Genetically modified mosquitoes can put a dent in dengue cases. The first evidence of the health effects of releasing the insects into the real world comes from a year’s worth of disease data from Brazil, says biotech company Oxitec, the mosquitoes’ engineer.
Over much of the city of Piracicaba, where conventional methods of mosquito control were used, cases of the debilitating virus dropped 52 percent from mid-2015 to mid-2016. But in neighborhoods where Oxitec released GM Aedes aegypti mosquitoes as an extra control, the results were even better. Dengue cases there dropped 91 percent, from 133 to 12, according to a press statement from Oxitec, based in Abingdon, England. SUBSCRIBE Oxitec’s genetically modified line of Ae. aegypti mosquitoes attack a wild population by romantic deception. The GM males sire offspring with built-in self-destruct DNA that kills the new generation off in the wild before they begin to bite. This is the modern biotech twist on a decades-old strategy for controlling insects by releasing sterile males in such numbers that many females waste their reproductive effort, and a population eventually breeds itself out of existence.
In tests around the world before this, Oxitec has published or released evidence that mosquito numbers go down when the GM decoys swarm through a neighborhood. But this is the first claim that reducing those mosquitoes indeed means less disease. That information — though not the result of a full epidemiological study — could address a gap in the debate in the Florida Keys over a proposed test release there. Opponents of introducing GM organisms, even ones pretty reliably programmed to die, have objected that there has been no evidence the measure brings any health benefit.
Brazil, where dengue and now Zika have wreaked havoc, has been much more open to the use of GM mosquitoes. In this case, Oxitec looked at the numbers of dengue cases reported mid-year to mid-year from Piracicaba’s epidemiologic surveillance program. The GM mosquito test focused on an area, called CECAP/Eldorado, of about 5,000 residents where the dengue rates were higher than in the rest of the city in 2014‒2015 — 2.66 percent incidence rate versus 0.902 percent. After a year of control measures including releasing the GM mosquitoes, the 2015‒2016 numbers show the test area now fares better than the rest of the city. Its dengue incident rate dropped to 0.24 percent compared with the municipality incidence rate of 0.437 percent.
Data on mosquito populations and diseases are rare and important, says Grayson Brown, who directs the Public Health Entomology lab at the University of Kentucky in Lexington. He wonders how far down the GM mosquitoes drove the wild population before dengue rates started dropping. (Oxitec reports that mosquito numbers dropped 82 percent, but, Brown asks, 82 percent of what?) Such a useful number turns out to be virtually unknown for most mosquito-borne diseases and their countermeasures, except for malaria, he says. Plenty of programs monitor disease outbreaks as they treat mosquitoes, but ethically and politically, “you can’t just leave a section of the city untreated.” Adding the extra measure of the GM treatments offers a way to fill that data gap.
Four and a half billion years ago, after Earth’s fiery birth, the infant planet began to radically reshape itself, separating into distinct layers. Metals — mostly iron with a bit of nickel — fell toward the center to form a core. The growing core also vacuumed up other metallic elements, such as platinum, iridium and gold.
By the time the core finished forming, about 30 million years later, it had sequestered more than 98 percent of these precious elements. The outer layers of the planet — the mantle and the crust — had barely any platinum and gold left. That’s why these metals are so rare today. Battles have been fought, and wars won, over the pull of shiny precious metals, which have long symbolized power and influence. But for scientists, the rare metals’ lure is less about their shimmering beauty than about the powerful stories they can tell about how the Earth, the moon and other planetary bodies formed and evolved.
By analyzing rare primordial materials, researchers are uncovering geochemical fingerprints that have survived essentially unchanged over billions of years. These fingerprints allow scientists to compare Earth rocks with moon rocks and test ideas about whether giant meteorites once dusted the inner solar system with extraterrestrial platinum and gold. Such research can help scientists learn how volatiles such as water may have spread, leaving some worlds water-rich and others bone-dry.
