As Much as Half of the Milky Way Likely Came From Distant Galaxies

We’re made of star stuff, as Carl Sagan famously put it in his TV series Cosmos. All of the elements that joined together to form our planet and everything on it were set in motion within the hearts of ancient stars. But not only are we star stuff, it appears that we’re actually made of alien star stuff.

Astrophysicists who were analyzing galaxy formation recently looked at how intergalactic gas and dust is transported over time and across great distances. They found that up to half of the matter in our Milky Way galaxy likely comes from other galaxies far, far away.

“Given how much of the matter out of which we formed may have come from other galaxies, we could consider ourselves space travelers or extragalactic immigrants,” Daniel Anglés-Alcázar, an astrophysics postdoctoral fellow from Northwestern University who led the study, said in a statement. “It is likely that much of the Milky Way’s matter was in other galaxies before it was kicked out by a powerful wind, traveled across intergalactic space and eventually found its new home in the Milky Way.”

This is a “first-of-its-kind analysis,” the team said, with the findings opening a new line of research into understanding galaxy formation. The study appears in the Monthly Notices of the Royal Astronomical Society.

Anglés-Alcázar and his fellow researchers used a supercomputer simulation based on the FIRE (Feedback in Realistic Environments) project, which is co-led by Northwestern physics and astronomy professor Claude-André Faucher-Giguère. FIRE uses numerical simulations that can produce realistic 3D models of galaxies. Anglés-Alcázar developed state-of-the-art algorithms to follow how a galaxy forms over time, from just after the Big Bang to the present day.

Using the equivalent of several million hours of continuous computing time, the team was able to quantify how galaxies acquire matter from the universe over time. They did this by “tracing cosmic inflows, galactic outflows, gas recycling, and merger histories,” according to their paper.

The findings on galactic evolution were unexpected, and the researchers coined a new term to explain the phenomenon: intergalactic transfer.

The simulations showed that supernova explosions within galaxies eject enormous amounts of gas, which causes atoms to be transported from one galaxy to another via powerful galactic winds. Even though galaxies are far apart from each other, the galactic winds propagate material at several hundred kilometers per second, and over several billion years this process infused new material into galaxies, sparking star formation.

“We show that in situ star formation fueled by fresh accretion dominates the early growth of galaxies of all masses, while the re-accretion of gas previously ejected in galactic winds often dominates the gas supply for a large portion of every galaxy’s evolution,” the team wrote. “Externally processed material contributes increasingly to the growth of central galaxies at lower redshifts.”

By tracking in detail the complex flows of matter in the simulations, the research team found that gas flows from smaller galaxies to larger galaxies, such as the Milky Way, where the gas forms stars. Additionally, even stars formed in one galaxy could be transferred to another. This transfer of mass through galactic winds can account for up to 50 percent of matter in the larger galaxies, the researchers said.

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Newly Discovered Dinosaur Was Modern-Day Ornery Bird’s Doppelganger

Artistic representation of Corythoraptor jacobs

Birds evolved from dinosaurs, but it is often hard to imagine how these animals could be related to one another. Tiny songbirds hardly conjure up mental images of Tyrannosaurus rex.

A newfound Late Cretaceous carnivorous dinosaur, however, is a doppelganger for living cassowaries, which are the third-tallest and second-heaviest modern birds, smaller only than the emu and ostrich. Cassowaries have the ability to kill animals, including humans, by charging and kicking them.

The new dinosaur, described in an article in the journal Scientific Reports, was — like cassowaries, emus, and ostriches — covered with feathers, yet it could not fly. Lead author Junchang Lu and colleagues think it is possible that today’s flightless birds never did have ancestors that took to the skies. Feathers can serve functions other than enabling flight, such as by providing insulation and enabling forms of visual communication.

