Galaxies may grow by swiping gas from their neighbors.

New simulations suggest that nearly half the matter in the Milky Way may have been siphoned from the gas of other galaxies. That gas provides the raw material that galaxies use to build their bulk. The finding, scheduled to appear in the Monthly Notices of the Royal Astronomical Society, reveals a new, unexpected way for galaxies to acquire matter and could give clues to how they evolve.
“These simulations show a huge amount of interaction among galaxies, a huge dance that’s going on,” says astronomer Romeel Davé of the University of Edinburgh. That dance, and the subsequent exchange of atoms, could be what establishes a galaxy’s character — whether it’s small or big, elliptical or spiral, quiet or bursting with star formation. If the simulation results are confirmed with observations, it could be a major advancement in understanding galaxy formation, Davé says.

It makes sense that much of the material in one galaxy actually came from other galaxies, says study coauthor Claude-André Faucher-Giguère, a theoretical astrophysicist at Northwestern University in Evanston, Ill. “Still, the result was really unexpected,” he says.

Astronomers thought galaxies got their matter in two main ways. First, atoms clumped together to form stars and then galaxies, not long after the Big Bang about 13.8 billion years ago. Then some of those atoms were eventually ejected by supernovas but rained back onto the same galaxy, recycling the gas again and again.

The new simulations showed a third way galaxies could score gas. Powerful supernova explosions would eject atoms, in the form of gas, far from their home galaxies into intergalactic space. Those atoms would then travel through space, pushed toward other galaxies by galactic winds that move at several hundred kilometers per second. When the particles neared a galaxy’s gravitational pull, they would get sucked in, where they would serve as the basis for stars, planets, dust and other material in their new galactic home. Still, this exchange of atoms is extremely difficult to spot in space because the gas atoms, don’t give off light like stars do.
Faucher-Giguère and colleagues spotted the exchange in computer simulations that show how galaxies formed just after the Big Bang and how they have evolved over time. The team tracked gas atoms as they moved through the model universe, formed stars and then were ejected from galaxies as those stars exploded.

In the simulations, up to half of the atoms in large galaxies were pulled in from other galaxies. Because more massive galaxies have more gravity, they tended to pull atoms from the ejected material of small galaxies. The exchange appears to take billions of years as atoms travel the vast space between galaxies, the team notes.

“It’s that not surprising to see a galaxy kick out matter, which is then pulled in by other galaxies,” Davé says. What is surprising, he says, is the amount of material that’s transferred. Before seeing the simulations, he would have guessed that about 5 percent of gas was transferred among galaxies this way. “To see that it is up to 50 percent is pretty remarkable,” he says.

Already, astronomers are searching for evidence of this material-swapping behavior among galaxies. Faucher-Giguère and colleagues, working with researchers using the Hubble Space Telescope, hope to observe intergalactic transfer of gas among galaxies soon.

The largest marsupial to ever walk the Earth just got another accolade: It’s also the only marsupial known to migrate seasonally.

Diprotodon optatum was a massive wombat-like herbivore that lived in what’s now Australia and New Guinea during the Pleistocene, until about 40,000 years ago. Now, an analysis of one animal’s teeth suggests that it undertook long, seasonal migrations like those made by zebras and wildebeests in Africa.

Animals pick up the chemical element strontium through their diet, and it leaves a record in their teeth. The ratio of different strontium isotopes varies from place to place, so it can provide clues about where an animal lived. Strontium isotope ratios in an incisor from one D. optatum revealed a repeating pattern. That suggests the animal migrated seasonally — it moved around, but generally hit up the same rest stops each year, researchers report September 27 in the Proceedings of the Royal Society B.

It’s the first evidence to show a marsupial — living or extinct — migrating in this way, says study coauthor Gilbert Price, a paleoecologist at the University of Queensland in Brisbane, Australia. It’s not clear exactly why this mega-marsupial might have migrated, but an analysis of the carbon isotopes in its teeth suggests it ate a fairly limited diet. So it might have migrated to follow food sources that popped up seasonally in different places, the authors suggest.

