When my friend Steve Finkel and I get together, the talk is almost always about bacteria. He and I are both huge fans, from different angles. I’m a spectator. He studies them (E. coli) in his lab at the University of Southern California. I used to work down the hall from him, so I’m sure that some of my enthusiasm for the tiny creatures can be blamed on him, along with USC’s out-of-control microbe-lover Ken Nealson (Shewanella oneidensis is his bug, among others).
Single-celled though they may be, bacteria and other microbes are far from simple. They can thrive in hostile spots — from the acidic, low-oxygen environment of the stomach to boiling hot springs or frozen tundra. Some even breathe rock (see Nealson’s bug). They can adapt rapidly in rough times, switching their metabolic scheme or just going dormant. Bacteria have many admirable qualities that many of us would want for our children: grit, perseverance, flexibility and seemingly limitless creativity (albeit mostly biochemical).

Their flexibility and creativity were on full display at a recent meeting, a few blocks away from the Science News offices (and the occasion for Finkel’s visit to Washington, D.C.). Reports from the meeting all involve science that takes advantage of the latest techniques for probing the bacterial experience — be that finding out how bacteria can survive without “essential” enzymes and how offensive attacks can actually give rise to bacterial cooperation. Now that bacterial genome sequencing is cheap, Finkel and fellow scientists can watch microbes evolve in the lab, in real time. Taking genetic snapshots along the way, scientists are building up a detailed picture of the genetic shifts that allow a new strain to become dominant in a given experiment. It is watching evolution in action, Finkel says, quite literally.

But microbes are organisms, much more than little sacks of evolving biochemistry. They have immune systems, of a sort. It was through studies of one bacterium’s antiviral defense that scientists first discovered what’s become the most versatile and headline-grabbing gene editor of all time: CRISPR/Cas9. These ingenious molecular scissors work within microbes to target viral DNA that has invaded bacteria and literally cut it to shreds. Harnessed and aimed at the DNA of other organisms, CRISPR/Cas9 has proved much easier to work with, cheaper and more precise than existing editing tools. It’s been wildly successful at precisely deleting genes, helping to reveal gene functions that have long remained hidden, as Tina Hesman Saey reports in “CRISPR gets a makeover.”

But even this wonder tool has its limits. So, as a legal battle over who owns the patent to the technique rages on, scientists (including the current patent holder) are already tweaking it, adjusting it, engineering it and searching for CRISPR-like alternatives, an effort Saey describes in her cover story. Some scientists are going back to the source (bacterial immune systems) to find new enzymes that might help build a library of precision gene-editing tools — one for each job.

That brings me back to why I love microbes — resilient, creative survivors that they are. Like the best humans, they are always coming up with new solutions.

The fate of Africa’s elephants may be decided before the weekend is out. Members of the International Union for the Conservation of Nature World Conservation Congress, happening this week in Honolulu, will decide on Motion 7, whichwould call on the IUCN to encourage governments to shut down the ivory trade — and provide help in doing so. The hope is that ending the demand for ivory — and with it, hopefully, the large-scale elephant poaching that has been going on for more than a decade — would allow both savannah and forest elephants to recover. But two new studies show that the species have declined so much that, even after poaching ends, their populations will take decades to recover.

The first study presents results from the Great Elephant Census, the first-ever continent-wide effort to survey savannah elephants (Loxodonta africana), the more common of the two species of elephant in Africa. Wildlife researchers, conservation organizations and government agencies worked together to conduct aerial surveys of elephant herds in 18 African nations. They cataloged more than 350,000 elephants (not including the 22,700 counted in Namibia in 2015, or elephants in South Sudan and Central African Republic, which have yet to be counted). An estimated 84 percent of the animals were living in protected areas, the team reports August 31 in PeerJ.

While that may sound like a lot of elephants, the raw numbers are a bit misleading. That’s because not long ago there were so many more. The researchers estimate that 144,000 savannah elephants were lost between 2007 and 2014, with elephant numbers in the surveyed populations falling by about 8 percent per year largely due to poaching. If these populations continue to decline at that rate, their numbers would be halved every nine years, and smaller populations could be wiped out completely, the researchers warn.

