An itinerant interstellar asteroid may actually be a comet in disguise.

Known as ‘Oumuamua, the object was detected in October and is the first visitor from another star spotted touring our solar system (SN: 11/ 25/17, p. 14). Early observations suggested the vagabond was rocky. But after additional analysis, a team of researchers suggests December 18 in Nature Astronomy that the object might have an icy core.

In general, comets are icy and asteroids are rocky. Ice gives comets their characteristic tails: As a comet passes near the sun, the heat warms the ice, causing it to sublimate, releasing gas and dust. Because no tail appeared despite ‘Oumuamua’s passage by the sun, the mysterious visitor was dubbed an asteroid — a surprising conclusion since the vast majority of objects ejected from star systems are expected to be icy.
“Everybody’s been assuming that this is just a lump of rock,” says astronomer Alan Fitzsimmons of Queen’s University Belfast in Northern Ireland. “This may not be the case.” So ‘Oumuamua might not be as odd as originally thought.

Fitzsimmons and colleagues used the Very Large Telescope in Chile and the William Herschel Telescope in La Palma, Spain to capture the object’s spectrum — its light sliced up according to wavelength. “It’s an impressive piece of work,” says astronomer Olivier Hainaut of the European Southern Observatory in Garching, Germany, who was not involved with the research. “It was a very faint object and to observe such a faint moving target is horribly difficult.”

The object’s spectrum revealed a reddish hue with no signs of ice. But ‘Oumuamua could have an exterior crust — about half a meter thick or thicker — which hid the ice and insulated it from the sun’s heat, the researchers calculated. “You could have a lot of ice in this thing and really not know it,” says astronomer Jessica Sunshine of the University of Maryland in College Park, who was not involved with the research. Such a crust could have formed as energetic particles known as cosmic rays bombarded the object over its lifetime, creating an ice-free surface rich in organic compounds. ‘Oumuamua’s spectrum is similar to those of other objects in the solar system suspected of concealing such icy interiors.
Studies of ‘Oumuamua continue — with some researchers looking for evidence of even more surprising hypotheses. Using the Green Bank Telescope in West Virginia, scientists with the Breakthrough Listen project are searching for signatures of artificial origin — that is, aliens — on the off chance that the object might be an interstellar spacecraft. Sorry, X-Files fans: So far no such signals have been detected.

Some reports from 2017 hint at potentially big discoveries — if the research holds up to additional scientific scrutiny.

Under pressure
Putting the squeeze on hydrogen gas turned it into a long-elusive metal that may superconduct, Harvard University physicists claimed (SN: 2/18/17, p. 14). A diamond vise, supercold temperatures and intense pressure made the element reflective — a key property of metals. But other researchers in the field don’t buy it; one experiment with a slew of caveats isn’t enough to confirm the claim, those scientists say.
Woman warrior?
The skeleton of a 10th century Viking woman buried in full warrior regalia has scientists sparring over women’s roles in Viking society (SN: 10/14/17, p. 6). Researchers who confirmed the skeleton’s sex through DNA analysis contend that the woman was a high-ranking Viking warrior, the first Viking woman warrior known. But other archaeologists argue that the bones — with no obvious signs of injury or strenuous physical activity — are too pristine to have seen battle.
A far-flung star’s extra wink, spotted in data from the Kepler space telescope and further probed by the Hubble Space Telescope, may be the first evidence for an exomoon — a moon orbiting a planet orbiting a distant star. If it exists, the Neptune-sized candidate moon (dubbed Kepler 1625b i) is roughly 4,000 light-years away and orbits a planet a tad larger than Jupiter (SN: 8/19/17, p. 15).

Rooting out hominid origins
The first members of the human evolutionary family may have originated in Europe, not Africa. New analyses of a fossilized jaw (shown) and teeth from Graecopithecus, a chimpanzee-sized primate that lived in southeastern Europe roughly 7 million years ago, suggest that it may be the earliest known hominid (SN: 6/24/17, p. 9). But more complete fossils are needed to determine whether Graecopithecus was truly a hominid.

In December, astronomers and space enthusiasts received an early present: 86 newly official star names.

