Richard Conniff's Blog, page 7

Microbes Can Wreck A Great Painting–Or Bring It Salvation

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by Richard Conniff/Scientific American

People have worried about the effects of fungi and other microorganisms on cultural objects almost as long as there have been cultural objects to worry about. In fact, the entire science of microbiology began with a fungus damaging a cultural object. In his 1665 book Micrographia the British polymath Robert Hooke included his sketch of what looked like a flower garden on spindly stalks. It was the first known depiction of a microbe, showing the reproductive structures of a fungus from “a small spot of a hairy mould” found on the leather cover of a book.

And yet modern microbiology has played surprisingly little role in efforts to conserve some of humanity’s most precious cultural objects: the easel paintings, typically oil on canvas, that adorn the walls of great museums everywhere. A new study published Wednesday in PLOS ONEaims to change that—and proposes using microbes themselves to prevent microbial damage.

A team from the University of Ferrara in Italy examined a 500-year-old painting called “Coronation of the Virgin Mary” (pictured above), by the early Baroque artist Carlo Bononi. This circular work, nine feet in diameter, had been painted on canvas and then applied directly to the ceiling of the Basilica of Santa Maria in Ferrara’s Vado neighborhood. It was Bononi’s masterpiece, and earned him praise for having “mixed his colors with a liquid heart.” But a 2012 earthquake

tore the painting down the middle and necessitated its removal, which revealed further damage from infestation of the dome ceiling by insects, mice and pigeons.

The restoration proceeded on conventional lines. But along the way, clinical microbiologist Elisabetta Caselli and her co-authors took microbial samples by gently rubbing both the front and back of the painting with sterile swabs, then culturing them in sterile tubes and petri dishes. They found thriving bacterial communities of Staphylococcus and Bacillus genera colonizing the painting, along with Aspergillus, Penicillium and other filamentous fungi. Knowing what they were dealing with helped guide conservator and co-author Fabio Bevilacqua as he chose chemical biocides to remove these microbes during the restoration.

Such biocides are problematic, however, because they can be toxic for the people who work with them. Microbial communities also tend to be highly diverse, and a chemical that kills one kind of microbe can inadvertently open up habitat for a neighboring species that is more resistant—and potentially more destructive. In 2001, for instance, conservators began intense treatments using chemical biocides to control a white fungal growth on the spectacular paintings in the Lascaux Caves in southwestern France, estimated to be up to 20,000 years old. The unexpected result was that a previously unknown fungal species called Ochroconis lascauxensis suddenly flourished, staining painted surfaces with black mold.

For the new study, Caselli and her co-authors wondered if—instead of inadvertently opening up new habitats—it might be possible to use beneficial microbes to occupy habitats instead, thereby crowding out harmful microbes. They placed microbial samples from the painting in a petri dish with a growth medium, then added a natural compound that had previously been used mainly to prevent bacterial and fungal growth in hospitals. Its active ingredients are three Bacillus species “that are able to counteract the growth of bacteria and fungi by competitive antagonism and simultaneous production of antimicrobial compounds,” Caselli says. “The advantage of using live Bacillus instead of biocide compounds is that they colonize the treated surface,” she notes, explaining that these microbes displace and gradually eliminate contaminants, reconfigure the painting’s microbiome and prevent recolonization. The test produced “encouraging preliminary results,” she adds. But it will take further testing on a variety of artistic materials and painting fragments to verify that the technique does not “induce any damage to the painted surface.”

Use of microbial and other bio-based methods is further along in other areas of art conservation that are less complex than easel paintings. Restoration companies currently use certain bacteria types, for instance, to remove animal glue from documents or encrusted pollution from buildings and statues. At Catholic University of Portugal, microbiologist Patrícia Moreira is currently experimenting with an antimicrobial nanofilm derived from the exoskeletons of shrimp, with the aim of applying it to protect public sculptures in the city of Porto late next year.

But easel paintings, especially on canvas, are far more challenging. “The problem with canvas paintings is that in one little area it’s possible to have 10 different materials—organic and inorganic together,” says Fatima Morales Marín of the University of Murcia in Spain, who co-authored a 2017 study on biodeterioration in canvas paintings. A painting may support a different assortment of microbes depending on whether: the canvas backing is made of linen, hemp or cotton; it is covered with a thin coat of animal glues or linseed oils; and the pigments in the painting itself include natural materials like red lac (made from insects or plants) or red and yellow earths.

Kristin deGhetaldi, a Delaware-based conservator specializing in hurricane-damaged paintings, who was not involved in the new study, thinks this is an argument for caution. Caselli may have “found that there is potential to inhibit growth of harmful microbes—but it means you now have to apply an additional material to the painting,” deGhetaldi says. “And we have learned from our past that we really have to be careful when spraying new varnishes on paintings or feeding new compounds into cracks. Who knows what complications there could be? Or what interactions with pigments or materials?”

Fernando Poyatos, a professor of painting at the University of Seville who also did not participate in the current work, likewise urges extensive further studies on a variety of artistic materials. He also contends the new study should have employed genetic methods to characterize the microbial community more thoroughly. (Caselli replies that she avoided genetic analysis in this case because it “does not distinguish live or dead microbial cells whereas the aim of our study was isolating all live, cultivable microbes to test their susceptibility” to the Bacillus compound.) Poyatos adds, “the best biocide method is prevention, to keep the paint in good environmental conditions, with proper humidity control.”

Bononi’s restored Coronation of the Virgin Mary is, however, now back in the Basilica of Santa Maria where it belongs. For paintings in such circumstances, Caselli’s study suggests protection may someday come in the form of a better microbiome.

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Richard Conniff’s books include “The Species Seekers–Heroes, Fools, and the Mad Pursuit of Life On Earth (Norton).

Confused Animals Look Around and Sing: “This Is Where We Used to Live”

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by Richard Conniff/Yale Environment 360

A shift in home range by a handful of bird species along an obscure ridge in the Peruvian Andes might once have seemed like sleepy stuff, even to ecologists. Instead, it made headlines last month when researchers reported that the birds’ uphill push for cooler terrain has already resulted in population losses for most species and the probable extirpation of five species that were common at the top of the ridge just 33 years ago.

It was some of the strongest evidence yet for the long-standing prediction by scientists that climate change will lead — is leading now — to widespread loss of wildlife. University of British Columbia ecologist Ben Freeman and his co-authors summed up their findings with a chilling metaphor: Mountain birds, they wrote, are “riding an escalator to extinction.”