The dinosaur’s most distinctive feature had nothing to do with feathers, though, but did inspired its name: Corythoraptor jacobsi. Corythoraptor refers to a “raptor bearing a cassowary-like crest” on its head. The crest, technically known as a casque, was like a horn helmet covered with keratinous skin. Keratin is a fibrous protein that forms the main structural constituent of hair, claws, and other tough tissues.

A Southern cassowary.

“The casque may have been a multifunctional structure, utilized in display and communication,” said Lu, who is a researcher at the Chinese Academy of Geological Sciences. “It might have served as an expression of fitness during the mating season.”

Like horns on deer and antelope, the dinosaur’s casque might have helped choosy individuals to select their mates by using the size, shape, and other features of the head structure as visual fitness cues.

Cassowaries use their casques for similar reasons, although scientists continue to debate other possible functions. Some suggest the head feature is great for cutting through underbrush, while others think it might amplify the big bird’s deep sounds.

Cassowary calls are so creepy sounding that they have been included in horror film soundtracks. It is possible that dinosaurs like Corythoraptor produced similar vocalizations.

The researchers suspect that Corythoraptor craved meat.

“They might have eaten lizards, small dinosaurs, and other small animals,” Lu explained.

The dinosaur hunted such prey at what is now Jiangxi Province, China. Its remains, dating to 66-100 million years ago, were unearthed there near the Ganzhou Railway Station. The individual was at least eight years old when it died, the scientists suspect, but it was just a young adult that had not fully grown.

Lu and his team now believe that Ganzhou “was home to the world’s greatest known dinosaur diversity.”

Numerous other dinosaurs of all shapes and sizes have been discovered at this location over the years. Banji long, for example, once lived there and was a small and scrappy carnivore with a parrot-like face. It and many other dinosaurs once flourished where high-speed trains now zip through Ganzhou.

The past could also meet the present in terms of Corythoraptor’s lineage. The researchers cannot confirm that the dinosaur was directly related to today’s cassowaries, but the similarities between these birds and the dinosaur are numerous: head casques, long necks, chubby feathered bodies, muscular legs, an appetite for meat and more.

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DNA Analysis Reveals Why ‘Water Bears’ Are the World’s Toughest Animal

Scanning electron microscope image of Ramazzottius varieornatus

Tardigrades, also known as water bears, are less than a fraction of an inch in length, yet they are believed to be Earth’s toughest, hardiest animals. They are virtually indestructible. Tardigrades have the ability to withstand complete dehydration. Once desiccated, they have been frozen in blocks of ice, exposed to radiation, and sent into the vacuum of space, and yet they still usually spring back to life when water becomes available again.

New genetic research, published in the journal PLOS Biology, reveals how tardigrades achieve such resurrections after drying to a crisp. The authors now even believe that alien life forms could possess this remarkable ability.

“If life exists on other planets, and it is water-based, then those organisms that live out of water will evolve to resist extreme events, including the threat of drying out,” said co-author Mark Blaxter of the University of Edinburgh’s Institute of Evolutionary Biology.

He added that the ability to undergo anhydrobiosis — the desiccated, dormant state — “has evolved multiple times on Earth, so I am sure it will have evolved on other living planets.”

Blaxter and his colleagues took a clever approach to unravel the scientific secrets behind anhydrobiosis in tardigrades.

Muscles of the tardigrade H. dujardini labeled with a fluorescent stain. Each muscle is a single cell.

The scientists re-sequenced and reassembled the genome of Hypsibius dujardini, a tardigrade that can only undergo desiccation after extensive pre-exposure to drying conditions. They then compared the tiny animal’s DNA with that of Ramazzottius varieornatus, a related species with tolerance to rapid desiccation.

The researchers then looked at a particular set of genes, the so-called HOX genes, which establish the nose-to-tail pattern in embryos. There are usually about ten different HOX genes in animals, but tardigrades are missing five. Nematodes (roundworms) lack these same five genes.

“This could be because they share a common ancestor with tardigrades, and the loss happened in this ancestor,” Blaxter said. “Alternatively, it could be that the loss is associated with both groups becoming miniaturized, and these ‘middle’ HOX genes are the ones that are the easiest to lose.”

