A male medium ground finch (left) next to a female small ground finch (right). It's unclear what the nature of their relationship is—but if the male is small for his kind, love could blossom. Photo Credit: Nick Athanas, flickr

When Looking for Love, Darwin’s Finches Choose Mates Just Like Their Parents

“Wow, you look just like my father” can be a surefire way to bring a date to a screeching halt. Unless, that is, you have hollow bones and live on a remote Pacific island.Today, in the journal PNAS, researchers <a href="http://www.pnas.org/cgi/doi/10.1073/pnas.1813662115">report</a> that the famous finches once studied by Darwin on the Galápagos Islands tend to choose mates that bear an uncanny resemblance to their parents. This strategy helps ensure that birds boost their chances of bunking up with partners of their own species—and may even help solve an age-old evolutionary puzzle.On the small sliver of Earth that Darwin’s finches call home, <a href="https://www.princeton.edu/news/2017/11/27/study-darwins-finches-reveals-new-species-can-develop-little-two-generations">18</a> <a href="http://science.sciencemag.org/content/early/2017/11/20/science.aao4593">species</a> of these birds speckle the skies. Each lineage has its own little quirks. For instance, the shapes and sizes of different finch beaks have been whittled around specific foods: Some more suited to crack open little seeds, while others are particularly adept at pecking at cacti.
<div class="ad"></div>
But it was only in the last million years or so that these diverse lineages truly start to crystallize. Even today, their distinguishing features are few and far between—which means breeding season can be a chaotic cross between speed dating and a family reunion. For years, biologists have wondered how so many finch lineages diverged in such close proximity, in such a short amount of time. Without geographical barriers to keep species separate, how did birds avoid interbreeding?Luckily for finches, they’re born with the most reliable role models nature can provide: their parents. By simply paying attention to the subtle features and habits of their primary caretakers, little finches can begin to acquire a sense of their species identity—and which subtle features distinguish one lineage from another. This time-sensitive process of learning is called imprinting.Some imprinted traits are vocal. When a male finch is single and ready to mingle, he can’t be a slouch with song: His winsome, species-specific warble is a big part of what will ultimately woo a female. But young birds aren’t born belting arias. Each male must earn his vocal heritage by studying dutifully under his father’s tutelage during his youth. Because these serenades are sung or recognized on a lineage-by-lineage basis, they help maintain finch fidelity—but imprinting is far from foolproof. If impressionable young males are exposed to the vocal stylings of another species during this period, they may spend the rest of their lives chasing the wrong tail.
<figure class="richtext-image full-width">
<img alt="" class="richtext-image full-width" src="https://www.pbs.org/wgbh/nova/media/images/Geospiza_scandens_female.width-990_W9U8GOJ.jpg"/>
<figcaption>A female cactus finch. When it comes time for her to select a mate, she may trend towards choosing with with a beak shaped like her father's. Photo Credit: Sergey Pisarevskiy, flickr
<div class="credit"></div>
</figcaption>
</figure>
Clearly, deciding on a date through one trait alone can be quite the gamble. If a finch is to carry on with its own kind, there’s a good chance it’s imprinting on other cues to tell who’s who in the avian community, reasoned evolutionary biologists <a href="https://eeb.princeton.edu/people/peter-grant">Peter</a> and <a href="https://eeb.princeton.edu/people/b-rosemary-grant">Rosemary</a> Grant of Princeton University. And if the Grants have a theory about Darwin’s finches, it’s probably right.The pair has studied the Galápagos Islands’ winged residents <a href="https://www.pbs.org/wgbh/evolution/library/01/6/l_016_01.html">since 1973</a>, observing evolution in real time as lineages of finches ebbed and flowed through the years. From 1976 to 2012, the Grants tracked thousands of finches on the tiny volcanic outcrop of Daphne Major, meticulously recording their beak and body dimensions and noting each bird’s parentage and mating habits (according to their report, the duo attempted to find every nest and identify the parents in every year of breeding from 1976 to 1998).
<div class="related"></div>
“There is so much power in long-term studies like these,” says <a href="http://www.massey.ac.nz/massey/expertise/profile.cfm?stref=136040">James Dale</a>, an evolutionary biologist who studies bird behavior at Massey University in New Zealand. The Grants, he adds, have “accumulated a vast database that allows them to test so many new theories.”The breadth of the Grants’ body of work is truly staggering. By 2012, the pair had amassed nearly 40 years of anatomical and behavioral data on two species of finch: the <a href="https://neotropical.birds.cornell.edu/Species-Account/nb/species/megfin1/overview">medium ground finch</a> (Geospiza fortis), a puff of a bird with a stubby beak suited for snacking on seeds; and the <a href="https://neotropical.birds.cornell.edu/Species-Account/nb/species/cocfin3">cactus finch</a> (Geospiza scandens), which sports a svelte, spiky beak apt for chowing down on—you guessed it—prickly pear cactus.The Grants quickly discovered each species of finch had a strong tendency to stick to its own kind—and, as they expected, the cues for their choices weren’t limited to song. For instance, in the medium ground finch, body size matched up consistently between mates and parents—especially the father. In the cactus finch, on the other hand, females also went for daddy doppelgängers, but instead prioritized the shape of their fathers’ beaks. Regardless of anatomy, these preferences meant that when most flirty finches were hot to trot, they were recalling the faces and forms they saw most often in their youth.“It was very rewarding to discover that [features] of the mates of both sons and daughters can be predicted from the same characteristics of the parents,” the Grants wrote in an email.Incredibly, because the differences between individual birds are so minor, many finches were selecting mates among anatomical variants of “just millimeters,” says <a href="http://www.utsc.utoronto.ca/~jweir/">Jason Weir</a>, a biologist who studies the evolution of birds at the University of Toronto, but was not involved in the work. Such a subtle pattern, he says, was only detectable through the sheer numbers of birds the Grants tagged and tracked over the years. “They basically know every individual and have every pedigree,” Weir explains.
<figure class="richtext-image full-width">
<img alt="" class="richtext-image full-width" src="https://www.pbs.org/wgbh/nova/media/images/Geospiza_scandens_male.width-990_jA5dMpy.jpg"/>
<figcaption>A male cactus finch. His pointed beak may appeal to a female looking to couple up—if it resembles her father's, that is. Credit: David Cook, flickr
<div class="credit"></div>
</figcaption>
</figure>
Every population, however, is graced by a few renegade romantics. Some medium ground finches ultimately strayed outside their own lineage, blurring the lines between species. But even mismatched lovebirds found common ground. Rather than sticking to their own, some medium ground finches sought the company of <a href="https://neotropical.birds.cornell.edu/Species-Account/nb/species/smgfin1">small ground finches</a> (Geospiza fuliginosa), which are closely related, but, as their name indicates, a bit more diminutive in size. When the Grants examined these oddballs, they realized the medium ground finches most likely to seek mini-mates were often pint-sized themselves.Some large finches took on a similar habit. Over the course of his 14-year life, one lothario from the <a href="https://neotropical.birds.cornell.edu/Species-Account/nb/species/larcaf2/overview">large cactus finch</a> (Geospiza conirostris) population swept no less than six female medium ground finches off their feet—several of whom were particularly big-bodied for their breed. Even in extra-species couplings, like mated with like.Imprinting on parents to find a mate “is a learning process that helps finches to navigate the adult world,” the Grants explain.
<div class="newsletter"></div>
And the findings of this study speak to much more than individual finches’ flights of fancy. By picking partners that parallel their parents, finches increase the likelihood that their mates—and future offspring—will be of their same ilk. Reusing the same imprinting template over and over means that the differences between lineages can get enhanced until they split away entirely. With this mirroring strategy, finches can breed diversity under even the most unexpected of circumstances.Turns out, birds of a feather really do flock together—especially in the Galapagos.