The study, in the Proceedings of the National Academy of Sciences, didn’t report any actual extinctions. The Cerro de

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A cousin of the now-extinct Bramble Cay melomys. (Photo: Luke Leung/University of Queensland)

Pantiacolla rises to a maximum height of only 4,642 feet, and the birds that disappeared from the ridgetop persist on higher and larger mountains — in effect, on other escalators — elsewhere in the area. Reliable scientific evidence that climate change has caused actual extinctions is in fact scarce so far, despite projections by climate modelers that such extinctions are likely. The only known example is a marsupial called the Bramble Cay melomys, which vanished sometime after 2009 from a low-lying island off northern Australia, after sea level rise and extreme weather caused repeated inundation of its habitat.

But the new study from Peru lends support to the predictions being made by climate modelers. It also fits into a rapidly expanding body of evidence that plants and animals everywhere are on the move as they struggle to adjust to climate change. The ecological upheaval is “happening right now and it will almost certainly continue to happen,” says Freeman, lead author of the Peru study, and “there is an immediacy to something happening right before our eyes that’s different from a study saying, ‘this is what it’s going to be like in 2100.’”

When plants and animals move uphill, they can lose habitat, simply because mountains become smaller the higher you climb. A shift in range can also mean the loss of old partnerships, the introduction of

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Extinction resistance, bird-style.

new rivalries, and the unraveling of entire ecosystems. Some of these emerging struggles are small-scale and tentative, a bit like a budding workplace rivalry: On Whiteface Mountain in northern New York, for instance, Bicknell’s thrush is state-listed as a species of “special concern.” (A petition to list it under the federal Endangered Species Act recently failed.) It’s a medium-sized brown bird with a speckled throat, and 40 years ago it had the mountaintop to itself. But climate change means that it must now share that landscape with the American robin and Swainson’s thrush, which have both moved in from downhill. Swainson’s thrush responds aggressively to the calls of Bicknell’s thrush. Whether it will eventually push Bicknell’s out of its old habitat may depend on a host of variables from nesting behavior to food preferences.

Other climate-induced range shifts are more like a hostile corporate takeover and can happen with astonishing speed and scale. In western Australia, for instance, ocean temperatures have risen steadily since the 1970s. But as recently as 2010, luxuriant kelp forests still dominated the shallows along 500 miles of coastline north of Perth. Then three exceptionally warm summers in a row wiped out 43 percent of the kelp. By the time the heat waves finally ended, tropical and sub-tropical fish had moved into what was formerly temperate habitat. They nibbled the kelp down to nothing as it attempted to re-sprout, leading to an ecological “regime shift.” The likelihood now is that “rapid local kelp extinction” will progress poleward down thousands of miles of coastline, according to a 2016 study in Science. And since kelp is a major nursery for marine productivity, that “would devastate lucrative fishing and tourism industries worth more than $10 billion (Australian) per year,” along with “catastrophic consequences” for thousands of endemic species.

The range shifts now in progress don’t necessarily stick to the predictable pattern of species heading uphill, or toward the poles, in search of cooler weather. When a team of researchers looked at three sites on protected federal lands in California’s Sierra Nevada, for instance, they found that about half the bird species had moved upslope over the previous 80 years, apparently in response to warming temperatures. But some species had moved downslope, because of increased precipitation — and still others didn’t move at all, or moved upslope in one location and down in another as local climate conditions dictated.

One emerging pattern is that climate change appears to displace tropical species more than their temperate counterparts, though the temperate zone has experienced greater warming. That may be because temperate zone plants and animals already live with “these dramatic fluctuations,” says Freeman. “They have to be able to deal with winter and summer. So it makes sense that a slight change in temperature might not be as consequential.”

Species living in the canopy of tropical rainforests may also be pre-adapted to temperature change, according to a 2017 study in the journal Global Ecology and Biogeography, because their treetop habitat already heats up and cools down so much over the course of the daily cycle. In one study of a rainforest in Panama, ants living in the canopy tolerated temperatures 3.5 to 5 degrees Celsius (6.3 to 9 degrees Fahrenheit) warmer than ground-dwelling species could handle. That suggests lowland species might be more inclined “to shift to mid-elevation, and mid-elevation species to high elevation,” as a first line of defense against climate change, says lead author Brett Scheffers, “and high-elevation species go extinct.” It also suggests the potential for what he calls “flattening forests,” with treetop species descending in search of cooler temperatures, leading to sudden overcrowding in some habitats.

“We are just now starting to see research coming out that is describing the effect of climate changes on species interactions,” says Scheffers, a University of Florida ecologist. “Understanding how species interact is really complicated. Trying to understand species in a tropical rainforest, where you have millions of variables … it makes your head hurt just thinking about it.” And yet being able to make reliable predictions about how or whether species will move can be essential for conservation planning — for instance, in deciding which habitats and corridors to protect for the climate 50 or 100 years in the future.

Those predictions can also shape the debate about when to intervene to save a species. In a controversial step known as “assisted colonization,” conservationists in western Australia have already relocated one species, the critically endangered western swamp tortoise, to a new habitat several hours south of its original home range, where it was threatened by urban development and sharply reduced water supply. But that kind of effort requires deep understanding of how the species lived in its old home and how it is likely to interact with other species in its new one. Conservationists, burned by past species introductions, are deeply conservative about assisted colonization. And yet a long list of other species, like a New Zealand bird called the hihi, face the loss of traditional habitats due to climate change.

“We are just starting to see extirpations,” says Scheffers. “The worry is not just that it may happen, but that it may pick up speed. You have all these species interacting, and now climate change is beginning to remove them. It’s like a big Jenga game,” a tower made of wooden blocks where the trick is to pull out the lower pieces one by one get without bringing down the whole thing. “You wonder not only when it’s going to collapse, but what the hell is going to replace it. That should be alarming, and not just to people who care about biodiversity,” he adds. “The exact same changes are also occurring in agriculture and forestry.”

Scientists trying to make sense of these changes now increasingly talk about “no-analog communities” — ecological communities unlike any seen before. But the more frightening reality, adds Freeman, is that we may be facing a “no-analog future.”

END

 

 

Wilfred Owen on the Horror of War

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Today marks the hundredth anniversary of the end of the first world war, and of the armistice that took place, in the mournful phrase seemingly designed for generations of sonorous broadcasters, “on the eleventh hour of the eleventh day of the eleventh month.”

