My youngest child, now just over a year old, has started to talk. Even though I’ve experienced this process with my older two, it’s absolutely thrilling. He is putting words to the thoughts that swirl around in his sweet little head, making his mind a little less mysterious to the rest of us.

But these early words may not mean what we think they mean, a new study hints. Unsurprisingly, when 2-year-olds were asked a series of “this or that” questions, the toddlers showed strong preferences — but not for the reasons you’d think. Overwhelmingly, the toddlers answered the questions with the last choice given.
That bias, described in PLOS ONE on June 12, suggests that young children’s answers to these sorts of questions don’t actually reflect their desires. Instead, kids may simply be echoing the last thing they heard.

This verbal quirk can be used by parents to great effect, as the researchers point out in the title of their paper: “Cake or broccoli?” More fundamentally, the results raise questions about what sort of information a verbal answer actually pulls out of a young child’s mind. This murkiness is especially troublesome when it comes to questions whose answers call for adult action, such as: “Did you hit your sister on purpose or on accident?”

In the first series of experiments, researchers led by Emily Sumner at the University of California, Irvine, asked 24 1- and 2-year-olds a bunch of two-choice questions, some of which involved a polar bear named Rori or a grizzly bear named Quinn. One question, for example, was, “Does Rori live in an igloo or a tepee?” Later, the researchers switched the bear and the order of the options, asking, for example, “Does Quinn live in a tepee or an igloo?”

The toddlers could answer either verbally or, for reluctant speakers, by pointing at one of two stickers that showed the choices. When the children answered the questions by pointing, they chose the second option about half the time, right around chance. But when the toddlers spoke their answers, they chose the second option 85 percent of the time, regardless of the bear.
SECOND BEST A toddler taking part in a study selects the second option in three either-or questions. This tendency, called the recency bias, may reflect kids’ inability to juggle several choices in their minds simultaneously. Credit: E. Sumner et al/PLOS ONE 2019

This abundance of second options selected — a habit known as the recency bias — might be due to the fact that young children have trouble holding the first option in mind, the researchers suspect. Other experiments showed that children’s tendency toward the second option got stronger when the words got longer.

Adults actually have the opposite tendency: We’re more inclined to choose the first option we’re given (the primacy bias). To see when this shift from last to first occurs, the researchers studied transcripts of conversations held between adults and children ages 1.5 to 4. In these natural conversations, 2-year-olds were more likely to choose the second option. But 3- and 4-year-olds didn’t show this bias, suggesting that the window closes around then.

The results hold a multitude of delightful parenting hacks: “Would you like to jump on the bed all night, or go to sleep?” But more importantly, the study serves as a reminder that the utterances of small children, while fascinating, may not carry the same meanings as those that come from more mature speakers. If you really want a straight answer, consider showing the two options to the toddler. But if you go that route, be prepared to hand over the cake.

A skull found in a cliffside cave on Greece’s southern coast in 1978 represents the oldest Homo sapiens fossil outside Africa, scientists say.

That skull, from an individual who lived at least 210,000 years ago, was encased in rock that also held a Neandertal skull dating to at least 170,000 years ago, contends a team led by paleoanthropologist Katerina Harvati of the University of Tübingen in Germany.

If these findings, reported online July 10 in Nature, hold up, the ancient Greek H. sapiens skull is more than 160,000 years older than the next oldest European H. sapiens fossils (SN Online: 11/2/11). It’s also older than a proposed H. sapiens jaw found at Israel’s Misliya Cave that dates to between around 177,000 and 194,000 years ago (SN: 2/17/18, p. 6).

“Multiple Homo sapiens populations dispersed out of Africa starting much earlier, and reaching much farther into Europe, than previously thought,” Harvati said at a July 8 news conference. African H. sapiens originated roughly 300,000 years ago (SN: 7/8/17, p. 6).
A small group of humans may have reached what’s now Greece more than 200,000 years ago, she suggested. Neandertals who settled in southeastern Europe not long after that may have replaced those first H. sapiens. Then humans arriving in Mediterranean Europe tens of thousands of years later would eventually have replaced resident Neandertals, who died out around 40,000 years ago (SN Online: 6/26/19).

But Harvati’s group can’t exclude the possibility that H. sapiens and Neandertals simultaneously inhabited southeastern Europe more than 200,000 years ago and sometimes interbred. A 2017 analysis of ancient and modern DNA concluded that humans likely mated with European Neandertals at that time.