Bringing home fellas that look just like dad might be a red flag to some. But for Galápagos finches, a pairing like this might just do papa proud.

Alcatraz Island still draws tourists for its history as a federal penitentiary. But it also has a rich past as little-known military base, erected to guard against foreign invasion. Image Credit: MBPROJEKT_Maciej_Bledowski, iStock

Ground-Penetrating Radar Reveals Military Structures Buried Beneath Alcatraz Penitentiary

Alcatraz might be best known as a popular tourist destination, the site of the former high-security prison that once held Al Capone. But a team of archaeologists has now unveiled new evidence of this San Francisco Bay island’s often overlooked military history.In the <a href="https://onlinelibrary.wiley.com/doi/full/10.1002/nsg.12031">study</a>, published last Thursday in the journal Near Surface Geophysics, researchers used non-invasive technologies to pull back the curtain on a stunningly well-preserved 19th century coastal fortification that lies beneath the ruins of this infamous federal penitentiary. The work confirms that while prison construction in the early 1900s destroyed much of the former military installation, several structures were buried more or less intact, enshrining a critical sliver of Alcatraz’s colorful past.
<div class="ad"></div>
“This really changes the picture of things,” says study author <a href="https://www.binghamton.edu/anthropology/faculty/postdoctoral.html">Timothy de Smet</a>, an archaeologist at Binghamton University. “These remains are so well preserved, and so close to the surface. They weren’t erased from the island—they’re right beneath your feet.”
<figure class="richtext-image full-width">
<img alt="" class="richtext-image full-width" src="https://www.pbs.org/wgbh/nova/media/images/Alcatraz_200MHz_Dec2012_Parade_Ground_Lighthou.width-990_qWfzscW.jpg"/>
<figcaption>Study author Timothy de Smet used non-invasive techniques to create a subsurface map of remains of Alcatraz Island's former military fortification. Image Credit: Timothy de Smet, Binghampton University
<div class="credit"></div>
</figcaption>
</figure>
Prior to the mid-1800s, Alcatraz Island was a barren strip of land capable of supporting little more than a raucous population of seabirds. But in the wake of the California Gold Rush, the United States government looked to the rocky outcrop as a potential military base to protect the newly bustling city from foreign invasion. Over the next several decades, a stone- and brick-based fortification was erected, then rebuilt as earthen structures better equipped to handle erosion. But Alcatraz struggled to keep pace with the rapid changes in artillery during and after the Civil War era, and by the late 1800s, the island’s defenses were essentially obsolete. Military pursuits on Alcatraz were abandoned shortly thereafter.
<div class="related"></div>
When the island’s prison was erected around the turn of the 20th century, little physical evidence of its former architecture remained—or so many thought. The new study, led by de Smet, says otherwise. To look beneath the surface, the researchers deployed ground-penetrating radar, which pulses electromagnetic waves into the earth, returning signals that can visualize remains without excavation. The strategy uncovered a labyrinth of subterranean structures, including an earthwork traverse, a kind of defensive trench, running beneath the penitentiary’s former recreation yard.“This really reinforces what several historians and archaeologists had long suspected,” says study author and Alcatraz historian <a href="http://www.johnamartini.com/">John Martini</a>. “Up until this point, we had nothing to go on except for a few visible trace remains and maps—and a lot of suspicion.”In a way, Martini says, the findings reflect just how limited real estate was on Alcatraz, which clocks in at less than 50 acres. “On a small island, there’s only so many places you can build,” he says. “And it’s unlikely they went to the trouble of demolishing all this stuff.”
<figure class="richtext-image full-width">
<img alt="" class="richtext-image full-width" src="https://www.pbs.org/wgbh/nova/media/images/Alcatraz_320_Rodman_Fortress-16.width-990_XY6ACuC.jpg"/>
<figcaption>A 15-inch Rodman cannon and its gun crew, 1869. These were the largest guns mounted on Alcatraz. Image Credit: National Park Service, Golden Gate National Recreation Area
<div class="credit"></div>
</figcaption>
</figure>
Because they’re both sensitive and non-destructive, techniques like ground-penetrating radar are crucial for these kinds of investigations, and can complement historical records that survived the era, says <a href="http://jolenebabyakauthor.com/">Jolene Babyak</a>, an Alcatraz historian who was not involved in the study.With these results in hand, de Smet and his colleagues plan to continue archaeological investigations under Alcatraz. Going forward, only time will tell what this rock will reveal, Martini says. “Below the surface, Alcatraz is still full of mysteries,” he says. “There’s still a whole lot to be learned.”
<figure class="richtext-image full-width">
<img alt="" class="richtext-image full-width" src="https://www.pbs.org/wgbh/nova/media/images/Alcatraz_616_ordnance_yard_BANC_Muybridge_Coll.width-990_JgPAUCa.jpg"/>
<figcaption>Soldiers posing in the island’s ordnance yard. A brick Citadel capped the summit of Alcatraz. 1869. Image Credit: National Park Service, Golden Gate National Recreation Area
<div class="credit"></div>
</figcaption>
</figure>

<div class="newsletter"></div>

Using non-invasive techniques, archaeologists have confirmed the presence of a coastal fortification beneath what was once the prison’s recreation yard.