It sent me back to re-read Wilfred Owen, the British poet who died a hundred years ago this past Sunday, and particularly to the poem where he asks the reader to join him as he watches through the panes of his gas mask as another soldier who did not get his mask on slowly dies:

If in some smothering dreams you too could pace

Behind the wagon that we flung him in,

And watch the white eyes writhing in his face,

His hanging face, like a devil’s sick of sin;

If you could hear, at every jolt, the blood

Come gargling from the froth-corrupted lungs,

Obscene as cancer, bitter as the cud

Of vile, incurable sores on innocent tongues,—

My friend, you would not tell with such high zest

To children ardent for some desperate glory,

The old Lie: Dulce et decorum est

Pro patria mori.

Owen’s message is the same message almost every soldier unlucky enough to experience war and lucky enough to survive it brings home to whoever will listen:  Honor the dead. But do not glorify this horror.

20,000-Year-Old Cave Art from Borneo Depicts Humans Dancing

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by Richard Conniff

A new study in the journal Nature dates this depiction of humans dancing to between 13,600 and 20,000 years ago. But I have to admit that the big news, for the researchers, is actually that another image from the same caves in East Kalimantan, Indonesian Borneo, is the oldest known figurative art of any kind, and it depicts an unidentified animal.

Let’s go to the press release (but stick around because my heart is in the dancing  and we are going to get back to that topic shortly):

[image error]The world’s earliest-known figurative painting is identified in a paper published online this week in Nature. The cave painting, from Borneo, depicts an indeterminate animal and dates back to at least 40,000 years ago.

The limestone caves of Borneo’s East Kalimantan province contain thousands of rock art images, grouped into three phases: red-orange paintings of animals (mainly wild cattle) and hand stencils; younger, mulberry-coloured hand stencils and intricate motifs, alongside depictions of humans; and a final phase of human figures, boats and geometric designs in black pigment. However, the exact timing of these works had been unclear.

Maxime Aubert and colleagues studied a large, red-orange coloured painting of an indeterminate animal in the Lubang Jeriji Saléh cave. Using a uranium-series analysis, the authors date the limestone crusts that have grown over the art. They determine a minimum age for the underlying painting of 40,000 years, making it the oldest-known figurative depiction.

Two other red-orange hand stencils from the same cave have minimum ages of 37,200 years, and a third had a maximum age of 51,800 years old. From these timings, the authors conclude that rock art locally developed in Borneo between around 52,000 and 40,000 years ago, at roughly the same time as the earliest known art from Europe attributed to modern humans. They additionally date several paintings from the mulberry-coloured art phase to between 21,000–20,000 years ago. This later phase is evidence for a cultural change from depicting large animals to consistently representing the human world.

But, even though I love animals, the dancing reminded me of an art exhibit I saw in Denver a few years ago, about dancing, and it gives me a chance to post some of those images here today.

Let’s say it’s to celebrate voting and the persistence of the democratic spirit.  Here we go:

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“Dance of the Haymakers” by William Sidney Mount

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“Capri Girl on a Rooftop” by John Singer Sargent

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Bull Dance, Mandan O-kee-pa Ceremony, by George Carlin

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“Cowboy Dance” by Jenne Magafan

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“The Egyptian Dancers” by Anne Estelle Rice

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“Girls Dancing” by Abastenia St. Leger Eberle

 

That’s it for now. Wear your “I voted” sticker proudly and may your heart be light and your dancing graceful.

Bison Begin to Return to Their Old Home on the Great Plains

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by Richard Conniff/Smithsonian Magazine

Sometime this winter, if all goes as planned, a caravan of livestock trucks will carry 60 American bison out of Yellowstone National Park on a 500-mile journey into the past. Unlike their ranched cousins, which are mainly the result of nineteenth-century attempts to cross bison with cattle, the Yellowstone animals are wild and genetically pure, descendants of the original herds that once astonished visitors to the Great Plains and made the bison the symbol of American abundance. Until, that is, unsustainable hunting made it a symbol of mindless ecological destruction.

When the appalling mass slaughter of 30 million or so bison finally ended early in the 20th century, just 23 wild bison remained in Yellowstone, holed up in Pelican Valley. Together with a roughly equal number of animals saved by ranchers, they became the basis for the recovery of the species, Bison bison, carefully nurtured back to strength within Yellowstone National Park.

Yellowstone has done its job so well, in fact, that the herd now routinely exceeds the limit of about 4000 bison thought to be sustainable within park boundaries. Park rangers have thus had the disheartening annual job of rounding up “excess” bison for slaughter or watching some step across the park’s northern border into a hunt that critics deride as a firing squad. Relocating the animals would be the humane alternative, except for one scary problem: Ranchers and others have long maintained that bison spread brucellosis, a bacterial infection that is devastating to both cattle and bison. But an authoritative 2017 study using whole genome sequencing determined that every case of brucellosis in cattle over the past 20 years “has come from infected elk, not bison.” That finding has made it harder for ranchers to resist the idea of allowing some wild bison out of the park. In addition, the park has instituted an elaborate quarantine protocol to ensure that brucellosis does not travel with them.

The park service will ship the bison to the Sioux and Assiniboine tribal nations at Fort Peck Indian Reservation, in northeastern Montana. A small herd of Yellowstone bison is already thriving there, the result of a modest 2012 feasibility experiment. The plan is to build up that herd and to create a sort of bison pipeline, says Robbie Magnan, the reservation’s fish and game director. As more animals arrive from Yellowstone and pass through a secondary quarantine stage, the Fort Peck tribes will gradually export bison—Magnan prefers to call them “buffalo,” the common name on the reservation—to start herds at other reservations and conservation areas around the Great Plains.

On a practical level, the relocation is simply a way to keep the Yellowstone population in check. But it is also much more than that. The move begins to restore wild bison to the Great Plains and the Plains Indians, who depended on them for food, clothing and shelter. “It has a real spiritual meaning for us,” says Magnan. “The buffalo were taking care of Native Americans from the beginning of time, and now we need to help them.” The fates of indigenous people and bison have long been intertwined in the eyes of government, too:  Federal agents 150 years ago proposed eradicating the bison as a way to get rid of the Plains Indians, in what General William Tecumseh Sherman called “one grand sweep of them all.”

Renewed interest in the future of wild bison—including the 2016 designation of the species as the U.S. National Mammal—comes as the conventional account of their near extinction is facing fresh scrutiny. The story eyewitnesses and historians have told and re-told since the 1870s is that the destruction of the bison herds, almost overnight, was the work of ruthless white hunters arriving by railroad and armed with the latest weaponry. But that account may be too simple.