He added that the shared genetic loss could also simply be due to independent evolution. Because of these remaining questions, scientists continue to debate whether or not tardigrades are more closely related to nematodes or to arthropods — insects, spiders, and crustaceans.

Underside of a tardigrade, showing its claws.

By asking which genes were turned on during tardigrade anhydrobiosis, the scientists could identify sets of proteins, which appear to replace the water that tardigrade cells lose, thus helping to preserve the microscopic structures until water is available again.

Arakawa explained that all cells contain around 60–80 percent water when they are active, including human cells.

The key proteins that they identified are highly soluble. They dissolve in water that, due to surface tension, clings to and surrounds intracellular molecules within tardigrades. Like a microscopic protective coating, they prevent the cells from denaturing when the animal otherwise desiccates. 

Arakawa added that tardigrades also possess additional genes that protect their DNA from damage. Because these small animals lack stress-sensing pathways, their cells do not usually die out when damaged. Instead, the identified proteins try to make repairs, and are often successful in doing so.

Due to these abilities, scientific consensus holds that tardigrades could be Earth’s last survivors. Such resilience is unexpected in a tiny creature that seems to exist in the slow lane.

“Tardigrades are slow walkers, and are not really aggressive animals,” Arakawa explained. “Therefore, they tend to lose competitions for food, or can become prey in a diversified ecosystem. But tardigrades fled to their own niche, where only tardigrades can survive, so paradoxically, tardigrades presumably acquired their extreme survival abilities due to their ecological incompetence.”

Arakawa and his colleagues can envision a day when enzymes, vaccines, human organs, tissues, and cells could be preserved in a state of anhydrobiosis instead of by liquid-nitrogen-based freezing.

“Some people have suggested that tardigrades could somehow travel through space to seed other planets with Earth-derived life,” Baxter said. “That obviously didn’t happen on Earth, as only some tardigrades are able to do anhydrobiosis, and tardigrades are derived from other, more ancient forms.”

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Traces of adaptation and cultural diversification found among early North American stone tools

Scientists analyzed three-dimensional models of Clovis projectile points from Smithsonian and other museum collections to examine how patterns and marks made in crafting these tools began to vary regionally 12,500 years ago. These regional differences signal cultural diversification and adaptation, suggesting that groups of early hunter-gatherer Americans may have changed the way they were social interacting at this time. This figure shows one analysis used to study shapes left behind from their production on either side of the projectile points.

Using new methods to analyze stone projectile points crafted by North America's earliest human inhabitants, Smithsonian scientists have found that these tools show evidence of a shift toward more experimentation in their production beginning about 12,500 years ago, following hundreds of years of consistent stone-tool production created using uniform techniques. The findings provide clues into changes in social interactions during a time when people are thought to have been spreading into new parts of North America and adapting to different environments, beginning a period of cultural diversification.

The research team, led by Sabrina Sholts, a curator in the Department of Anthropology at the Smithsonian's National Museum of Natural History, and Sebastian Wärmländer at Stockholm University, used digital 3-D models to scrutinize the angles and contours on the surfaces of North American projectile points. In doing so, they discovered a turning point at which the techniques used to produce the points became more variable. That variability suggests that individual toolmakers, who may have had fewer opportunities than their predecessors to learn from others, began working out how to make the tools on their own. The findings were reported July 12 in the journal PLOS ONE.

"Our study really allows stone tools to speak in a new way," said Joseph Gingerich, a research associate at the museum and assistant professor of anthropology at Ohio University. "By being able to document subtle changes in stone tool technology, we can better understand how social interactions among artisans changed in North America over 12,000 years ago."

The earliest well-documented group of people in North America, known as Clovis, is recognized by distinctive pointed stone projectiles that appear about 13,500 years ago. These culture-defining tools, called Clovis points, are sharp-edged and symmetrical, with a groove near the base -- called a flute -- where a spear shaft may have fit. Anthropologists consider them to be a very sophisticated technology.