Bobtail squid are never alone. Inside their bodies reside a teeming community of Vibrio fischeri bacteria. In exchange for food and housing, the bacteria emit a glow to mask the squid's silhouettes from the eyes of predators at night... and spark a cascade of changes throughout the squid's entire body. Image Credit: David_Slater, iStock

This Squid’s Glowing Microbes Can Reprogram Its Eyes From Afar

The Hawaiian bobtail squid might be small, but this walnut-sized critter is one of the sea’s mightiest masters of disguise. During its evening jaunts, the squid protects itself by casting an eerie glow to match the moonlight, obscuring its silhouette to predators lurking in the water column below.This cloak of invisibility is an illusion by collusion, all thanks to a luminous cache of Vibrio fischeri bacteria held within a specialized chamber within the squid’s body called the light organ. In exchange for canceling out the squid’s shadow, the microbes receive housing and a stipend of sugars.But it’s now clear that these microbes do far more than conjure a cloak of invisibility. From the moment it enters the light organ, V. fischeri sparks a cascade of changes that can even transform parts of the squid’s body, like its eyes and gills, which never physically encounter the bacteria themselves. The <a href="https://www.pnas.org/cgi/doi/10.1073/pnas.1819897116">finding</a>, published today in the journal PNAS, illustrates the far-reaching consequences of microbial colonization—and could illuminate similarly intimate partnerships in humans.“This will help create a real paradigm shift,” says <a href="https://micro.siu.edu/faculty-staff/faculty/rader.php">Bethany Rader</a>, a microbiologist at Southern Illinois University who was not involved in the study. “It’s folly to think about health without considering how microbes influence the entire body.”
<div class="ad"></div>
Decades of research have shown time and time again that the microbes that inhabit animal bodies dictate countless aspects of health. Perhaps most famously, the bacteria that inhabit the mammalian large intestine—the gut microbiota—can affect everything from the way the <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4109969/">immune system</a> functions, to the regularity of <a href="https://journals.sagepub.com/doi/abs/10.1177/0748730417729066?rfr_dat=cr_pub%3Dpubmed&amp;url_ver=Z39.88-2003&amp;rfr_id=ori%3Arid%3Acrossref.org&amp;journalCode=jbra">sleep-wake cycles</a>, to how the <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5127403/">brain interprets information</a>.But what’s been far less obvious is exactly how bacteria are sending out system-wide marching orders from isolated control centers like the colon. Complicating things is the fact that thousands of microbial species inhabit the bodies of mammals like humans, making it tough to disentangle who’s responsible for what effect.That’s where the bobtail squid comes in. Their light organs are notoriously picky: Only V. fischeri are permitted to enter, while interlopers are unceremoniously dumped back into the salty sea. “The beauty of this system is that it’s simple,” says study author <a href="http://glowingsquid.org/people_current_mm.php">Silvia Moriano-Gutierrez</a>, a marine biologist at the University of Hawaiʻi at Mānoa. “There are only two partners at play.”
<figure class="richtext-image full-width">
<img alt="" class="richtext-image full-width" src="https://www.pbs.org/wgbh/nova/media/images/mcfall_squid_feb2012_104_4SCMs7A.width-990_pcawGjZ.jpg"/>
<figcaption>The Hawaiian bobtail squid is the size of a walnut, but it's able to squeeze an entire population of microbes into a small sac in its body. Image Credit: Margaret McFall-Ngai and Edward Ruby, Squid Vibrio Labs, University of Hawaiʻi at Mānoa
<div class="credit"></div>
</figcaption>
</figure>
To parse out the extent of the squid-microbe relationship, a team led by Moriano-Gutierrez reared squid with or without V. fischeri (bacteria-free individuals have never been found in the wild, but get along swimmingly in the lab). When the researchers compared gene expression in the two groups over time, they found that the presence of microbes substantially retooled cells in not just the light organ where they were housed, but also organs elsewhere in the body, such as the eyes and gills, where V. fischeri never treads. Additionally, distinct genetic patterns arose in each location, signaling that each organ had interpreted V. fischeri in its own way.This was a striking find—akin to a guest entering an inn and simultaneously rearranging furniture behind the concierge desk, in its room upstairs, and in the dining room out back, all without leaving the foyer. As the humble patron of the Hotel Calamari, V. fischeri had shaped its surroundings on a squid-wide scale.
<div class="related"></div>
From the squid’s perspective, however, these might be important adjustments, says study author <a href="http://www.glowingsquid.org/people_mm.php">Margaret McFall-Ngai</a>, a squid biologist who supervises Moriano-Gutierrez’s work. Like the light organ, the eyes and gills have stakes (albeit, indirect ones) in microbial fraternizing. A keen sense of sight helps the squid gauge how bright its surroundings are, so it can fine-tune the output from its light organ. The gills, on the other hand, play a role in squid immunity, and need to remain on high alert for bacteria in the vicinity.And these different priorities shaped the nature of each organ’s response to the bacteria. When the researchers repeated their experiment, this time swapping out naturally glowing V. fischeri with mutants who couldn’t produce light, the bacteria elicited much less turnover in the light organ and eyes (the gills, however, didn’t seem to care either way). In other words, without their luminescence, the bacteria couldn’t trigger the normal suite of changes in the organs where light mattered most—causing the squid to turn a blind eye to their presence.“This underscores the importance of luminousness to the animal,” McFall-Ngai says. “From their perspective, it’s the most important thing the bacteria do.”
