From & To Sathish #7 - Page 47

https://psyche.co/ideas/the-hidden-calculations-that-determine-whether-you-will-cry

The hidden calculations that determine whether you will cry

by Daniel Sznycer & Debra Lieberman, psychologists

We think of tears as an overflow of emotion, but an evolutionary lens shows they’re a rational form of social signalling

You may have found yourself tearing up at the movies or after hearing certain news. And you may have also found yourself discreetly wiping those tears away, lest you seem overly emotional. Cry me a river, as the jazz standard goes. But are emotional tears really a sign of being irrational?

Modern evolutionary biology suggests a new take on this question: emotional tears – similar to reasoning and other mental traits – have been relentlessly optimised by natural selection for survival and reproduction. Your tears are, in a sense, rational. As adaptations that confer advantages in certain contexts, they are ecologically rational and shot through with strategic calculation.

Working out how tears provide these benefits requires what evolutionary scientists refer to as an adaptationist analysis – a kind of cost-benefit calculation (along with Asmir Gračanin, we recently published a formal version of this analysis in the journal Evolution and Human Behavior). Evolution, like a business, operates on the basis of a strict bottom line. Developing, maintaining and running adaptations involves material and metabolic costs. If these biological machines generate benefits that exceed their costs, they persist as part of the species’ makeup. If not, selection eliminates them – just as cavefish evolved eye loss in their dark habitats.

Amphibians evolved tears about 360 million years ago to prevent eye desiccation when on land. Keeping eyes in working ophthalmic order (lubricating them and nourishing them via basal and reflex tears) seems beneficial enough. But what benefits might emotional tears produce that offset their costs?

Emotional tears seem to repurpose the ancient tears for valuable new signalling functions. They have several properties that make them good signals: they are produced non-permanently; they have a rapid onset and offset, thereby demarcating transient states or events; and they draw attention, because people tend to focus on others’ faces, particularly their eyes. As indicators of physical distress, tears may have been easier to detect than other internal or external cues. These background conditions may have led the human brain to evolve adaptations for individuals to produce tears to signal their distress, and for observers to infer others’ physical or emotional distress from their production of tears.

That emotional tears serve as non-verbal signals of distress is suggested by what elicits them: current, anticipated, recalled or imagined negative events – death, separation, rejection, injury and hunger. (Of course, tearing can also occur in response to positive events such as weddings, childbirth, celebrations, acts of kindness, achievements and artistic performances – we’ll return to this phenomenon shortly.)

Another indication that emotional tears serve communicative functions is that they occur more often in the presence of others. For instance, as parents know, people often delay crying until a supportive person is nearby. Additionally, those with romantic partners cry more than singles. Lonely individuals – despite reporting lower wellbeing – cry less than those who feel socially connected. These facts suggest that emotional tears are non-verbal requests for help rather than mere reflections of distress. Causing others to stop mistreating you, or to give you food, assistance or support in a conflict with third parties may be some of the ways in which emotional tears pay for themselves.

Droplets running down your child’s cheeks are meaningful but droplets running down your car’s windshield are a non-event

To persist across generations, signals must also pass muster with their recipients. If receivers hadn’t come to see emotional tears as credible indicators of what the signaller was trying to communicate (eg, suffering), tears would have failed to generate net benefits and would have likely been selected out. Emotional tears may have remained mostly credible because faking them is difficult (though well-trained actors and people with manipulative tendencies can do it). Moreover, while crying may get you help, chronic crying makes others see you as weak and ineffectual – a less desirable social partner, especially in adulthood. English speakers aren’t kind to cry-babies, drama queens, wimps, snowflakes, waterworks, softies, wets and namby-pambies. So there’s an in-built incentive not to overdo it. Also, tears blur vision, making it harder to fight or flee during conflict – this may act as a built-in cost, or ‘handicap’ in biological terms. All these factors would have helped to keep emotional tears credible.

The messages that tears communicate are fundamentally about value – more specifically, the tearer’s evaluations of internal or external events affecting them. Consider again what people tear up about. You might cry if your spouse abandons you (but not if they leave home to run an errand), or if a blackout ruins $800 worth of frozen food (but not $2 worth), or if you fracture your femur (but not if you scratch your thigh). The negative evaluations that trigger crying surpass a certain threshold. The same goes for positive evaluations. You might cry if your child reaches a culturally meaningful developmental milestone (but not for a minor one like learning a new word).

Much of this might seem obvious, but only because humans have complex evaluative and communicative machinery – and because we assume that this is true about humans in general. Because of this, you view droplets running down your child’s cheeks as meaningful but droplets running down your car’s windshield as a non-event.

Tears convey the tearer’s internal evaluations not for their own sake, but as means to an end – to tweak the mental states and behaviour of others in ways that favour the tearer. For example, tearing up may cause your boyfriend to stop doing something that bothers you. And when and to whom we cry involves its own set of delicate calculations.