The highly mobile hunter-gatherers of the Clovis culture spread quickly across North America, and Clovis points have been found all over the continent. In 2012, Sholts and colleagues analyzed 50 authentic and replicate Clovis points, examining how their surfaces had been shaped as flakes of stone were chipped away to craft the tool. Using an approach Sholts and Wärmländer originally developed for studying bones, the researchers laser scanned each point to create a three-dimensional model and then analyzed its contours, measuring and comparing subtle surface features that cannot be discerned by eye. "It's a way to capture all the individual actions to reduce the core, which reflect the technique used to shape it," Sholts said.

The analysis revealed remarkable consistency among the ancient artifacts compared to almost perfect copies made by a modern knapper, an artisan that crafts stone tools using ancient techniques. The team concluded that the manufacturing technique used by the Clovis people was so uniform that it must have been passed on directly from one knapper to another.

According to the archaeological record, Clovis technology was used for several hundred years. A variety of other styles emerged later, though they never spread across the continent like Clovis points did. To learn more about the groups that manufactured these later styles, the authors of the new study analyzed the surface features of 100 projectile points from collections at several museums, including the Smithsonian collection, which is curated by anthropologist Dennis Stanford.

The new study included Clovis points and samples of four later styles of fluted points, which had been recovered from sites in the eastern United States. The team analyzed the points' surface contours as they had done in the earlier study and also introduced a new method of analyzing digital models to assess the objects' three-dimensional asymmetry.

Using another new technique developed by Wärmländer and co-author Stefan Schlager of the University of Freiburg, the team determined that the overall three-dimensional shapes of the points did not vary significantly. However, they did find increased variability in the surface contours among some of the later styles of points, indicating that those tools had not been produced using a consistent technique.

The increase in variability among the later points suggests a decrease in social learning and possibly a reduction in overall interactions among North American populations beginning around 12,500 years ago, the researchers say. This is consistent with anthropologists' current thinking about how people were living during this time. "There seems to be evidence of increased experimentation during this period, due to groups moving away from each other and pushing into new environments," Sholts said.

Read more at Science Daily

New bird that humans drove to extinction discovered in Azores

Reconstruction of Pyrrhula crassa (left) and skull (right).

Inside the crater of a volcano on Graciosa Island in the Azores archipelago, in the Atlantic Ocean, an international team of researchers has discovered the bones of a new extinct species of songbird, a bullfinch which they have named Pyrrhula crassa. The remains were found in a small cavity through which time ago the lava flowed. This bird disappeared a few hundreds of years ago due to human colonization of the islands and the introduction of invasive species.

Until hundreds of years ago, a species of bullfinch, a small songbird with a very short and robust beak, lived on Graciosa Island in the Azores archipelago. The arrival of humans to this island, however, depleted its population and it ended up going extinct, as was the case with numerous bird species on other islands, such as the Canaries and Madeira.

Now, an international team of scientists, backed by a project led by Josep Antoni Alcover, from the Mediterranean Institute for Advanced Studies (IMEDEA, CSIC-UIB), has discovered the bones of this bullfinch, called Pyrrhula crassa, in a cave located in a 12,000-year-old volcano in the southeast of the island.

"It is the first extinct passerine bird described in the archipelago, and it won't be the last," states Alcover, co-author of the study published in Zootaxa which focused on the analysis of beak morphology in order to determine the new species.

Despite there being few known remains of this bird, they are sufficiently distinctive for the scientists to have succeeded in establishing that they belong to a new extinct species of bullfinch.

The new bird, being the largest of its genus according to the size of the skull remains found, recalls due to its flying ability the existing bullfinch from the other Azores island (São Miguel) which is 'vulnerable' to extinction because of the expansion of agriculture and the disappearance of laurel forests.