And living in a protected area, like a park or nature reserve, doesn’t mean that the elephants are necessarily protected from poaching or conflict with humans. The Great Elephant Census team found high levels of elephant deaths, which could indicate poaching, in Tsavo East National Park in Kenya, Mozambique’s Niassa National Reserve and Rungwa Game Reserve in Tanzania. “Heightened antipoaching measures are needed in these and other protected areas to ensure that they do not become mere ‘paper parks’ for elephants,” the researchers write.

The situation may be worse for forest elephants (L. cyclotis), which scientists discovered only five years ago are a genetically distinct species. No one is quite sure how many forest elephants there are (the Great Elephant Census didn’t count them), but there are far fewer of these elephants than their savannah cousins. Like savannah elephants, forest elephants are dealing with losses from poaching, habitat loss and human conflict. A 2013 study estimated that they lost 62 percent of their numbers between 2002 and 2011, and a 2014 study estimated that as much as 10 to 18 percent of the forest elephant population disappears every year. And a new study finds that these elephants may be even less equipped than the savannah elephants to bounce back once poaching stops.
Because it has taken a long time to recognize that forest elephants are their own species, there isn’t a lot of basic biology known about them. But researchers collected data on more than 1,200 elephants that visited a forest clearing in the southwestern Central African Republic between 1990 and 2013, and have now used that data to make some startling observations about how forest elephants differ from savannah elephants. Their results appear August 31 in the Journal of Applied Ecology.

Biologically the two species of African elephants are fairly similar, but forest elephants have slowed down their reproduction. Female forest elephants can conceive when they are as young as 10 years — but most don’t. The elephants in the study reached sexual maturity as young as 13 and as old as 28 (the median was 23 years, compared with 12 for savannah elephants). And forest elephants breed only once every five to six years, compared with every three or four in savannah elephants. This means that a population of forest elephants would double in size at less than half the rate as savannah elephants.

The researchers suspect that this slow population growth is an outcome of living in the forest environment. Forest elephants rely on a diet of fruit, leaf matter and bark, but most forest growth happens at the treetops. So elephants are going to be limited in what and how much food they can find. “Low reproductive rates may in fact be the norm for large-bodied mammals in these rain forests,” the researchers write.

That wouldn’t be a problem except for the fact that their numbers are being driven lower and lower by poaching. The research team estimates that it could take 80 to 90 years for forest elephants to recover to their pre-poaching numbers — and that’s only if poaching stops. Savannah elephants would recover more quickly, but it would still take decades.

And that’s why the IUCN vote to potentially end the ivory trade is so important — because if we want to see elephants continue to roam Africa’s savannahs and forests, we need to stop the trade that is incentivizing people to kill them.

PASADENA, Calif. — It’s hard being a comet sometimes. Comet 67P/Churyumov-Gerasimenko is developing stress fractures and might break apart in the next several hundred years.

Comet 67P is famous for its oddball shape. With two lobes joined together at a neck, it vaguely resembles an interplanetary peanut. The Rosetta spacecraft, which ended its 26-month visit to the comet in September (SN Online: 9/29/16), noticed a large crack in the neck in 2014. After the comet made its closest approach to the sun in August 2015, the fissure grew by several hundred meters and new cracks appeared.

The fractures appear to be developing as forces subtly bend the comet to and fro, Stubbe Hviid, a planetary scientist at the German Aerospace Center Institute of Planetary Research in Berlin, reported October 17 in a press conference at a meeting of the American Astronomical Society’s Division for Planetary Sciences. Hviid and colleagues combined maps from Rosetta with computer simulations of all the forces at work within the comet to determine how the cracks develop. They found that the two bulbous ends rock in opposite directions as the comet spins, flexing the neck and creating severe stress. Because the comet isn’t held together strongly — it’s a conglomeration of dust and ice not much stickier than snow, Hviid said — the neck is starting to break. After a few hundred more years, he said, the comet could fold itself in half as the two lobes snap apart and smoosh together.

Buzzkill
Astronomers confirmed the existence of an exoplanet, Proxima b, only 4.2 light-years from Earth, Christopher Crockett reported in “Planet orbits sun’s nearest neighbor” (SN: 9/17/16, p. 6).

Some readers thought there was too much excitement over the new potentially habitable planet.