Many conditions must be in place for the tearer to actually receive help

To be clear, these calculations are not carried out consciously or deliberately, like solving a calculus problem. But the brain performs them automatically all the same – much like how the visual system uses binocular disparity to compute the depth of objects from two-dimensional retinal projections, without any effort or volition on the part of the observer.

One especially interesting case is when the intended target of the tear signal is also the source of the tearer’s suffering. The sufferer may not be able to compel the target to stop if they are weaker or less capable. But all is not lost for a sufferer with lower leverage because they can coax the target with a tearful, indirect threat that tacitly communicates: ‘Impose fewer costs on me (or provide more benefits) or, because your fate is tied to mine, you’ll suffer indirectly through my continued suffering.’This is a peculiar bid, and many conditions must be in place for the tearer to actually receive help. The target of one’s tears must interpret the tears as sincere, see the tearer as truly lacking the means to solve their problem, be capable of helping and, most importantly, value the tearer’s welfare. In addition, the target of one’s tears must think that helping will somehow benefit them more than not helping.

There is now a substantial research literature on tearing and crying, and the findings show that people cry precisely in these situations. For example, research shows that people are more likely to tear up when they feel they’re bearing heavier costs. Among nurses in Thailand, for instance, crying occurs more often when they are feeling overwhelmed by their caring responsibilities. Correspondingly, observers infer greater suffering from the presence of tears. In courtroom settings, for example, people are more likely to believe that tearful children – compared with non-tearful children – were sexually assaulted. Other research demonstrates the effect of interpersonal value. For instance, people tend to offer more support to tearful friends than to tearful strangers. Tearful individuals implicitly recognise this and tend not to cry as much in front of unresponsive audiences. For example, children are more likely to express sadness, including through tears, when they are near their parents than when they are with peers, regardless of how much time they spend with each group.

And what about tears of joy? These make up a nontrivial minority of tear episodes. These tears may function less to prompt immediate action and more to prompt observers to register what the tearer positively values. Thus, tears can express not only distress but also gratitude, pride and emotional connection. Tears of joy may also serve as signals that yield benefits for the tearer himself. By marking an experience as deeply meaningful, such tears can guide observers toward a more accurate understanding of the tearer’s values and priorities. In turn, this can elicit responsive behaviours – such as personalised gifts, increased support or affirmations of closeness – that benefit the tearer and strengthen social bonds.

Perceivers can often distinguish between positive and negative tears based on the context. For example, if you see a friend tearing up during an artistic performance or while gazing at the Grand Canyon, chances are those tears reflect positive evaluations.

We can use an adaptationist approach to answer further questions about tears. For example, why do some people cry more readily than others? Adaptationist thinking suggests that those with relatively lower aggressive formidability and wherewithal will tend to cry more. Indeed, women across cultures are much more likely to cry than men, and children cry more than adults.

It could be that suppressed tears paradoxically elicit more support than unbidden crying

What about the vocalisations people make when tearing up? Upon observing tears, observers seem to probe the situation to assess how much cost the tearer is bearing, how much cost it would take them to help, etc. But tearers conduct their own audits as well. For example, the tearer wants to know whether the intended target detected their tears and recognised them as signals of suffering. If not, the appeal for help may need to be adjusted or intensified. Sobs, whimpers, sniffles and other vocalisations may function to intensify the signalling.

If tearing and crying have the social functions that we’re proposing, you might be wondering why people sometimes cry when alone? In fact, many adaptations that are believed to serve social functions, such as language, and emotions like anger and shame, can likewise be activated when the individual is alone. Simulation, planning and recalibration are possible reasons why these adaptations, including emotional tears, sometimes activate in solo mode. For example, a vivid simulation of a catastrophic event may elicit sadness and tears.

The social function of crying also raises the question of why we sometimes try to suppress our tears. Our answer to this is that humans are complex, and while tears can elicit help, they can also lead others to view the tearer as weak and ineffectual. Also, tearing can elicit help from observers, but those observers may try to rule out exploitative appeals before helping. And as our colleague David Pinsof noted, suppressing tears may help the tearer conceal any intentions he may have to exploit the goodwill of others. While we are not aware of data on this point, it could be that suppressed tears paradoxically elicit more support than unbidden crying.