The two skulls were held in a small section of wall that had washed into Greece’s Apidima Cave from higher cliff sediment and then solidified roughly 150,000 years ago. Since one skull is older than the other, each must originally have been deposited in different sediment layers before ending up about 30 centimeters apart on the cave wall, the researchers say.
Earlier studies indicated that one Apidima skull, which retains the face and much of the braincase, was a Neandertal that lived at least 160,000 years ago. But fossilization and sediment pressures had distorted the skull’s shape. Based on four 3-D digital reconstructions of the specimen, Harvati’s team concluded that its heavy brow ridges, sloping face and other features resembled Neandertal skulls more than ancient and modern human skulls. An analysis of the decay rate of radioactive forms of uranium in skull bone fragments produced an age estimate of at least 170,000 years.

A second Apidima fossil, also dated using uranium analyses, consists of the back of a slightly distorted braincase. Its rounded shape in a digital reconstruction characterizes H. sapiens, not Neandertals, the researchers say. A bunlike bulge often protrudes from the back of Neandertals’ skulls.
But without any facial remains to confirm the species identity of the partial braincase, “it is still possible that both Apidima skulls are Neandertals,” says paleoanthropologist Israel Hershkovitz of Tel Aviv University. Hershkovitz led the team that discovered the Misliya jaw and assigned it to H. sapiens.

Harvati and her colleagues will try to extract DNA and species-distinguishing proteins (SN: 6/8/19, p. 6) from the Greek skulls to determine their evolutionary identities and to look for signs of interbreeding between humans and Neandertals.

The find does little to resolve competing explanations of how ancient humans made their way out of Africa. Harvati’s suggestion that humans trekked from Africa to Eurasia several times starting more than 200,000 years ago is plausible, says paleoanthropologist Eric Delson of City University of New York’s Lehman College in an accompanying commentary. And the idea that some H. sapiens newcomers gave way to Neandertals probably also applied to humans who reached Misliya Cave and nearby Middle Eastern sites as late as around 90,000 years ago, before Neandertals occupied the area by 60,000 years ago, Delson says.

Hershkovitz disagrees. Ancient humans and Neandertals lived side-by-side in the Middle East for 100,000 years or more and occasionally interbred, he contends. Misliya Cave sediment bearing stone tools dates to as early as 274,000 years ago, Hershkovitz says. Since only H. sapiens remains have been found in the Israeli cave, ancient humans probably made those stone artifacts and could have been forerunners of Greek H. sapiens.

Bacteria can slip into the brain by commandeering cells in the brain’s protective layers, a new study finds. The results hint at how a deadly infection called bacterial meningitis takes hold.

In mice infected with meningitis-causing bacteria, the microbes exploit previously unknown communication between pain-sensing nerve cells and immune cells to slip by the brain’s defenses, researchers report March 1 in Nature. The results also hint at a new way to possibly delay the invasion — using migraine medicines to interrupt those cell-to-cell conversations.
Bacterial meningitis is an infection of the protective layers, or meninges, of the brain that affects 2.5 million people globally per year. It can cause severe headaches and sometimes lasting neurological injury or death.

“Unexpectedly, pain fibers are actually hijacked by the bacteria as they’re trying to invade the brain,” says Isaac Chiu, an immunologist at Harvard Medical School in Boston. Normally, one might expect pain to be a warning system for us to shut down the bacteria in some way, he says. “We found the opposite…. This [pain] signal is being used by the bacteria for an advantage.”

It’s known that pain-sensing neurons and immune cells coexist in the meninges, particularly in the outermost layer called the dura mater (SN: 11/11/20). So to see what role the pain and immune cells play in bacterial meningitis, Chiu’s team infected mice with two of the bacteria known to cause the infection in humans: Streptococcus pneumoniae and S. agalactiae. The researchers then observed where that bacteria ended up in mice genetically tweaked to lack pain-sensing nerve cells and compared those resting spots to those in mice with the nerve cells intact.

Mice without pain-sensing neurons had fewer bacteria in the meninges and brain than those with the nerve cells, the team found. This contradicts the idea that pain in meningitis serves as a warning signal to the body’s immune system, mobilizing it for action.

Further tests showed that the bacteria triggered a chain of immune-suppressing events, starting with the microbes secreting toxins in the dura mater.

The toxins hitched onto the pain neurons, which in turn released a molecule called CGRP. This molecule is already known to bind to a receptor on immune cells, where it helps control the dura mater’s immune responses. Injecting infected mice with more CGRP lowered the number of dural immune cells and helped the infection along, the researchers found.