These explorations, motivated by a growing appreciation of what such rare metals reveal about Earth’s history, are now possible thanks to new analytical techniques. “They give us a window into all kinds of processes that we want to understand,” says Richard Walker, a geochemist at the University of Maryland in College Park.
Geochemical memory Platinum and gold are among eight occupants of the periodic table belonging to the category known as the highly siderophile elements. That name dates back to the 1920s, when Victor Goldschmidt, a mineralogist at the University of Oslo, divided the elements into groups depending on what they liked to combine with in nature. His four classifications are still used today: the lithophiles (rock-lovers), the chalcophiles (ore- or sulfur-lovers), the atmophiles (gas-lovers) and siderophiles, the iron-lovers.
The siderophile elements tend not to ally themselves with the oxygen- and silicon-based compounds that form the bulk of Earth’s crust. They form dense alloys with iron instead. One such element, tungsten (symbolized by W in the periodic table), is an iron-lover that has been important in recent scientific studies of Earth’s geologic history. A step beyond tungsten are those highly siderophile elements, which are even bigger fans of iron. They are ruthenium, rhodium, palladium, rhenium, osmium and iridium along with platinum and gold.
Because highly siderophile elements are relatively abundant in the core and scarce in the mantle and crust, they help scientists trace how Earth’s insides have evolved over time. Dig up a rock from deep within a mine, or pick up one from a freshly erupted volcano, and you can measure the siderophile elements within. The measurements might show whether a radioactive version of one such element has decayed into another, or whether the rock has higher amounts of one particular variety of siderophile. In turn, that information can reveal how material has shifted around and been chemically processed deep within the planet. By analyzing the iron-lovers within each rock, scientists can probe what the rock has been doing for billions of years. “We can trace the entire evolutionary process of how a planet formed,” says James Day, a geochemist at the Scripps Institution of Oceanography in La Jolla, Calif. “That’s why someone like me is interested.”
For instance, Walker and his colleagues have explored siderophile elements in some of the oldest rocks on Earth. Through the process of plate tectonics, in which plates of Earth’s crust grind against, pull apart from and occasionally dive beneath one another, most ancient rocks have been dragged back into the planet and destroyed by melting. But in southwestern Greenland, in a place called Isua, a chunk of ancient crust never got pulled down by plate tectonics (SN: 3/24/07, p. 179). Walker and colleagues, led by Hanika Rizo of the University of Quebec in Montreal, recently studied siderophile elements in these 3.3-billion- to 3.8-billion-year-old rocks.
The scientists looked at the abundance of highly siderophile elements in the Greenland rocks but found that, in this case, the biggest clues came from the slightly less iron-loving tungsten. The rocks contain more of one variety of tungsten, known as tungsten-182, than expected. That isotope forms from the radioactive decay of hafnium-182, which existed only during Earth’s first 50 million years. The Greenland rocks thus serve as a sort of time capsule that helps reveal the history of the early solar system, Rizo, Walker and colleagues wrote in February in Geochimica et Cosmochimica Acta.
“We believe we are accessing parts of Earth’s mantle that formed and took on some of their chemical characteristics while the Earth was still growing,” Walker says. “You can call it accessing a building block of the Earth.”
Studies of these remnants of the ancient planet suggest that Earth’s mantle has remained chemically patchy. Like lumps of flour in poorly mixed cake batter, clumps of primordial material, with higher amounts of tungsten-182, are studded throughout a smoother, more evenly mixed matrix. That’s surprising because researchers thought that the hot, churning insides of the Earth would have stirred everything around over the course of billions of years. Somehow portions of the mantle resisted the planet’s best blending efforts, Walker reported in June at the Goldschmidt geochemistry meeting in Yokohama, Japan.