So, next time you tear up at a movie or see someone crying over bad news, take a moment to appreciate the cognitive complexity behind those tears. They reflect the outcome of evolutionarily ancient evaluative and emotional systems that guide our behaviour adaptively. On a purely physical level, they are water-based mixtures containing electrolytes, mucins, oils and enzymes. But, at the same time, they are so much more – part of a sophisticated signalling process that is vital to the success of our social relationships.

https://psyche.co/ideas/fears-about-being-a-dangerous-or-immoral-person-can-fuel-ocd?utm_source=Psyche+Magazine&utm_campaign=523fba4606-EMAIL_CAMPAIGN_2025_06_27&utm_medium=email&utm_term=0_-8e23a7006c-838120577

Fears about being a dangerous or immoral person can fuel OCD

by Richard Moulding and Kelvin (Shiu Fung) Wong, clinical psychologists

Intrusive thoughts about doing bad things are common, but for people with OCD they provoke deep fears about the self

For anyone who is unfamiliar with obsessive compulsive disorder (OCD) – or who knows about it only through TV or movies – it might seem like a collection of quirks, random tics or an undue focus on organisation. In reality, people with OCD can feel like prisoners of their own minds. They are tormented by thoughts, images and urges that can seem irrational even to them, but that demand a response. For example, someone concerned about germs in their food might avoid eating all but specific foods, use elaborate rituals to eat them, and wash their hands until their skin is red and raw. Another person might experience chronic doubts about safety – What if I left the house unlocked? – prompting them to check and repeatedly lock, lock and lock doors again.

Also common, but even less well known about, is the version of OCD where people experience thoughts and images that are incredibly abhorrent to them. Often, they are related to themes such as sex, violence and religion. These unwanted intrusions continue despite a person’s attempts to push them away or replace them with another thought. For example, a new parent might experience recurrent and distressing thoughts about violently harming their infant child. This may lead to compulsive responses such as seeking reassurance that they could never do such a thing, or even avoiding being alone with the child.

It’s not that thoughts like these are unique to people with OCD. There is actually evidence that almost everyone experiences OCD-like intrusive thoughts sometimes, but they tend to not talk about them. For example, one study found that around half of participants reported occasional, unwanted thoughts of swerving into traffic or thoughts about authority figures being naked. In one of our studies, conducted in samples of university students across 13 different countries, more than 90 per cent of individuals reported occasional OCD-like thoughts. Psychological approaches to treating OCD suggest that what distinguishes someone who has the disorder is not the mere existence of such unwanted thoughts, but rather that they respond more negatively to such thoughts. While everyone has unwanted thoughts, most people will find such thoughts a little unpleasant and be able to shake them off. Someone with OCD, though, will feel a responsibility and a need to act on the thought, as if to ward off danger.

The themes of these intrusive thoughts are not haphazard; they often relate to concerns about personal culpability or morality. In fact, people with OCD tend to be gentle and scrupulous, often having what’s been called a ‘tender conscience’. A person’s specific symptoms are commonly linked to themes that are particularly triggering for them, personally. As a therapy client once summarised it, OCD ‘hits you where it hurts’. For someone who cares deeply about being a good parent, that might mean intrusive thoughts about harming his child. Someone who is highly religious might get stuck on thoughts and images that feel blasphemous. And for a person who is worried about being a faithful partner, unwanted sexual thoughts could be the most prominent ones.

Observations like these have led us and other researchers to explore the role of concerns about one’s self in OCD. We’ve drawn upon a rich tapestry of research in social psychology focused on depression and on anxiety more broadly. This work suggests that when someone’s view of themselves is different from who they ideally want to be (their desires and wishes for themselves) it can lead to dissatisfaction and depression. In contrast, when someone’s view of themselves falls short of who they think they ought to be (their obligations and responsibilities) it can lead to anxiety. In OCD, however, we find that the focus is not necessarily on the possible selves that people want to or ought to be, but rather on who they should not be – the feared self.

The thoughts, images and urges that torment someone with OCD are not based in reality. But for the person who has them, the sense that they could even possibly be true or say something meaningful about one’s true self leads to intense distress. Their responses can be seen as an attempt to escape the feared self. To build on the example introduced earlier, a tender-hearted father who fears the possibility that he is (or could become) a violent person might have a sudden, unwanted thought about harming his child – which reinforces his fear. He might compulsively respond by attempting to replace the thought with a different one, by leaving the room where his child is, or by scrutinising the thought and trying to make himself feel certain that he isn’t really violent. He’ll also be on guard for future thoughts. Paradoxically, though, all this vigilance can actually increase the frequency of troubling thoughts, the distress they cause, and the attempts to neutralise them.

Around 80 per cent of participants reported having OCD-like intrusive thoughts

An early study on this subject asked people with OCD, people with other forms of anxiety, and additional participants about their possible selves. The individuals with OCD stood out due to their identification with a ‘dangerous self’ theme – concerning the possibility of being out-of-control, or of causing harm to others directly or indirectly (by failing to prevent it). This reflected a suspicion that they were potentially bad, evil, dangerous, immoral or insane, despite the lack of evidence that this was true. Multiple studies now provide evidence for the importance of a feared self in OCD. Even among those not diagnosed with the condition, the fear of one’s possible self is associated with OCD symptoms.