"Its short and wide beak was not just considerably bigger, but also relatively higher than that of the common bullfinch or that from São Miguel, with a very robust configuration reminiscent to an extent of the beak of a small parrot," asserts the researcher.

Invasions wiped out the birds

These islands were colonized during the 13th century by the Portuguese, although they could have been visited by Vikings over one thousand years ago. Just as has happened on many other islands, such as the Canaries or Madeira, different bird species have disappeared throughout the last millennium due to the arrival of humans along with various invasive species.

Human colonization led to the destruction and burning of the islands' habitats in which humans started settling, and they impacted on the birds which were part of the indigenous fauna. P. crassa was no exception, finding itself affected until its extinction.

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Dawn of the cosmos: Seeing galaxies that appeared soon after the Big Bang

Milestones in the history of the Universe (not to scale). The intergalactic gas was in a neutral state from about 300,000 years after the Big Bang until light from the first generation of stars and galaxies began to ionize it. The gas was completely ionized after 1 billion years. The LAGER study takes a close look at the state of the Universe at 800 million years (yellow box) to investigate when and how this transformation occurred.

Arizona State University astronomers Sangeeta Malhotra and James Rhoads, working with international teams in Chile and China, have discovered 23 young galaxies, seen as they were 800 million years after the Big Bang. The results from this sample have been recently published in the Astrophysical Journal.

Long ago, about 300,000 years after the beginning of the universe (the Big Bang), the universe was dark. There were no stars or galaxies, and the universe was filled with neutral hydrogen gas. In the next half billion years or so the first galaxies and stars appeared. Their energetic radiation ionized their surroundings, illuminating and transforming the universe.

This dramatic transformation, known as re-ionization, occurred sometime in the interval between 300 million years and one billion years after the Big Bang. Astronomers are trying to pinpoint this milestone more precisely and the galaxies found in this study help in this determination.

"Before re-ionization, these galaxies were very hard to see, because their light is scattered by gas between galaxies, like a car's headlights in fog," says Malhotra. "As enough galaxies turn on and 'burn off the fog' they become easier to see. By doing so, they help provide a diagnostic to see how much of the 'fog' remains at any time in the early universe."

The Dark Energy Camera

To detect these galaxies, Malhotra and Rhoads have been using the Dark Energy Camera (DECam), one of the new powerful instruments in the astronomy field. DECam is installed at the National Optical Astronomy Observatory (NOAO)'s 4-meter Blanco Telescope, located at the Cerro Tololo Inter-American Observatory (CTIO), in northern Chile, at an altitude of 7,200 feet.

"Several years ago, we carried out a similar study using a 64-megapixel camera that covers the same amount of sky as the full moon," says Rhoads. "DECam, by comparison, is a 570-megapixel camera and covers 15 times the area of the full moon in a single image."

DECam was recently made even more powerful when it was equipped with a special narrowband filter, designed at ASU's School of Earth and Space Exploration (SESE), primarily by Rhoads and Zheng (who was a SESE postdoctoral fellow and is currently at the Shanghai Astronomical Observatory in China), with assistance from Alistair Walker of NOAO.

"We spent several months refining the design of the filter profile, optimizing the design to get maximum sensitivity in our search" says Zheng, the lead author of this study.

Touching the Cosmic Dawn

The galaxy search using the ASU-designed filter and DECam is part of the ongoing "Lyman Alpha Galaxies in the Epoch of Reionization" project (LAGER). It is the largest uniformly selected sample that goes far enough back in the history of the universe to reach cosmic dawn.

"The combination of large survey size and sensitivity of this survey enables us to study galaxies that are common but faint, as well as those that are bright but rare, at this early stage in the universe," says Malhotra.

Junxian Wang, a co-author on this study and the lead of the Chinese LAGER team, adds that "our findings in this survey imply that a large fraction of the first galaxies that ionized and illuminated the universe formed early, less than 800 million years after the Big Bang."