The team also looked more closely at the receptor that CGRP binds to. In infected mice bred without the receptor, fewer bacteria made it into the brain. But in ones with the receptor, immune cells that would otherwise engulf bacteria and recruit reinforcements were disabled.
The findings suggest that either preventing the release of CGRP or preventing it from binding to immune cells might help delay infection.

In humans, neuroscientists know that CGRP is a driver of headaches — it’s already a target of migraine medications (SN: 6/5/18). So the researchers gave five mice the migraine medication olcegepant, which blocks CGRP’s effects, and infected them with S. pneumoniae. After infection, the medicated mice had less bacteria in the meninges and brain, took longer to show symptoms, didn’t lose as much weight and survived longer than mice that were not given the medication.

The finding suggests olcegepant slowed the infection. Even though it only bought mice a few extra hours, that’s crucial in meningitis, which can develop just as quickly. Were olcegepant to work the same way in humans, it might give doctors more time to treat meningitis. But the effect is probably not as dramatic in people, cautions Michael Wilson, a neurologist at the University of California, San Francisco who wasn’t involved with the work.

Scientists still need to determine whether pain-sensing nerve cells and immune cells have the same rapport in human dura mater, and whether migraine drugs could help treat bacterial meningitis in people.

Neurologist Avindra Nath has doubts. Clinicians think the immune response and inflammation damage the brain during meningitis, says Nath, who heads the team investigating nervous system infections at the National Institute of Neurological Disorders and Stroke in Bethesda, Md. So treatment involves drugs that suppress the immune response, rather than enhance it as migraine medications might.

Chiu acknowledges this but notes there might be room for both approaches. If dural mater immune cells could head the infection off at the pass, it may keep some bacteria from penetrating the defenses, minimizing brain inflammation.

This study might not ultimately change how clinicians treat patients, Wilson says. But it still reveals something new about one of the first lines of defense for the brain.

The Milky Way is churning out far more stars than previously thought, according to a new estimate of its star formation rate.

Gamma rays from aluminum-26, a radioactive isotope that arises primarily from massive stars, reveal that the Milky Way converts four to eight solar masses of interstellar gas and dust into new stars each year, researchers report in work submitted to arXiv.org on January 24. That range is two to four times the conventional estimate and corresponds to an annual birthrate in our galaxy of about 10 to 20 stars, because most stars are less massive than the sun.
At this rate, every million years — a blink of the eye in astronomical terms — our galaxy spawns 10 million to 20 million new stars. That’s enough to fill roughly 10,000 star clusters like the beautiful Pleiades cluster in the constellation Taurus. In contrast, many galaxies, including most of the ones that orbit the Milky Way, make no new stars at all.

“The star formation rate is very important to understand for galaxy evolution,” says Thomas Siegert, an astrophysicist at the University of Würzburg in Germany. The more stars a galaxy makes, the faster it enriches itself with oxygen, iron and the other elements that stars create. Those elements then alter star-making gas clouds and can change the relative number of large and small stars that the gas clouds form.

Siegert and his colleagues studied the observed intensity and spatial distribution of emission from aluminum-26 in our galaxy. A massive star creates this isotope during both life and death. During its life, the star blows the aluminum into space via a strong wind. If the star explodes when it dies, the resulting supernova forges more. The isotope, with a half-life of 700,000 years, decays and gives off gamma rays.

Like X-rays, and unlike visible light, gamma rays penetrate the dust that cloaks the youngest stars. “We’re looking through the entire galaxy,” Siegert says. “We’re not X-raying it; here we’re gamma-raying it.”

The more stars our galaxy spawns, the more gamma rays emerge. The best match with the observations, the researchers find, is a star formation rate of four to eight solar masses a year. That is much higher than the standard estimate for the Milky Way of about two solar masses a year.

The revised rate is very realistic, says Pavel Kroupa, an astronomer at the University of Bonn in Germany who was not involved in the work. “I’m very impressed by the detailed modeling of how they account for the star formation process,” he says. “It’s a very beautiful work. I can see some ways of improving it, but this is really a major step in the absolutely correct direction.”

Siegert cautions that it is difficult to tell how far the gamma rays have traveled before reaching us. In particular, if some of the observed emission arises nearby — within just a few hundred light-years of us — then the galaxy has less aluminum-26 than the researchers have calculated, which means the star formation rate is on the lower side of the new estimate. Still, he says it’s unlikely to be as low as the standard two solar masses per year.
In any event, the Milky Way is the most vigorous star creator in a collection of more than 100 nearby galaxies called the Local Group. The largest Local Group galaxy, Andromeda, converts only a fraction of a solar mass of gas and dust into new stars a year. Among Local Group galaxies, the Milky Way ranks second in size, but its high star formation rate means that we definitely try a lot harder.