<figure class="richtext-image full-width">
<img alt="" class="richtext-image full-width" src="https://www.pbs.org/wgbh/nova/media/images/Adult3_copy.width-990_unQp6DF.jpg"/>
<figcaption>A dissected bobtail squid, tentacle-up. The ink sac (black) is shown in the middle; the light organ is nestled against it, looking like two kidneys stuck together. The animal's eyes are just below its tentacles, while the gills are the fluffy, whitish areas near the top of its body (bottom of the photo). All of these organs are affected by the presence of Vibrio fischeri. Image Credit: Margaret McFall-Ngai and Edward Ruby, Squid Vibrio Labs, University of Hawaiʻi at Mānoa
<div class="credit"></div>
</figcaption>
</figure>
How exactly V. fischeri communicates with the eyes and gills is still unclear. One obvious signal for the eyes might be light itself—but the squid actually doesn’t have the best view of its own glow. And that wouldn’t explain how the gills are tuning in.One possibility is that microbes are churning out chemical cues that enter the squid’s bloodstream, says study author <a href="http://glowingsquid.org/people_nr.php">Edward Ruby</a>, a microbiologist who runs the partner lab to McFall-Ngai’s at the University of Hawaiʻi at Mānoa. Then, depending on the organ at which they arrive, the messages might be interpreted differently by the specialized cells at each site. That would be the equivalent of every service team in a hotel hearing a guest’s footsteps in the doorway: Depending on its specialty, each would be spurred onto a different course of action.Rader, the Southern Illinois University microbiologist, proposes an alternative. Rather than sending out an all-purpose SOS, the bacteria could also be dispatching distinct instructions to individual organs—like the same hotel guest calling the kitchen’s direct line, rather than using a building-wide intercom. That way, specific memos about light, for instance, wouldn’t get wasted on the gills.These possibilities aren’t mutually exclusive. Either way, Ruby says, it’s a reminder that there’s complexity on both sides of the equation: a multitude of bacteria producing signals, and a troupe of target tissues waiting to receive them.These relationships are likely echoed in other animals as well—including humans, Rader says. “Squid may not look a lot like us, but we possess a lot of the same types of tissues and share [part of] our immune system,” she says. “The answers we get from squid are just as valid and informative as those from mice.”Studies like these show us that animals more than just isolated, single bodies, says <a href="http://biology-web.nmsu.edu/~castillo/">Maria Castillo</a>, a bobtail squid researcher at New Mexico State University who was not involved in the study. Whether we like it or not, we are all growing and changing under the influence of our microbial allies, she says.
<figure class="richtext-image full-width">
<img alt="" class="richtext-image full-width" src="https://www.pbs.org/wgbh/nova/media/images/adult2.width-990_R8MzOUu.jpg"/>
<figcaption>A Hawaiian bobtail squid, scooped into a human hand. These critters can be just an inch or so long in adulthood. Image Credit: Margaret McFall-Ngai and Edward Ruby, Squid Vibrio Labs, University of Hawaiʻi at Mānoa
<div class="credit"></div>
</figcaption>
</figure>
But all this does raise the question: In this lifelong dialogue, who’s really in charge—the squid or its Vibrio?For McFall-Ngai and Ruby, this has historically been a point of contention. The two are professional (and romantic) partners: McFall-Ngai, a zoologist by training, represents the squid half of the equation, while Ruby bats for Team Vibrio. After decades of work, the two settled on an answer: “I’ve had to concede that the host is clearly in charge,” Ruby says.The squid does have a lot of say in this unconventional union. Every morning, they’ll jettison about 90 percent of their resident V. fischeri before settling down to sleep—essentially shutting off an unneeded nightlight. And if any bacteria fail to light up, the squid can evict the would-be freeloaders without a second thought. “If you’re not doing your job, you’re gone!” McFall-Ngai says. Microbes might be honored guests, but their hosts still have final say on checkout time.Others, however, are a bit more hesitant to yield microbial ground. “I can’t answer that question!” Castillo says with a laugh. “They need each other.”Rader points to the fateful first meeting of squid and bacteria. It’s unclear who makes the first move—but from day one, the two enter a conversation, rather than a dictation. Host and microbe guide each other’s development through a delicate back and forth, down to levels of chemicals, molecules, and genes.“Really, it’s probably an equal partnership,” Rader adds. If she’s going by her gut, she says, “it’s a relationship as equal as one can be.”But then again, maybe that’s the microbes talking.
<div class="newsletter"></div>

