16 in Cretaceous Research, suggests that mosasaurs were evolving experimental physical traits and lifestyles right up until their abrupt extinction 66 million years ago.
Phosphate miners in Morocco found the curious fossil: a chunk of upper jaw studded with teeth. The jaw came from a mosasaur living at the very end of the Cretaceous Period. Many mosasaurs were massive predators, some stretching longer than a school bus. But this fossil belonged to an animal just over a meter long, Nick Longrich, a paleontologist at the University of Bath in England, and his colleagues determined.
Longrich says the animal’s small size is interesting, but that’s not what caught his eye. “Those teeth are just unlike anything I’ve seen in a lizard before,” Longrich says. The team named the mosasaur Xenodens calminechari — Xenodens means “strange tooth;” calminechari is Arabic for “like a saw.”
Longrich says the closest match for X. calminechari’s teeth appear to be those of modern-day dogfish sharks, which can “cut large bolts of flesh out as they scavenge,” he says. “Probably these slicing teeth allowed it to process a huge range of foods,” says Longrich, noting that dogfish sharks use their teeth to chop up everything from fish to sea anemones. Despite its small size, X. calminechari may have been able to prey upon quite large animals or scavenge their remains, since it shared its watery home with big fish and cephalopods, as well as orca-sized, long-necked plesiosaurs.
The fossil is “completely bizarre,” says Paulina Jiménez-Huidobro, a paleontologist at the University of Bonn in Germany not involved with this research, noting the teeth may have been used to “slice and dice” crustaceans, shell and all.
She has doubts about the comparison to shark feeding methods and diet based solely on the tooth shape, though, because of fundamental differences between how sharks and mosasaurs bite prey. Shark teeth cut into flesh on jaws that extend outwards towards prey independently of the skull.
“This mechanism does not occur in mosasaurs, even if Xenodens has a shark-like tooth shape,” Jiménez-Huidobro says. “No lizard can do that.”
For Longrich, X. calminechari’sdiscovery helps paint a picture of the late Cretaceous’ tropical seas as teeming with biodiversity before a dinosaur-era-ending asteroid hit Earth (SN: 6/17/20). The ocean ecosystem was thriving at the time, so there may have been dozens of mosasaur species in a single habitat, he says, and they weren’t done producing weird prototypes like Xenodens.
“The mosasaurs were still experimenting with new ways of feeding, new morphologies, new lifestyles just before that asteroid came down,” Longrich says.
Learning more about this nimble, barracuda-like sea lizard will reveal more of the evolutionary experimentation going on at the time, but gaining that understand requires the discovery of more fossil material, which could take a while, Longrich says. In half a dozen years of searching, he’s seen only one fossil of this species.
“Eventually something has to turn up, but it’s a waiting game.”
COVID-19 precautions may be reducing cases of flu and other respiratory infections
Heading into the dead of winter, doctors and scientists have noticed something odd: Missing cases of non-COVID-19 respiratory illnesses, specifically flu and respiratory syncytial virus, or RSV.
“We’re seeing very low numbers of both of these infections, even now, while we’re in the peak season,” says Rachel Baker, an epidemiologist at Princeton University. “We really should be seeing cases go up.”
Instead, positive flu tests reported in December are a little less than one one-hundredth of all of those tallied in December 2019, according to data from the U.S. Centers for Disease Control and Prevention. RSV’s drop in reported cases — to one two-hundredth of those a year earlier — is even bigger.
This dramatic dip is probably due to COVID-19 precautions. The same handwashing and social distancing that can prevent the spread of SARS-CoV-2, the virus that causes COVID-19, can prevent the spread of other viruses and pathogens. But that could mean trouble ahead. A lack of cases ironically leads to a growing population susceptible to infection, so future outbreaks could be larger and more unpredictable.
In a typical year in the United States, RSV hospitalizes an estimated 58,000 children under age 5 and more than 177,000 older adults. “Most people recover in a week or two,” says Benjamin Silk, an epidemiologist at the CDC. “But RSV infections can be serious, especially for infants, older adults and people with certain chronic medical conditions.” Worldwide, 3.4 million children under 5 years old are hospitalized with RSV each year, accounting for about 5 percent of deaths in this age group.