For the first time, researchers have harnessed the body’s own chemistry to “grow” electrodes inside the tissues of living fish, blurring the boundary between biology and machines.

The technique uses the body’s sugars to turn an injected gel into a flexible electrode without damaging tissues, experiments show. Zebrafish with these electrodes grown in their brains, hearts and tail fins showed no signs of ill effects, and ones tested in leeches successfully stimulated a nerve, researchers report in the Feb. 24 Science.
Someday, these electrodes could be useful for applications ranging from studying how biological systems work to improving human-machine interfaces. They also could be used in “bioelectronic medicine,” such as brain stimulation therapies for depression, Parkinson’s disease and other conditions (SN: 2/10/19).

Soft electronics aim to bridge the gap between soft, curvy biology and electronic hardware. But these electronics typically still must carry certain parts that can be prone to cracks and other issues, and inserting these devices inevitably causes damage to tissues.

“All the devices we have made, even though we have made them flexible, to make them more soft, when we introduce them, there will still be a scar. It’s like sticking a knife into the organ,” says Magnus Berggren, a materials scientist at Linköping University in Sweden. That scarring and inflammation can degrade electrode performance over time.

Previous efforts to grow soft electronics inside tissues have drawbacks. One approach uses electrical or chemical signals to power the transformation from chemical soup to conducting electrodes, but these zaps also cause damage. A 2020 study got around this problem by genetically modifying cells in worms to produce an engineered enzyme that does the job, but the new method achieves its results without genetic alterations.

Berggren and colleagues’ electrodes instead exploit a natural energy source already present in the body: sugars. The gel cocktail contains molecules called oxidases that react with the sugars — glucose or lactate — to produce hydrogen peroxide. That then activates another ingredient in the cocktail, an enzyme called hydrogen peroxidase, which is the catalyst needed to transform the gel into a conducting electrode.

“The approach leverages elegant chemistry to overcome many of the technical challenges,” says biomedical engineer Christopher Bettinger of Carnegie Mellon University in Pittsburgh, who was not involved in the study.

To test the technique, the researchers injected the cocktail into the brains, hearts and tail fins of transparent zebrafish. The gel turns blue when it becomes conductive, giving a visual readout of its success.
“The beautiful thing is you can see it: The zebrafishes’ tail changes color, and we know that blue indicates a conducting polymer,” says materials scientist Xenofon Strakosas, also of Linköping University. “The first time I saw it, I thought ‘Wow, it’s really working!’”

The fish appeared to suffer no ill effects, and the researchers saw no evidence of tissue damage. In partially dissected leeches, the team showed that delivering a current to a nerve via a soft electrode could induce muscle contractions. Ultimately, devices like this could be paired with various wireless technologies in development.

Long-term implant performance remains to be determined, however. “The demonstrations are impressive,” Bettinger says. “What remains to be seen is the stability of the electrode.” Over time, substances in the body could react with the electrode materials, degrading it or even producing toxic substances.

The team still needs to refine how precisely the electrodes can stimulate nerves, says chemical engineer Zhenan Bao of Stanford University, who was not involved in the work. She and colleagues developed the way to “grow” electrical components using genetic modifications. Ensuring stimulation is concentrated where it’s needed for a treatment, while preventing the leakage of current to unwanted regions will be important, she says.

In the new study, the relative abundance of different sugars in different tissues determines exactly where electrodes form. But in the future, a component of the main ingredient could be swapped out for elements that attach to specific bits of biology to make targeting much more precise, Berggren says. “We’re conducting experiments right now where we’re trying to bind these materials directly on individual cells.” Notes Strakosas: “There are some applications where precision is really important; that’s where we have to invest effort.”

The best shot we have at minimizing the future impacts of climate change is to limit global warming to 1.5 degrees Celsius. Since the Industrial Revolution began, humankind has already raised the average global temperature by about 1.1 degrees. If we continue to emit greenhouse gases at the current rate, the world will probably surpass the 1.5-degree threshold by the end of the decade.

That sobering fact makes clear that climate change isn’t just a problem to solve someday soon; it’s an emergency to respond to now. And yet, most people don’t act like we’re in the midst of the greatest crisis humans have ever faced — not politicians, not the media, not your neighbor, not myself, if I’m honest. That’s what I realized after finishing The Climate Book by Greta Thunberg.