A squid’s eye view of its own microbes shows the intimate link between a nocturnal sea-dweller and its cache of bioluminescent bacteria.

A T cell infected with HIV, the virus that causes AIDS. T cells play a critical role in the body's immune response, and when compromised by infection, can leave patients vulnerable to disease. Twice in history, stem cell transplants from donors with HIV-resistant cells have successfully put patients into long-term remission from the virus. Image Credit: NIAID, flickr

A second patient has entered long-term remission from HIV

For the second time, a patient is in long-term remission from HIV, the virus that causes AIDS. With the help of a stem cell transplant from a virus-resistant donor, the anonymous individual—referred to by researchers as the “London patient”—has now been off antiretroviral drugs for about a year and a half.The procedure is far from a panacea, however. This particular intervention is likely to be effective in only a small fraction of the 37 million people worldwide who currently harbor the virus in their bodies. Even so, the announcement, <a href="https://www.nature.com/articles/s41586-019-1027-4">published today</a> in the journal Nature, represents a long-awaited advance, in part by reaffirming that a similar case reported 12 years prior “wasn’t a one-off,” Sharon Lewin, who heads the Peter Doherty Institute for Infection and Immunity in Melbourne, Australia and was not involved in the study, <a href="https://www.sciencemag.org/news/2019/03/has-second-person-hiv-been-cured">told Jon Cohen at Science</a>.
<div class="related"></div>
In several ways, the newly reported London patient echoes the first case of sustained remission from HIV: Timothy Brown, known in medical circles as the “Berlin patient,” who was effectively rid of the virus in 2007. Both milestones were achieved following a transplant of bone marrow, where the immune cells most susceptible to the virus originate, from a person with a mutation in the gene that encodes CCR5, a protein that many HIV strains use to infiltrate cells. In other words, the procedure effectively swapped out vulnerable tissue for hardier stock. Notably, neither treatment was originally intended to eliminate the infection itself, but to treat blood cancers that had spread in both individuals.A few key differences exist between Brown’s case and that of the London patient, however. To complete the transplant, doctors administered harsh immunosuppressive drugs, causing him to suffer severe complications in the months after receiving the cells. At one point, Brown had to be placed in an induced coma and nearly died.The London patient, on the other hand, was able to undergo a far gentler regimen with similar results, though the broad therapeutic strokes were more or less equivalent. This crystallizes the idea that invasive, life-threatening treatments aren’t required to achieve remission from HIV.“I think this does change the game a little bit,” study author Ravindra Gupta, a virologist at University College London <a href="https://www.nytimes.com/2019/03/04/health/aids-cure-london-patient.html">told Apoorva Mandavilli at The New York Times</a>. “Everybody believed after the Berlin patient that you needed to nearly die basically to cure H.I.V. But now maybe you don’t.”
<div class="ad"></div>
On the whole, though, bone marrow transplants remain risky and expensive, and, apart from the two aforementioned patients, have a poor track record of clearing HIV from the system, despite numerous attempts. As such, this procedure is unlikely to become a realistic treatment for HIV in the future—especially given that the antiretroviral drugs prescribed for the infection have been shown to be extremely effective. “[This] doesn’t change things for the average person with HIV right now,” the Ragon Institute’s Bruce Walker, who was not involved in the study, <a href="https://www.statnews.com/2019/03/04/second-person-effectively-cured-of-hiv/">told Kate Sheridan at STAT News</a>.However, current treatments must be administered throughout a patient’s life, and millions worldwide lack access to a source of consistent therapy. On top of this, drug-resistant strains of HIV continue to surface, throwing a wrench in current formulations.As such, the findings provide a glimmer of hope for researchers who plan to build on this knowledge to explore new treatment options. One possibility would be to alter the CCR5 gene, and thus compromise one of HIV’s most prominent entry points into human cells. This is not a new idea: the CCR5 gene was infamously targeted by Chinese scientist He Jiankui, whose (possibly failed) attempt to edit human embryos to make them immune to HIV <a href="https://www.pbs.org/wgbh/nova/article/crispr-gene-editing-live-births/">sparked an international scandal</a> last fall.He’s experiment was widely condemned as unethical and reckless. But many other groups of researchers are taking more cautious approaches to manipulating CCR5.Still, CCR5 is not the only gateway for HIV: Some strains are able to bypass this molecule entirely on their way into cells. But if achievable, such treatments could set an important precedent going forward.
<figure class="richtext-image full-width">
<img alt="" class="richtext-image full-width" src="https://www.pbs.org/wgbh/nova/media/images/32483530942_5af1b5a193_o.width-990_23gQaGS.jpg"/>
<figcaption>Though modern antiretroviral drugs are effective, prescribed regimens are lifelong, and not all communities worldwide have access to treatment. Image Credit: NIAID, flickr
<div class="credit"></div>
</figcaption>
</figure>
Though the London patient is choosing not to disclose his name for the time being, he described the experience as “surreal” and “overwhelming” in an email to Mandavilli at The New York Times. “I never thought that there would be a cure during my lifetime,” he wrote.Of course, remission is not necessarily a “cure” (though many have referred to this landmark achievement as such), Gupta told Cohen at Science. The researchers drew their conclusions based exclusively on the London patient’s blood, and will continue to monitor his health in the years to come.In the meantime, though, the team is tentatively optimistic. And Timothy Brown, who has held a solo spotlight for the last 12 years, is relieved to finally have someone to share it. “If something has happened once in medical science, it can happen again,” Brown told Mandavilli at The New York Times. “I’ve been waiting for company for a long time.”
<div class="newsletter"></div>

Twelve years after the first man was declared to be rid of HIV, a second patient has achieved a similar milestone, sparking hope that a cure may someday be possible.

Chimpanzees suffering the highest degree of impact are 88 percent less likely to display the traditions and behaviors passed down through the generations, compared to those in relatively untouched communities. Image Credit: USAID Africa Bureau, Wikimedia Commons

Humans are Driving Chimpanzee Culture Out of Existence

From opposable thumbs to the curse of ticklishness, humans and chimpanzees have a lot in common. So perhaps it’s no surprise that both species cultivate unique behaviors and intricate traditions that vary between communities are passed down through the generations.In other words, we both have culture. But that might not be the case for much longer. According to a <a href="http://science.sciencemag.org/content/early/2019/03/06/science.aau4532">study</a> published today in the journal Science, the culture of chimpanzees is vanishing alongside their habitats—and we’re to blame.
<div class="ad"></div>
“It’s amazing to think that just 60 years ago, we knew next to nothing of the behavior of our sister species in the wild,” Andrew Whiten, a zoologist at the University of St. Andrews in the UK who was not involved in the study, <a href="https://www.theatlantic.com/science/archive/2019/03/we-are-destroying-chimpanzee-cultures/584146/">told Ed Yong at The Atlantic</a>. “But now, just as we are truly getting to know our primate cousins, the actions of humans are closing the window on all we have discovered.”
<div class="related"></div>
Thanks to decades of habitat destruction, poaching, and the spread of disease—all at the hands of humans—chimpanzees haven’t budged from their spot on the endangered species list since they joined it in 1990. But even when acreage itself isn’t at stake, human interference can take its toll on the wellbeing of these great apes, the study shows.By cataloguing the activities of 144 chimpanzee communities in Africa, a team of researchers led by Hjalmar Kühl and Ammie Kalan, primatologists at the Max Planck Institute, found that 31 culturally ingrained behaviors, including nut cracking, termite collection, and bathing, tended to be stifled in the vicinity of human establishments. Across populations, the chimpanzees influenced most by humans had an 88 percent lower probability of displaying these distinctive behaviors.As is the case with humans, culture for chimpanzees is more than a set of whimsical quirks. Some traditions have evolved within regional communities, outside of which they might not exist, <a href="https://gizmodo.com/chimpanzee-traditions-are-being-lost-along-with-their-h-1833127975">reports Sarah Wells at Gizmodo</a>. And many form the basis of key adaptations that, in several environments, could have a huge impact on survival.
<figure class="richtext-image full-width">
<img alt="" class="richtext-image full-width" src="https://www.pbs.org/wgbh/nova/media/images/Chimpanzees_Chester_Zoo.width-990_PaCSjWv.jpg"/>
<figcaption>Wild chimpanzees have been listed as endangered since 1990; captive populations recently joined them. Image Credit: Nigel Swales, Wikimedia Commons
<div class="credit"></div>
</figcaption>
</figure>
How exactly humans are censoring chimpanzee culture is still being investigated, but the researchers already have some ideas. For instance, culling chimpanzee numbers could limit the opportunities individuals have to pass skills on to others. Alternatively, chimps might be hesitant to perform conspicuously noisy behaviors in an effort to avoid attracting human attention. Humans might even be sapping chimpanzee traditions indirectly by depleting key resources, like the tree nuts frequently cracked in certain communities.All this goes to say that, when it comes to the urgency of conservation, more is at stake than once thought. “We need to pay attention to the social and cultural knowledge that these species use to survive” when trying to protect them, <a href="https://www.sciencemag.org/news/2019/03/humans-are-wiping-out-chimpanzee-cultures">Kalan told Gretchen Vogel at Science</a>.And culture, once curbed, might be a difficult thing to reinstate. “An event might only have a small impact on the total population of chimpanzees, but it may wipe out an entire community—an entire culture,” Cat Hobaiter, a primatologist at the University of St. Andrews who was not involved in the study, told Yong at The Atlantic. “No matter what we do to restore habitat or support population growth, we may never be able to restore that culture.”
<div class="newsletter"></div>

Sophisticated chimpanzee behaviors like fishing, nut cracking, and bathing are fading in the presence of humans.