Such designations are often derived from Arabic, Greek or Latin origins. But the new monikers also draw inspiration from ancient mythologies and historical star names from indigenous cultures around the world, including in China, Australia and southern Africa. The star names were officially recognized by the International Astronomical Union, which oversees the naming of objects in space, and announced on December 11. Here are some of the names we thought shined the brightest.
Xamidimura
Constellation: Scorpius
According to South African lore, the indigenous Khoikhoi people nicknamed the pair of stars just before the end of the scorpion’s tail “xami di mura,” meaning “eyes of the lion.”

Fafnir
Constellation: Draco
Fafnir is a dwarf from Norse mythology who became a dragon to guard his treasure. He was slain by the hero Sigurd.
Pipirima
Constellation: Scorpius
Pipirima is named for a pair of fraternal twins, the boy Pipiri and his sister Rehua, from a Tahitian legend. When their parents didn’t share a meal of fish one night, the two kids ran away. As the parents came closer to finding them, the twins climbed onto the back of a passing stag beetle and were carried into the sky.

Chalawan
Constellation: Ursa Major
Chalawan, a villainous crocodile king from a Thai folktale, lived in an underwater cave. A man named Krai Thong fell in love with one of Chalawan’s two wives and killed the crocodile king.

Ran
Constellation: Eridanus
Ran, a Norse goddess of the sea, created peril by capturing sailors in her net.

Unurgunite
Constellation: Canis Major
In stories from Australia’s aboriginal people, Unurgunite has two wives, which are represented by stars on either side of the named star. When Mityan, who represents the moon in the stories, fell in love with one of the wives, Unurgunite fought Mityan and won. Mityan has been wandering the universe ever since.

Alsephina
Constellation: Vela
Alsephina is the brightest star in this new list. “Al-safinah” in Arabic means “the ship,” referring to the ancient Greek constellation Argo Navis (named for the Argonauts’ ship and now split into three modern constellations). The bright star, located in one of those constellations called Vela, has been unofficially called Alsephina since at least 1660, when the Dutch-German mapmaker Andreas Cellarius illustrated the star in Harmonia Macrocosmica, a book about the cosmos.

Tianguan
Constellation: Taurus
Tianguan is a binary star that was unofficially named roughly 2,000 years ago during China’s Han period in the Tianguan shu, the first Chinese systematic description of the stars. In 1898, Édouard Chavannes translated the text to French, introducing Chinese constellations in their proper astrological positions to the western world.

Cervantes
Constellation: Ara
Cervantes is named after Miguel de Cervantes, a Spanish writer who wrote the famous novel Don Quixote. The star is orbited by an exoplanet named Quijote, referring to the story’s protagonist.

Titawin
Constellation: Andromeda
Titawin is named after Medina of Tétouan, a UNESCO World Heritage Site in northern Morocco that was a central point of contact between Spaniards and Arabs beginning in the 8th century.

There’s a new largest known prime number in town, with a whopping 23,249,425 digits. The figure is calculated by multiplying 2 by itself 77,232,917 times and then subtracting 1. Announced on January 3, the number is almost a million digits longer than the last record-breaking prime.

A prime number can’t be divided by anything other than 1 and itself. If you started counting at 1, you’d encounter prime numbers relatively frequently at first. But as numbers get larger, primes become sparse.
Jonathan Pace, an electrical engineer in Germantown, Tenn., found the number using software provided by the Great Internet Mersenne Prime Search. GIMPS is a volunteer-based project that’s seeking ever-higher Mersenne primes, which are found by multiplying the number 2 by itself some number of times and subtracting 1. These primes are easier to find than other types, Pace says, because the computer doesn’t need to calculate a number’s divisors to determine whether or not it’s prime.

Pace started hunting for primes 14 years ago, when there was a cash reward for finding a prime number with more than 10 million digits. “I missed out on the big prize,” he says. “But by then I was sort of hooked.” He runs the prime-seeking program in the background of the dozen or so computers for which he’s a volunteer network administrator. And, he says, the element of competition is fun.

Anyone can download the software for free. So you, too, could discover a record-breaking prime number — if you have enough patience.

SAN FRANCISCO — Even moderate light pollution can roughly double the time a house sparrow remains a risk for passing along the worrisome West Nile virus.