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(Painting: George Catlin)

Citing fur trade records, archaeological data and contemporary accounts, environmental historians such as Andrew Isenberg at the University of Kansas and Dan Flores at the University of Montana argue that white hunters administered the crushing final blow—but only after a century of environmental challenges and over-hunting by Native Americans. The arrival of horses on the Great Plains from 1690 onward gave tribes a new and highly efficient means of pursuing their prey. More native Americans were also eking out a living from the fiercely variable Great Plains environment, as settlers displaced them from traditional territories. And commercial demand gave them a huge new outlet for bison hides.

Other researchers worry that this contrarian version of history will invite misunderstanding. “People hear only ‘Indians were involved, too,’” says Philip J. Deloria, a Harvard professor of Native American history, “and that has the effect of letting the others off the hook, and of letting the explicit military strategy of destroying Native American resources off the hook.” Deloria argues that the Native Americans’ culture, based on the idea of subsistence, prevented them from decimating the bison in the same devastating way the market hunters did.

It’s tempting to look for a happier ending in the current restoration of the American bison: A great people working together—cowboy and Indian alike–can pull a species back from the cusp of extinction. (The International Union for Conservation of Nature ranks bison as “near threatened.”) But that doesn’t sound right, does it? The bison is a shaggy, snorting reminder that we Americans like to fight about our icons, and one other big fight surely lies ahead. Cattle ranchers will have to face up to their real fear about a resurgent bison herd: It is not about brucellosis, after all. It’s about competition for grass, and a slow turning of the tables, with their own uncertain future in the resource-limited West at stake.

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(Photo: Joel Sartore/National Geographic Creative)

Death of a Fossil Hunter

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Junchang Lu and friend (Photos: Richard Conniff)

by Richard Conniff/Scientific American

When I travel to an unfamiliar country to report a story, I seldom know in advance about the personalities of the people I need to work with: Will they be helpful or in a hurry, plainspoken or obscure? But the moment I met the paleontologist Junchang Lü a few years ago in northeastern China, I knew I had lucked out.

So I was stunned, along with fossil lovers worldwide, to learn that Junchang Lü, a professor at the Chinese Academy of Geological Sciences in Beijing, had died on October 8, age 53. The night before, he was pushing students to complete their manuscripts for publication and talking with fellow fossil-hunter Xu Xing about a joint project, according to an email [image error]from Hokkaido University Museum paleontologist Yoshi Kobayashi, Junchang’s “academic brother,” from their years together as doctoral students at Southern Methodist University in Dallas. “His wife heard Junchang eating and closing windows around midnight. On the next morning, she found Junchang cold. It was a sudden death. Probably heart attack, they said. It is so like Junchang that he talked about manuscripts until the last minute he was gone.”

Junchang Lü made his reputation in part for his numerous discoveries of new pterosaurs. Since parting ways in 2001, he and Xiaolin Wang of Beijing’s Institute of Vertebrate Paleontology and Paleoanthropology (IVPP) had repeatedly one-upped each other in one of the most productive paleontological rivalries of our time, describing a combined total of more than 50 new species, roughly a quarter of all pterosaurs now known.

Among Junchang’s most celebrated finds, he and his co-authors described Darwinopterus modularis—named for Darwin of course, but also for “a remarkable modular combination” of traits from two separate pterosaur groups, suggesting that tightly-linked characteristics could pass down by a process of “modular evolution.” One Darwinopterus specimen, dubbed “Mrs. T” (for Mrs. Pterosaur), came with an egg apparently pushed out on death and another still in her oviduct. It was the first certain evidence of gender in any pterosaur.

On hearing of Junchang’s death, University of Leicester paleontologist David M. Unwin, a co-author on Darwinopterus and many other discoveries, remarked, “I can hear his voice in my head chiding me for having not finished some manuscript or another, or for writing something he didn’t agree with. I hope it never goes away.”

[image error]Junchang Lü was also a leading authority on the dinosaurs called oviraptorosaurs (“egg-thief lizards”).  In an email, University of Alberta paleontologist Philip J. Currie recalled field research with him in Canada, China, and Mongolia. The two described the uncharacteristically tiny oviraptorosaur Yulong mini together, and Junchang was also “instrumental in having Baby Louie (the cover story of a National Geographic article in 1996) repatriated to China, so that we could finish our description of this specimen.”

This embryo squeezed out of a gigantic 18-inch-long egg was first discovered during the early-1990s Wild West period in Chinese paleontology. Amateur fossil hunters quickly sold it into the international trade and it would have remained there, undescribed in science. Instead, Baby Louie now belongs to the Henan Geological Museum in Zhengzhou, near the site of its discovery, and it is properly named Beibeilong sinensis, the embryo of one of the largest oviraptorids known.

“Junchang was the lynchpin that connected so many of China’s fossil collectors and small regional museums to the international academic community,” said University of Edinburgh paleontologist Stephen Brusatte, also by email. “There are dozens of new dinosaur and pterosaur species that the world would have never known about without him. Every time I saw him, he got out his computer and showed me photos of the newest fossils he was working on, always with a big smirk on his face.”

On Twitter, Brusatte recalled Junchang gleefully inducing him to eat rodent-tail stir fry, boiled bull testicles, and mule penis during visits to China. But he also recalled being “led down a narrow hallway, into a side room where a big slab of rock perched dangerously on a much-too-small table. I was speechless. Before us was a skeleton of a dinosaur, its chocolate-brown bones standing out from the drab limestone surrounding it. And all around the bones were feathers. The arms even had full-on wings. We figured out that it was a new species of dinosaur, a close cousin of Velociraptor. We called it Zhenyuanlong”—meaning the Fluffy Poodle from Hell, he notes—“and it is by far the most gorgeous fossil I’ve ever had the privilege of studying, and that was all because of Junchang. He is one of the most important dinosaur researchers of the past half century, and he should be remembered as a scientific titan.”

END

NOTE: You can read my story about pterosaurs for National Geographic here, resulting in part from my visit with Junchang in December 2016. That trip also resulted in a cover story earlier this year for Smithsonian.

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Take a Deep Breath and Say Hi to Your Exposome

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Pig-Pen in his element (Illustration: Charles M. Schulz)

by Richard Conniff/Scientific American

Over the past few decades, researchers have opened up the extraordinary world of microbes living on and within the human body, linking their influence to everything from rheumatoid arthritis to healthy brain function. Yet we know comparatively little about the rich broth of microbes and chemicals in the air around us, even though we inhale them with every breath.