Two spotted hyenas engage in coalitionary aggression against a third. Coalitions such as this one usually reinforce, but occasionally disrupt, the social hierarchy. Image Credit: Kate Yoshida

For Hyenas, Climbing the Social Ladder is Easier with Friends

For Waffles, the only direction to go was up.And as the lowest-ranking female in her clan of spotted hyenas (Crocuta crocuta), she had little to lose. Among her peers, Waffles was neither the biggest nor the brawniest; by all accounts, she was—physically speaking—unremarkable.But to the amazement of <a href="https://straussed.github.io/">Eli Strauss</a> and <a href="https://www.holekamplab.org/">Kay Holekamp</a>, the Michigan State University evolutionary biologists tracking the hyenas’ behavior, over the course of just a single year, Waffles steadily ascended her group’s hierarchy, unseating high-ranking female after high-ranking female—until, at long last, the former underdog had attained the coveted alpha position.“She was just so persistent,” Holekamp says. “It was absolutely stunning.”
<div class="ad"></div>
The secret to Waffles’ success? According to Strauss and Holekamp’s <a href="https://www.pnas.org/cgi/doi/10.1073/pnas.1810384116">research</a>, published today in the journal PNAS, Waffles battled her way to the top not by leveraging stature or might, but by arming herself with the most powerful weapon of all: a troupe of loyal comrades at her side. And though her case was extraodinary, Waffles was—by several metrics—far from alone. Even when born into a low station in life, with ironclad alliances to bolster confrontations with higher-ranked individuals, female spotted hyenas can shirk the lottery of birth and clamber atop the social pyramid.“The quality of this work is outstanding,” says <a href="https://sites.nd.edu/archielab/">Elizabeth Archie</a>, a behavioral ecologist at the University of Notre Dame who was not involved in the study. “This shows that animals that navigate the social arena can turn a hierarchy on its head.”This tactic sounds simple, but it was an answer hard won. To arrive at these chummy conclusions, Strauss and Holekamp had to sift through 27 years’ worth of data, tracking over 12,500 aggressive interactions among 249 adult female hyenas in Kenya.“Such a huge sample size over such a long time is not something we have the luxury of doing in behavioral research very often,” says <a href="https://suzannemacdonald.ca/">Suzanne MacDonald</a>, a biologist who studies primate behavior at York University and was not involved in the study. “They’ve gotten data we often theorize about, but can’t often test. It’s awesome.”
<figure class="richtext-image full-width">
<img alt="" class="richtext-image full-width" src="https://www.pbs.org/wgbh/nova/media/images/Waffles.width-990_be3AnCy.jpg"/>
<figcaption>This hyena, named Waffles, ascended to become the alpha female of her social group through coalitionary support from her allies. Image Credit: Tracy Montgomery.
<div class="credit"></div>
</figcaption>
</figure>
It turns out hyena social climbing, even on a small scale, is a relative rarity (making Waffles all the more anomalous). Their hierarchies are actually remarkably stable—perhaps due in part to the fact that, like many primates, spotted hyenas are intelligent, highly adept puzzle solvers capable of cultivating <a href="https://royalsocietypublishing.org/doi/abs/10.1098/rstb.2006.1993">rich social networks</a>. A single spotted hyena can individually recognize each member of a clan of dozens, and will invest this social savvy in allies and adversaries alike.While many other animals give top billing to individuals with the most prominent or powerful physical attributes—like the seal with the greatest girth, or the bird with the flashiest feathers—spotted hyenas structure their societies like female-centric monarchies. Offspring inherit ranks directly below that of their mothers and above those of their older siblings. In this nepotistic system, might and stature hold little sway, and even small, frail, and sickly individuals can hold dominion over their peers through heritage alone.
<div class="related"></div>
This dynastic dictum poses a bit of a puzzle, however. With tantalizing incentives, like better access to food and mates, high up on the social ladder, Holekamp says, you might expect big-bodied individuals to constantly be “beating up weaker, older, more fragile individuals higher up in the hierarchy to improve their position.”Quite the opposite is true. In fact, only a small fraction of the thousands of encounters Strauss and Holekamp had tracked actually involved a lower-ranking female staging a successful coup d’état (far more actually involved females in the upper echelons reaffirming their dominance).When these revolutions did occur, however, it wasn’t the females with the hardiest physiques that were overthrowing their superiors—but the ones with the most robust friendships.In the realm of the hyena, it seemed, the name of the throne-toppling game was camaraderie.A classic confrontation might go something like this. Two females team up and swagger, shoulder to shoulder, in the direction of their higher-ranking rival, tails bristled and ears cocked, using pure posture to communicate their intent, Strauss says. The hyena on the receiving end would then have a choice to make: reassert her dominance, or yield. If daunted by the pair loping towards her, she might simply hunker down and tuck her tail between her legs—a clear signal of defeat.In other words, these weren’t necessarily violent mutinies, Strauss says. “When people think of aggression, they think of hair flying and blood and intestines,” he says. “That’s not what’s going on here.”Occasionally, standoffs did escalate to the point of bodily harm—especially when a high-ranking female decided to stand her ground in the face of a challenge. Despite these risks, though, uprisings appeared to paid dividends: By ascending the social ladder, females and their accomplices boosted their reproductive success. The repercussions of these revolts were even passed on to future generations, who reaped the benefits of their mother’s newly acquired clout.Although these status switchups weren’t happening on a daily basis, they support the idea that “rank inheritance isn’t a foregone conclusion,” Archie says. “There could be this impression that animals are born with a silver spoon in their mouth and they pass that on. But there’s nuance to that.”The power of partnership isn’t terribly surprising, says <a href="http://tropbiolab.org/FMKU/">Floria Mora-Kepfer Uy</a>, who studies social behavior in animals at Cornell University and was not involved in the study. Hyenas, like many other social species, thrive on strong social bonds—and the allegiances that allow individuals to clamber up to higher echelons might be the same ones that <a href="https://www.nature.com/articles/s41559-018-0718-9?WT.feed_name=subjects_behavioural-ecology">reinforce the ranks</a> once they’ve resettled. In this way, social currency might form two sides of the same coin: It’s what maintains, and occasionally disrupts, the hyena hierarchy.
<figure class="richtext-image full-width">
<img alt="" class="richtext-image full-width" src="https://www.pbs.org/wgbh/nova/media/images/Soc_snf_DSG-copy.width-990_IGbMdh5.jpg"/>
<figcaption>Spotted hyenas have primate-like societies in which individual hyenas form strong social bonds with their preferred partners. Image Credit: David Green. 
<div class="credit"></div>
</figcaption>
</figure>
“This is all the more reason animals on the bottom need to not kick their friends, but to hold them up,” says <a href="http://choosyfemale.com/index.html">Emily Weigel</a>, an evolutionary biologist at the Georgia Institute of Technology who was not involved in the study. “Social environment matters. And it’s shaping evolution way more than we thought.”What’s more, spotted hyenas are unlikely to bear this congenial mantle alone. Other primates, like macaques and baboons, also inherit status through strict and stable matrilines. Such parallels hint that these “very impressive” results might translate into other species, says <a href="https://www.stefanokaburu.com/">Stefano Kaburu</a>, an evolutionary biologist and primatologist at the University of Wolverhampton in the United Kingdom who was not involved in the study.“I was nodding as I was reading this paper,” MacDonald says. “This makes perfect sense. I was almost salivating, thinking that I should look at my own data with these methods.”And there’s one other notable primate for whom these conventions might ring true: humans. Differences exist between the two species, of course—but there’s an undeniable familiarity to the idea that coalitions can make or break social standing, Holekamp says.“Our own societies are largely convention-based,” she says. “My feeling is that, ultimately, it will be wonderful if we can take some of this knowledge and use it to someday make human society more egalitarian.”But that won’t happen on its own, Holekamp says. “Social inequality, even though it is a highly common characteristic in human and animal societies, can be understood and quantified, and managed,” she says. “If we have the brains to do it.”
<div class="newsletter"></div>