What looks like a spider, but with a segmented rear plus a long spike of a tail, has turned up in amber that’s about 100 million years old.

Roughly the size of a peppercorn (not including the tail, which stretches several times the body length), this newly described extinct species lived in forests in what is now Myanmar during the dinosaur-rich Cretaceous Period.

Spiders as their own distinctive group had evolved long before. Whether this tailed creature should be considered a true spider (of the group Araneae) is debatable though, researchers acknowledge February 5 in two studies in Nature Ecology & Evolution. In one of the papers, the fossils’ chimeric mash-up of traits both spidery and nonspidery inspired Bo Wang of the Chinese Academy of Sciences in Nanjing and colleagues to name the species Chimerarachne yingi.
C. yingi indeed has some anatomy that, among living animals, would be unique to spiders, says Gonzalo Giribet of Harvard University, a coauthor of the other paper. The fossils have what look like little structures that could have exuded spider silk, as well as distinctive male spider sex organs. Called pedipalps, these modified legs have no direct connection to a sperm-producing organ. Spiders need to load them before mating, for instance by ejaculating a sperm droplet and dipping pedipalps in it, so the structures can deliver the sperm a bit like a syringe.

But the abdomen-like end of a true spider’s body isn’t segmented and certainly doesn’t have a tail. Giribet and his colleagues’ analysis puts C. yingi in an ancient sister group of spiders. That’s startling in itself, Giribet says, because researchers have speculated that this Uraraneida group had gone extinct much earlier. So, spider or not, C. yingi remains intriguing.

China’s Chang’e-4 lander and rover just became the first spacecraft to land on the farside of the moon.

The lander touched down at 9:26 p.m. Eastern time on January 2, according to an announcement from the China National Space Administration. The spacecraft is part of a series of Chinese space missions named Chang’e (pronounced CHONG-uh) for the Chinese goddess of the moon.

A small rover dubbed Yutu 2, or Jade Rabbit 2, rolled off the craft several hours after landing. The rover will explore the terrain around the 186-kilometer-wide Von Kármán crater located inside the 2,500-kilometer-wide South Pole–Aitken basin. The basin, one of the largest and oldest impact features in the solar system, could contain exposed parts of the moon’s interior that might reveal details of its formation and early history (SN: 11/24/18, p. 14).
Chang’e-4 will measure some of the region’s composition, use ground-penetrating radar to probe just below the surface, and take panoramic images of a landscape that has never been seen from the ground before. It will also make measurements of charged particles and radiation, which could help support future astronaut missions, and test whether plants and insects can grow together on the moon.
Because the moon always shows the same face to Earth, it is impossible to communicate directly with spacecraft on the farside. A relay satellite named Queqiao, or Magpie Bridge, that launched in May 2018 will beam signals between Chang’e-4 and Earth (SN Online: 5/20/18).
The landing marks China’s second lunar landing, and a step towards more ambitious moon missions. The Chinese space agency is planning another mission to collect moon rock samples later in 2019.

A genetic hack to make photosynthesis more efficient could be a boon for agricultural production, at least for some plants.

This feat of genetic engineering simplifies a complex, energy-expensive operation that many plants must perform during photosynthesis known as photorespiration. In field tests, genetically modifying tobacco in this way increased plant growth by over 40 percent. If it produces similar results in other crops, that could help farmers meet the food demands of a growing global population, researchers report in the Jan. 4 Science.
Streamlining photorespiration is “a great step forward in efforts to enhance photosynthesis,” says Spencer Whitney, a plant biochemist at Australian National University in Canberra not involved in the work.

Now that the agricultural industry has mostly optimized the use of yield-boosting tools like pesticides, fertilizers and irrigation, researchers are trying to micromanage and improve plant growth by designing ways to make photosynthesis more efficient (SN: 12/24/16, p. 6).

Photorespiration is a major roadblock to achieving such efficiency. It occurs in many plants, such as soybeans, rice and wheat, when an enzyme called Rubisco — whose main job is to help transform carbon dioxide from the atmosphere into sugars that fuel plant growth — accidentally snatches an oxygen molecule out of the atmosphere instead.