Highly contagious, RSV is transmitted through respiratory droplets, which can remain infectious for more than six hours on hard surfaces. Prevention is rooted in strict hand hygiene — using hand sanitizer or washing with soap and water.
In the United States, RSV season usually starts in the fall, peaking between December and mid-February. This year, there essentially is no peak. In December 2020, the CDC’s National Respiratory and Enteric Virus Surveillance System — which collects voluntarily reported data —reported just 120 RSV cases, compared with 24,280 in December 2019.
“RSV, in particular, is so stable — it does the same thing year after year,” Baker says. “I don’t think there’s much else that could explain [the drop] apart from the COVID-19 phenomena as a whole, particularly the control measures.”
Influenza infections are also down drastically. Flu regularly infects between 3 percent and 11 percent of the U.S. population and is especially deadly for older or immunocompromised people. The CDC estimates that in an average year, flu kills around 36,000 people and hospitalizes almost half a million.
According to the CDC’s lead flu tracker Lynnette Brammer, the adoption of COVID-19 prevention measures in the spring of 2020 coincided with a drop in the percent of positive flu tests from more than 20 percent to less than 1 percent — and that number has stayed low through the fall and now into winter (SN: 9/18/20). In December 2019, the CDC’s clinical lab FluVue reported 50,526 positive flu tests. In December 2020, that number was just 454. Preliminary data suggest this trend is continuing into January, when flu season typically peaks.
Brammer says the numbers of flu tests are steady, so it’s not that people aren’t going to get tested. They just aren’t spreading it around as much.
Dropping diseases
Positive tests for influenza and RSV have dropped drastically since COVID-19 prevention measures were put into place in March 2020.
Positive U.S. flu and RSV tests, October 2019–January 2021
Source: CDC National Respiratory and Enteric Virus Surveillance System, CDC FluView
Some other infections, like parainfluenza, also seem to have declined with COVID-19 prevention measures, but viruses like rhinoviruses continue near their normal season levels. It could be because these viruses, unlike flu and RSV, aren’t as thoroughly destroyed by handwashing and using sanitizers.
This great news comes with a warning, though. Fewer infections means fewer people being exposed and gaining immunity to these viruses, building up a population susceptible to these infections later. That could fuel a deadly rebound in infections post COVID-19, Baker, the Princeton epidemiologist, and her colleagues reported December 1 in Proceedings of the National Academy of Sciences. In the analysis, the team assumed COVID-19 precautions would reduce RSV and influenza infections by 20 percent, but the decrease is proving to be much larger.
“We need to be prepared for offseason outbreaks and potentially large outbreaks,” Baker says.
That’s what’s happening right now in Australia’s New South Wales. Clinical nurse Gemma Saravanos and her colleagues observed a more than 85 percent reduction of positive RSV tests during the peak of their season, between April and June, the team reported in the Lancet in September. But now, after beating back COVID-19 and lifting stringent protective measures, they have a record-breaking offseason RSV outbreak on their hands. In the last two weeks of December 2020, NSW reported more than 6,000 positive RSV tests — during a time they typically have a few hundred. In 2019, the RSV season peaked at around 4,695 detections in May.
“It’s really extraordinarily unusual,” says Saravanos, who works at the University of Sydney. “It’s never been seen before.”
A rebound outbreak might hit the United States, too, Baker says. Australia “could be an interesting foreshadowing of what is to come in the Northern Hemisphere.”
That worries Carla Burroughs, a mother of four and former medic in Mobile, Ala., who has experienced RSV first hand. “The first time I heard of RSV, I was working on an ambulance, and I [transported] a child who passed away [from it],” she says. Then in December 2019, Burroughs’ 3-year-old daughter, Kaylee, caught RSV and was hospitalized for three days. “The second the doctor told us RSV with Kaylee, it just brought flashbacks. It just sent me into such a panic mode; I immediately knew this is going to be bad.”
It did get bad. A week later, Burroughs’ infant twins caught RSV. One, Mackenzie, was intubated for two weeks and stayed in the hospital for over a month. Seeing her daughter struggling to breathe, Boroughs says, “just changed everything. It took more of a toll on me than I expected.”