Nevertheless, one can ask if having a feared self actually drives the symptoms of OCD, or if it is simply a consequence of the distressing thoughts. Some of our recent work has been aimed at addressing this question. In one study, we gave people a series of smartphone prompts for two weeks, asking about their experiences of intrusive thoughts. Though the study did not focus only on people with OCD, around 80 per cent of participants reported having OCD-like intrusive thoughts, including intrusions relating to doubt, contamination, harm or sexual, immoral or religious themes.

We found that people who more strongly endorsed feared-self beliefs (eg, ‘I’m afraid of the kind of person I might become if I’m not very careful’) reported a greater number of OCD-like thoughts – as well as greater distress about the thoughts, urges to respond to the thoughts, and need to control the thoughts. When we gave study participants daily prompts that either reminded them about their feared self or instead asked them about sports, those reminded of their feared self subsequently reported a greater urge to respond to their intrusive thoughts. This and other studies are providing evidence that a feared self worsens the experience of intrusive thoughts, rather than just reflecting them.

Researchers are also exploring how the feared self relates to other beliefs in OCD, in order to better understand how this complex disorder works; how the feared self relates to different presentations of OCD; and even how it relates to other disorders, such as eating disorders and body dysmorphic disorder. An individual with these disorders might restrict their food intake or repetitively check their mirror for physical flaws in part because they are trying to avoid a feared self that they imagine as malformed.

Encouragingly, reductions in one’s fear of self are associated with improvements in OCD symptoms, in particular those related to ‘repugnant’ themes (eg, blasphemous, aggressive, or sexual intrusive thoughts). This suggests that directly targeting the feared self in treatment may bring relief for someone with OCD or OCD-like symptoms. While more research is required to understand how best to do this, some existing approaches show promise.

In our clinical work, we have found that thinking about the concept of a feared self with a therapist may help someone to understand why certain obsessive thoughts stick with them – and to challenge the idea that such obsessions mean they are actually a bad, corrupted or dangerous person. It can help them recontextualise obsessive thoughts as untrue narratives that arise around a feared self. It can also help reduce the motivation to perform compulsive responses to the thoughts, as it becomes easier to see that compulsions are not removing any real-life danger, but are rather attempts to distance the individual from their feared self. With a therapist’s support, individuals can then learn to better tolerate uncertainty about the self, challenge black-and-white moral beliefs, and work to be more compassionate towards themselves.

Another way to target the feared self might be to cast doubt on its very possibility, helping someone examine the evidence for and against its existence, but without engaging in compulsions – a common technique in cognitive behavioural therapy (CBT) called cognitive restructuring. Inference-based CBT, which was developed to treat people with OCD, also has ways of lowering the credibility of a feared self, helping the individual understand how they constructed this narrative around their self-concept through reasoning and the imagination. Ultimately, the aim is a realisation that the feared self is just one of many stories that we can tell about ourselves.

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A visit to dog college

From disaster response to disease detection, these canines choose their own career paths.

By Lauren Leffer

The wind is blowing hard, changing direction every few seconds, and whipping hair into my eyes. Despite the cold breeze, Andy is hot on a smell trail. The black lab, at just over a year old and months into his education, deftly navigates the expanse of concrete chunks, bricks, metal grates, and wooden pallets. With sure paws and a keen nose, he finds the person hiding amid the rubble pile in a matter of seconds, barking continually until rewarded with his squishy basketball toy and eager words of praise from his trainers.

Each of the four dogs tested on the rubble field homed in on the mock-victim, but Andy did it the fastest–clear evidence that he’s close to graduating and nearly ready to enter the workforce. Staff at the Penn Vet Working Dog Center (PVWDC) agree, which is why Ken, a member of Canada Task Force 2, has recently arrived to spend two weeks getting to know Andy. If all goes well, he and the dog will leave Philadelphia for Alberta together as a united search and rescue team.

It’s just one of the careers the Working Dog Center prepares its canine students for. In the more than 12 years since the center’s founding, nearly 200 furry graduates of varying breeds have gone on to work in fields like disaster response, cadaver search, explosive and drug detection, invasive species monitoring, and even disease detection research. Almost every dog who enters PVWDC exits into a stable nose-related job, because–unlike more specified training programs for seeing eye or police dogs–the humans at PVWDC try their best to follow the dog’s lead. If a dog proves to be a square peg, then there’s almost certainly a hole to match.