That Rubisco-oxygen interaction, which happens about 20 percent of the time, generates the toxic compound glycolate, which a plant must recycle into useful molecules through photorespiration. This process comprises a long chain of chemical reactions that span four compartments in a plant cell. All told, completing a cycle of photorespiration is like driving from Maine to Florida by way of California. That waste of energy can cut crop yields by 20 to 50 percent, depending on plant species and environmental conditions.Streamlining photorespiration is “a great step forward in efforts to enhance photosynthesis,” says Spencer Whitney, a plant biochemist at Australian National University in Canberra not involved in the work.

Now that the agricultural industry has mostly optimized the use of yield-boosting tools like pesticides, fertilizers and irrigation, researchers are trying to micromanage and improve plant growth by designing ways to make photosynthesis more efficient (SN: 12/24/16, p. 6).

Photorespiration is a major roadblock to achieving such efficiency. It occurs in many plants, such as soybeans, rice and wheat, when an enzyme called Rubisco — whose main job is to help transform carbon dioxide from the atmosphere into sugars that fuel plant growth — accidentally snatches an oxygen molecule out of the atmosphere instead.

That Rubisco-oxygen interaction, which happens about 20 percent of the time, generates the toxic compound glycolate, which a plant must recycle into useful molecules through photorespiration. This process comprises a long chain of chemical reactions that span four compartments in a plant cell. All told, completing a cycle of photorespiration is like driving from Maine to Florida by way of California. That waste of energy can cut crop yields by 20 to 50 percent, depending on plant species and environmental conditions.
Using genetic engineering, researchers have now designed a more direct chemical pathway for photorespiration that is confined to a single cell compartment — the cellular equivalent of a Maine-to-Florida road trip straight down the East Coast.

Paul South, a molecular biologist with the U.S. Department of Agriculture in Urbana, Ill., and colleagues embedded genetic directions for this shortcut, written on pieces of algae and pumpkin DNA, in tobacco plant cells. The researchers also genetically engineered the cells to not produce a chemical that allows glycolate to travel between cell compartments to prevent the glycolate from taking its normal route through the cell.
Unlike previous experiments with human-designed photorespiration pathways, South’s team tested its photorespiration detour in plants grown in fields under real-world farming conditions. Genetically altered tobacco produced 41 percent more biomass than tobacco that hadn’t been modified.
“It’s very exciting” to see how well this genetic tweak worked in tobacco, says Veronica Maurino, a plant physiologist at Heinrich Heine University Düsseldorf in Germany not involved in the research, but “you can’t say, ‘It’s functioning. Now it will function everywhere.’”

Experiments with different types of plants will reveal whether this photorespiration fix creates the same benefits for other crops as it does for tobacco. South’s team is currently running greenhouse experiments on potatoes with the new set of genetic modifications, and plans to do similar tests with soybeans, black-eyed peas and rice.

The vetting process for such genetic modifications to be approved for use on commercial farms, including more field testing, will probably take at least another five to 10 years, says Andreas Weber, a plant biochemist also at Heinrich Heine University Düsseldorf who coauthored a commentary on the study that appears in the same issue of Science. In the meantime, he expects that researchers will continue trying to design even more efficient photorespiration shortcuts, but South’s team “has now set a pretty high bar.”

Treatments for pain and other common health problems often fall short, leading to untold misery and frustration. So it’s not hard to understand the lure of a treatment that promises to be benign, natural and good for just about everything that ails you. Enter cannabidiol, or CBD.

So far, the U.S. Food and Drug Administration has approved only one drug containing the chemical: a treatment for rare and severe forms of epilepsy. But that hasn’t stopped people from trying CBD to relieve arthritis, morning sickness, pain, depression, anxiety, addiction, inflammation and acne. And it hasn’t kept companies from marketing the heck out of CBD-infused anything. It’s the sort of situation that gets us wondering: What’s the science here?
The science is skimpy at best, neuroscience writer Laura Sanders reports in this issue. Clinical trials, some of which included children, were conducted to determine safety and efficacy before the FDA approved the first CBD-based epilepsy drug in 2018. But much less research has been done on CBD with regard to other ailments.