Burroughs’ children recovered, and she says now the new data show just how important basic hygiene behaviors are to helping prevent the spread of these viruses, saving thousands of lives every RSV and flu season — even without a pandemic. “It’s sad that [the pandemic] is what it came down to,” Burroughs says. “We should have already been doing all these things.”
What do COVID-19 vaccines mean for daily life in the months ahead?
As more COVID-19 vaccines show signs of being able to protect people from getting really sick, they’re fueling hopes that some sense of normalcy is within reach. Two vaccines have been authorized for emergency use in the United States and are slowly getting into arms across the country. And two more vaccine makers have just reported fairly positive results — a crucial step on the path toward adding tools to quell the pandemic.
As a result, people are looking forward to finally being able to safely hug loved ones, travel and go to work, school or the store without fear of falling ill. But the rocky vaccine rollout across the country — plus ensuring enough people are vaccinated to reach herd immunity and slow the virus’ spread — means it’s likely going to take time for such hope to become reality (SN: 10/19/20). Exactly how much time is unclear, though public health experts have said it may take until late summer or fall.
Still, every shot means that the person who received it is less likely to get sick. And every vaccinated person, along with continued public health measures like wearing masks, brings us one step closer to the end of the pandemic and a breath of relief.
Amidst the whirlwind of information about the peril and promise of COVID-19 vaccines, here are answers to some commonly asked questions about the shots.
How many different vaccines are there in the United States?
Two mRNA vaccines — developed by Pfizer/BioNTech and Moderna — are making it into arms across the United States. And the shots could soon be joined by at least one or two others.
Novavax announced January 28 that its vaccine has 89.3 percent efficacy against COVID-19, according to a Phase III clinical trial in the United Kingdom. However, that vaccine is less effective against a coronavirus variant that has emerged in South Africa (SN:1/28/21).
And Johnson & Johnson announced on January 29 that its vaccine had an efficacy of 72 percent against moderate to severe COVID-19 in the United States. That vaccine is also less effective against preventing that level of sickness in people exposed to the variant from South Africa, though it did prevent deaths (SN: 1/29/21).
Johnson & Johnson plans to submit applications for emergency use authorization to the U.S. Food and Drug Administration in early February. It is unclear whether Novavax will do the same, as the company’s clinical trial in the United States is ongoing.
The FDA said the mRNA vaccines were safe when it OK’d their use. Is that still true?
Yes. Health experts have been watching newly vaccinated people closely and so far, the vaccine has proven safe.
“We really have to weigh [vaccine risks] against a very imminent risk [of] becoming infected and becoming sick with this virus that is circulating everywhere,” says Natalie Dean, a biostatistician at the University of Florida in Gainesville. And so far, both Moderna’s and Pfizer’s vaccines come with low risks compared with those of COVID-19.
The FDA required vaccine developers to have two months of safety data from clinical trials before applying for emergency use authorization. The vaccines do have some side effects, including fever, arm soreness, redness at the injection site, headache and feeling sick. Such symptoms are not unexpected, as they are a sign that the immune system is kicking into gear and are common side effects for vaccinations in general.
Some people have had severe allergic reactions to Pfizer’s and Moderna’s vaccines. But all were quickly treated and none died.
Two U.S. Centers for Disease Control and Prevention–led studies found that both vaccines have higher rates of allergic reactions — 11.1 cases per 1 million vaccine doses for Pfizer’s and 2.5 cases per 1 million vaccine doses for Moderna’s — than allergic reactions to the flu vaccine, which is 1.3 cases per 1 million doses. Still, such reactions are “exceedingly rare,” Nancy Messonnier, director of the CDC’s National Center for Immunization and Respiratory diseases said in a Jan. 6 news briefing (SN:1/6/21).
Why is it so hard to get a vaccine?
Vaccine distribution in the United States has been plagued with problems. Not only are limited doses available to people in currently eligible groups but everyone who gets Moderna’s or Pfizer’s vaccines needs two shots for full protection (SN: 12/3/20).
The logistical issues also come in part because each state — sometimes down to the county or town level — is handling the situation in their own way, Barry Bloom, an immunologist at Harvard T.H. Chan School of Public Health, said January 28 in a call with journalists. Who is even eligible for the shots varies from place to place, causing confusion and frustration. Such a local response “is very difficult to coordinate, which I think is a real tragedy and a hindrance to knowing exactly where the vaccines are needed, exactly how many doses should go, which vaccines they have the facilities for,” Bloom said
The situation may change as the Biden administration begins implementing plans to help states fast-track vaccine rollout, including administering at least 100 million doses before April 30 (SN: 1/20/21).