“The most important thing is they’re doing what they love,” says Ruth Desiderio, the center’s volunteer and outreach coordinator leading the public tour I’ve joined in on. The dogs, she explains, indicate their interests and aptitude through apparent eagerness and ambivalence, and are allowed to proceed accordingly. If a dog relishes the challenge of sniffing out a hidden human, but reacts with fear to loud, sudden banging sounds–perhaps they’re destined for wilderness over urban search and rescue. If they love to smell and be rewarded, but crave routine, then a long-term post in the lab could be the perfect fit.

Dogs are generally donated to the facility from breeders of working dogs, and begin their training at just eight weeks old. They come from well-established lineages of successful sniffers. Most are Laboradors, Malinois, and shepherds of varying origin– though an Italian truffle dog and a German Shorthaired Pointer were also present on the day I visited. Even with pedigree on their side, PVWDC’s boasts an impressive graduation rate above 90 percent. The few dogs who don’t make it generally drop out for medical, not behavioral reasons, the scientists and staff say.

Each puppy who bounds through the doors is given the chance to shine. “We assume that all dogs will be superstars,” says Cindy Otto, the center’s executive director and a professor of Veterinary Medicine at the University of Pennsylvania. High-intensity urban search and rescue is the job all dogs start out training for, but when a pup isn’t clearly excited about a challenge, they pivot to alternate opportunities, Otto explains. Through this collaborative, canine-centric approach, the PVWDC has advanced our understanding of what dogs are capable of, how to best ensure their health and safety on the job, and the science of smell detection.

The seeds of the center were planted in the immediate aftermath of September 11, 2001, when Otto spent 10 days at Ground Zero helping to care for the search and rescue (and later cadaver) dogs on site. The event prompted her to consider new questions about the animals’ well being, as well as how working dogs could be trained and cared for to maximize their abilities. In an initial, long-term research project, she and colleagues kept tabs on 95 dogs that deployed to Ground Zero and compared them with 55 that didn’t over 15 years. Amid that study, in 2012, the PVWDC was opened. Ultimately, the researchers found that the dogs that had helped to sniff out 9/11 survivors and the deceased did not suffer significant long term health consequences or increased disease risk (unlike the human first responders). Yet that one line of inquiry has led to many others.

Now, five days a week, about two dozen rotating dogs are dropped off at PVWDC by their foster families (who in some cases are also center staff), as if it’s a day school. The small, one-story building houses a handful of foam-floored rooms full of toys, ramps, barrels and other training tools, along with a research area where computerized smell boxes and cameras can be set up to carefully record dogs through various smell trials.

Outside, among the parking lots and industrial sprawl of Forgotten Bottom, Philadelphia there is the agility course–with ladders, balance beams, platforms, and see-saws–and the rubble field outfitted with about 50 different human hiding spots. Each animal’s routine is customized, but generally includes some combination of physical fitness (planks, squats, side steps, and pivots are all part of the routine); training tasks like agility trials or search and rescue challenges; smell practice; and plenty of playtime, rest, and walks. A subset of the dogs who are there as working research animals also spend a portion of their days participating in detection experiments, trying to find the hidden scent sample or responding to new odor concentrations or scent stimuli.

Training or testing sessions are brief, sometimes no more than a few minutes long, but productive nonetheless. Just like muscles take regular work to maintain, so too do noses. “Sniffing is a diaphragmatic workout,” says Emma Gaalaas Mullaney, the center’s search and rescue director. It’s also a mental challenge and can be a frustrating, emotionally taxing task. “You have to condition them for sniffing duration,” she adds.

While training dogs for service careers, the scientists at the center also study the animals and the process of educating them. Recently, the researchers have characterized what behavioral traits make for the most successful search and rescue dogs, devised and tested protocols to reduce dangerous overheating for canines laboring on in hot conditions, fine-tuned fitness training and assessment to help dogs avoid and recover from injuries, and discovered that dogs can detect infections associated with prosthetics.

Smell is fundamentally the ability to recognize and identify things based on their chemical makeup and it’s dogs’ primary sense for navigating the world, says Amritha Mallikarjun, a cognitive scientist and post-doctoral researcher at PVWDC. Dogs assess and understand their surroundings via the ambient molecules that are constantly mixing and floating through the air. Their keen ability to pick up on teeny odor traces coupled with how well dogs and humans are able to communicate can be harnessed as an invaluable tool for the detection of all sorts of things, including disease and environmental contaminants, Mallikarjun says.

Our four-legged friends are so adept at smelling that, in many instances, they’re more sensitive detectors than existing machines and technologies. Dogs “smell in color,” explains Otto. “It’s like Where’s Waldo, where we are visual, they use their nose to pick out that one tiny little thing that’s different,” she adds. Canine noses can be well-tuned enough that researchers occasionally have to re-revisit and revise their initial study designs, notes Clara Wilson, a canine olfaction and behavior scientist and postdoc at PVWDC. In one 2010 medical study , a detection dog correctly identified an early case of prostate cancer from a sample that had initially been classified as a healthy control via biopsy. The patient was rebiopsied after the dog’s insistence it was cancer positive, and cancer was found.