The urgency to act now, to kick the addiction to fossil fuels, practically jumps off the page to punch you in the gut. So while not a pleasant read — it’s quite stressful — it’s a book I can’t recommend enough. The book’s aim is not to convince skeptics that climate change is real. We’re well past that. Instead, it’s a wake-up call for anyone concerned about the future.

A collection of bite-size essays, The Climate Book provides an encyclopedic overview of all aspects of the climate crisis, including the basic science, the history of denialism and inaction, and what to do next. Thunberg, who became the face of climate activism after starting the Fridays For Future protests as a teenager (SN: 12/16/19), assembles an all-star roster of experts to write the essays.

The first two sections of the book lay out how a small amount of warming can have major, far-reaching effects. For some readers, this will be familiar territory. But as each essay builds on the next, it becomes clear just how delicate Earth’s climate system is. What also becomes clear is the significance of 1.5 degrees (SN: 12/17/18). Beyond this point, scientists fear, various aspects of the natural world might reach tipping points that usher in irreversible changes, even if greenhouse gas emissions are later brought under control. Ice sheets could melt, raise sea levels and drown coastal areas. The Amazon rainforest could become a dry grassland.

The cumulative effect would be a complete transformation of the climate. Our health and the livelihood of other species and entire ecosystems would be in danger, the book shows. Not surprisingly, essay after essay ends with the same message: We must cut greenhouse gas emissions, now and quickly.

Repetition is found elsewhere in the book. Numerous essays offer overlapping scientific explanations, stats about emissions, historical notes and thoughts about the future. Rather than being tedious, the repetition reinforces the message that we know what the climate change threat is, we know how to tackle it and we’ve known for a long time.
Thunberg’s anger and frustration over the decades of inaction, false starts and broken pledges are palpable in her own essays that run throughout the book. The world has known about human-caused climate change for decades, yet about half of all human-related carbon dioxide emissions ever released have occurred since 1990. That’s the year the Intergovernmental Panel on Climate Change released its first report and just two years before world leaders met in Rio de Janeiro in 1992 to sign the first international treaty to curb emissions (SN: 6/23/90).

Perversely, the people who will bear the brunt of the extreme storms, heat waves, rising seas and other impacts of climate change are those who are least culpable. The richest 10 percent of the world’s population accounts for half of all carbon dioxide emissions while the top 1 percent emits more than twice as much as the bottom half. But because of a lack of resources, poorer populations are the least equipped to deal with the fallout. “Humankind has not created this crisis,” Thunberg writes, “it was created by those in power.”

That injustice must be confronted and accounted for as the world addresses climate change, perhaps even through reparations, Olúfẹ́mi O. Táíwò, a philosopher at Georgetown University, argues in one essay.

So what is the path forward? Thunberg and many of her coauthors are generally skeptical that new tech alone will be our savior. Carbon capture and storage, or CCS, for example, has been heralded as one way to curb emissions. But less than a third of the roughly 150 planned CCS projects that were supposed to be operational by 2020 are up and running.

Progress has been impeded by expenses and technology fails, science writer Ketan Joshi explains. An alternative might be “rewilding,” restoring damaged mangrove forests, seagrass meadows and other ecosystems that naturally suck CO2 out of the air (SN: 9/14/22), suggest environmental activists George Monbiot and Rebecca Wrigley.

Fixing the climate problem will not only require transforming our energy and transportation systems, which often get the most attention, but also our economies (endless growth is not sustainable), political systems and connection to nature and with each other, the book’s authors argue.

The last fifth of the book lays out how we could meet this daunting challenge. What’s needed is a critical mass of individuals who are willing to make lifestyle changes and be heard. This could trigger a social movement strong enough to force politicians to listen and create systemic and structural change. In other words, it’s time to start acting like we’re in a crisis. Thunberg doesn’t end the book by offering hope. Instead, she argues we each have to make our own hope.

“To me, hope is not something that is given to you, it is something you have to earn, to create,” she writes. “It cannot be gained passively, through standing by and waiting for someone else to do something. Hope is taking action.”

Psychedelics go beneath the cell surface to unleash their potentially therapeutic effects.

These drugs are showing promise in clinical trials as treatments for mental health disorders (SN: 12/3/21). Now, scientists might know why. These substances can get inside nerve cells in the cortex — the brain region important for consciousness — and tell the neurons to grow, researchers report in the Feb. 17 Science.