There are also stark disparities among which regions of the world are getting vaccines. The great majority of vaccine doses — more than 39 million — have gone to the world’s richest 49 countries. So while vaccines are hard to come by in places like the United States, it’s even more difficult in countries with lower incomes.
After getting a shot, do we need to continue to wear masks and social distance?
Yes, wearing a mask and keeping distance are still essential, even for individuals who have already gotten a shot.
The vaccines are very effective at preventing people from developing COVID-19 symptoms, but it’s unknown whether vaccinated people could still get infected without having symptoms and unknowingly spread the coronavirus to others (SN: 12/8/20). Not all vaccines stop both disease and transmission. Vaccinations for influenza, pertussis and polio, for example, can stop people from getting severely ill if infected, but those people could still be contagious.
People who have been vaccinated should follow public health guidelines to protect those who have not yet gotten shots, at least until scientists know more about the vaccines and transmission. Also, Pfizer’s and Moderna’s vaccines aren’t 100 percent effective, meaning not everyone who gets vaccinated develops a robust immune response that protects against COVID-19. So, with transmission rates still high in many parts of the world, including the United States, and large swaths of the population still unvaccinated, it’s best to err on the side of caution.
The Johnson & Johnson vaccine reported lower efficacy than Pfizer’s and Moderna’s. Should I get it?
Here are some reasons why it’s worth getting the Johnson & Johnson vaccine if that’s the one available to you.
It was 85 percent effective at preventing people from dying of COVID-19. That’s still a really high level of protection. In clinical trials, vaccine efficacy measures how many fewer cases of disease happen in vaccinated people compared with in unvaccinated people.
“We would be celebrating a seasonal influenza vaccine with 60 percent efficacy,” Jay Butler, the CDC’s deputy director for infectious diseases said January 29 during a news conference sponsored by the Infectious Diseases Society of America. (Flu shots are typically around 40 to 60 percent effective.) “While it’s disappointing compared with the 95 percent efficacy from the Phase III clinical trials of the [Pfizer and Moderna] vaccines… it’s still not something that would make me want to not utilize or receive the vaccine myself,” Butler said.
It’s also a single shot, so people don’t need a second vaccination to get full protection. Besides only needing to get jabbed once, that also means less of a logistical hassle to try and set up multiple appointments.
And if the FDA authorizes Johnson & Johnson’s vaccine for emergency use, that would make millions of additional doses available in the United States and help alleviate dose shortages. That could speed up vaccinations and get us back to normal faster.
I’m vaccinated. Can I spend time with other people?
Yes, but still with proper precautions for now.
Having highly effective vaccines on hand certainly changes the ways we might evaluate risk, Dean says. But since it’s still unknown what the vaccine might mean for transmission, vaccinated people should follow guidelines like masking up around people who haven’t yet gotten a shot and staying physically distanced. So, for instance, a vaccinated employee should still mask up at work if their colleagues and the people they might encounter aren’t vaccinated yet.
But if all members of a group have been fully vaccinated — and it’s been at least a week after the second dose to let the immune system mount optimal protection — there is some room to be more lenient.
“There are things I would be more willing to do once vaccinated,” Dean says. For her, that means spending time outside with a friend who also has been vaccinated. That equation may be different for others.
Vaccination status is only one piece of the puzzle. It’s also important to consider how much transmission is happening in the community or how many people others in the group are in contact with, Dean says, since the vaccines aren’t 100 percent effective.
And for now, it’s best to avoid travel, especially with emerging, more contagious variants, the CDC says. One that originated in the United Kingdom is on track to become the dominant strain in the United States in March (SN: 1/15/21). And the first two cases of a worrisome South Africa strain were detected in South Carolina on January 28. Neither person had traveled nor had connections with each other, suggesting that variant is already circulating in communities.
When will researchers figure out if COVID-19 vaccines can stop transmission?
It’s hard to say.