Smelling ability can be quantified via odor detection threshold, or the relative amount of target molecules in an air sample necessary for a scent to be noticeable. Different odors are detectable at different levels, but dogs are unambiguously champion sniffers. In training and acclimating the dogs to lab experiments, the staff at PVWDC rely on a musty-smelling synthetic odorant called “Universal Detection Compound.” The average human nose can detect UDC on the order of parts per 10,000, says Wilson. A dog, on the other hand, can sniff out UDC when it’s present in concentrations as low as just a few molecules per million.

Critically, dogs can still detect target scents at this low threshold when they’re presented with many other smells in a messy odor stew, Wilson notes. This means that, even when many people are around or the wind is carrying faraway scents on the breeze, a well-trained search and rescue dog can track down the hidden human scent of a person beneath rubble. It also means that, amid all other compounds present in a person’s body odor or blood sample, a detection dog can parse whether or not they smell like cancer or infection.

During my visit, I watch as the scientists run Mallikarjun’s foster and research dog, Dalton, through a slate of scent-box trials. Black plastic cubes about the size of a large toaster oven, outfitted with a precise smell release system, emit small puffs of odor from a circular hole in a randomized order. Dalton is trained to stand and freeze at a particular box, with his nose in the hole, when he detects the target odor (in this case UDC and not a disease sample). Infrared detection beams at the top of the box measure how long Dalton’s snout has stayed put at any given box, and the contraptions beep after a pre-programmed number of seconds have passed, confirming the dog’s choice. Once the beep releases Dalton, he bounds over to a trainer for a reward (a bit of cheese, some enthusiastic pets, or a toy). To avoid interfering with the test, the humans stand behind a partition wall and observe from a computer screen.

The goal of this particular exercise is basic: the researchers are simply trying to re-acclimate Dalton to this type of detection, after a few weeks performing other scent tasks. But still, the outcome is impressive. Round after round, Dalton quickly identifies the correct box, which would smell like nothing to the average person–often walking directly to it from across the room, without so much as glancing at the others. Even in a test where none of the boxes emit a smell, the 5-year old labrador knows exactly what to do. He briefly surveys each option and then returns to the threshold of the testing zone, looking expectantly at the trainer.

Communication and training aren’t a one-way street, points out Gaalaas Mullaney, who frequently goes on search and rescue deployments with her own dog, Toby, as part of a volunteer task force. Dogs, she says, are continually providing feedback and shaping how their humans respond. “We have a very nuanced conversion with the dog once we are trained to understand what they are telling us,” she explains. Often, in scent detection, people are posing questions to dogs that they don’t know the answer to. In order to decode what responses mean, there has to be a relationship. Other animals, like pigs, elephants, and bears may be just as good, or even better at smelling, than dogs–but few animals are able to translate that incredible sense into human terms.

During a nasal tumor detection study, Mallikarjun recalls a trial where she and her co-researchers suddenly switched from offering dogs blood plasma samples to smell to presenting mucus samples. “We wanted to see what their reaction to this novel sample type would be,” she explains. Presumably, some aspect of the scent marker would still be present in the disease positive samples, but the dogs might not recognize it against the novel background. In response, one of the dogs improvised: she stood hovering her open mouth over the positive sample, while looking back at her trainer. It wasn’t the sit alert she’d been trained to do in response to blood plasma positives, but it clearly indicated she understood there was something worth paying attention to in the particular mucus sample, while also communicating uncertainty and seeking direction. “That’s a full conversation,” Mallikarjun says.

Detection dogs are expensive to train and maintain. At PVWDC, Desiderio notes that caring for and educating each dog costs upwards of $50,000. (Though affiliated with the University of Pennsylvania, the center receives no direct funding from the school. Instead, they sustain their efforts with donations and grants.) The idea is not that every medical test could or should be replaced by a dog’s nose. Instead, by assessing what dogs are able to pick up on, researchers hope to isolate the chemical components that make up a disease’s signature scent and develop better diagnostic tools.

In a 2022 study, Mallikarjun, Otto, and their co-authors trained dogs to pick out blood samples from people positive for ovarian cancer. Then, they ran multiple tests to see which components of the blood samples the dogs were responding to. They discovered that ovarian cancer is detectable through many volatile organic compounds, and that the most important biomarkers are the lightest and quickest to evaporate. Knowing this could inform how blood samples from patients are collected, stored, and tested. With further research, the scientists could help build better, more specific and accurate screening tests.

Scent science isn’t just useful for human diseases. PVWDC researchers have also shown that dogs can be used to detect a lethal and difficult to diagnose a form of canine cancer. In another ongoing project, Mallikarjun and colleagues have discovered dogs can suss out a pernicious environmental pathogen both in the lab and the field.