Several mental health conditions, including depression and post-traumatic stress disorder, are tied to chronic stress, which degrades neurons in the cortex over time. Scientists have long thought that repairing the cells could provide therapeutic benefits, like lowered anxiety and improved mood.
Psychedelics — including psilocin, which comes from magic mushrooms, and LSD — do that repairing by promoting the growth of nerve cell branches that receive information, called dendrites (SN: 11/17/20). The behavior might explain the drugs’ positive outcomes in research. But how they trigger cell growth was a mystery.

It was already known that, in cortical neurons, psychedelics activate a certain protein that receives signals and gives instructions to cells. This protein, called the 5-HT2A receptor, is also stimulated by serotonin, a chemical made by the body and implicated in mood. But a study in 2018 determined that serotonin doesn’t make these neurons grow. That finding “was really leaving us scratching our heads,” says chemical neuroscientist David Olson, director of the Institute for Psychedelics and Neurotherapeutics at the University of California, Davis.

To figure out why these two types of chemicals affect neurons differently, Olson and colleagues tweaked some substances to change how well they activated the receptor. But those better equipped to turn it on didn’t make neurons grow. Instead, the team noticed that “greasy” substances, like LSD, that easily pass through cells’ fatty outer layers resulted in neurons branching out.

Polar chemicals such as serotonin, which have unevenly distributed electrical charges and therefore can’t get into cells, didn’t induce growth. Further experiments showed that most cortical neurons’ 5-HT2A receptors are located inside the cell, not at the surface where scientists have mainly studied them.

But once serotonin gained access to the cortical neurons’ interior — via artificially added gateways in the cell surface — it too led to growth. It also induced antidepressant-like effects in mice. A day after receiving a surge in serotonin, animals whose brain cells contained unnatural entry points didn’t give up as quickly as normal mice when forced to swim. In this test, the longer the mice tread water, the more effective an antidepressant is predicted to be, showing that inside access to 5-HT2A receptors is key for possible therapeutic effects.

“It seems to overturn a lot about what we think should be true about how these drugs work,” says neuroscientist Alex Kwan of Cornell University, who was not involved in the study. “Everybody, including myself, thought that [psychedelics] act on receptors that are on the cell surface.”
That’s where most receptors that function like 5-HT2A are found, says biochemist Javier González-Maeso of the Virginia Commonwealth University in Richmond, who was also not involved in the work.

Because serotonin can’t reach 5-HT2A receptors inside typical cortical neurons, Olson proposes that the receptors might respond to a different chemical made by the body. “If it’s there, it must have some kind of role,” he says. DMT, for example, is a naturally occurring psychedelic made by plants and animals, including humans, and can reach a cell’s interior.

Kwan disagrees. “It’s interesting that psychedelics can act on them, but I don’t know if the brain necessarily needs to use them when performing its normal function.” Instead, he suggests that the internal receptors might be a reserve pool, ready to replace those that get degraded on the cell surface.

Either way, understanding the cellular mechanisms behind psychedelics’ potential therapeutic effects could help scientists develop safer and more effective treatments for mental health disorders.

“Ultimately, I hope this leads to better medicines,” Olson says.

Nearly 3 million years ago, hominids employed stone tool kits to butcher hippos and pound plants along what’s now the shores of Kenya’s Lake Victoria, researchers say.

Evidence of those food preparation activities pushes back hominids’ use of these tool kits, known as Oldowan implements, by roughly 300,000 years, say paleoanthropologist Thomas Plummer of Queen’s College, City University of New York and colleagues. That makes these finds possibly the oldest known stone tools.

Several dating techniques place discoveries at the Kenyan site, known as Nyayanga, at between around 2.6 million and 3 million years old. Based on where artifacts lay in dated sediment layers, these finds are probably close to about 2.9 million years old, the scientists report in the Feb. 10 Science.
Until now, the oldest Oldowan tools dated to roughly 2.6 million years ago at an Ethiopian site more than 1,200 kilometers north of Nyayanga (SN: 6/3/19). Excavations at another site in Kenya, called Lomekwi 3, have yielded large, irregularly shaped rocks dating to about 3.3 million years ago (SN: 5/20/15). But claims that these finds, which include some sharp edges, represent the oldest known stone tools are controversial.

Similarities of the Nyayanga artifacts to those found at sites dating to as late as around 1.7 million years ago “reinforce the long trajectory of Oldowan technology in the early stages of human evolution,” says archaeologist Manuel Domínguez-Rodrigo of Rice University in Houston and the University of Alcalá in Madrid. He did not participate in the new study.