By studying where those patches are and what they are made of, researchers can investigate such questions as how much convection there was inside the early Earth, and whether any volcanoes today tap into this primordial material. In May, for instance, Walker’s team reported that it had used siderophile elements to identify geochemically primitive lavas in Canada’s Baffin Bay and in the South Pacific (SN: 6/11/16, p. 13). Like the ancient Greenland crust, these rocks also had an overabundance of tungsten-182. Apparently the Canadian and Pacific volcanoes tapped into a deep reservoir of primordial material, which flowed up through the throat of a volcano and out onto the surface. Studying the iron-loving elements in those rocks is like taking a siderophile time machine into the past and seeing what the Earth was like 4.5 billion years ago.
“It never ceases to amaze me what the rocks can tell,” says Amy Riches, a geochemist at Durham University in England.
A dusting from space Highly siderophile elements can teach about more than just the planet Earth. They can reveal secrets about the history of the moon, Mars and other nearby planetary bodies. That’s because all the worlds in the inner solar system apparently got a dusting of gold, platinum and other highly siderophile elements during meteorite bombardments around 4 billion years ago.
The early solar system was something of a cosmic shooting gallery. After the planets coalesced, there were still a lot of leftover space rocks careening around. One enormous impact is thought to have smashed the Earth and spalled off enough debris to form the moon. Other, smaller impacts continued to pummel the inner planets for the first half-billion years or so of their existence. Each collision would have brought a little more fresh material to each world.
On Earth, meteorite impacts could have delivered half a percent to 1 percent of the planet’s total mass. Many meteorites that fall to Earth and are analyzed contain relatively high amounts of highly siderophile elements, which suggests that meteorites hitting the early Earth would have carried a lot of them, too. If so, then the cosmic smashups regularly showered Earth with a fresh coating of gold, platinum and other precious elements. By this time, Earth had already finished forming its core, so the highly siderophile elements remained sprinkled throughout its upper layers rather than being vacuumed into its depths.
This “late accretion” of fresh material could help explain a long-standing puzzle. The amounts of highly siderophile elements in Earth’s mantle are higher than predicted, according to laboratory experiments that try to mimic how molten metal separated from rock as Earth was forming. But a shower of meteorites hitting soon after core formation stopped could have done the trick, a process that Day, Walker and Alan Brandon of the University of Houston discuss in the January Reviews in Mineralogy & Geochemistry. Not everyone accepts the late accretion idea. Some scientists, including Kevin Righter at NASA’s Johnson Space Center in Houston, note that siderophile elements become less iron-loving when squeezed at high pressures and temperatures. That could mean fewer of them dived deep into Earth’s core, and more of them would be left behind for the mantle and the crust. No need for an express meteorite delivery.
Debate probably won’t end anytime soon, as various laboratory experiments seem to support both conclusions. “People are still hacking away at trying to understand this,” says James Brenan, a geochemist at Dalhousie University in Halifax, Canada. Clarity is important for getting to the heart of what the highly siderophile elements can tell scientists — where they came from, how they separated out within the primordial Earth, and what they have been doing since then.
Less precious moon Another big unanswered question is why the Earth and the moon seem to be so different from each other when it comes to highly siderophile elements.
Researchers have a very limited sample of moon rocks to study — just those brought back by the Apollo astronauts, and a few lunar meteorites that happened to fall on Earth and were picked up. None of these samples come from the moon’s deep interior. But by extrapolating from the chemistry of the rocks they have in hand, researchers have calculated that the moon’s mantle has surprisingly lower amounts of the highly siderophile elements than Earth’s mantle — just about 2 percent as much.
If the late-accretion idea is right, then both Earth and the moon should have been dusted by the same meteoritic bombardment of gold, platinum and other elements, and they should have similar amounts of highly siderophile elements in their mantles. That doesn’t seem to be the case. The explanation may lie partly in the fact that the moon is a lot smaller than the Earth, Day and Walker noted last year in Earth and Planetary Science Letters.
Think of the meteorite bombardment as someone throwing snowballs at a pair of very different-sized dogs, Day says. “The statistical chance of these snowballs colliding with a Rottweiler are much higher than with a Chihuahua,” he says. In other words, Earth acquired more platinum and gold simply because it is so much larger than the moon. Both went through the same snowball bombardment, but the bigger object collected more snow coating.