That struck Stanford University genomics researcher Michael Snyder as a major knowledge gap, as he pursued long-term research using biological markers to understand and predict the development of disease in human test subjects. “The one thing that was missing was their exposure” to microbes and chemicals in the air, Snyder says. “Human health is clearly dependent not just on the genome or the microbiome, but on the environment. And sampling the environment was the big hole.”

In a new study published September 20 in Cell, Snyder and his co-authors aim to fix that, with a wearable device that monitors an individual’s daily

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Stanford’s Michael Snyder with monitor

exposure to airborne bacteria, viruses, protozoa, fungi and chemicals—the so-called exposome. Similar studies in the past have largely relied on a few fixed sampling stations; the Stanford researchers instead modified an existing monitoring device, the size of a big kitchen matchbox, to be strapped to a person’s upper arm or kept nearby. The device continually sipped the air around the 15 test subjects at home, at work and on the road, passing the air through separate filters to collect both biological and chemical compounds. DNA sequencing, together with comparisons of the results against a reference genome database of 40,000 species, indicated that the 15 participants had been exposed to 2,560 biological species—more than a thousand of those after wearing the device for just three months.

Mass spectrometry analysis added 3,300 chemical signals to the mix. The researchers were able to identify fewer than a third of them—but they note that all the chemicals had passed through a pore-sized filter for the biological assay and could thus potentially reach deep into a person’s lower respiratory tract. Almost all of these samples contained diethylene glycol, used in products from brake fluid to skin cream. The insect repellant DEET also popped up everywhere, apparently an artifact of sampling mainly during the San Francisco area’s insect-friendly springtime. The study calls this “a previously unrecognized type of potentially hazardous exposure,” noting that no government agency “has evaluated possible health risks associated with inhalation” of such compounds.

Snyder and his co-authors suggest that any given person’s exposome is a product of two separate but interacting “clouds”—a term redolent of the dusty shadow around the character Pig-Pen in the Peanuts cartoon. One cloud is environmental and shared with immediate neighbors; the other is more personal, consisting of human- and pet-centric bacteria, fungi, parasites and protozoa. The test subjects lived scattered across the Bay Area, but the interaction of these two clouds meant that individual exposomes were often strikingly different.

Snyder’s exposome, for instance, showed relatively low exposure to pyridine, apparently because the paint in his house lacks this common antifungal additive; he also lives with a rich fungal flora as a result. By comparing the timing of a mild allergy with his exposome results, he also discovered that the pollen causing his symptoms came not from the pine trees in his yard, as he had suspected, but from a eucalyptus.

Beyond human health, says the study’s first author Chao Jiang, a postdoctoral researcher in Snyder’s lab, the exposome monitor “is a great tool for studying the evolution and ecology of the things living around us, for exploring the diversity of life.” It can even provide insights into our own hidden emotions. Many of the study’s samples, for instance, contained geosmin—the chemical compound responsible for the earthy smell that causes us to inhale deeply, and often with a hint of joy, when rain comes after a drought. “It’s not just about things that can kill us,” Jiang says.

David Relman, a Stanford microbiologist who was not involved in the study, described the new research as “fascinating for the set of questions it raises, more so than for anything it might answer.” Environmental health studies often cannot explain the puzzling variability in individual health among people living in the same area and exposed to the same pollutants, he says. The conventional explanation is a kind of epidemiological shrug: Maybe some people experienced a different dosage? Maybe they were genetically predisposed to be vulnerable?

Exposome monitoring, on the other hand, “allows for massively parallel collection of data,” Relman says. “And that means we can look for combinations of environmental factors that are present at the same place or time, and that might have synergistic or even antagonistic effects for human health.” Imagine a group of people is exposed to the same toxic chemical, he suggests. It might turn out that severe symptoms occur only in those victims also exposed to a certain fungal spore at the same time, for example, and not in people who do not encounter that particular fungus.

“The technology is great. The ability to collect both microbial and chemical components you are exposed to is brilliant,” adds University of Chicago microbiome researcher Jack Gilbert, who also was not involved in the study. “I want the technology. I want it for my own research.”

But Gilbert adds that “the general design of the study was not ideal,” mainly because he believes there were too few test subjects and too few replications in comparable circumstances. A better design, he suggests, might involve comparing the daily exposomes over a month for 10 or 20 health care workers in the hospital, versus an equal number based at home. Gilbert adds that Snyder “has been very open about the fact that the amount of data in the study design wasn’t perfect,” largely for budgetary reasons.

Each monitoring device cost $2,700 before modification, according to the study, and testing of samples was even more expensive. But Snyder says that his team now hopes to deploy a miniaturized version of the monitor—this one about the size of a small pocket matchbox—on 1,000 test subjects a year from now, with the ultimate goal of commercializing a smartwatch version of the exposome monitor.

Snyder adds that he is currently wearing eight different monitoring devices, including three smartwatches, either to collect data or to evaluate new technologies. The first version of the exposome monitor was “a bit clunky,” he admits. “And as they get older they hum more. My wife notices it. There are times when she says, ‘Do you have to have that thing?’” But he adds, in the course of an interview, that it is on his desk, still monitoring as he speaks.

“The Dinosaur Artist” Review: Bad Boy Makes Old Bones Big Business

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by Richard Conniff/The Wall Street Journal

On a Thursday afternoon in May 2012, a paleontologist named Bolortsetseg Minjin was having lunch near the American Museum of Natural History in New York when she heard a news broadcast about a spectacular dinosaur being put up for auction. It was a specimen of Tarbosaurus bataar, a 70-million-year-old close kin and look-alike of Tyrannosaurus rex.

Heritage Auctions, which bills itself as “the world’s largest collectibles auctioneer,” had it splashed across the centerfold of its sale catalog. In midstride, with the mouth on the 4-foot-long skull gaping to show its spiky teeth, and its counterbalancing tail stretched out behind, Lot 49135 stood 8 feet tall and 24 feet long. The auction would take place that Sunday afternoon, just three days off, at a converted warehouse a short subway ride south of the museum. The estimate was that it would sell for $950,000 to $1.5 million. There was only one hitch: T. bataar specimens come from the fossil mother lode of the Gobi Desert, and the sale of fossils from Mongolia is by definition illegal.