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A Universal ‘Language’ of Arousal Connects Humans and the Animal Kingdom

Orpheus Charming the Animals by Jacob Hoefnagel (1613)

Over a century ago, naturalist Charles Darwin observed that all humans, as well as other animals, exhibit and express emotion in remarkably similar ways. He theorized that vocal expressions of feelings date back to the earliest terrestrial species, hinting that all land animals — and birds too — share a basic, inherent understanding of each other.

New research not only supports Darwin’s views, but also identifies a universal “language” of arousal emitted and understood by amphibians, reptiles, birds, and mammals. The findings, published in the journal Proceedings of the Royal Society B, suggest that we are at least somewhat like the famous fictional character Doctor Dolittle, who could decipher animal communications with ease.

“Our study shows that humans are naturally able to recognize emotional arousal across all classes of vocalizing animals,” said lead author Piera Filippi, a postdoctoral researcher at the University of Aix-Marseille and the Max Planck Institute for Psycholinguistics. “This outcome may find an important application in animal welfare, suggesting that humans may rely on their intuition to assess when animals are stressed.”

Prior research additionally suggests that animals understand human emotional vocal expressions. Pet owners are often more attuned to this, given the reactions that dogs, cats, horses, birds, rodents, and more have to a range of owner outbursts, from angry scolding to happy praise.

For the latest study, Filippi, senior author Onur Gunturkun, and their team went beyond investigating such a familiar collection of animal pets. They instead gathered 180 recordings of vocalizations from nine different and very diverse species: hourglass treefrog, black-capped chickadee, common raven, American alligator, African bush elephant, giant panda, domestic pig, and Barbary macaque. People who spoke English, Mandarin, and German were then recruited to evaluate the levels of arousal communicated in each animal recording.

The human listeners, no matter their native language, aced the tests. This indicates that human ability to assess vocal expressions of arousal — whether emitted due to sexual bliss, infant distress, or terror over a predator — is biologically rooted and somehow cemented in our DNA.

The scientists further conducted an acoustic analysis of the recordings. Pairing this data with the findings concerning the human listeners, the researchers discovered that people use multiple acoustic parameters to infer levels of arousal in vocalizations. Mainly, however, humans rely on fundamental frequency cues and the forcefulness of the sounds.  

The primary explanation for the ability, seemingly shared across much of the animal kingdom, has to do with the body-sound connection.

“Across vocalizing animals, higher levels of emotional intensity may induce the contraction of muscles that are required for vocal production,” Filippi explained. “This modification alters the quality of the sounds produced, often resulting in changes related to the perceived frequency of the sound.”

Whether the vocalizer is a pissed off pig or a playful elephant, the resulting sounds will then be directly affected by muscle contractions that, in turn, are impacted by the animal’s emotions at the time.

The researchers believe their study’s findings could extend to marine species with audible forms of communication. We therefore should be able to identify a dolphin’s levels of arousal, for example, just by hearing its vocalizations, and vice versa.

It may be that skills for vocal expression in marine and terrestrial species evolved from a common ancestor. This underlying connection, as well as the shared basic universal “language,” are tied to critical life-and-death concerns.

“The ability to recognize emotional content across diverse species may have favored the perception of heightened levels of threat or danger in the surrounding environment,” Filippi said. “This may have increased survival opportunities.”

Infant distress calls appear to be the most easily understood, from baby alligators calling for their mothers to young giant pandas squeaking, growling, barking, and huffing. The researchers suspect that this primal ability to decipher baby speak is “particularly salient to caregivers.”

Some animals can even manipulate humans via their infant-resembling cries. Earlier research, for example, found that cats can purr in the same frequency range of a crying baby when soliciting food from their owners.

It remains unclear if insects share the ability of other animals in deciphering the arousal levels of various species’ communications. Filippi explained that insects produce sounds that differ in the level of emotional intensity through stridulation, which refers to vibration resulting from rubbing two body structures against each other. Since the sound-production mechanism is different from that of most other animals, insects may not be included in the universal “language” that connects other creatures.