Christina Gullion believes keeping Earth habitable in the face of a changing climate is more important than searching for other planets. “Off-planet exploration seems to me to be a counterproductive diversion of funds and scientific knowledge,” she wrote. “I think it is self-indulgently romantic to invest scarce resources in curiosity about life out there in the universe when we could be protecting and enhancing life here on Earth.” Although Proxima b is relatively close to Earth, Gullion correctly noted that it is still too far away to reach anytime soon.
Even if humans could travel to Proxima b, reader Steve Moore pointed out, scientists don’t know much about the planet. It could be tidally locked with its star and vulnerable to solar flares, he said, which would make it hard, if not impossible, for humans to live on.

Crockett agrees that enthusiasm for Proxima b should be tempered by the little we know about the planet — so far, only its minimum mass, orbit and a few details about its star. Tidal locking is possible, Crockett says, “though there’s an active debate about whether that would be OK for habitability or not.” And though solar flares also pose a threat to habitability, “a denser atmosphere might be able to withstand Proxima’s flares,” he says. “We just won’t know until we get better data on the planet.”
Despite all of the unknowns, Crockett still thinks it’s an exciting discovery. “The proximity of the planet means it’s probably going to come under a lot of scrutiny in the years and decades to come,” he says. “And knowing that there’s a planet right next door is pretty neat. I can’t wait to see what we learn about it.”
Pavlov’s fish
Researchers worry that escapes of farmed salmon, cobia and other fish into the ocean could weaken or harm native wildlife, Roberta Kwok reported in “Runaway fish” (SN: 9/17/16, p. 22).

“I wondered if anyone had considered training farm-raised fish to associate a sound or some other stimulus with food,” Rick Gelbmann asked. “Then when fish escape, the sound could be used to attract the fish, making it easier to recapture them.”

Scientists have successfully trained species such as Atlantic salmon to swim to a food source in response to a tone. But for runaways, this strategy “is basically impractical,” says Tim Dempster, a sustainable aqua­culture researcher. Fish often escape d­uring storms when it’s tough to deploy equipment. Escapees tend to flee quickly, so the sounds might not reach them. And farmers would have to train a huge number of fish just to potentially recapture a small fraction.

Bioacoustician Frédéric Bertucci notes that adding another source of human-made noise to the ocean could also affect nearby wild animals.

Star struck
Despite a new analysis of data from the Kepler Space Telescope, the slow-dimming and sporadic flickering of Tabby’s star remains a mystery, Christopher C­rockett reported in “Fading star still baffles a­stronomers” (SN: 9/17/16, p. 12).

Walt Davis wondered if the dimming could be caused by the star orbiting a black hole. “As the star moves closer to alignment behind [the black hole] … the star’s light rays are being more and more bent away from us,” he wrote.

“As weird as this star is, a black hole is probably not the culprit,” Crockett says. Astronomers would be able to detect the star’s orbital motion if it were orbiting a black hole, but the star appears to stay put. “And if gravity of a companion black hole was occasionally bending the starlight directed toward Earth, it would make the star appear brighter, not darker,” he says.

The 20th century will go down in history — it pretty much already has — as the century of the physicist. Physicists’ revolutionizing of the scientific world view with relativity and quantum mechanics might have been enough to warrant that conclusion. Future historians may emphasize even more, though, the role of physicists in war and government. Two such physicists, one born at the century’s beginning and one still living today, typify that role through their work in developing weapons, advising politicians and shaping policy while still performing outstanding science.

Best known of the two is Enrico Fermi, the Italian intellectual giant who escaped from fascist Italy to America after winning a Nobel Prize for his research in nuclear physics.
When he arrived in the United States in 1939, Fermi almost immediately went to work studying nuclear fission, discovered only weeks earlier in Hitler’s Germany. Eventually Fermi took a major role in the Manhattan Project, leading the team that first demonstrated a controlled nuclear fission chain reaction.

Fermi, a foreigner, assumed a lead role because he was so widely recognized among the world’s physicists as infallible — hence his nickname “the pope.” In The Pope of Physics, Gino Segrè and Bettina Hoerlin chronicle Fermi’s life and science with insight and rich detail.
Fermi is often cited as the last of the great physicists who excelled both at theory and experiment. His theory of the weak nuclear interactions, produced in the early 1930s, remains a key segment of modern physicists’ understanding of matter and forces. His experimental work on neutrons won the Nobel (even though aspects of those experiments turned out to have been incorrectly interpreted).