Some preliminary clinical trial data from Moderna hint that its vaccine might not only protect vaccinated people from developing symptoms, but also prevent infection in general (SN: 12/18/20). If people aren’t getting infected in the first place, then they won’t spread the virus to others. It’s still unclear if that’s the case, however, and clinical trials that could help figure that out are still ongoing, Dean says.
One way that researchers could figure out if vaccinated people are still getting infected but not showing symptoms is by monitoring their blood for immune responses against parts of the virus that aren’t in the vaccine. The primary target of a vaccine-induced immune response is the coronavirus’s spike protein, which helps the virus break into cells (SN: 4/28/20). But if people have antibodies against other parts of the virus, too, it’s a sign that they probably were infected by the real thing.
Even if the vaccines don’t prevent infection, they might still reduce transmission. Vaccinated people who get infected with the coronavirus may have fewer symptoms or carry less virus in their bodies, for instance. So they might be both less infectious and only able to spread the virus for a shorter time. That would require specialized studies to determine, though.
“It’s pretty easy to see if the vaccine is preventing an infection, so if it’s doing a great job against that then we have our answer,” Dean says. But if a vaccine’s protection falls in-between — curbing transmission but not infection — that will take more time to confirm.
What about these new coronavirus variants? Will vaccines protect people from them?
The vaccines appear to provide some protection. Recent studies have shown that antibodies circulating in the blood can still stop some viral variants from getting into lab-grown cells (SN: 1/27/21).
In the lab, antibodies still recognize a coronavirus variant called B.1.1.7 that was first identified in the United Kingdom. Another variant that emerged in South Africa, called 501Y.V2 or B.1.351, appears to pose a tougher challenge for current vaccines, evading some — but not all — antibodies.
Researchers are now getting hints at how that might play out in the real world. While Novavax’s vaccine had an efficacy of 85.6 percent against B.1.1.7 in a clinical trial conducted in the United Kingdom, efficacy dropped to 60 percent against B.1.351 in a South Africa clinical trial. Johnson & Johnson’s vaccine had 57 percent efficacy in South Africa, but did prevent people there from getting severely ill.
The emergence of such variants makes it all the more crucial to bring infection levels down, says Stuart Ray, a virologist and infectious disease physician at Johns Hopkins University. More infections mean more chances for the virus to mutate even more and dodge our defenses. Multiple vaccine makers — including Novavax, Pfizer and Moderna — are designing new vaccines based on the emerging versions of the coronavirus.
But for now, even with effective vaccines, public health measures like wearing masks, social distancing and avoiding crowds are still essential tools to help reduce infections and control the pandemic.
If we still have to wear masks and physically distance, what’s the benefit of getting the shot?
On a personal level, getting vaccinated make it less likely that you’ll get sick and require hospitalization.
Bigger picture, if fewer people are getting severely ill because they are getting vaccinated and because they continue to wear masks and physically distance, that’s fewer people in the overwhelmed health care systems that are already struggling to take care of severely sick COVID-19 patients.
And eventually, once enough people are vaccinated, hugs, travel and other rituals of normalcy will become less perilous. When is unclear, but every vaccination is a step closer.
Staff writer Jonathan Lambert contributed to this story.
One-shot COVID-19 vaccine is effective against severe disease
A single-shot coronavirus vaccine made by Johnson & Johnson is 85 percent effective at preventing severe disease and death, even against new variants of the virus, the company announced in its interim analysis January 29.
The vaccine didn’t fare as well at preventing more moderate cases of COVID-19, particularly in Latin America and South Africa, where variants that spread more easily have arisen. Depending on location, the shot was only 72 percent to 57 percent effective against moderate to severe bouts of the illness.
Other vaccines, particularly the two mRNA vaccines that have emergency use authorization in the United States, have reported levels of overall efficiency of up to 95 percent against the coronavirus (SN: 12/18/20). That discrepancy could make people reluctant to accept a less effective vaccine, Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, said during a Jan. 29 conference call about the results. It shouldn’t, he added.
“If you walk up and say, ‘Well, go to the door on the left and you get 94 to 95 percent [effective vaccine]. Go to the door on the right and get 72 percent.’ What door do you want to go to?’” But what people need to understand, he said, is that real importance of the vaccine is keeping people out of the hospital and preventing the most severe complications of the disease.