Another identified disconnect exists between how humans mentally process speech versus nonverbal emotional communications like screams of pain, pleasure, and fear. “Spoken language can be highly emotional,” Filippi said. “However, the fine-tuned articulatory movements involved in speech production may constrain the perception of emotional intensity encoded in the signal.”

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The Sperm Counts of Western Men Have Declined Dramatically, Alarming Experts

In 1992, scientists from Denmark published a study claiming that there had been a decline in the quality of men’s semen over the preceding 50 years. Though worries have persisted since then, it has been hard to back up this claim. Now a comprehensive new study has emerged that appears to support the research from decades ago.

The latest study was a meta-analysis of English-language studies on sperm count and concentration that was published this week in the journal Human Reproduction Update. Led by researchers from the Hebrew University-Hadassah Braun School of Public Health and Community Medicine and the Icahn School of Medicine at Mount Sinai, the work analyzed 185 studies on sperm count and quality that were published between 1973 and 2011.

The findings, the researchers say, are unnerving.

After combing through the material, the researchers found a large decrease in sperm quality among men from North America, Europe, Australia, and New Zealand. The drop was particularly notable among men who had never had kids and were unaware of their fertility status. In these men, they found a 52.5 percent drop in sperm concentration, and a 59.3 percent decrease in total sperm count.

They did not find the same decrease in men from non-Western countries, although the authors acknowledged that this could potentially be due to a lack of data.

The authors of the study also pointed out the fact that the decline doesn’t seem to be leveling off. “This study is an urgent wake-up call for researchers and health authorities around the world to investigate the causes of the sharp ongoing drop in sperm count,” said lead author Dr. Hagai Levine, an epidemiologist from the Hebrew University of Jerusalem's faculty of medicine, in a statement.

Birth and fertility rates in the United States have continually gone down since around 2007. According to data from the World Bank, the current US birth rate is about 12.4 babies per population of 1,000 people, down from 14.8 in 1973 (the year that researchers began looking at the data).

In addition, low sperm count has more consequences than fertility and childbirth. The researchers pointed out in their meta-analysis that “poor sperm count is associated with overall morbidity and mortality.” In other words, men who have low sperm count tend to have other health problems as well.

It is important to note that there is so far no conclusive evidence about why the sperm count has dropped. The authors speculate it is due to environmental and lifestyle causes, including pesticides, smoking, and obesity. Their assessment didn’t establish any causal links, however.

“If we will not change the ways that we are living and the environment and the chemicals that we are exposed to, I am very worried about what will happen in the future," Levine told the BBC, warning ominously that “it may be the extinction of the human species.”

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Detecting Alien Life Will Likely Be a Protracted Process, Not a Eureka Moment

Would it be easy to determine if the source of a mysterious radio signal was aliens? Probably not. A new paper argues that contact with extraterrestrials will likely be discovered through a prolonged, incremental process rather than an instantaneous eureka-like moment. Eureka — what the ancient Greek mathematician Archimedes allegedly said when he cracked a tough science problem about water displacement — tends to be the exception in science rather than the rule.

Attributing scientific progress to eureka moments is popular because it is easy to understand, argues Milan Cirkovic, a senior research associate at the Astronomical Observatory of Belgrade and an assistant physics professor at the University of Novi Sad in Serbia and Montenegro. But, he writes in the journal Space Policy, "It puts too big an emphasis on the 'origin myths' and the role of great personalities, key moments, events, and circumstances in any historical process.”

Cirkovic said in an email that the community involved in the search for extraterrestrial intelligence (SETI) should instead be prepared for a process that would take a very long time. It may take decades as the SETI community looks at all the reasons aliens might not be the source of a mysterious signal.

"I have only tried to point out that both history of science and logic and common sense suggest — on a descriptive level — that contact will be a protracted affair, probably not recognizable as such over timescales of years or decades," Cirkovic said. He was careful not to say how contact might proceed, but that it would take a long time and repeated observations.