Segrè (whose uncle was a collaborator of Fermi’s) and Hoerlin explore the personal and political influences on Fermi’s science and relate in detail his experiences in the effort during World War II to develop the atomic bomb. His postwar government service included membership on the General Advisory Committee to the new U.S. Atomic Energy Commission. He was also on the University of Chicago faculty until his abrupt death in 1954 from stomach cancer. He was 53.
Briefly mentioned in Segrè and Hoerlin’s account is a visit near the end of Fermi’s life from one of his former graduate students, Richard Garwin. To Garwin, Fermi mentioned regret at not having been even more involved in public policy. Perhaps, Segrè and Hoerlin suggest, that conversation inspired Garwin, “who went on to have an extraordinarily distinguished career as a presidential adviser on science and security issues.”

As Fermi’s postdoc at Chicago, Garwin also spent time at the lab in Los Alamos, N.M., where the atomic bomb had been built. By 1951, the lab’s focus was on the hydrogen bomb, or the Super, powered by fusion in addition to fission. Despite input from Fermi and significant insights from the mathematician Stanislaw Ulam and physicist Edward Teller, designing the Super had proven an insuperable problem. Garwin offered to help; Teller assigned him the task of designing an experiment demonstrating how the Super could work. In a couple of weeks, Garwin handed in the blueprint for the actual bomb itself.

In True Genius, veteran science writer Joel Shurkin recounts this story in detail for the first time. For decades, popularizations credited Teller with the development of the hydrogen bomb; Garwin’s role was long classified. Late in life, Teller, who died in 2003, revealed Garwin’s crucial role, which was eventually reported in the New York Times.

As Shurkin emphasizes, Garwin designed the bomb because it was a technical problem that he knew how to solve. But he spent the rest of his career devoted to arms control (both as an adviser inside government and a critic from the outside).

Garwin made significant contributions to physics as well — many modern technological conveniences, such as the GPS satellite system, owe their existence to Garwin’s insights. Last November, in recognition of all these achievements, President Barack Obama awarded Garwin the Presidential Medal of Freedom.

Shurkin’s account of Garwin’s life is detailed but often hard to follow, sometimes jumping from decade to decade (not always in order) in the space of a few paragraphs. And the book is marred by poor fact-checking (tritium is certainly not an isotope of lithium; Otto Hahn was a chemist, not a physicist; and Niels Bohr’s mother was Jewish, not his father). And peculiarly the title, the book’s publicity material says, refers to Fermi’s description of Garwin as a “true genius,” while the text of the book quotes Fermi as calling Garwin a “real” genius.

Nevertheless, Shurkin’s account is by far the best (virtually only) complete record of the life of a scientist who devoted his career to serving the public good — while also doing extraordinary science. Garwin really, truly, is a genius.

In 1959, Lyudmila Trut rode trains through Siberia to visit fox farms. She wasn’t looking for furs. She needed a farm to host an audacious experiment dreamed up by geneticist Dmitry Belyaev: to create a domestic animal as docile as a dog from aggressive, wily silver foxes.

Evolutionary biologist Lee Alan Dugatkin helps Trut recount this ongoing attempt to replay domestication in How to Tame a Fox. The mechanics of domestication are still a matter of intense scientific debate. Belyaev’s idea was that ancient humans picked wolves and other animals for docility and that this artificial selection jump-started an evolutionary path toward domestication.
Back in the 1950s, testing the idea was dangerous work, and not just because untamed foxes bite. In 1948, the Soviet Union, under the scientific leadership of Trofim Lysenko, outlawed genetics research. Lysenko had risen to power based on fabricated claims that freezing seeds in water could increase crop yields. “With Stalin as his ally, he launched a crusade to discredit work in genetics, in part, because proof of the genetic theory of evolution would expose him as a fraud,” Dugatkin and Trut write. Geneticists often lost their jobs, were jailed or even killed, as was Belyaev’s own brother. So Belyaev cloaked his domestication experiments in the guise of improving the fur-farming business.