Skeletal remains of at least three hippos unearthed near a total of 56 stone artifacts at Nyayanga display butchery marks, the investigators say. Wear patterns on another 30 stone tools from Nyayanga indicate that these items were used to cut, scrape and pound animal tissue and a variety of plants. And antelope fossils found at Nyayanga display damage from hominids removing meat with sharp stones and crushing bones with large stones to remove marrow.
These discoveries are among 330 Oldowan artifacts and 1,776 animal bones unearthed at Nyayanga from 2015 through 2017. Oldowan finds included three parts of an ancient tool kit — rounded hammerstones, angular or oval cores and sharp-edged flakes. Toolmakers struck a core held in one hand with a hammerstone held in the other hand, splitting off flakes that could be used to cut or scrape.

Whoever wielded stone tools at the Kenya site close to 3 million years ago “had access to a well-balanced diet for hunter-gatherers,” says coauthor Rick Potts, a paleoanthropologist at the Smithsonian Institution in Washington, D.C.
The evolutionary identity of ancient Nyayanga toolmakers remains a mystery. Plummer’s group unearthed two large, peg-shaped molars belonging to Paranthropus, a big-jawed, small-brained hominid line that inhabited eastern and southern parts of Africa until around 1 million years ago. The Nyayanga teeth are the oldest known Paranthropus fossils.

But there is no way to confirm that Paranthropus made and used the newly recovered stone tools. Individuals who died at Nyayanga and left behind their fossilized teeth were not necessarily part of groups that periodically butchered hippos there, Domínguez-Rodrigo says.

Members of the Homo genus appeared in East Africa as early as around 2.8 million years ago and could have made Oldowan tools at Nyayanga, says archaeologist Sileshi Semaw of the National Research Center for Human Evolution in Burgos, Spain (SN: 3/4/15). But Paranthropus can’t be discounted as a toolmaker. A large male Paranthropus skull discovered in 1959, dubbed Nutcracker Man, lay near Oldowan artifacts dated to 1.89 million years ago, says Semaw, who was not part of Plummer’s group (SN: 3/3/20).

Previous discoveries indicated that Oldowan toolmakers eventually occupied much of Africa, Asia and Europe, either via the spread of toolmaking groups or through independent inventions.

Discoveries at Nyayanga fit a current consensus that stone-tool making must have begun shortly after hominids evolved substantially smaller canine teeth around 5 million years ago, says archaeologist John Shea of Stony Brook University in New York, who was not involved in the new study. Stone tools did the work formerly performed by big canines, including slicing prey carcasses, mashing edible plants and helping individuals communicate anger or dominance over others, Shea suspects.

If that tool-crafting timeline is correct, then even Australopithecus afarensis, known for Lucy’s famous partial skeleton, might have made and used stone tools by around 3.4 million years ago (SN: 8/11/10).

Any way you slice it, Oldowan finds at Nyayanga now provide the earliest hard evidence of stone tools.

Modern birds evolved from dinosaurs, but it’s not clear how well birds’ ancient dino ancestors could fly (SN: 10/28/16). Now, a look at the fossilized feet of one nonavian dinosaur suggests that it may have hunted on the wing, like some hawks today.

The crow-sized Microraptor had toe pads very similar to those of modern raptors that can hunt in the air, researchers report December 20 in Nature Communications. That means the feathered, four-winged dinosaur probably used its feet to catch flying prey too, paleobiologist Michael Pittman of the Chinese University of Hong Kong and colleagues say (SN: 7/16/20).
Other researchers caution that toe pads alone aren’t enough to declare Microraptor an aerial hunter. But if the claim holds up, such a hunting style would reinforce a debated hypothesis that powered flight evolved multiple times among dinosaurs, a feat once attributed solely to birds.

Toe pads are bundles of scale-covered flesh on the undersides of dinosaur feet, similar to “toe beans” on dogs and cats. Because the pads are points where the living animal interacted with surfaces, toe pads give paleontologists a “sense of where the rubber meets the road,” says Alexander Dececchi, a paleontologist at Mount Marty University in Yankton, S.D., who was not involved in the new study.

These contact points can paint a clearer picture of an animal’s behavior by providing “details that the skeleton itself wouldn’t show,” says Thomas Holtz Jr., a dinosaur paleobiologist at the University of Maryland in College Park, who was also not involved in the study.