Adding to the intrigue, CBD can be extracted from marijuana, though CBD lacks the capacity to induce a buzzy high like its sister molecule THC. So government restrictions have been tight, and scientists have had a hard time getting access to CBD for studies. That makes it less likely that we’ll get clear answers anytime soon on whether CBD is indeed a panacea, or just another triumph of hype.

The surplus of unknowns hasn’t stopped companies from marketing hundreds of CBD products as treatments, attempting to avoid scrutiny by adding disclaimers that the products “are not intended to diagnose, treat or cure or prevent any disease.” But with such large gaps in the research, people trying these products in the hope of benefit become inadvertent guinea pigs.

The process of science may be frustratingly slow, but it can get the job done. In the last decade, clinical trials on vitamin D, for example, have found that despite much excitement surrounding the “sunshine vitamin,” there’s no definitive evidence of benefits in preventing heart disease or cancer. In our recent cover story “Vitamin D supplements aren’t living up to their hype,” contributing correspondent Laura Beil described the years of effort needed to develop that data (SN: 2/2/19, p. 16).
As journalists, we see a big part of our mission as making sure that people have access to accurate, timely information about medical research, so people can make informed decisions for themselves and their families. That’s especially important when it involves products that people can self-prescribe. These two articles — by skilled journalists who put weeks of effort into reading studies, talking with researchers and investigating the business side — are great examples of how sophisticated and useful consumer science journalism can be. Most people look for health information online, but Googling a term like “CBD oil” serves up a muddle of marketing masquerading as impartial information.

CBD may end up being a worthwhile treatment for some problems beyond epilepsy; it’s too early to know. But while we wait for the evidence, it’s essential to know where the science stands right now.

THE WOODLANDS, Texas — Grains of dust from the edge of the solar system could be finding their way to Earth. And NASA may already have a handful of the debris, researchers report.

With an estimated 40,000 tons of space dust settling in Earth’s stratosphere every year, the U.S. space agency has been flying balloon and aircraft missions since the 1970s to collect samples. The particles, which can be just a few tens of micrometers wide, have long been thought to come mostly from comets and asteroids closer to the sun than Jupiter (SN Online: 3/19/19).

But it turns out that some of the particles may have come from the Kuiper Belt, a distant region of icy objects orbiting beyond Neptune, NASA planetary scientist Lindsay Keller said March 21 at the Lunar and Planetary Science Conference. Studying those particles could reveal what distant, mysterious objects in the Kuiper Belt are made of, and perhaps how they formed (SN Online: 3/18/19).

“We’re not going to get a mission out to a Kuiper Belt object to actually collect [dust] samples anytime soon,” Keller said. “But we have samples of these things in the stratospheric dust collections here at NASA.”
One way to find a dust grain’s home is to probe the particle for microscopic tracks where heavy charged particles from solar flares punched through. The more tracks a grain has, the longer it has wandered in space — and the more likely it originated far from Earth, says Keller, who works at the Johnson Space Center in Houston.

But to determine precisely how long a dust grain has spent traveling space, Keller first needed to know how many tracks a grain typically picks up per year. Measuring that rate required a sample with a known age and known track density — criteria met only by moon rocks brought back on the Apollo missions. But the last track-rate estimate was done in 1975 and with less precise instruments than are available today.
So Keller and planetary scientist George Flynn of SUNY Plattsburgh reexamined that same Apollo rock with a modern electron microscope. They found that the rate at which rocks pick up flare tracks was about 20 times lower than the previous study estimated.

That means it takes longer for dust flakes to pick up tracks than astronomers assumed. When Keller and Flynn counted the number of tracks in 14 atmospheric dust grains, the pair found that some of the particles must have spent millions of years out in space — far too long to have come just from between Mars and Jupiter.