Chronic wasting disease is a deadly and untreatable prion infection that affects wild deer, elk, and moose and has been spreading across the United States for decades. The visible symptoms of the illness among a deer population can take a long time to manifest, but by smelling poop pellets (or even just cotton balls stored for a period of time near poop pellets), dogs can readily recognize the presence of the disease with more than 80% accuracy, according to a 2023 study. If, in follow-up work, dogs do prove able to quickly survey an area for chronic wasting disease earlier than other detection methods, it could help wildlife managers establish quarantines and management protocols sooner–potentially slowing the spread. Conservation dogs have previously been used in similar applications to find hidden pockets of invasive species, track down endangered plants or animals, and identify fungal pathogens.

“I think everything has a scent,” says Otto. And she means everything. Some of Wilson’s previous research found that dogs can smell stress and negative human emotional states. The main question in all detection dog research is not if the smell exists, it’s if any given scent is something we can isolate and then train animals to recognize, Otto adds. As scientists at PVWDC and elsewhere continue to probe that question, the answer has repeatedly and routinely been yes. Asking has uncovered new odor markers of disease, new ways to boost search and rescue scent detection and save lives, and new ways to assess environmental health. So far, the only thing she and her collaborators–human and canine alike–haven’t yet found are the limits of what’s possible.

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What your fingernails can reveal about your health

Jasmin Fox-Skelly

Fingernails help protect the underlying skin from injury, and they also come in handy when you want to scratch an itch or peel a satsuma. But what do they reveal about your health?

There's no shortage of folk wisdom about how to glean the state of your overall health from your nails, such as the pervasive idea that the white flecks that sometimes turn up – known as leukonychia – are a sign of calcium deficiency. But is there any truth to these ideas?

First up some basic anatomy. Nails are an extension of the skin. They are made from keratin, a super tough protein that shields the toes and tops of your fingers from trauma. The half-moon shape seen at the base of the nail is the lunula, which serves as the "growth centre" for the nail, producing the cells that will eventually harden into the nail plate . It sits above the cuticle, a layer of dead cells joining the base of the nailbed to the skin. The cuticle offers extra protection by acting as the nail's security guard, stopping bacteria, fungi and other pathogens in their tracks.

While the eyes might be the windows to the soul, to a doctor the nails can be the windows to your health. Physicians can use them to diagnose all sorts of conditions, from dermatological problems to kidney disease or even autoimmune disorders.

A sign of something serious

"One of the first things I learned in medical school was to look for something called clubbing, where there is this loss of the angle between the nail and the nail bed itself," says Dan Baumgardt, a general practitioner in medicine and lecturer in neuroscience and physiology at the University of Bristol.

With clubbing, the nail beds soften, and the nails almost seem to "float" instead of being firmly attached to the finger. The fingertips also appear large or bulging. "It causes an unusual sort of swollen finger appearance where the finger looks a little bit like a drumstick," says Baumgardt.

Clubbing is a sign of extremely low blood oxygen levels. It is most commonly associated with lung cancer, but it can also indicate an infection of the lining of the heart chambers and heart valves, among other things. Other conditions where it is observed include celiac disease, cirrhosis of the liver and lung infections amongst others.

"If you do see a patient with clubbing the rule of thumb is to get them an x-ray as an urgency, because it could be an underlying lung cancer that could be explaining it," says Baumgardt. "Having said that even though it's one of the first things that we learned in medical school. I really don't know why, because in all the 14 years I've been a doctor, I've only ever seen it once," he says.

White flecks on the nail – known as leukonychia – are often touted to be a sign of vitamin or mineral deficiencies. However, the evidence to support this is mixed. In one small study of undergraduates, there was no correlation between this symptom and a person's intake of either zinc or calcium. However, in one case report of a patient with Crohn's disease who developed severe leukonychia on his fingernails while deficient in selenium, it disappeared after treatment with this mineral.

In general, leukonychia are more likely to be a result of nail trauma. Stubbing your toe, trapping your fingernail in a door, too many manicures, or dropping a heavy object on your foot may cause such a mark.

Nevertheless, white discolouration on the nail could suggest an underlying health issue. For instance, white marks can be a sign of heavy metal poisoning with lead or arsenic. White discolouration of the nail could be a sign of psoriasis, a chronic skin condition that causes raised, inflamed, scaly patches of skin. If the entire nail turns white, this could suggest a deficiency of protein in the bloodstream, which can indicate kidney disease, liver disease or diabetes.

"If people have low protein levels in their bloodstream it [often] causes the whole nail to go white," says Baumgardt. "We tend to associate that with people who've got liver disease, so things like cirrhosis of the liver, perhaps as a result of alcoholism."