That’s what the new vaccine does, Mathai Mammen, global head of research and development for Janssen, Johnson & Johnson’s pharmaceutical division, said during the news conference. “We can prevent COVID, in many cases,” he said. “We can prevent hospitalization. In those that that contract COVID and have moderate disease, [they] have a milder course of disease. Nobody doesn’t benefit from this vaccine.”
Johnson & Johnson’s vaccine uses a common cold virus — adenovirus 26 — that has been altered so that it can’t replicate in the body to cause disease. The adenovirus ferries instructions for making the coronavirus’s spike protein into human cells. Human cells then make the spike protein, triggering the immune system to produce antibodies and fire up cellular immune defenses from T cells, which attack the coronavirus should it be encountered later.
The company has used this adenovirus system to make an Ebola vaccine as well as still-experimental vaccines against Zika, HIV and respiratory syncytial virus, or RSV. Using adenoviruses as carriers, or vectors, has also been used for COVID-19 vaccines made by the University of Oxford with AstraZeneca, the Canadian-Chinese company CanSino, and for the Russian Sputnik V vaccine (SN: 11/23/20; SN: 7/21/20; SN: 8/11/20).
Johnson & Johnson tested their vaccine in 44,325 adults in Argentina, Brazil, Chile, Colombia, Mexico, Peru, South Africa and the United States. Among the participants, 468 cases of COVID-19 arose, the company and U.S. National Institutes of Health each reported in news releases.
Deaths occurred in the placebo group, but none in the vaccine group. But the company declined to give specific numbers of cases and deaths in both groups until it files for emergency use authorization with the U.S. Food and Drug Administration. That filing could come next week.
Effectiveness against moderate to severe disease varied by region, ranging from 72 percent in the United States to 66 percent in Latin America to 57 percent in South Africa. Overall, the vaccine is 66 percent effective at preventing moderate to severe disease. The vaccine was similarly effective in young adults and people 60 and older, and for people with and without underlying health issues, such as obesity, type 2 diabetes and other conditions that increase the risk of complications from COVID-19 (SN: 4/22/20; SN: 3/20/20).
At first glance, the declining effectiveness in Latin America and South Africa might appear discouraging, Mammen said. More transmissible variants of SARS-CoV-2, the coronavirus that causes COVID-19 have been discovered in Brazil and South Africa.
The South Africa variant, known as either 501Y.V2 or B.1.351, has been causing particular concern because of both its increased transmissibility and ability to evade some antibodies that provide protection against the coronavirus. But the vaccine protects against the most severe consequences of the disease even against those variants, Mammen said. “Not a single South African after 28 days post-vaccination ended up needing to go to the hospital. No South African died that was vaccinated.”
The other companies ran their studies at a different stage of the pandemic before the new variants appeared, so the numbers aren’t really comparable, Mammen said. “The pandemic has changed.” Now, “the majority of cases are coming from an evolved set of viruses.”
Novavax, a Gaithersburg, Md.–based company, announced January 28 that its protein-based vaccine prevents illness with 89 percent effectiveness, but was also less effective against the South Africa variant (SN: 1/28/21). The same day, officials in South Carolina announced that two unconnected people with no history of travel had contracted the South Africa variant. That finding probably means the variant is circulating undetected in the state and elsewhere in the country.
Despite lower efficacy, Johnson & Johnson’s vaccine has some advantages over the mRNA vaccines. It is given in a single shot instead of two, so it can vaccinate twice as many people with the same number of doses. It needs to be refrigerated, but not frozen the way those vaccines do (SN: 11/20/20). And the vaccine has milder side effects than the already authorized Moderna and Pfizer vaccines. Some people had fever, fatigue or pain at the injection site after inoculation, but “the vast majority of people felt nothing at all,” Mammen said.
Other public health officials and scientists point out that the coronavirus vaccines have greater effectiveness than many approved vaccines for other diseases.
“We would be celebrating a seasonal influenza vaccine with 60 percent efficacy,” Jay Butler, deputy director for infectious diseases at the U.S. Centers for Disease Control and Prevention, said January 29 during a news conference sponsored by the Infectious Diseases Society of America. “While it’s disappointing compared with the 95 percent efficacy from the Phase III trials of the two mRNA vaccines prior to the emergence of these variants, it’s still not something that would make me want to not utilize or receive the vaccine myself.”