Fox researchers started by testing the temperament of about 100 silver foxes each year. About a dozen of the foxes, slightly calmer than most, were bred annually. Within a few generations, some foxes were a bit more accepting of people than the starting population. That small difference convinced Belyaev of the experiment’s promise, and he recruited Trut to carry out a larger breeding program.
After choosing a farm, in 1960, Trut brought a dozen calm foxes from the preliminary project, including two that would let her pick them up. She also chose the calmest 10 percent of the foxes at the new farm for breeding, both to increase the number of animals and to increase genetic diversity. Eventually, she began breeding aggressive foxes as a comparison group for the tame ones.
Trut and Dugatkin lovingly recount some of the experiment’s milestones, including the first fox born with a wagging tail and the first one with droopy ears — two hallmarks of domesticated animals. Trut recalls the foxes she’s lived with and, heartbreakingly, the ones she lost, or had to sacrifice to keep the experiment going after the collapse of the Russian economy in 1998 led to funding problems. At every step, the authors skillfully weave the science of domestication into the narrative of foxes becoming ever-more doglike.
Trut has kept Belyaev’s dream alive for nearly 60 years. Now in her 80s, she still runs the experiment and has eagerly collaborated with others to squeeze every drop of knowledge from the project. The work has shown that selecting for tameness alone can also produce a whole suite of other changes (curly tails, droopy ears, spotted coats, juvenile facial features) dubbed the domestication syndrome. With the help of geneticist Anna Kukekova, Trut is searching for the genes involved in this process.

The project now sells some of the foxes as pets to raise money, although one could argue they aren’t fully domesticated. The foxes may wag their tails and flop on their backs to get their bellies rubbed, but Trut says they still don’t follow commands like dogs do. It probably took Stone Age humans hundreds or thousands of years to domesticate wolves. The silver fox experiment has replayed the process in fast-forward. It may speed scientists’ quest to understand the DNA changes that transformed a wolf into a dog.

A warmer climate could put some damselflies in distress, as others get bigger and hungrier.

Because of differences in hatching time, nymphs — the immature form of the insects — vary in size. Sometimes when ponds are overcrowded, other food options are scarce or size differences are significant, bigger, older nymphs nosh on the little nymphs. While temperature doesn’t typically affect when damselflies hatch, it does affect how fast they grow.

So a team at the University of Toronto tested whether a warmer world would also be a damselfly-eat-damselfly one. Using damselfly nymphs (Lestes congener) hatched in the lab, researchers put nymphs of various sizes in two different temperature environments, one a balmy 18° Celsius and the other a toastier 24° Celsius.

Damselflies in the hotter setting displayed bigger differences in body size, higher activity levels and increased cannibalism rates. Both size extremes and more frequent foraging probably contribute to the increase in intraspecific dining tendencies, the researchers write May 16 in Biology Letters.

Sure, students in the classroom have to remember facts, but they also have to apply them. Some research efforts to enhance learning zero in on methods to strengthen memory and recall, while others bolster students’ abilities to stay on task, think more fluidly and mentally track and juggle information.

But there’s a catch. The science behind student learning is so far based on carefully controlled studies, primarily with college students. Do the same approaches work with younger students? Will they work in a classroom of 25 or 30 kids of varying abilities?
These are questions researchers are asking now, says Erin Higgins of the U.S. Department of Education’s National Center for Education Research. Moving from the lab to a classroom, with all its disruptions and distractions, is key for pinning down what works, under what conditions and for whom. In the process of tweaking some of the most promising tools and strategies for classroom use, educators hope to find ways to help low-performing students gain skills that already pay off for their more successful peers. The efforts described here draw on new, innovative training methods to boost learning in K-12 classrooms. Higgins calls them “great examples” of the work under way.

Recall with cues
For college students, “free recall” is one of the most effective ways to make new knowledge stick, says psychologist Jeffrey Karpicke of Purdue University in West Lafayette, Ind. Students who read a passage and then jotted down details they remembered from the material recalled about 50 percent more information a week later than did students who just reviewed the material.
The trick for younger learners, Karpicke found, is to provide cues to help recall, without making the task too easy. After studying lists of unrelated words (banana and football), fourth-graders either restudied the words or practiced retrieving them from memory before taking a free recall test. Findings, published last year in Frontiers in Psychology, show that children at all reading levels remembered at least 25 percent more words when they practiced retrieving with the help of some cues compared with just rereading the lists.