As with most things geochemical, there is another possible explanation. The moon does not have a core that would have sucked highly siderophile elements into its interior. But it’s possible that something else could be holding the gold and platinum deep within the moon, Brenan says. That something is sulfur.
The iron-lovers are also sulfur-likers. In the absence of metal, highly siderophile elements tend to clump with sulfur instead. By studying the interplay between the two, geochemists can start to tease out how the various elements behave as rocks are squeezed, melted and otherwise altered over billions of years of geologic history.
In recent laboratory experiments, Brenan mixed up a recipe of rock meant to simulate the lunar mantle. Earlier work had suggested that there was simply not enough sulfur deep in the moon for iron sulfide to be present. But his work, which used a more realistic representation of the lunar mantle, suggests that iron sulfide can indeed exist and be stable there. That iron sulfide would have kept the iron-lovers deep inside the moon — trapping the highly siderophile elements out of sight. The sulfur work may have even broader implications for understanding how the Earth, moon and other worlds in the inner solar system got their water. Both sulfur and water are relatively volatile compounds that often appear together. Researchers thought both had been lost from the moon long ago. After all, the lunar surface today is dry and barren. But in recent years, scientists have been analyzing droplets of melt in lunar rocks and have found surprisingly high amounts of sulfur and water. That indicates that the moon may once have been wetter than thought. “That has really changed our thinking,” Brenan says.
By looking at the concentration of these elements in lunar rocks, geochemists can cross-check their measurements of sulfur and water — and begin to understand the differences between Earth and the moon.
Still searching At the University of Münster in Germany, geochemist Mario Fischer-Gödde has been working to pull together the various threads of what highly siderophile elements can reveal. Many researchers have suggested that Earth may have gotten much of its water and other volatile elements during the meteorite bombardment of the late accretion. So Fischer-Gödde is systematically analyzing different types of meteorites found on Earth to see if they could have actually delivered these volatiles.
He focuses on the element ruthenium. Like the other highly siderophile elements, it probably arrived on Earth aboard meteorites during the late accretion. Weirdly, though, none of the dozens of meteorites Fischer-Gödde has analyzed contain ruthenium isotopes that match those found in the mantle. He concludes that none of the meteorite types found on Earth so far could be the source of the late accretion materials. Some other source — maybe other rocky bits that were flying around the inner solar system — must have brought ruthenium and other siderophiles to Earth, he reported at the Durham workshop.
And that means the highly siderophile elements still have many mysteries to reveal, and there’s plenty of work to be done. With new ever-more-sensitive techniques under development — such as scans that reveal individual atoms of highly siderophile elements within small grains of metal — researchers are pushing forward in their efforts to analyze the siderophile elements, hoping to squeeze more stories of Earth’s beginning from the discreet iron-lovers.
Alcoholism may stem from using genes incorrectly, a study of hard-drinking rats suggests.
Rats bred either to drink heavily or to shun alcohol have revealed 930 genes linked to a preference for drinking alcohol, researchers in Indiana report August 4 in PLOS Genetics.
Human genetic studies have not found most of the genetic variants that put people at risk for alcoholism, says Michael Miles, a neurogenomicist at Virginia Commonwealth University in Richmond. The new study takes a “significant and somewhat novel approach” to find the genetic differences that separate those who will become addicted to alcohol from those who drink in moderation. It took decades to craft the experiment, says study coauthor William Muir, a population geneticist at Purdue University in West Lafayette, Ind. Starting in the 1980s, rats bred at Indiana University School of Medicine in Indianapolis were given a choice to drink pure water or water mixed with 10 percent ethanol, about the same amount of alcohol as in a weak wine. For more than 40 generations, researchers selected rats from each generation that voluntarily drank the most alcohol and bred them to create a line of rats that consume the rat equivalent of 25 cans of beer a day. Simultaneously, the researchers also selected rats that drank the least alcohol and bred them to make a line of low-drinking rats. A concurrent breeding program produced another line of high-drinking and teetotaling rats.