Ms. Minjin, though living in the U.S. and married to an American, was also a product of Mongolia, raised in the capital city of Ulaanbaatar, the child of a paleontologist at the Mongolian University of Science and Technology. “For years, she had been trying to raise awareness in her country and beyond of the importance of Gobi fossils,” Paige Williams writes in “The Dinosaur Artist.” It bothered her that “Mongolian paleontologists ceded too much authority to foreign scientists who had built their careers on Gobi fossils and given too little in return.” Even worse, the surging international demand for fossils as decorative objects had encouraged local fossil poachers and an international network of buyers to treat the Gobi as their treasure chest.

Unlike legitimate commercial fossil hunters, who often collaborate with museum paleontologists, poachers almost invariably destroy valuable scientific evidence about the context of the specimens they find. They like to say that most fossils would otherwise erode away to nothing as they weather out of remote and inaccessible hillsides. But that hardly justifies the damage they do. Ms. Minjin fired off an email to a friend in Ulaanbaatar who was an assistant to the then-president of Mongolia. It reached Oyungerel Tsedevdamba as she was getting ready for work Friday morning. “You’re talking to me about dinosaurs?” the president asked her, incredulously. But Ms. Tsedevdamba was soon on the phone arranging for a Texas lawyer named Robert Painter to obtain a court injunction to block the sale of the T. bataar on Mongolia’s behalf.

The man who brought Tarbosaurus bataar to auction—and the main subject of Ms. Williams’s book—was a Florida fossil dealer, then in his late 30s, named Eric Prokopi. Ms. Williams first encountered him while researching a New Yorker profile in 2013 and has dug deep in the years since.

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Prokopi with wife, kids, and family friend

Prokopi started out as a child collecting fossil shark’s teeth on the beach and soon advanced into a full-blown adolescent obsession with paleontology. In college, he volunteered at the Florida Museum of Natural History. But he soon fell out with the scientists there after collecting at a quarry that had banned fossil hunting, and it seemed to set the pattern for everything that followed. Fossils were “just basically rocks,” Prokopi rationalized. “It’s not like antiquities, where it’s somebody’s heritage and culture and all that.”

Prokopi began to make a living less like the “dinosaur artist” of the book’s title and more like a shrewd huckster dealing in shark’s teeth, sunken cypress logs recovered from river bottoms, renovated houses and ultimately—because that’s where the money was—big dinosaurs. Fossils from Mongolia and China, both illegal, became his specialty. In 2007, he sold a T. bataar skull at an auction where two rival bidders drove the final price up to $276,000. The winner, Ms. Williams reports, was the Hollywood actor Nicolas Cage, and the underbidder was Leonardo DiCaprio, who soon placed an order with Prokopi for his own T. bataar.

Prokopi no doubt wanted to believe his rationalization about fossils being “just basically rocks.” But a more accurate way to phrase his approach to the business might have been, “Everybody else was doing it, too.” Ms. Williams quotes a headline from the leading science journal Nature blasting another journal for featuring a new dinosaur from Mongolia sold by a commercial dealer: “Paper Sparks Fossil Fury: Paleontologists Criticize Publication of Specimen With Questionable Origin.” She doesn’t point out, however, that such papers describing new species also routinely appear in Nature itself, as well as in Science and other journals, written by legitimate scientists but based on specimens that have almost certainly been collected illegally by poachers in China. (One key difference: Those specimens at least end up in museums and are available to other researchers.) The combination of limited funding for academic fieldwork, spectacular new discoveries, complicated foreign laws and widespread political corruption continues to set up a thorny trap even for the most scrupulous scientists.

Prokopi wasn’t one of them, however. Among other damning details, Ms. Williams depicts Prokopi spray-painting a bicycle black to facilitate nighttime raids on a private quarry, breaking into abandoned houses to salvage architectural details, and filing false documents to conceal the origin and value of imported specimens. On the personal side, he and his wife and two kids were living without savings or health insurance, according to Ms. Williams, but in a pricey house and with high-end vehicles and, for Eric Prokopi, an extramarital affair, all supported by a mountain of debt—a way of life that made big scores a matter of survival.

[image error]Ms. Williams’s writing is often concise and evocative. Of Prokopi, as his world is falling apart, she writes: “His eyes, brown as acorns, were bracketed by deepening crow’s-feet. His right eye had developed an inflamed twitch. His dark hair sprouted silver like crabgrass after a dense rain.” But at other times, weirdly, she can also sound like a cowboy poet during open-mic night at the Yippee-Ki-Yay Saloon: “In Old West Tampa, there lived a son of New York named Frank Garcia.” Or: “With that, Eric stepped into something he in no way foresaw, and hand to God it started with Genghis Khan.”

Maybe it’s a passing infection from the colorful people she meets in the dinosaur world. But those characters also leave Ms. Williams’s narrative feeling padded, even at 278 pages. The pioneering work of fossil hunter Mary Anning (1800-47) has been abundantly celebrated in recent years, for instance, and it’s not clear how another potted biography here advances the story. Mr. Williams’s 89 pages of endnotes, including a lengthy account of the death of Pliny the Elder in A.D. 79, are also symptomatic of runaway research.

But the story, when she sticks to it, is gripping and cinematic. The Texas lawyer Robert Painter, tied to Mongolia by mining interests and a kind of missionary movement for right-wing American political values, quickly wins his court injunction to block the T. bataar sale. When the auction house decides to proceed regardless, he jumps on a plane to New York. That Sunday afternoon, just after the auctioneer introduces Lot 49135, saying, “It can fit in all rooms ten feet high, so it’s also a great decorative piece,” Mr. Painter rises, holding his BlackBerry up with an angry Texas judge on the other end of the line, and says, “I hate to interrupt this . . . ” The bidders, undiscouraged, take the final price to $1,052,500, “contingent,” in the auctioneer’s phrase, “upon a satisfactory resolution of a court proceeding.”

And the resolution is indeed satisfying. The U.S. attorney for the Southern District of New York promptly issues a warrant for the T. bataar, backs up a truck to a Heritage Auctions warehouse and hauls away the dinosaur. Imprudently, Prokopi fights the forfeiture and, according to Ms. Williams, continues trying to sell his other specimens from Mongolia on the side. Facing criminal charges, he hides his passport under the house and leaves his cellphone at home to minimize the danger of being traced. Agents from the Department of Homeland Security find him anyway and haul him off in handcuffs. A plea bargain and an agreement to cooperate with prosecutors ultimately gets him a short term in a medium-security prison, generously timed so that he can spend the summer with his kids.