Johnson & Johnson says that it could produce 1 billion doses of its COVID-19 vaccine — enough to vaccinate about an eighth of the world’s population — by the end of the year. That includes 100 million doses promised to lower-income countries through the Vaccine Alliance, or Gavi, and the World Health Organization’s COVAX program. The United States has a deal for 100 million doses, with an option to buy 200 million more doses.
If authorized by the FDA and other regulatory agencies around the world, the vaccine could be an important public health tool, which is crucial as more contagious variants of the virus continue to emerge, experts say. “This virus will continue to evolve and to mutate for certain,” Fauci said. That’s an incentive to use every available safe and effective vaccine available, he said. “The best way to prevent further evolution of a virus is to prevent it from replicating, and you do that by vaccinating people as quickly as you possibly can.”
Staff writer Jonathan Lambert contributed to this story.
Lizard-like tuatara carry two distinct mitochondrial genomes
The lizard-like tuatara already was an oddball. Its superpowers include a century-long lifespan, resistance to many diseases and a unique tolerance (for a reptile) to the cold. Now, it turns out, a part of the animal’s genetic instruction book is as weird as its life history — and may help explain its ability to withstand extreme temperatures.
Tuatara have two distinct copies of the instruction manual for mitochondrial DNA, researchers report January 29 in Communications Biology.
“It’s the first evidence of a full additional copy of the mitochondrial genome in a vertebrate,” says Chris Schneider, a herpetologist at Boston University not involved in the study. Other vertebrates have only one copy of a mitochondrial genome. Mussels are the only other animal ever found to have two.
Mitochondria are tiny energy factories, and their genetic material, typically inherited from the mother, is essential for making cells operate. Recent studies show that mitochondrial DNA plays major roles in aging and various human cancers, as well as metabolic, muscular and neurogenerative diseases (SN: 10/24/12). Studying the mitochondrial genomes of other animals could offer clues to the inner workings of human disease, the researchers say.
“The mitochondrial genome is much more important than people realize, given its association with aging and disease,” says Robert Macey, a genomicist at the Peralta Genomics Institute in Oakland, Calif. “How that operates in an animal that ages slowly in a cool environment might tell us something significant about how mitochondria work.”
Efforts to decode the tuatara’s genetic makeup began in 2012, with the launch of the Tuatara Genome Project led by Neil Gemmell, an evolutionary biologist at the University of Otago in Dunedin, New Zealand. After getting the blessing of the Maori people to sample the reptile’s blood (tuatara are a taonga (special treasure) to the Maori), the team found the its genome to be 50 percent larger than the human genome (SN: 8/5/20).
This discovery led to deeper exploration of the mitochondrial part of the genome. Most techniques that decipher, or sequence, DNA chop it into small pieces, “read” it, then reassemble the pieces. That provides a high resolution look at individual puzzle pieces. Piloting a new technique that reads long DNA segments, Macey’s lab sequenced the tuatara’s mitochondrial genome in one fell swoop, showing its overall structure. The technique, called Oxford Nanopore, “is undoubtedly the future of gene sequencing, that we can sequence whole molecules in one pop!” Macey says.
Dan Mulcahy, a molecular biologist at the Smithsonian’s Global Genome Initiative in Washington, D.C., and Macey were mulling over the data when Mulcahy recalls saying, “I think there may be two mt-genomes!”
The revelation came from comparing both the chopped puzzle pieces and the overall structure, and noticing that sections from the same part of the mitochondrial DNA had striking differences in their gene sequences — like the way the notes of song might be arranged differently by two different composers. The variation raised eyebrows; mitochondrial DNA is usually inherited only from a mother’s egg, so the scientists expected to see a single copy of the mitochondrial genome, not two copies like they would see in nuclear DNA, which is inherited from both mother and father.
Together, the scientists painstakingly assembled two fully functional mitochondrial genomes. They found the genomes differed by an eye-popping 10.4 percent. In comparison, human and chimpanzee mitochondrial genomes differ by 8.9 percent. “The tuatara’s arrangement of genes is unlike any other vertebrate,” Mulcahy says.