For the new study, Muir and colleagues collected DNA from 10 rats from each of the high- and low-drinking lines. Comparing complete sets of genetic instructions from all the rats identified 930 genes that differ between the two lines.
Such a large number of genes, “shows how complex the genetic underpinnings of the drive to consume alcohol might be,” says Miles.
Often, human genetic studies known as genome-wide association studies, or GWAS, can’t determine which of many genes in a particular region of DNA is involved in a disease or addiction. But the Indiana researchers’ DNA data allowed them to pinpoint the exact genetic tweaks implicated in the rats’ drinking. “With GWAS, they’re just trying to get down to the gene — we’ve got it down to the parts of the genes,” Muir says.
That precision “is clearly an advance,” says John Crabbe, a neuroscientist at the Portland VA Medical Center in Oregon. “No one has gone into this much detail before in any alcohol-related trait.” Most of the time, the genetic variant associated with drinking behavior wasn’t located within the part of the gene containing blueprints for a protein, the researchers discovered. Only four genes contained variants in their protein-producing parts. The majority of the differences were in surrounding DNA that regulates gene activity. Those changes could alter how much protein is produced from the genes, says study coauthor Feng Zhou, a neurobiologist at Indiana University School of Medicine. In turn, altering amounts of proteins could shift biochemical reactions important for determining behavior.
Until recently, scientists thought alcoholism and other problems stemmed from inheriting altered forms of genes that would produce faulty proteins. “Well, that game’s over,” says Crabbe. Now researchers realize that regulating gene activity is often just as important as changing the genes themselves.
The researchers don’t yet know whether the genes identified in the rats are the same ones that lead to drinking problems in people.
Understanding sea anemones’ exceptional healing abilities may help scientists figure out how to restore hearing.
Proteins that the marine invertebrates use to repair damaged cells can also repair mice’s sound-sensing cells, a new study shows. The findings provide insights into the mechanics of hearing and could lead to future treatments for traumatic hearing loss, researchers report in the Aug. 1 Journal of Experimental Biology.
“This is a preliminary step, but it’s a very useful step in looking at restoring the structure and function of these damaged cells,” says Lavinia Sheets, a hearing researcher at Harvard Medical School who was not involved in the study. Tentacles of starlet sea anemones (Nematostella vectensis) are covered in tiny hairlike cells that sense vibrations in the water from prey swimming nearby. The cells are similar to sound-sensing cells found in the ears of humans and other mammals. When loud noises damage or kill these hair cells, the result can range from temporary to permanent hearing loss.
Anemones’ repair proteins restore their damaged hairlike cells, but landlubbing creatures aren’t as lucky. Glen Watson, a biologist at the University of Louisiana at Lafayette, wondered if anemones’ proteins — which have previously been shown to mend similar cells in blind cave fish — might also work in mammals.
Watson and colleagues mimicked traumatic hearing loss in mice hair cells by depriving them of calcium ions, which are crucial for maintaining cell structure and transmitting sounds. Within a few hours, the normally stiff, hairlike structures that detect sound “looked like spaghetti,” he says. Researchers bathed the damaged hair cells in a cocktail of anemone repair proteins. After an hour, the cells showed remarkable improvement compared with untreated cells. Proteins rebuilt molecular tethers that bundle hair cells and act as gatekeepers for calcium ions. As a result, the cells absorbed more fluorescent dye — an indication of how well calcium flows into the cells.
What’s more, researchers identified a bevy of mice proteins that are analogs of anemones’ repair proteins. But mammalian versions work less effectively than anemone proteins, if at all. More research could point the way to one day harnessing human repair proteins, Sheets says.
Moving forward, Watson plans to investigate the ability of the anemones’ proteins to repair damaged cells in the ears of living mice. “If we could get to those hair cells before they commit to die and treat them, there’s a possibility we could reduce hearing loss,” he says.
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.