With psychologist Michael Jones of Indiana University Bloomington, Karpicke is creating a computer-based self-test to help kids hone their retrieval skills. Students might have to answer fill-in-the-blank questions or rearrange scrambled words. Teachers will be able to tailor the tests to the curriculum. Parts of the program are being tested in schools in West Lafayette this year. The program gets harder as children succeed but easier if they struggle. “It’s important that students experience success,” Karpicke says, while keeping the task challenging.
Hold that thought

Working memory, which allows a person to hold on to information long enough to use it, is often a weakness in children who struggle with math, says educational psychologist Lynn Fuchs of Vanderbilt University in Nashville.
Handy for remembering a phone number long enough to find a pen to write it down or for multiplying numbers in our heads, working memory can be strengthened through exercises that put progressively tougher demands on it. But general training may not be enough to help struggling math learners, according to a 2015 review of school-based programs, published in the Journal of Educational Psychology.

Fuchs has developed a routine that embeds working memory exercises within math lessons. Designed for second-graders at risk for math difficulties, the program has students focus on key words in a word problem and hold the words in mind while breaking the problem into smaller segments and choosing the right math tools to solve the problem.

Aiming to catch young learners before they fall behind, researchers are testing the program in Nashville classrooms this school year.

Sum of the parts
Researchers typically test one new strategy in isolation, but in real classrooms, educators may try more than one approach at once. Jodi Davenport of WestEd, a San Francisco–based education research and development group, codirected a multi-institutional effort to revise a seventh-grade math curriculum using a handful of promising strategies.
Lessons were spaced out to expose students to key concepts or procedures multiple times and were combined with frequent quizzes. Graphics accompanied examples of how to work a problem, to strengthen the connection between the visual and verbal material. Researchers trained 181 teachers at 114 schools and then tracked 2,465 students in 22 states over a full school year.

Strategies such as showing incorrect examples along with correct ones (to point out common errors) and removing distracting information were especially helpful to underperforming students, Davenport says. Students with lower pretest scores scored higher on posttests in six of eight math units when using the new curriculum versus the traditional materials, the researchers reported in March in Washington, D.C., at the Society for Research on Educational Effectiveness meeting.

Testing the program in so many schools amid teacher turnover and other real-life challenges made control­ling for variance hard, so the data weren’t as robust as researchers had hoped. But there appeared to be improvements, particularly in girls, underrepresented minorities, English-language learners and special education students. The methods work by helping students focus and link related info, Davenport speculates. “Successful students have these skills,” she says. “They’ve developed strategies … to focus their attention and employ problem-solving skills as they work through a problem.” She hopes to help teachers give struggling kids those same skills.

Granting executive powers
Students must learn to stay focused in the face of distraction, to direct actions toward a goal and to hold what they have just seen or heard in mind while they work with it. These abilities are part of a set of cognitive skills called executive function.
There’s strong evidence that well-designed video games can improve executive function among teens and adults, says psychologist Bruce Homer of the City University of New York. “But we need more research to determine if — and how well — these skills transfer to the classroom to … improve academic performance,” he says. With psychologist Richard Mayer of the University of California, Santa Barbara, and Jan Plass of New York University’s game design center, Homer is developing a series of video games for students from middle school to college. Each game targets a specific area of executive function, such as shifting attention or avoiding distractions.

The first of three games is in testing, assigned as homework for 300 kids in Santa Barbara and New York City schools. In the game, students must quickly adapt to rule changes as aliens land on Earth and request help gathering supplies. Preliminary findings show that after eight 30-minute sessions, players of the alien game showed substantially greater improvements in ability to shift strategies in standard cognitive tests compared with students who played a different game. This fall, researchers plan to study whether gains in executive function from game play can improve actual performance in specific academic areas.

Tiny balls of melanin could someday paint the rainbow. They’re one of the key ingredients in a new way to craft a spectrum of structural colors — hues created when light interacts with special nanostructures.