Grains specifically from the Kuiper Belt would have wandered 10 million years to reach Earth’s stratosphere, the researchers calculated. That’s “pretty solid evidence that we’re collecting Kuiper Belt dust right here,” Keller says.
Four of the particles contained minerals that had to have formed through interactions with liquid water. That’s surprising; the Kuiper Belt is thought to be too cold for water to be liquid.

“Many of these particles, if they in fact are from the Kuiper Belt, tell you that some of the minerals in Kuiper Belt objects formed in the presence of liquid water,” Keller says. The water probably came from collisions between Kuiper Belt objects that produced enough heat to melt ice, he says.

“I think it’s incredible if Lindsay Keller has shown that he has pieces of Kuiper Belt dust in his lab,” says planetary scientist Carey Lisse of the Johns Hopkins University Applied Physics Laboratory in Laurel, Md. But more work needs to be done to confirm that the dust really came from the Kuiper Belt, he says, and wasn’t just sitting on an asteroid for millions of years. “Lindsay needs to get a lot more samples,” Lisse says. “But I do think he’s on to something.”

Lisse works on NASA’s New Horizons mission, which found plenty of dust in the outer solar system and measured its abundance near Pluto when the spacecraft flew past the dwarf planet in 2015. Based on those results, he finds it unsurprising that some of that dust has made it to Earth. But it is “really cool,” he says. “We can actually try to figure out what the Kuiper Belt is made of.”

Editor’s note: This story was updated April 8, 2019, to correct that the newly calculated flare track rate was about 20 times lower than the rate calculated in 1975, not two orders of a magnitude lower.

A new member of the human genus has been found in a cave in the Philippines, researchers report.

Fossils with distinctive features indicate that the hominid species inhabited the island now known as Luzon at least 50,000 years ago, according to a study in the April 11 Nature. That species, which the scientists have dubbed Homo luzonensis, lived at the same time that controversial half-sized hominids named Homo floresiensis and nicknamed hobbits were roaming an Indonesian island to the south called Flores (SN: 7/9/16, p. 6).
In shape and size, some of the fossils match those of corresponding bones from other Homo species. “But if you take the whole combination of features for H. luzonensis, no other Homo species is similar,” says study coauthor and paleoanthropologist Florent Détroit of the French National Museum of Natural History in Paris.

If the find holds up to further scientific scrutiny, it would add to recent fossil and DNA evidence indicating that several Homo lineages already occupied East Asia and Southeast Asian islands by the time Homo sapiens reached what’s now southern China between 80,000 and 120,000 years ago (SN: 11/14/15, p. 15). The result: an increasingly complicated picture of hominid evolution in Asia.

Excavations in 2007, 2011 and 2015 at Luzon’s Callao Cave yielded a dozen H. luzonensis fossils at first — seven isolated teeth (five from the same individual), two finger bones, two toe bones and an upper leg bone missing its ends, the scientists say. Analysis of the radioactive decay of uranium in one tooth suggested a minimum age of 50,000 years. Based on those fossils, a hominid foot bone found in 2007 in the same cave sediment was also identified as H. luzonensis. It dates to at least 67,000 years ago.
had molars that were especially small, even smaller than those of hobbits, with some features similar to modern humans’ molars. The hominid also had relatively large premolars that, surprisingly, had two or three roots rather than one. Hominids dating to several hundred thousand years ago or more, such as Homo erectus , typically had premolars with multiple roots. H. luzonensis finger and toe bones are curved, suggesting a tree-climbing ability comparable to hominids from 2 million years ago or more.
It’s unclear whether H. luzonensis was as small as hobbits, Détroit says. The best-preserved hobbit skeleton comes from a female who stood about a meter tall. Based on the length of the Callao Cave foot bone, Détroit’s team suspects that H. luzonensis was taller than that, although still smaller than most human adults today.