When Laura Urban, a genomicist at the University of Otago, analyzed which sets of genes differed between the two genomes, she noticed changes in ones related to metabolism. An animal’s cell metabolism adjusts to help it cope with environmental extremes. The double mitochondrial genome might give tuatara flexibility in how their metabolisms respond to temperature extremes, the scientists say.
“The tuatara has the most complicated mitochondrial genome I’ve ever seen,” Macey says. Finding the genetic basis for the animal’s metabolic feats could clarify the mitochondrial genome’s function, helping to find treatments for human metabolic diseases.
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Naked mole-rat colonies speak with unique dialects
When one naked mole-rat encounters another, the accent of their chirps might reveal whether they’re friends or foes.
These social rodents are famous for their wrinkly, hairless appearance. But hang around one of their colonies for a while, and you’ll notice something else — they’re a chatty bunch. Their underground burrows resound with near-constant chirps, grunts, squeaks and squeals.
Now, computer algorithms have uncovered a hidden order within this cacophony, researchers report in the Jan. 29 Science. These distinctive chirps, which pups learn when they’re young, help the mostly blind, xenophobic rodents discern who belongs, strengthening the bonds that maintain cohesion in these highly cooperative groups.
“Language is really important for extreme social behavior, in humans, dolphins, elephants or birds,” says Thomas Park, a biologist at the University of Illinois Chicago who wasn’t involved in the study. This work shows naked mole-rats (Heterocephalus glaber) belong in those ranks as well, Park says.
Naked mole-rat groups seem more like ant or termite colonies than mammalian societies. Every colony has a single breeding queen who suppresses the reproduction of tens to hundreds of nonbreeding worker rats that dig elaborate subterranean tunnels in search of tubers in eastern Africa (SN: 10/18/04). Food is scarce, and the rodents vigorously attack intruders from other colonies. While researchers have long noted the rat’s raucous chatter, few actually studied it.
“Naked mole-rats are incredibly cooperative and incredibly vocal, and no one has really looked into how these two features influence one another,” says Alison Barker, a neuroscientist at the Max Delbrück Center for Molecular Medicine in Berlin.
To start, she and her colleagues leveraged the computing power of machine learning to analyze over 30,000 “soft chirps” — a common vocalization — from seven laboratory colonies over two years. The analysis revealed that each colony had a unique sound, varying primarily in frequency and how much that frequency changes within a single chirp.
Naked mole-rats pick up on these differences too, replying to the sounds of their own colony with frequent chirping, but largely ignoring foreign dialects, the researchers found. “That surprised us, and suggests soft chirps might signal that a naked mole-rat belongs to the colony,” Barker says. The naked mole-rats aren’t just responding to voices they’ve heard before either, as artificially concocted calls matched to a specific dialect also elicited a response.
A bit of luck allowed Barker and her colleagues to test whether these dialects are learned or genetically encoded. Most colonies reject outsiders, but sometimes pups from other groups can get adopted by a colony (SN: 10/20/20). Multiple laboratory populations produced new litters around the same time, allowing the researchers to switch three youngsters to new colonies. If dialect stems from genetics, these outsiders should still sound like outsiders. But if dialects are learned, transplanted pups should sound like their new brethren.
The latter was true. And the closer to birth a pup was moved, the more closely it matched the dialect of its new home.
“A sample size of three is small, but these are really difficult experiments to do,” says Chris Faulkes, an evolutionary biologist at Queen Mary University of London who wasn’t involved in the study. Still, he says the results strongly suggest that dialects of naked mole-rats are learned, similar to those of humans, cetaceans and some birds (SN: 7/2/20).
While a colony’s sound is distinctive, it’s not fixed. In periods of anarchy — when a queen dies and is not yet replaced — dialects started to dissolve, becoming much more variable, the researchers found. Once a new queen emerged, the colony cohered again, suggesting that in addition to suppressing reproduction, queens also somehow control a colony’s voice.
Dialects probably play a role in maintaining the “exquisite cooperation” of naked mole-rat societies, Barker says. But they also reflect how vocal communication is another means by which queens suppress the individual interests of colony members for the good of the group.
“We tend to think of this communication and cooperation as positive aspects of naked mole-rat culture, but individuals are rigidly controlled in their behavior by the queen,” Barker says. “It gives them a huge survival advantage, but it’s a bit like living in an oppressive regime.”