Structural colors are a longer-lasting alternative to chemical pigments, which lose all pizazz when they break down. Examples of durable hues abound in nature. For instance, many bird feathers and butterfly wings get their brilliant colors in part from nanoscale texturing (SN: 6/11/16, p. 32). But finding a simple way to generate these complex structural colors — a technique that can be scaled up and used to create many different hues — has been a tricky task.
In the new study, researchers made nano-sized balls of melanin aggregate into clusters called supraballs. Melanin, the pigment that darkens skin, appears black in the individual nanoparticles. But altering the spacing of the nanoparticles in the ball affects how the particles scatter light, generating a spectrum of structural colors, says study coauthor Ali Dhinojwala, a polymer scientist at the University of Akron in Ohio. So he and colleagues added a thin silica coating to the outside of the melanin nanoparticles. The coating acts like a bumper, limiting how close the particles can pack together.

Varying the diameter of the melanin core and the thickness of the silica shell creates supraballs in a range of colors, including olive, orange-red and navy blue, the researchers report September 15 in Science Advances.

This recipe is simpler than other ways of making structural colors in the lab, Dhinojwala says. The nanoparticles cluster into supraballs at room temperature in a mixture of water and an alcohol called octanol, and are easy to extract as a powder. Plus, nanoparticles with different dimensions can be mixed in one supraball to create any shade imaginable.

Orangutans living in forested foothills on the Indonesian island of Sumatra represent a previously unknown species, researchers say.

Skeletal and genetic evidence puts these apes on a separate evolutionary trajectory from other orangutans in Sumatra (Pongo abelii) and Bornean orangutans (Pongo pygmaeus), says a team led by evolutionary anthropologist Michael Krützen of the University of Zurich. The researchers named the new species Pongo tapanuliensis, or the Tapanuli orangutan. Krützen’s team reports its findings online November 2 in Current Biology.
The name P. tapanuliensis refers to three north Sumatran districts — North, Central and South Tapanuli — where no more than 800 of these orangutans inhabit several forested areas. Tapanuli orangutans live on the brink of extinction due to road construction, illegal forest clearing and killings by villagers and hunters, the scientists say. Estimates vary, but the World Wildlife Fund puts the total number of living orangutans at nearly 120,000.

Researchers observed Tapanuli orangutans in their hilly habitat as early as the 1930s. Yet these apes have long been overlooked in favor of Sumatran orangutans that live in swampy forests north of the Tapanuli population. Bornean orangutans also live in swampy forests.

A chance to explore Tapanuli orangutans’ biology came in 2013. Krützen’s team gained permission to study the museum-held skeleton of an adult male Tapanuli orangutan that had been killed by villagers. Comparisons with skeletons of 33 Sumatran and Bornean male orangutans revealed a range of differences in the skull and teeth of the Tapanuli ape, including a distinctively narrow palate and a relatively short jaw joint.

An analysis of DNA from 37 living orangutans, including two Tapanuli animals, indicated that Tapanuli and Sumatran orangutans diverged from a common ancestor around 3.4 million years ago. Shared gene variants pointed to interbreeding between the two species after their evolutionary split. Cross-species hookups declined sharply around 100,000 years ago and then stopped between 10,000 and 20,000 years ago, the scientists say. Sumatran and Bornean orangutans separated around 674,000 years ago, the team estimates.
Only Tapanuli orangutans appear to be direct descendants of the first mainland Asian orangutan ancestors to reach Sumatra, the investigators find. Later migrations of mainland animals may have led to the evolution of Sumatran and Bornean orangutans

Scenarios in which closely related ape species interbred after evolving into distinctive biological populations probably occurred frequently, Krützen says. DNA studies suggest ancient chimpanzees and bonobos interbred, as did Homo sapiens and Neandertals (SN: 10/15/16, p. 22). Such evidence has fueled a long-standing debate over how to define the term “species” (SN: 11/11/17, p. 22).

Krützen’s team makes a good case for a third orangutan species that interbred for a long time with a closely related species, says biological anthropologist Rebecca Ackermann of the University of Cape Town in South Africa. “I’d go out on a limb and say not only that [interbreeding] played an important role in the evolution of all living apes, but that it shaped the evolution of extinct ones as well.”