Think about the protracted debate concerning "Tabby's star," which is showing strange brightening and dimming. Some say it's due to a possible "alien megastructure," while others are pointing to various natural processes, such as exocomets.

"More structure is obviously necessary, as far as signals are concerned," Cirkovic said. "The example often quoted (first due to Nikola Tesla, who was somewhat forgotten as a SETI pioneer) is the presence of prime numbers 2, 3, 5, 7, 11, ... etc. in the signal."

Prime numbers are a non-natural process that are considered by SETI scholars an indication of possible life.

"However," Cirkovic added, "this is the classic understanding of the first contact which I actually intend to undermine in the present paper. I argue — after some of the SETI ‘founding fathers,’ notably Nikolai Kardashev — that we are more likely to detect an anomalous astrophysical phenomenon, which would be a signpost of massive engineering effort by extraterrestrial intelligence.”

He added that in recent years the SETI community has said it expects contact to come through detecting one of these engineering signatures rather than through a radio signal. Cirkovic and some other experts call this "Dysonian SETI", after a 2011 paper that Cirkovic co-authored and was led by Robert Bradbury of the Astronomical Observatory of Belgrade.

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Giant ‘Rogue’ Planets Are Less Common Than Scientists Thought

Rogue planet microlensing event

There probably aren't nearly as many giant planets zooming alone through the Milky Way galaxy as scientists had thought, a new study reports.

Previous research had suggested that huge "rogue" or "unbound" worlds, which have no discernible host star, are extremely common in the Milky Way, perhaps outnumbering stars by a factor of 2 to 1. But that's probably not the case, according to the new study.

"We found that Jupiter-mass [rogue] planets are at least 10 times less frequent than previously thought," study lead author Przemek Mróz, a researcher at the Warsaw University Observatory in Poland, told Space.com via email.

Astronomers think most rogue planets were likely booted out of their native solar systems by interactions with neighboring planets. Scientists generally hunt for these lonely worlds using a technique called gravitational microlensing, which involves watching for a foreground object to pass in front of a distant star. When this happens, the closer body's gravity bends and magnifies the star's light, in ways that can reveal clues about the foreground object's mass and other characteristics.

A 2011 study, based on 474 microlensing events detected by a telescope in New Zealand, estimated that gas-giant rogue worlds are nearly twice as common as main-sequence ("normal") stars in the Milky Way. (The number of stars in our galaxy is a matter of debate, with estimates ranging from 100 billion to 1 trillion.)

In the new study, Mróz and his team analyzed a much bigger data set — more than 2,600 microlensing events that were detected between 2010 and 2015 by the Optical Gravitational Lensing Experiment (OGLE). This survey, which is run by researchers at the University of Warsaw, depends primarily on observations made at the Las Campanas Observatory in Chile.

The researchers determined that the Milky Way likely hosts a maximum of one Jupiter-like rogue for every four main-sequence stars — still a lot, to be sure, but not nearly as many as the previous study had suggested.

The new results make sense on a number of levels, Mróz said.

"Our new microlensing observations are in agreement with theoretical expectations on the frequency of free-floating Jupiters and with infrared surveys for planetary-mass objects in star-forming regions," he said.

Intriguingly, the OGLE survey also spotted a few extremely brief microlensing events, which Mróz said were likely caused by much smaller worlds — ones about the size of Earth, or just a bit bigger.

"Because our sensitivity to such short events was very low, free-floating Earths should be very common, perhaps more frequent than stars, but we are unable to provide a precise number owing to [the] small number of detections," he told Space.com.

Increasing the number of ground-based microlensing detections would give astronomers a somewhat better understanding of the population of small rogue planets, Mróz said. But big gains may have to wait for future space observatories, such as Europe's Euclid mission and NASA's Wide-Field Infrared Survey Telescope (WFIRST).

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