Ms. Williams leaves lots of tantalizing loose ends. For instance: Why would a man purporting to be “Steven Spielberg’s dinosaur advisor” working “closely with the Mongolian government” attempt to broker a deal immediately after the auction, as Ms. Williams puts it, to “resolve the T. bataar situation quietly”? After the mysterious death of Prokopi’s main supplier in Mongolia, and two of his supplier’s associates, is there anything to one observer’s speculation that a rich financier there is getting rid of witnesses? And does she buy Prokopi’s implication that U.S. federal authorities prosecuted him mainly to encourage “friendly relations” with Mongolia at a time when U.S. companies were hoping to win mining contracts there? She presents no evidence for it.

The case has at least caused other fossil dealers and auction houses, and perhaps Prokopi himself, to get the message about the need to obtain valid permits before trading in any specimen. The selling of fossils from Mongolia and China has gone underground.

The most satisfying part of the story is that at least 20 major fossils from Mongolia have since been confiscated from U.S. buyers (including Nicolas Cage but not Leonardo DiCaprio, who, Prokopi heard, had already traded up for a better specimen). They are now back home in Mongolia. Better still, the two women who kicked off the investigation—the paleontologist Ms. Minjin and her friend Ms. Tsedevdamba, who had become minister of culture, sports and tourism—personally managed the triumphant return of Prokopi’s Tarbosaurus bataar, in a hugely popular pop-up exhibit in Ulaanbaatar’s central square, unleashing a national bout of what Ms. Williams calls “Tarbomania.” Lot 49135 is now the star attraction of the city’s new (but of course chronically underfunded) Central Museum of Mongolian Dinosaurs.

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Mr. Conniff is the author of, among other books, “The Species Seekers: Heroes, Fools, and the Mad Pursuit of Life on Earth” and “House of Lost Worlds: Dinosaurs, Dynasties and the Story of Life on Earth.“

Digging Out From the Ashes of a Ruined Museum

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by Richard Conniff/Scientific American

With the hollowed-out shell of their old building standing in ruins nearby, and its history-rich contents in ashes, staff and scientists of Brazil’s National Museum met Wednesday morning for the first time since Sunday’s fire. They face a future suddenly bereft of a vast assortment of items from Brazil’s natural and cultural heritage, which explorers and researchers had collected and preserved over the museum’s 200-year history.

No one died or was injured in the fire—astonishingly, given staffers’ last-minute efforts to salvage specimens and equipment as parts of the building’s interior tumbled down around them. But one museum official estimated up to 18 million of the institution’s original 20 million specimens might have been destroyed in the raging blaze, which began soon after the building closed Sunday evening. Among the unique items missing and presumed lost were the only recordings of languages of tribes that have vanished, and the only specimens of plants and animals that have gone extinct, from places that in some cases no longer exist.

Museum Director Alexander Kellner told Scientific American that a meeting with members of Brazil’s congress, cabinet and Pres. Michel Temer had secured an immediate guarantee of $2.4 million to stabilize the museum’s gutted shell, located in a park on the north side of Rio de Janeiro, “and to recover what can be recovered.” This will inevitably be a slow process. Some paleontology specimens, for instance, may have survived within heavy-duty storage containers called compactors. But those compactors are now singed and covered with [image error]rubble—which itself needs to be picked through for fallen remnants of other collections from the upper floors. Kellner said an additional $1.2 million is under discussion to “make the building habitable.” Beyond that, “we are discussing the possibility for next year” of an additional $19.2 million to rebuild the structure of the museum, originally a palace dating from the early 19th century.

But those discussions are taking place as Brazil’s presidential election campaign is about to enter its final month, when promises, and recriminations, come more easily to politicians. On Twitter, Temer called the loss to Brazilian history and culture “irreparable” and a “sad day for all Brazilians.” Critics, however, immediately noted Temer’s right-wing government had drastically cut federal funding for science and education as part of an austerity program. Others countered that he had only deepened cuts begun by his left-wing predecessors. Either way, the budget for the National Museum has plummeted to less than a fifth of what it was just five years ago, and staff have sometimes resorted to crowdfunding to keep exhibits open to the public.

In a television interview, as the building still smoldered behind him, Luiz Fernando Dias Duarte, the museum’s deputy director, noted the government’s lavish expenditures on stadiums to host the World Cup in 2014. “The money spent on each one of those stadiums—a quarter of that would have been enough to make this museum safe and resplendent,” he said. A bitterly repeated rumor, according to American entomologist Steve Lingafelter, who had deposited specimens in the Brazil museum, was “that the cleaning budget for the fleet of cars for high-government officials in Brazil was actually more than the security and maintenance for the [National Museum].”

Investigators have not yet determined the cause of the fire, although government officials said faulty electrical wiring may be to blame. It is also common in Brazil for people to release fire-propelled paper balloons as a rite of celebration, and one of them might have landed on the building’s roof. The government’s development bank had recently committed to spend about $5 million on a renovation program for the museum, including fire-suppression—but no such system had been installed when the blaze broke out. (Kellner said those funds would remain available for the rebuilding program.)

[image error]Firefighters called to the scene Sunday night struggled to slow the fire’s spread because nearby hydrants were dry. They eventually obtained water from a lake in the park. Meanwhile, museum staff broke through doors and entered collections in areas the fire had not yet reached, rescuing specimens and equipment. Museum ichthyologist Paulo Andreas Buckup went into the burning main building with a technician who knew the location of the malacology department’s most important specimens—that is, mollusks—which they began to carry out by the drawerful. “Others were doing the same thing in the crustacean laboratory,” Buckup says. “We could feel the smoke, and what little light we had was from the fire raging just outside.” But that effort quickly ended because of debris dropping down from the building’s pine interior, which Buckup describes as “tinder.”

[image error]The museum’s botany and vertebrate biology departments, its classrooms and some invertebrate collections survived in separate, modernized buildings. Even within the main building many mineralogy and paleontology specimens may have withstood the flames. But the anthropology collection and most of entomology are almost certainly lost, according to Buckup, and the vast library of anthropology and natural history may now survive only in digitized form. Luzia Woman, an 11,500-year-old partial skeleton that is thought to be among the oldest human remains found in South America, is probably also lost.

On Facebook and Twitter, researchers worldwide began to add up the loss to science. Lingafelter described the Brazil museum’s collection of cerambycid (or long-horned) beetles as “among the best in the world.” He wrote that the collection included more than 1,000 holotypes—the specimens by which a species is forever defined—“and hundreds of thousands of specimens. I know the curators there well and my heart is broken for them.”