House sparrows, about as widespread across the United States as artificial lighting itself, make a useful test species for a first-of-its-kind study of how night illumination might contribute to disease spread, said Meredith Kernbach, an eco-immunologist at the University of South Florida in Tampa. Passer domesticus brought into the lab and kept dimly illuminated at night were slower in fighting off West Nile infections than lab sparrows allowed full darkness, Kernbach reported January 7 at the annual meeting of the Society for Integrative and Comparative Biology.
Sparrows kept under a dim night light typically had enough virus in their bloodstreams for at least four days to turn biting mosquitoes into disease spreaders, she said. Sparrows housed in darkness had high virus concentrations for only about two days. Doubling the time a bird can pass along a big dose of virus could in theory increase the likelihood that a disease will spread.

The broader question of whether light pollution affects human health has been a concern for shift workers. Researchers have also looked at possible changes in reproduction and other behavior in wildlife (SN: 12/26/15, p. 29).

Kernbach’s project opens new territory by testing the effects of light on physiological factors that control how diseases that can infect humans might hopscotch among animals, says Jenny Ouyang, of the University of Nevada, Reno. As light pollution studies go, “I don’t know of anything like this,” says Ouyang, an integrative physiologist who also has studied light pollution and birds.

The tests intensify Ouyang’s curiosity about whether light might affect the spread of malaria among humans. There have been hints and speculation in the scientific literature, she says, that vector mosquitoes might be drawn to light sources in some circumstances, which could mean that excess illumination might compound urban disease risks.
Kernbach based much of her lab test on real-world conditions. The viral dose she gave the birds was strong enough to kill about 40 percent of them, and it was well within what a mosquito might pick up vampirizing birds or mammals. She used white incandescent lighting, basically the last century’s universal light bulb, which is still common despite inroads by LED lighting.

The white incandescence in the experiment has plenty of warmer tones, but does include some of blue wavelengths from common cool white LEDs, or light-emitting diodes. The sparrows on average experienced about 8 lux of this white incandescence during their seven-hour nights. (A heavily overcast day, by comparison, ranks at about 100 lux.)

Other studies in birds are showing that artificial night lighting can affect concentrations of the hormone corticosterone, which helps orchestrate reactions of the immune system. But Kernbach said she found no signs in her experiment that corticosterone controlled the results she saw in house sparrows.

What lights do to the birds is only part of the story, points out Davide Dominoni, an eco-physiologist at the Netherlands Institute of Ecology in Wageningen. Researchers will also need to look for effects on the virus itself. And on the mosquitoes.

OXON HILL, Md. — Observations of a trio of dead stars have confirmed that a foundation of Einstein’s gravitational theory holds even for ultradense objects with strong gravitational fields.

The complex orbital dance of the three former stars conforms to a rule known as the strong equivalence principle, researchers reported January 10 at a meeting of the American Astronomical Society. That agreement limits theories that predict Einstein’s theory, general relativity, should fail at some level.
According to general relativity, an object’s composition has no impact on how gravity pulls on it: Earth’s gravity accelerates a sphere of iron at the same rate as a sphere of lead. That’s what’s known as the weak equivalence principle. A slew of experiments have confirmed that principle — beginning with Galileo’s purported test of dropping balls from the Leaning Tower of Pisa (SN: 1/20/18, p. 9).

But the strong equivalence principle is more stringent and difficult to test than the weak version. According to the strong equivalence principle, not only do different materials fall at the same rate, but so does the energy bound up in gravitational fields. That means that an incredibly dense, massive object with a correspondingly strong gravitational field, should fall with the same acceleration as other objects.

“We’re asking, ‘How does gravity fall?’” says astronomer Anne Archibald of the University of Amsterdam, who presented the preliminary result at the meeting. “That sounds weird, but Einstein says energy and mass are the same.” That means that the energy bound up in a gravitational field can fall just as mass can. If the strong equivalence principle were violated, an object with an intense gravitational field would fall with a different acceleration than one with a weaker field.

To test this theory, scientists measured the timing of signals from a pulsar — a spinning, ultradense collapsed star that emits beams of electromagnetic radiation that sweep past Earth at regular intervals. The pulsar in question, PSR J0337+1715, isn’t just any pulsar: It has two companions (SN: 2/22/14, p.8). The pulsar orbits with a type of burnt-out star called a white dwarf. That pair is accompanied by another white dwarf, farther away.
If the strong equivalence principle holds, the paired-up pulsar and white dwarf should both fall at the same rate in the gravitational field of the second white dwarf. But if the pulsar, with its intense gravitational field, fell faster toward the outermost white dwarf than its nearby companion, the pulsar’s orbit would be pulled toward the outermost white dwarf, tracing a path in the shape of a rotating ellipse.