In these female-dominated clans, the name of the throne-toppling game might just be camaraderie.

Humpbacks and many other whales use baleen—the overlapping structures in their mouths where teeth might otherwise be—to filter tiny prey like krill and plankton out of water. But because baleen has the texture of hair or fingernails, it doesn't preserve well in the fossil record. New research now indicates that some whales may have fed by suction in the evolutionary interim between teeth and baleen. Photo Credit: Ari S. Friedlaender/University of California, Santa Cruz under NOAA permit

This 33-Million-Year-Old Whale Sucked Up Food Like A Giant Vacuum

It takes a lot to feed a <a href="http://www.pbs.org/big-blue-live/animals/blue-whale/">blue whale</a>. One of these super-sized swimmers can consume as much as 8,000 pounds of food—about the weight of a Hummer H2—on a daily basis. Which means blue whales need to be exquisitely equipped for some serious eating.The secret to this behemoth’s success? Baleen: a hyper-efficient filter-feeding system found exclusively in whales, composed of a comb-like series of overlapping plates with the texture of fingernails. After taking a massive gulp of ocean water, <a href="http://www.pbs.org/wnet/nature/ocean-giants-whale-fact-sheet/7567/">baleen whales</a>—including blue whales and <a href="https://www.pbs.org/video/life-reef-humpback-whales/">humpbacks</a>—expel unwanted liquid through this sieve, leaving behind a nutrient-dense mouthful of tiny, freshly-strained prey like krill and plankton that are easily swallowed whole.But scientists continue to grapple with the evolutionary origins of nature’s biggest oral colander. Baleen whales’ ancestors had teeth—and many of the details behind the transition to baleen, which preserves poorly in the fossil record, remain mysterious.Now, with the re-examination of a 33-million-year-old fossil, researchers are filling in a piece of this long-standing puzzle. According to <a href="https://www.cell.com/current-biology/fulltext/S0960-9822(18)31414-3">a new study</a> published today in the journal Current Biology, some whales jettisoned their teeth entirely before the acquisition of baleen, and in the interim, adopted a third method of feeding: suctioning up their food like giant vacuum cleaners.
<div class="ad"></div>
“If this is right, this fossil fills in a missing spot on the [whale family] tree,” says <a href="https://www.uprovidence.edu/bio/jessica-martin/">Jessica Martin</a>, a paleontologist at the University of Providence who was not involved in the research. “This might change the way we look at the big picture of this transition.”The fossil in question, newly anointed Maiabalaena nesbittae, was first unearthed in Oregon in the 1970s, but spent decades in the collections of the Smithsonian’s National Museum of Natural History still shrouded in rock. “This fossil’s been languishing for years,” says study author <a href="https://paleobiology.si.edu/staff/individuals/pyenson.html">Nicholas Pyenson</a>, the Museum’s curator of fossil marine mammals. “It’s amazing to finally be able to weigh in on it.”At about 33 million years old, M. nesbittae likely swam the seas of the early Oligocene—a period of rapid and vast geologic change. It was around this time that the southern tip of what’s now South America broke free of Antarctica, rejiggering ocean currents and cooling marine temperatures worldwide. Though it’s still unclear exactly how this transition affected ocean biodiversity, if there was a paleontological moment for a lineage of whales to ditch its dentition, it very well could have been this.
<figure class="richtext-image full-width">
<img alt="" class="richtext-image full-width" src="https://www.pbs.org/wgbh/nova/media/images/Carlos_Peredo_-_NMNH-2018-03422.width-990_nTMPSDA.jpg"/>
<figcaption>The upper jaw and skull of Maiabalaena nesbittae, an extinct whale species that lived 33 million years ago. M. nesbittae was toothless, and may have been a suction feeder that gave rise to modern baleen whales. Photo Credit: Smithsonian Institution
<div class="credit"></div>
</figcaption>
</figure>
Which makes M. nesbittae a potential watershed whale. Only one precious specimen of the species has been uncovered to date, and the fossil is incomplete. Luckily, most of what’s left involves the skull—which is key to studying how this species managed its massive, yet often microscopic, meals. To interrogate this fossil’s feeding forte, a team of scientists led by Carlos Peredo, a palaeobiologist at George Mason University, decided to reopen the 40-year-old case on M. nesbittae.One thing was quickly obvious to Peredo. “I looked for teeth, and it had no teeth,” he explains with a laugh. “That was the easy one.” Teeth, unlike baleen, are hardened and encased in enamel, and thus far more likely to preserve as fossils. Even if its chompers had somehow been lost to time, the roof of M. nesbittae’s mouth also appeared to be structurally inhospitable to sockets that might otherwise house true dentition. This made it unlikely that this whale was munching on large-bodied prey, à la its toothier ancestors.
<div class="related"></div>
Next, the team used CT scanning to more closely analyze the skull’s internal architecture without compromising the fossil. As there was little point in searching for ephemeral baleen, Peredo and his colleagues instead searched for attachment sites from which the baleen might have been suspended like vertical window blinds. They discovered the upper jaw was thin and narrow, without enough surface area to accommodate the gums from which baleen plates might grow. To the researchers, this was a clear strike against filter feeding.The researchers believe M. nesbittae utilized another option entirely on the road to baleen: simply slurping prey out of the surrounding waters through the sheer force of suction. Although the fossil’s facial muscles were long gone, the bones of its throat indicated that the whale was capable of retracting its tongue, creating negative pressure that would have drawn in water and small creatures from the surrounding environment. The toothless whale would have had no means to chew its prey, simply swallowing them whole. But the switch to suction was likely a move that would have averted a significant cost: Teeth are energetically expensive to produce. And it was on this blank canvas, the authors propose, that baleen eventually took shape a few million years later.