[image error]Protesters—some of them in tears—gathered on Monday outside the museum ruins, and many were treating the loss as a symbol of government corruption and economic policies critics say have lately devastated Brazilian cultural and educational institutions, its health care system and its infrastructure. “They’re burning our history and they’re burning our dreams,” a high school teacher told The New York Times.

For the global natural history museum community, the loss was also emblematic of the chronic underfunding that has imperiled their work in recent decades. An extensive collection of Brazilian specimens vanished when a fire ravaged Portugal’s Museum of Natural History and Science in 1978—and subsequent fires had damaged other Brazilian museum collections in 2010 and 2015. The loss of Brazil’s National Museum also echoes the 2016 destruction by fire of the entire collection of the National Museum of Natural History in New Delhi, India’s largest assemblage of its plant and animal heritage. Even in the absence of such catastrophic losses, though, the lack of staff and of such basic equipment as climate and humidity control systems also threaten collections almost everywhere—a situation that led the journal Nature to worry in a 2015 article that natural history collections are becoming “the endangered dead.”

“Times like these are a sobering reminder that natural history matters,” the directors of 12 of the world’s largest natural history museums declared in a joint response issued after Sunday’s fire. “Natural history museums document, protect and celebrate the natural world,” the directors said. “Our collections are an invaluable library of moments of life on Earth—each artifact and specimen is a crucial record of how the world became what it is today and a clue into how we can protect it in the future.” The letter also committed the directors’ respective museums to rebuilding the Brazilian collection. Kirk Johnson, director of the U.S. National Museum of Natural History, said curators there are also working “on a larger Smithsonian effort as well.”

In Rio de Janeiro museum staffers called for residents of the neighborhood to bring “fragments of documents, books” and other objects found in the aftermath of the fire to a collecting point in the facility’s garden. Students from UNIRIO, a museum studies program in Brazil, also put out a call for museum visitors to send photos of specimens, adding, “With any luck, some photos will have legible labels, which may help recover at least some data.” (E-mail photos to thg.museo@gmail.com or lusantosmuseo@gmail.com or isabelasfreitas@gmail.com)

“At this point,” Buckup says, “we have enough resources to take care of the immediate needs.” This means finding room for colleagues—90 scientists, 150 technicians, and 500 students—to work in the portions of the museum that have survived. “What we mostly need is a strong commitment from the Brazil government, or even private enterprise, to provide the means for scientists to be restored to minimal working conditions,” Buckup adds. “We have lost lots of history. What we cannot afford to lose is the future of science in this institution.”

Hello, My Name is Denisova 11. And Mom Is S-O-O-O-O Weird. Or Is It Dad?

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Artist’s conception of a Neanderthal: This would be Denny’s mom.  (Photo: Joe McNally/National Geographic)

by Richard Conniff/Scientific American

In a remarkable twist in the story line of early human evolution, scientists have announced the discovery of “Denisova 11”—a female who was at least 13 years old, lived more than 50,000 years ago, and was the child of an early mixed marriage.

That is, her parents were not just of different races, but two different and now-extinct early human types. Their exact taxonomic designations—whether they were separate species or subspecies—is still a matter of scientific debate. But the bottom line for Denisova 11 is that mom was a Neandertal and dad was a Denisovan.

The research, published Wednesday in Nature, is the work of a team led by pioneering paleogeneticist Svante Pääbo at Max Planck Institute for Evolutionary Anthropology in Germany. He and his co-authors presented the first description of the Denisovans in 2010, based on genetic evidence from one of the 2,000 or so bone fragments found in Denisova Cave in the Altai Mountains,

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The Telltale Bone, in 360 degrees (Photo Thomas Higham/Oxford University)

where Siberia borders Mongolia and China. The new discovery is based on another bone fragment from that lot, a 2.5-centimeter-long fragment of what was a femur or humerus, from which the researchers extracted six DNA samples and then cloned them for detailed analysis.

Molecular dating indicates that Denisovans, who are so far known only from Denisova Cave, and Neanderthals, known mainly from sites in Europe, diverged from each other almost 400,000 years ago. They coexisted, probably in relatively small populations scattered across the vast Eurasian landmass, until both became extinct some 30,000 to 40,000 years ago.

But the genetic evidence from Denisova 11 and other recent studies suggests that, on the occasions when they met, Denisovans and Neandertals commonly mated with each other—and with modern humans. Denisova 11’s father carried a small amount of Neandertal ancestry, the study notes, from “possibly as far back as 300 to 600 generations before his lifetime.”

Sharon Browning, a statistical geneticist at the University of Washington who was not involved in the research, praised the new study. “I’m really kind of blown away by it,” she said. “Just to catch the offspring of these two different groups is really remarkable.”

“It looks absolutely solid,” added University of Utah population geneticist Alan Rogers, who also was not part of the work. “I think these guys, as usual, have done a great job.” Asked if Denisova 11 might have simply been the offspring of a mixed Neandertal–Denisovan population—rather than of a mother and father of two such starkly separate backgrounds—Rogers said, “I felt that their analysis made sense. I was convinced by that. It’s not surprising that the two species would mate, if they were together at the same place and time,” he added. “But I don’t think we knew before now that they were together at the same place and time—and if they were, it raises the question of why they were so different.” That is, why didn’t they evolve into a single species?

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View from Denisova Cave (Photo: Bence Viola, Max Planck Institute for Evolutionary Anthropology)

“It’s a really interesting question,” said Harvard University geneticist David Reich, who did not take part in Pääbo’s study. “At Denisova Cave we are clearly looking at an area where these two groups washed across one another, within walking distance of the cave. But there must have been a lot of isolation, as well as mixture.” The hybrid offspring from such divergent populations, Reich said, may have experienced biological problems. Or they may have faced cultural bias, Pääbo noted, if people of mixed backgrounds were “not very well accepted in the cultures of that time.”

Even so, both Neandertals and Denisovans have persisted in the modern human genome. A small percentage of Neandertal ancestry is common in all modern human populations outside Africa; some Denisovan lineage is also common among people from east Asia and Oceania. Earlier this year a study led by Browning indicated the modern Denisovan inheritance derives from at least two separate populations, suggesting they were once dispersed far beyond the Denisova Cave. Pääbo said the next step for his laboratory will be extracting DNA from sediment in the Denisova Cave floors to determine “just when Neandertals were there, when Denisovans were there and when both were there together.”

The dream that scientists could document such interactions in the prehistory of humankind “used to seem impossible,” Reich said. “But now we are getting to witness the dream.”