A radio signal detected last year has sparked speculation that an advanced alien civilization is broadcasting from a relatively nearby planet. But recent scans have turned up nothing, suggesting the blip was a false alarm and nothing more than earthly interference.
In May 2015, astronomers detected a blast of radio waves coming from the direction of HD 164595, a sunlike star about 94 light-years away in the constellation Hercules. The signal, reported online August 27 on the blog Centauri Dreams, lasted just a few seconds and reached a peak power of about 750 millijansky — fairly strong by radio astronomy standards (1 jansky equals 10-26 watts per square meter per hertz). The researchers aren’t claiming that they found E.T., but they are asking other astronomers to monitor the star — home to a planet at least 16 times as massive as Earth — in case the signal repeats. So far, all is quiet.
Scientists with the SETI Institute, whose mission is to seek out signs of extraterrestrial intelligence, turned the Green Bank Telescope in West Virginia toward HD 164595 on August 28 to scan for signals. “There was nothing there,” says Dan Werthimer, a SETI astronomer at the University of California, Berkeley. The original claim, however, “is consistent with someone pushing the button on a CB radio for a couple of seconds.”
Radio telescopes have to contend with interference from the civilization on this planet before picking out transmissions from our galactic neighbors. Earth-based satellites, power lines and cellphones all emit radio waves that can overwhelm cosmic signals. One type of radio chirp whose origin had eluded astronomers for years recently turned out to be coming from microwave ovens, a fact discovered when researchers at the Parkes observatory in Australia who were tracking the signal prematurely opened an oven door without waiting for the ding signal (SN: 5/16/15, p. 5).
“We see strong signals like this all the time,” says Werthimer. With enough information, such as frequency and location, researchers can usually figure out the cause of an incoming signal. But this latest finding, recorded at the RATAN-600 radio observatory near the Caucasus Mountains in Russia, is missing a lot of details that could help astronomers assess its origin. Without precise frequency measurements or statistics on how often the observatory detects comparable events, says Werthimer, it’s hard to tell how unusual this signal is.
The signal was detected around a frequency of 11 gigahertz. That suggests interference from telecommunication devices, says Italian astronomer Claudio Maccone, who was part of the discovery team. “This is precisely why many countries have to watch the star with different technologies,” he says. “By comparing results, we may be able to find the answer.” The long delay in sharing the results, he says, comes from a reluctance among his Russian colleagues to interact with Western researchers. “They are a closed community,” he says. “It’s an unfortunate circumstance.” The team will present the findings September 27 at a meeting of the International Academy of Astronautics in Guadalajara, Mexico. If the signal didn’t originate on Earth, there are also plenty of natural cosmic sources. Jean Schneider, an astrophysicist at the Paris Observatory in Meudon, France, contends that a gravitational microlens might be responsible. Gravity from an object, such as a star or planet, can temporarily amplify light — including radio waves — received on Earth from other more distant bodies that the interloper passes in front of. Testing that idea would require meticulously tracking the movement of stars that lie in the direction of the radio signal, says Schneider, and seeing if anything could have lined up on the day of the detection.
The discovery is reminiscent of an infamous — and still unexplained — detection known as the “Wow!” signal, named after what astronomer Jerry Ehman wrote on a printout of the signal. Detected in 1977 at the Big Ear radio telescope in Delaware, Ohio, the Wow! signal was at least 70 times as powerful as the one at RATAN-600, lasted for about 72 seconds and appeared to originate in the constellation Sagittarius. Many ideas have been put forth about the signal’s origin, including comets in our solar system, Earth-orbiting space debris and, of course, extraterrestrials.
If aliens do reside around HD 164595, and they are trying to get our attention, they could do so with precisely aimed transmitters no more powerful than anything on Earth, Werthimer says. But if we eavesdropped on a signal that was blasting in all directions into space, then our neighbors are far more advanced than us; such a device would require tapping into the entire power output of their sun.
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.