<figure class="richtext-image full-width">
<img alt="" class="richtext-image full-width" src="https://www.pbs.org/wgbh/nova/media/images/Carlos_Peredo_-_Maiabalaena_Final_Cover.width-990_qCIUmOD.jpg"/>
<figcaption>An artist's imagining of a Maiabalaena nesbittae calf nursing from its mother. Artist Credit: Alex Boersma
<div class="credit"></div>
</figcaption>
</figure>
As modern humans can attest, teeth come in handy. They allow creatures to both latch onto their prey and grind them down to swallowable portions, significantly increasing the size and breadth of an animal’s viable menu items. Suction feeding, on the other hand, doesn’t pulverize prey before it goes down the gullet, and favors smaller, softer-bodied meals. But suction feeding’s lack of oral ornamentation means it’s a relatively cheap strategy. Even toothy mammals like humans are no stranger to its efficiency: Suckling is the only way babies can eat before their teeth come in.Some scientists, however, are a little more hesitant to embrace the idea that M. nesbittae was a suction feeder. “I’m not convinced it didn’t have teeth,” says <a href="https://www.rachelracicot.org/">Rachel Racicot</a>, a paleobiologist who studies marine mammals at the Keck Science Center. Critical pieces of the fossil’s jaw are fairly worn or incomplete, she points out, muddying the conclusions that can be drawn about the presence or absence of dentition. Until more fossils from this time period reveal themselves, suction feeding will be difficult to confirm, Racicot adds. Alternatively, evidence of <a href="https://www.frontiersin.org/articles/10.3389/fmars.2017.00067/full">a more stepwise transition</a> from teeth to baleen may exist—which could mean there were once intermediate whale species that harbored both in their mouths. The two theories on this interim aren’t necessarily mutually exclusive.
<div class="newsletter"></div>
Regardless of how these whales fed in the years after they lost their teeth, the ultimate advent of baleen was revolutionary. According to Peredo, “it’s like growing fingernails out of the roof of your mouth.” There’s nothing else quite like baleen in the animal kingdom, and we probably wouldn’t have the sea’s biggest creatures without it. By dispensing of the sea water “filler” in each gulp, filter-feeding ensures that baleen whales can engulf gargantuan amounts of food in one go: A blue whale can take up <a href="http://blogs.discovermagazine.com/notrocketscience/2010/12/09/blue-whales-can-eat-half-a-million-calories-in-a-single-mouthful/">half a million calories</a> in a single mouthful.“If you drink coffee, you’re taking advantage of filter feeding,” Pyenson explains. “It’s just separating fluid out from a substance.” Though in the case of whales, he adds, they’re hungry for the grinds, not the liquid coffee, so to speak. A good filter means that especially tiny forms of prey—which don’t require chewing—can comprise a viable meal.
<figure class="richtext-image full-width">
<img alt="" class="richtext-image full-width" src="https://www.pbs.org/wgbh/nova/media/images/asf_bestof035.width-990_reOS7BP.jpg"/>
<figcaption>Modern baleen whales, like humpbacks, employ a filter-feeding strategy that enormously ups the nutritional value of each mouthful compared to suction feeding. This has enabled many whale species to grow to gargantuan sizes. Photo Credit: Ari S. Friedlaender/University of California, Santa Cruz under NOAA permit
<div class="credit"></div>
</figcaption>
</figure>
Chomping and suction feeding still have their perks, though. All three feeding strategies exist in modern whales, helping many species comfortably share the seas. And adopting one tactic doesn’t preclude a whale from utilizing another. While some toothed whales do chew on their prey, many like orcas or beluga whales simply use their teeth as graspers before swallowing food whole. Others like the beaked whale or narwhal have only rudimentary tooth structures, and must rely on suction to more or less inhale their prey. Though gray whales are equipped with baleen, they happily suction feed as well.This sort of flexibility may become increasingly important as the planet continues to change under the influence of human intervention. “Maiabalaena is like its own little case study,” Peredo says. “The oceans changed dramatically, and this is what happened—whales changed what they ate, the physical structures of their mouths.”But whales aren’t infinitely adaptable; even baleen took millions of years to come into being. It remains unclear how sea life will fare in an age of <a href="https://www.pbs.org/wgbh/nova/article/climate-change-plants-high-temperature/">rising temperatures</a> and increasingly pervasive <a href="https://www.pbs.org/wgbh/nova/article/ships-noises-humpback-whale-song/">acoustic pollution</a>. For now, researchers are keeping an eye on the past. The search for baleen’s origins may yet reveal the climactic changes that triggered its rise—and how whales weathered the storm with their mysterious shuttered smiles.

After discarding their teeth, the ancestors of today’s filter-feeding whales may have fed by suction before evolving baleen.

Katherine J. Wu

Articles