Scientists can use the timing of a pulsar’s signals to deduce its orbit. As a pulsar moves away from Earth, for example, its pulses fall a little bit behind its regular beat. So if J0337+1715’s orbit were rotating, signals received on Earth would undergo regular changes in their timing as a result. Archibald and colleagues saw no such variation. That means the pulsar and the white dwarf must have had matching accelerations, to within 0.16 thousandths of a percent.

Many physicists expect the strong equivalence principle to be violated on some level. General relativity doesn’t mesh well with quantum mechanics, the theory that reigns on very small scales. Adjustments to general relativity that attempt to combine these theories tend to result in a violation of the strong equivalence principle, says physicist Clifford Will of the University of Florida in Gainesville, who was not involved with the research.

The strong equivalence principle might still fail at levels too tiny for this test to catch. So the door remains open for adjustments to general relativity. But the new measurement constrains many such theories better than any previous test. The result is “really tremendous,” says Will. It’s “a great improvement in this class of theories … which is why this triple system is so beautiful.”

OXON HILL, Md. — Future spacecraft could navigate by the light of dead stars.

Using only the timing of radiation bursts from pulsating stellar corpses, an experiment on the International Space Station was able to pinpoint its location in space in a first-ever demonstration. The technique operates like a stellar version of GPS, researchers with the Station Explorer for X-ray Timing and Navigation Technology experiment, SEXTANT, reported at a news conference January 11 during a meeting of the American Astronomical Society.
Known as pulsars, the dead stars emit beams of radiation that sweep past Earth at regular intervals, like the rotating beams from a lighthouse. Those radiation blips could allow a spaceship to find its location in space (SN: 12/18/10, p. 11). It’s similar to how GPS uses the timing of satellite signals to determine the position of your cell phone – and it would mean spacecraft would no longer have to rely on radio telescope communications to find their coordinates. That system becomes less accurate the further a spaceship gets from Earth.

SEXTANT used an array of 52 X-ray telescopes to measure the signals from five pulsars. By analyzing those signals, the researchers were able to locate SEXTANT’s position to within 10 kilometers as it orbited Earth on the space station, astronomer Keith Gendreau of NASA’s Goddard Space Flight Center in Greenbelt, Md., reported.

On Earth, knowing your location within 10 kilometers isn’t that impressive — GPS can do much better. But “if you’re going out to Pluto, there is no GPS navigation system,” Gendreau said. Far from Earth, pulsar navigation could improve upon the position estimates made using radio telescopes.

To build resilient colonies, bacteria make a surprising tweak to a common substance found in cells.

A biochemical addition to the cellulose produced by E. coli and other species of bacteria lets them create colonies that are resistant to disruption, researchers report in the Jan. 19 Science. Called biofilms, these microbial colonies can form on medical devices or inside the body, leading to hard-to-treat infections that can resist antibiotics. Figuring out how to weaken these films by altering bacteria’s cellulose could lead to new treatments.
Cellulose is the most abundant natural polymer on the planet. It makes celery stringy and plants’ cell walls rigid. The basic structure of the substance is simple: a bunch of copies of the sugar glucose — the exact number can vary — strung together like beads on a string.

While the polymer is best associated with plants, some bacteria make cellulose, too. The microbes secrete it and use it to build scaffolding around cells that supports the growth of biofilms. In a biofilm, cellulose is like “the mortar to hold together all the bricks,” says study coauthor Lynette Cegelski, a chemical biologist at Stanford University.
When Cegelski and her colleagues used a technique called nuclear magnetic resonance spectroscopy to analyze the biofilm around samples of E. coli, the researchers got a surprise. The cellulose made by bacteria was different from the cellulose made by plants.
Instead of being only a string of glucose units, bacterial cellulose also had an appendage containing nitrogen and phosphorus. E. coli’s appendage add-on affects the way the bacteria form colonies, experiments show. Normally, bacterial cellulose spins into long tendrils that, along with a different kind of sticky, protein-based fiber, form basketlike structures that cradle individual bacteria and tie them together into an elastic web. But when the researchers genetically engineered the bacteria to produce unmodified cellulose, the cellulose formed shorter fibers. That made the biofilm matrix weaker. The resulting film also appeared less resistant to microorganisms that produce cellulose-destroying enzymes.

Other studies have looked at bacterial cellulose before. But nobody had realized that it was modified. That’s because a commonly used method for examining biofilms involves dissolving the materials in an acid at one step of the process, which breaks down this modification.