Anna Frebel can’t explain her fascination with the stars. It’d be like explaining why “berry purple-pink” is one of her favorite colors. “They are just a part of me,” says Frebel, an astronomer at MIT. “What’s going on with them and what they can tell us — there is something magical.”
Frebel’s fascination has led to the discovery of at least three record-breaking stars. Dating back roughly 13 billion years, the stars — all within the Milky Way galaxy — might be elders from the second generation of stars ever formed in the universe. She has also found that one of the tiny galaxies flitting around outside the Milky Way might be a fossil that has survived from not long after the Big Bang. The light from these ancient relics encodes stories about the birth of the first stars, the assembling of galaxies and the origin of elements essential to creating planets and life as we know i “Anna has a really good track record of finding these amazing things,” says Alexander Ji, one of the three graduate students Frebel mentors at MIT. “She’s always finding things that change our understanding of the universe.” As a young girl living in Germany, Frebel wanted to be an astronaut, but she passed on that dream when she learned about the centrifuge that whips trainees around to simulate launch acceleration. Not for her. She instead studied physics and astronomy, first at the University of Freiburg in Germany and then at the Australian National University in Canberra. Since then, Frebel, now 36, has earned a reputation as a “stellar archaeologist,” with the patience and perseverance to search through the universe’s most ancient debris.
Only someone with a galaxy’s worth of patience could sift through the tiny rainbows of light, the spectra, produced by thousands of stars, handpicking the specimens that might preserve clues to the conditions shortly after the first stars lit up the universe. And only a persistent person would spend more than two years pointing Australia’s 2.3-meter-wide Advanced Technology Telescope at 1,200 of the most promising candidates (“105 stars per night was my record,” she says) and eventually, with observations from other telescopes too, land on one star that was, for a while, among the oldest known.
She was first drawn to this research after hearing astronomer Norbert Christlieb, then a visiting researcher at the Australian National University, talk about his work on old stars. “It hit me: Oh my God, this project combines all my interests,” Frebel says. There were stars, chemistry, nuclear physics and the periodic table. “There are so many, for me, cool topics that come together.”
In combing through her stars, Frebel was looking for ones that contained hydrogen and helium — but little else. Most heavier elements up to iron are forged in the cores of stars, where atomic nuclei smash together. As the universe aged, its inventory of atoms such as carbon, silicon and iron steadily increased. The earliest stars, however, came on the scene when there were far fewer of these pollutants floating around. Her efforts paid off in 2005 with a star branded HE 1327-2326, reported in
Nature
asthe most pristine star known at the time
. “She found one that took us closer back to the beginning of time as we know it,” says Frebel’s Ph.D. adviser, astronomer John Norris of Australian National. “It became clear to us early on that she was quite gifted.”
Her gifts netted her the Charlene Heisler Prize in 2007, given by the Astronomical Society of Australia for outstanding Ph.D. thesis. She has since won several recognitions, including the Annie Jump Cannon Award in 2010, given to notable young female researchers by the American Astronomical Society, for her “pioneering work in advancing our understanding of the earliest epochs of the Milky Way galaxy through the study of its oldest stars.”
Carbon seeding The geriatric stars that Frebel finds are not perfectly pristine; they preserve in their atmospheres the chemical makeup of interstellar gas that had been seeded with a smidgen of heavy elements from the explosions of stars that came before. Chemical abundances in many of these stellar fossils are out of balance compared with modern stars. The fossil stars have much more carbon relative to iron, for example — carbon that had to have come from the debris of that very first crop of stars.
Frebel worked with theorists to show that excess carbon could have allowed successive generations of stars (and planets) to form, reporting the work in 2007 in Monthly Notices of the Royal Astronomical Society Letters. “I’ve always been interested in understanding the main message of the data,” she says, which leads her away from the telescope to computer simulations and theory. In this case, the message is that carbon “might have been the most important element in the universe.”