To investigate dinosaur toe pads, Pittman and colleagues turned to the Shandong Tianyu Museum of Nature in Linyi, China. It “has arguably the largest collection of feathered dinosaurs in the world, and, importantly, they haven’t been prepared extensively,” Pittman says. Many of these dinosaur skeletons are still surrounded by rock, which is where soft tissues can be preserved. Such a specimen “gives us the best chance of finding this wonderful soft tissue information,” he says.
Using special lasers that cause the otherwise nearly invisible soft tissue in the fossils to fluoresce, the team found 12 specimens with exceptionally well-preserved toe pads among the thousands examined (SN: 3/20/17).

The team compared the fossil toe pads with those of 36 types of modern birds, whose toe pads vary with their lifestyle. Predatory birds, for example, have protruding toe pads with spiky scales for grasping prey, while ground birds that spend their time walking and running have flatter toe pads. The analysis showed that Microraptor’s toe pads and other aspects of the feet, like the shape of the toe joints and claws, are most like those of modern hawks. That similarity suggests that the dinosaur could hunt prey midair and on the ground like hawks do, the team says.

Other dinosaurs, like the feathered Anchiornis, had flatter toe pads and straighter claws, suggesting a terrestrial lifestyle. That’s in line with ideas about this dinosaur being a poor flier, Pittman says.
The idea that Microraptor hunted like a hawk is consistent with other fossil evidence. One Microraptor fossil has been found with a bird in its stomach, and Microraptor‘s skeletal and soft tissue anatomy suggest some powered flight capability.

There’s still more work to do to figure out how well the dinosaur may have flown. “Microraptor is not a bird, but a close relative. Just because it has feet like a predatory bird doesn’t necessarily mean it must be catching prey in the exact same way,” Pittman says. But Microraptor’s hawklike lifestyle “is a strong possibility,” he adds.
Flight could have been useful to Microraptor when hunting, even if it couldn’t stack up to today’s fliers. Dececchi speculates that Microraptor’s anatomy probably prevented it from outflying birds, but may have helped it surprise otherwise out-of-reach prey, including flying and gliding animals.

“You only have to be fast or aerobatic enough to catch other things in your environment,” Holtz says. “So, it’s not improbable that [Microraptor was] catching things in the air on occasion.”

Other paleontologists are more skeptical that Microraptor hunted on the wing. “It would be a bit of a stretch to me to suggest that Microraptor was pursuing prey in an aerial context,” says Albert Chen, a paleobiologist at the University of Cambridge. The new findings inform only “what the foot was used for.”

Alternative hypotheses, such as a completely or partially terrestrial hunting style, could fit the data too, Holtz says, but the “feet are definitely playing a major role in their prey capture,” whether on the ground or in the air.

For now, the picture of Microraptor’s ecology remains fuzzy, but as lasers continue to increase the picture’s resolution, our understanding of dinosaur flight may reach new heights.

Tanklike armored dinosaurs probably pummeled each other — not just predators — with huge, bony knobs attached to the ends of their tails. Thanks to new fossil findings, researchers are getting a clearer understanding of how these rugged plant eaters may have used their wicked weaponry.

Many dinosaurs known as ankylosaurids sported a heavy, potentially microwave-sized tail club. This natural sledgehammer has long been considered by both scientists and artists as a defensive weapon against predators, says Victoria Arbour, a paleontologist at the Royal British Columbia Museum in Victoria, Canada.

Fossil evidence for tail clubs’ targets was largely lacking, until Arbour and her colleagues chipped more rock away from the same skeleton they used to describe a new armored dinosaur, Zuul crurivastator, in 2017 (SN: 6/12/17).

The dinosaur had five broken spikes on its sides. The team’s statistical analyses showed the damaged spikes clustered in specific regions of the body. If a large carnivorous dinosaur made these injuries, says Arbour, they’d likely be more randomly distributed and include bite and scratch marks.
Instead, the injuries are more consistent with clubbing, the researchers report December 7 in Biology Letters.

Armored dinosaurs’ tail clubs start out either absent or too tiny to mount a major defense, and they get proportionally larger with age. Similar growth patterns occur in some modern animal weaponry like antlers. It’s possible that tanklike dinosaurs sparred with each other for mates, food or territory much like male deer and giraffes do today.

And that tail could also be useful in a pinch. “Having a tail club you can swing around at the ankles of a two-legged predator is a pretty effective weapon,” says Arbour.

“Ankylosaurs are often portrayed as stupid, loner dinosaurs,” she adds. The findings “show that they probably had much more complex behaviors than we give them credit for.”