The new study also pins down the role of a gene that researchers knew was somehow involved in cellulose production in bacteria, but weren’t sure how. This gene gives instructions for an enzyme that attaches the appendage to the glucose chain after it’s produced, altering the cellulose just before it leaves the cell. Targeting the gene or enzyme responsible for this modification could eventually be a way to weaken biofilms, Cegelski says.

The process by which bacteria make cellulose and secrete it to build biofilms is already quite complex, regulated by more than a dozen different genes working together. Adding an enzyme that can “sneak into this machinery” and tack on an appendage makes the story even more complicated, says Jean-Marc Ghigo, a microbial geneticist at the Institut Pasteur in Paris, who wasn’t involved in the study. “I think it’s cool.”

Other species of bacteria, such as Salmonella, also produce the modified cellulose, Cegelski and her team found. She plans to do a wider survey of bacteria to figure out just how widespread it is.

West Virginia basketball coach Bob Huggins found himself embroiled in a controversy on Monday, and it's one of his own making.

The Mountaineers' terrific offseason, which saw the program land three of the top players in the transfer portal, was interrupted by Huggins' own words, potentially putting his status with the team in question.

In the arena, Huggins has been one of the most successful college basketball coaches without a national championship. He's one of six coaches with at least 900 Division I wins and has reached the Final Four at both West Virginia and Cincinnati.

The Hall of Famer is entering his 17th season as the Mountaineers' head coach, but he'll do so under a cloud.
Here's what you need to know about the controversy surrounding Huggins.

Bob Huggins controversy, explained
Huggins directed a homophobic slur at Xavier fans twice during a radio interview with Cincinnati's 700WLW on Monday.

"It was, was all those f—, those Catholic f—, I think," Huggins said as he spoke with host Bill Cunningham about an alleged incident at a game between Xavier and Cincinnati.

Huggins' comments prompted a very brief but awkward silence on the air, though Cunningham didn't seem too bothered by the slur as he kept laughing throughout the rest of the interview.

Cunningham originally had asked Huggins whether West Virginia was accepting players from Xavier in the transfer portal. Xavier was a bitter rival of Huggins during his 17 years at crosstown Cincinnati.

Huggins released a statement later Monday admitting he used a "completely insensitive and abhorrent phrase that there is simply no excuse for."
The Hall of Fame coach said he deeply apologizes and will "fully accept" any consequence for his comments.

West Virginia released a statement of its own, calling Huggins' comments "offensive" and adding that the situation is under review and will be addressed.
Xavier president Colleen Hanycz released a statement on Tuesday addressing the comments, saying the school's mission is to "prepare students for a world that is increasingly diverse, complex, and interdependent." Hanycz did not mention Huggins by name.
What did Bob Huggins say?
Huggins directed a homophobic slur at Xavier fans during a radio interview, saying "It was, was all those f—, those Catholic f—, I think," in reference to an alleged incident at a game between Xavier and Cincinnati.
The slur has cost prominent figures their jobs in the past. That includes former Reds play-by-play commentator Thom Brennaman, who was caught on a hot mic calling a certain city "one of the f— capitals of the world" during a game against the Royals in 2020.

His on-air apology became infamous for being interrupted by Nick Castellanos' untimely home run, but it wasn't enough to save his job.

Huggins has close ties to Brennaman and his father, Marty, who served as the Reds' play-by-play man for decades. Huggins had the younger Brennaman speak to his players in 2020, three months after the incident and Brennaman's subsequent exit.

While any usage of the word will spark immediate condemnation, Huggins used it while knowingly on the air, unlike Brennaman.

Will Bob Huggins be fired?
West Virginia will not fire Bob Huggins, as originally reported by ESPN's Pete Thamel. Instead, the Mountaineers coach will be suspended three games, see $1 million of his salary docked and undergo sensitivity training.
Response by West Virginia
West Virginia later confirmed Huggins would not be fired, though the university was blunt in its reprimand of Huggins' comments:

"On Monday, May 8, head men's basketball coach Bob Huggins was interviewed on a Cincinnati radio show where he used derogatory and offensive language. It was inexcusable," the statement reads. "It was a moment that unfairly and inappropriately hurt many people and has tarnished West Virginia University.