Gas needs to be cold, around –270° Celsius, just a few degrees above absolute zero, to clump and form stars. And carbon is an excellent coolant; its electrons are arranged in such a way to let it efficiently radiate energy. The first generation of stars didn’t have carbon’s help. They were probably slow to form and ended up as gargantuan fluffy orbs hundreds of times as massive as the sun. But once those stars exploded and seeded the cosmos with carbon, Frebel’s data suggest, subsequent generations of stars formed that would have looked more like the stars we see today.
Frebel likens her studies to watching her young son learn to walk and talk. “My overall interpretation is that the universe was still trialing things.”
Before she became a parent, she regularly went to one of the twin Magellan telescopes, 2,380 meters above sea level in the Chilean Atacama Desert. On long nights, while waiting for the telescope to soak up light from a star tens of thousands of light-years away, Frebel would feel the pull of the night sky. “I just lie on the ground and stare into the sky and get lost in the universe,” she says.
In recent years, Frebel has expanded her repertoire to include a horde of teeny galaxies that orbit the Milky Way and also serve as archaeological sites. “Now we can use not just one star,” she says. “We can use the entire galaxy as a fossil record.” One of these runts, called Segue 1, appears to be a remnant from the cosmic dawn and might be typical of the pieces that assembled into large galaxies like the Milky Way.
Frebel and her student Ji discovered that another dwarf galaxy, dubbed Reticulum II, contains clues about one of the mechanisms responsible for creating most of the elements heavier than iron. A long-ago smashup between two neutron stars once bombarded the gas in Reticulum II with neutrons, producing atoms, such as uranium, that can’t be formed in stellar cores. Similar run-ins in other galaxies might have helped build up the universe’s stockpile of heavy elements.
Frebel plans to continue her quest to understand the origin of atoms, stars and galaxies. Though the celestial bodies she studies are ancient, “my days never get old,” she says.
DENVER — Barnacles can tell a whale of a tale. Chemical clues inside barnacles that hitched rides on baleen whales millions of years ago could divulge ancient whale migration routes, new research suggests.
Modern baleen whales migrate thousands of kilometers annually between breeding and feeding grounds, but almost nothing is known about how these epic journeys have changed over time. Scientists can glean where an aquatic animal has lived based on its teeth. The mix of oxygen isotopes embedded inside newly formed tooth material depends on the region and local temperature, with more oxygen-18 used near the poles than near the equator. That oxygen provides a timeline of the animal’s travels. Baleen whales don’t have teeth, though. So paleobiologists Larry Taylor and Seth Finnegan, both of the University of California, Berkeley, looked at something else growing on whales: barnacles. Like teeth, barnacle shells take in oxygen as they grow. Patterns of oxygen isotopes in layers of barnacle shells collected from modern beached whales matched known whale migration routes, Taylor said September 25 at the Geological Society of America’s annual meeting. Roughly 2-million-year-old barnacle fossils have analogous oxygen isotope changes, preliminary results suggest. Converting those changes into migration maps, however, will require reconstructing how oxygen isotopes were distributed long ago, Taylor said.
A South African flower catches flies with honey, or in this case, the smell of honeybees.
Several plant species lure potential pollinators with false promises of sweet nectar, sex or even rotting flesh. But Ceropegia sandersonii attracts its primary pollinator, Desmometopa flies, with the scent of fear. The flower mimics the chemical signals, or pheromones, released by alarmed western honeybees (Apis mellifera) during a predator attack. For flies that feast on the bees’ guts, it’s the perfect bait, Stefan Dötterl, a chemical ecologist at the University of Salzburg in Austria, and colleagues report online October 6 in Current Biology. The team compared the compounds that make up the flower’s scent with pheromones released by the bees during simulated attacks. Not only did the two odors have several compounds in common, but the flies were strongly attracted to a mixture of a few of the shared compounds. That chemical cocktail has so far been observed only in the bees and C. sandersonii, the researchers say.
Before flies have a chance to wise up to the trickery, they become trapped inside the flower. The flies eventually escape about a day later, once the flower wilts, only to be duped by other flowers to finish the fertilizing task, Dötterl says.