As with hobbits, H. luzonensis’ evolutionary origins are unknown. Scientists think that hobbits may have descended from seagoing H. erectus groups, and perhaps H. luzonensis did too, writes paleoanthropologist Matthew Tocheri of Lakehead University in Thunder Bay, Canada, in a commentary published with the new report. Evidence suggests that hominids reached Luzon by around 700,000 years ago (SN Online: 5/2/18). So H. erectus may have also crossed the sea from other Indonesian islands or mainland Asia to Luzon and then evolved into H. luzonensis with its smaller body and unusual skeletal traits, Détroit speculates, a process known as island dwarfing.

But some scientists not involved in the research say it’s too soon to declare the Luzon fossils a brand-new Homo species. Détroit’s group, so far, has been unable to extract ancient DNA from the fossils. So “all [evolutionary] possibilities must remain open,” says archaeologist Katerina Douka of the Max Planck Institute for the Science of Human History in Jena, Germany.

The mosaic of fossil features that the team interprets as distinctive, for instance, may have been a product of interbreeding between two or more earlier Homo species, creating hybrids, but not a new species.

Or perhaps a small population of, say, H. erectus that survived on an isolated island like Luzon for possibly hundreds of thousands of years simply acquired some skeletal features that its mainland peers lacked, rather than evolving into an entirely new species, says paleoanthropologist María Martinón-Torres.

Those questions make the new fossils “an exciting and puzzling discovery,” says Martinón-Torres, director of the National Research Centre on Human Evolution in Burgos, Spain.

If the unusual teeth and climbing-ready hand and foot bones found at Callao Cave occurred as a package among Luzon’s ancient Homo crowd, “then that combination is unique and unknown so far” among hominids, Martinón-Torres says. Only a more complete set of fossils, ideally complemented by ancient DNA, she adds, can illuminate whether such traits marked a new Homo member.

Ketamine banishes depression by slowly coaxing nerve cells to sprout new connections, a study of mice suggests. The finding, published in the April 12 Science, may help explain how the hallucinogenic anesthetic can ease some people’s severe depression.

The results are timely, coming on the heels of the U.S. Food and Drug Administration’s March 5 approval of a nasal spray containing a form of ketamine called esketamine for hard-to-treat depression (SN Online: 3/21/19). But lots of questions remain about the drug.
“There is still a lot of mystery in terms of how ketamine works in the brain,” says neuroscientist Alex Kwan of Yale University. The new study adds strong evidence that newly created nerve cell connections are involved in ketamine’s antidepressant effects, he says.

While typical antidepressants can take weeks to begin working, ketamine can make people feel better in hours. Scientists led by neuroscientist Conor Liston suspected that ketamine might quickly be remodeling the brain by spurring new nerve cell connections called synapses. “As it turned out, that wasn’t true, not in the way we expected, anyway,” says Liston, of Cornell University.

Newly created synapses aren’t involved in ketamine’s immediate effects on behavior, the researchers found. But the nerve cell connections do appear to help sustain the drug’s antidepressant benefits over the longer term.

To approximate depression in people, researchers studied mice that had been stressed for weeks, either by being restrained daily in mesh tubes, or by receiving injections of the stress hormone corticosterone. These mice began showing signs of despair, such as losing their taste for sweet water and giving up a struggle when dangled by their tails.
Three hours after a dose of ketamine, the mice’s behavior righted, as the researchers expected. But the team found no effects of the drug on nerve cells’ dendritic spines — tiny signal-receiving blebs that help make new neural connections. So the creation of new synapses couldn’t be responsible for ketamine’s immediate effects on behavior, “because the behavior came first,” Liston says.

When the researchers looked over a longer time span, though, they found that these new synapses were key. About 12 hours after ketamine treatment, new dendritic spines began to pop into existence on nerve cells in part of the mice’s prefrontal cortex, the brain area responsible for complex thinking. These dendritic spines seemed to be replacing those lost during the period of stress, often along the same stretch of neuron.

To test if these newly created spines were important for the mice’s improved behavior, the researchers destroyed the spines with a laser a day after the ketamine treatment. That effectively erased ketamine’s effects, and the mice again exhibited behavior resembling depression, including struggling less when held by their tails. (The mice kept their regained sugar preference.)