"It is also a moment that provides the opportunity for learning. A moment that can shine a light on the injustice and hate that often befall the members of our marginalized communities. While the University has never and will never condone the language used on Monday, we will use this moment to educate how the casual use of inflammatory language and implicit bias affect our culture, our community and our health and well-being."

The university all provided details on the stipulations of Huggins' return. Those include:

Huggins will be suspended for the first three regular season games of the 2023-2024 season;
His contract will be amended from a multi-year agreement to a year-by-year agreement, beginning on May 10, 2023 and ending on April 30, 2024;
Huggins' annual salary will be reduced by $1 million; the money will be donated to support WVU's LGBTQ+ Center, the Carruth Center and other state and national organizations that support marginalized communities;
Any similar incidents in the future will result in immediate termination.
Moreover, WVU's athletics department will partner with the university LGBTQ+ Center to "develop annual training sessions" to address aspects such as homophobia, transphobia, sexism, ableism and more. The training curriculum will be required of Huggins and all athletics coaching staff.

Huggins will also be required to meet with LGBTQ+ leaders from across West Virginia with the expectation of engaging in additional opportunities to support the LGBTQ+ community. He will also be expected to meet with leaders from WVU's Carruth Center to "better understand the mental health crisis facing our college students, particularly those in marginalized communities."

Huggins has also agreed to make a sizable donation to Xavier University's Center for Faith and Justice and Center for Diversity and Inclusion.
"We will never truly know the damage that has been done by the words said in those 90 seconds. Words matter and they can leave scars that can never be seen," the statement reads. "But words can also heal. And by taking this moment to learn more about another's perspective, speak respectfully and lead with understanding, perhaps the words 'do better' will lead to meaningful change for all."

Zac Al-Khateeb contributed to this report.

Big brains outpaced well-rounded brains in human evolution.

Around the time of the origins of our species 300,000 years ago, the brains of Homo sapiens had about the same relatively large size as they do today, new research suggests. But rounder noggins rising well above the forehead — considered a hallmark of human anatomy — didn’t appear until between about 100,000 and 35,000 years ago, say physical anthropologist Simon Neubauer and his colleagues.

Using CT scans of ancient and modern human skulls, the researchers created digital brain reconstructions, based on the shape of the inner surface of each skull’s braincase. Human brains gradually evolved from a relatively flatter and elongated shape — more like that of Neandertals’ — to a globe shape thanks to a series of genetic tweaks to brain development early in life, the researchers propose January 24 in Science Advances.
A gradual transition to round brains may have stimulated considerable neural reorganization by around 50,000 years ago. That cognitive reworking could have enabled a blossoming of artwork and other forms of symbolic behavior among Stone Age humans, the team suspects. Other researchers have argued, however, that abstract and symbolic thinking flourished even before H. sapiens emerged (SN: 12/27/14, p. 6).
Ancient DNA studies indicate that genes involved in brain development changed in H. sapiens
following a split from Neandertals more than 600,000 years ago ( SN Online: 3/14/16 ). “Those genetic changes might be responsible for differences in neural wiring and brain growth that led to brain [rounding] in modern humans, but not in Neandertals,” says Neubauer of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany.
Still, a lack of fossilized brains means scientists have to rely on braincase data. But these data don’t directly measure brain shape, making it difficult to untangle precisely how quickly or slowly human brains became as round as they are today, says paleoanthropologist Christoph Zollikofer of the University of Zurich. In general, though, the faces of H. sapiens got smaller over time, a skull change that Zollikofer contends critically influenced the evolution of rounded braincases described in the new report.

Neubauer’s team studied 20 ancient H. sapiens skulls. The three oldest specimens included two Moroccan finds dating to around 315,000 years ago that may be the earliest known H. sapiens (SN: 7/8/17, p. 6). A second group of four skulls date to between 120,000 and 115,000 years ago. Estimated ages for the remaining 13 skulls range from around 36,000 to 8,000 years old.

Comparison skulls came from 89 present-day humans, eight Neandertals dating to between 75,000 and 40,000 years ago and 10 members of other ancient Homo species dating to between 1.78 million and 200,000 years ago. Progressive rounding of braincases appeared only in the sample of ancient H. sapiens.

Neubauer considers it unlikely that the gradual evolution of smaller faces with the same general skull shape altered braincase shapes. The oldest known H. sapiens skulls, which his team considers to be the two Moroccan finds, have faces shaped like those of modern humans, Neubauer says.