Research on humans has also suggested that depressed people have diminished synapses, says Ronald S. Duman, a neuroscientist at Yale University not involved in the study. The new work adds more support to those findings by showing that destroying new synapses can block ketamine’s behavioral effects. “That’s a huge contribution and advance,” Duman says.

The sun’s rhythm may have set the pace of each day, but when early humans needed a way to keep time beyond a single day and night, they looked to a second light in the sky. The moon was one of humankind’s first timepieces long before the first written language, before the earliest organized cities and well before structured religions. The moon’s face changes nightly and with the regularity of the seasons, making it a reliable marker of time.

“It’s an obvious timepiece,” Anthony Aveni says of the moon. Aveni is a professor emeritus of astronomy and anthropology at Colgate University in Hamilton, N.Y., and a founder of the field of archaeoastronomy. “There is good evidence that [lunar timekeeping] was around as early as 25,000, 30,000, 35,000 years before the present.”

When people began depicting what they saw in the natural world, two common motifs were animals and the night sky. One of the earliest known cave paintings, dated to at least 40,000 years ago in a cave on the island of Borneo, includes a wild bull with horns. European cave art dating to about 37,000 years ago depicts wild cattle too, as well as geometric shapes that some researchers interpret as star patterns and the moon.

For decades, prehistorians and other archaeologists believed that ancient humans were portraying what they saw in the natural world because of an innate creative streak.
The modern idea that Paleolithic people were depicting nature for more than artistic reasons gained traction at the end of the 19th century and was further developed in the early 20th century by Abbé Henri Breuil, a French Catholic priest and archaeologist. He interpreted the stylistic bison and lions in the cave paintings and carvings of southern France as ritual art designed to bring luck to the hunt.

In the 1960s, a journalist–turned–amateur anthropologist proposed even more practical purposes for these drawings and other artifacts: They were created for telling time.

In the early days of the Apollo space missions, the journalist, Alexander Marshack, was writing a book about how the course of human history culminated in the moon shot. He delved into prehistory, trying to understand the earliest concepts of timekeeping and agriculture (SN: 4/14/79, p. 252).

“I had a profound sense of something missing,” Marshack wrote in his 1972 book, The Roots of Civilization. Formal science, including astronomy and math, apparently had begun “suddenly,” he noted. Same with writing, agriculture, art and the calendar. But surely these cognitive leaps took thousands of years of preparation, Marshack reasoned: “How many thousands was the question.”

To find out, he examined ancient bone carvings and wall art from locations including caves in Western Europe and fishing villages of equatorial Africa. He interpreted what was seen by some as simple dots and dashes or depictions of animals and people as sophisticated tools for keeping track of time — via the moon. Today, some experts support his thesis; others remain unconvinced.
It’s easy enough to keep track of the seasons just by paying attention to the environment, of course. Throughout the world, animals like deer and cattle are pregnant through the winter’s dark privation; they give birth when the leaves appear on trees and when grasses grow tall.

Early humans of 30,000 years ago frequently connected the changes in these “phenophases,” the seasonal stages of flora and fauna, with the appearance of certain stars and the phases of the moon, says science historian and astronomer Michael Rappenglück of the Adult Education Center and Observatory in Gilching, Germany. He refers to early cave depictions as “paleo-almanacs” because they combined time-reckoning with information related to the cycles of life.

As Rappenglück puts it, simply noting the spinning of the seasons would not be enough to keep time. For one thing, flora and fauna change from place to place, and even 30,000 years ago, humans were traveling great distances in search of food. They needed something more constant to help them tell time.

“People carefully watched the course of the moon, noting its position over the natural horizon and the change of its phases,” Rappenglück wrote in the 2015 Handbook of Archaeoastronomy and Ethnoastronomy.

In the 1960s, Marshack, the first to argue that Paleolithic people were connecting the moon with time, sifted through dusty cabinets in French museums, retrieving bone and antler pieces that had been worked by humans. Others had interpreted the etchings on these objects as the by-product of point-sharpening, or maybe, as most before Breuil thought, abstract artworks made by idle hands.

But Marshack saw the earliest examples of sky almanacs. The etchings were numerical and notational, he argued. On a bone shard from a prehistoric settlement called Abri Blanchard in France, dating to 28,000 years ago, he found a pattern of pits, some with commalike curves and some round. He viewed it as a record of lunar cycles.

Deeply excited by the find, Marshack soon brought his conclusions to archaeologists and anthropologists throughout Europe and the United States. Some of these experts were impressed, according to accounts at the time.

Hunters who could figure out when the night would be illuminated by moonlight would have had an “adaptive advantage,” Aveni says. “That is so much what the cave paintings are about,” he says, referring to the tally marks near the animals on the walls of the Chauvet Cave in France and elsewhere.

Regarding Marshack’s speculations about the Blanchard bone shard, paleoanthropologist Ian Tattersall is still unsure. “We know Ice Age European art was highly symbolic, and there is no doubt that [ancient people] perceived symbols all around them in nature. And it is pretty certain that the moon played a huge role in their cosmology, and that they were fully aware of its cycle,” says Tattersall, curator emeritus of human origins at the American Museum of Natural History in New York City. “Beyond that, all bets are off.”

Thirteen notches
In the decades after Marshack published his findings, historians and anthropologists began noticing similar lunar motifs throughout the archaeological record of this time period and afterward, Aveni notes. “There are more than one of these items that have markings on them that might relate to the moon,” he says.

The Venus of Laussel is one extraordinary example. It is a carving of a voluptuous woman, one hand resting on her abdomen, the other raised and holding a bison horn etched with 13 notches. Her face is turned toward the horn. The figure was carved between 22,000 and 27,000 years ago, in a rock-shelter in the Dordogne region of southwestern France.
Some archaeologists now think the 13 notches represent the number of lunar cycles in a solar year — and, approximately, the average number of menstrual cycles. Though modern scientists have debunked any direct connection between the cycles of the moon and human fertility, ancient people would have recognized the parallel timing; the lunar cycle repeats every 29.5 days, roughly the same schedule as the average woman’s menstrual cycle. People of 30,000 years ago could have used the moon and stars to plan their pregnancies, Rappenglück speculates.

Cave paintings in the Dordogne region may be depictions of the lunar and menstrual cycles. Specifically, the Lascaux cave paintings, dating to 17,000 years ago, are best known for their curvy, sweeping depictions of horses and bulls. Beyond the cave entrance, past what is called the Hall of Bulls, is a dead-end passage called the Axial Gallery. Red aurochs, an extinct form of cattle, stand in a group. A huge black bull stands apart from them. Across the gallery, a pregnant horse gallops above a row of 26 black dots. The mare is running toward a massive stag, with front legs invisible behind 13 additional evenly spaced dots.

The animals may represent seasons, Rappenglück suggests. In Europe, bovines calve in the spring; horses both foal and mate in the late spring. The deer rut takes place in early autumn, and the wild goats known as ibex mate around the winter solstice.

To Rappenglück, the dots depict the 13 full moons of the lunar cycle. The 26 dots may roughly represent the days of a sidereal month, or the time it takes the moon to return to the same position in the sky relative to the stars. “The striking row of dots is a kind of a time-unit,” he wrote in 2004.

Critics have said Marshack’s work overinterprets many artifacts from Africa and Europe, some of which contain markings at the limit of naked-eye visibility (SN: 6/9/90, p. 357).

“By modern standards of evidence, he is playing with numerological coincidences,” art historian James Elkins wrote in 1996 in an article that is part critique and part celebration. Elkins noted that Marshack countered his doubters by throwing their uncertainty back at them, arguing that better explanations were lacking.

“Nights were real nights at that time, and Paleolithic people certainly had deep insights into what was going on in the sky,” says Harald Floss, an anthropologist at the University of Tübingen in Germany who studies the origin of art. “But I would not risk saying more.”