Blue nails, on the other hand, are a sign that the body might be lacking oxygen. It could be a sign of serious heart disease or emphysema and is something you should get checked out by a doctor as soon as possible. This is also the case if you see dark lines underneath the nail, as although this can be caused by trauma, it could also be a sign of subungual melanoma, a rare but serious type of skin cancer.

Bleeding beneath the nail – if it doesn't heal – could also indicate something more serious. "You can get what we call splinter haemorrhages, which look like little red streaks of blood, similar to if you imagine a splinter stuck under your nail," says Baumgardt. "That haemorrhage can sometimes be suggestive of vasculitis, which is an inflammation of the blood vessels. One of the main underlying causes can be an infection of the heart valve, which causes these odd little red swellings," he says.

A touch of fungus

Other, more common conditions can also be diagnosed by looking at the nails. When examining a patient, doctors typically look for alterations in colour, thickness and shape.

For example, in a healthy nail the underlying nail bed should be pink except for the white tips. Other colours could indicate an infection of the nail itself, or an underlying health condition.

Nails are extensions of the skin, effectively, and your skin can tell you so much about what's going on in your body – Dan Baumgardt

"If you see either white or yellow discolouration on your toes, especially on your toenails, that is a sign of a fungal infection," says Holly Wilkinson, a lecturer in wound healing at the University of Hull.

Although in many countries, such as the US and the UK, you can buy over-the-counter topical medication for mild fungal nail infections, if you leave it too late then it can become more difficult to treat. (It's important to always consult a doctor if you suspect that you have a nail infection.)

"I think a lot of the time when people have discolouration in the nails they don't realise that it's an infection, so it can get to a point where it becomes quite bad, and then they have to go and see a podiatrist," says Wilkinson.

Fragile nails

Meanwhile the shape of the nail can also reveal underlying problems. Healthy toe and fingernails should be convex, which means they curve slightly outwards. They shouldn't contain any dips or craters. If they do, it may be a sign that you have koilonychia, a condition where the nail curves inwards and looks thin and brittle. In some cases, people with koilonychia have a central depression in their nail deep enough to hold a drop of fluid, hence the condition is often referred to as "spoon nails".

If your any of your nails bear a resemblance to a spoon, this could be a sign of anaemia, when the body doesn't have enough healthy blood cells to carry oxygen to the tissues. Anaemia can be caused by iron deficiency. However, it can also be a sign of coeliac disease, among other conditions.

On the other hand, some changes in the nail can indicate nutritional deficiencies. Some people have horizontal ridges, known as Beau's lines, that run horizontally across their nails. This could indicate a deficiency such as insufficient protein. However, this feature could also be a sign of diabetes and peripheral vascular disease – a disorder involving reduced circulation of blood to certain parts of the body, usually due to the buildup of fat and cholesterol in the arteries – so it is still important to get it checked out.

"Beau's lines can indicate zinc deficiency, while brittle nails are a sign of hypothyroidism or vitamin B7 deficiency," says Mary Pearson, a paediatrician working at the University Hospital of Wales. "In some cases we might be more diligent about looking for these, for example in safeguarding cases where we are concerned about a child's nutrition, or where we suspect chronic disease," she says.

In other cases, nail changes may be caused by lifestyle factors rather than health problems. For example peeling nails, also known as onychoschizia, occurs when thin layers of the nails literally separate from the free nail edge and peel back. "Onychoschizia may be the result of excessive hand washing, nail dryness, and the use of acrylics and other nail polishes," says Joshua Zeichner, professor of dermatology at The Mount Sinai Hospital in New York.

You may wonder what it is about nails that makes them so revealing of a person's underlying health. One of the main reasons is that nails are obviously one of the few parts of the body that you can see from the outside.

"Nails are extensions of the skin, effectively, and your skin can tell you so much about what's going on in your body," says Baumgardt. "Your first impression of a patient often starts from the bedside, so you look them all over and you start off with their nails, you look in their eyes and their mouth. And you start to do an end-of-the-bed assessment, trying to pick out diagnostic pictures from that point early on. So nails are one of the first things we see," he says.

While most of the time changes in the nail are harmless, and are simply down to a nail injury, if you notice that the change in shape, colour, or texture is more permanent, then you should always consult the advice of a doctor.

All content within this column is provided for general information only, and should not be treated as a substitute for the medical advice of your own doctor or any other health care professional. The BBC is not responsible or liable for any diagnosis made by a user based on the content of this site. The BBC is not liable for the contents of any external internet sites listed, nor does it endorse any commercial product or service mentioned or advised on any of the sites. Always consult your own GP if you're in any way concerned about your health.

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Excavating a Language at the End of the World

How an old dictionary is revealing new perspectives on an Indigenous culture.

By Katarina Zimmer

Deep in the southern hemisphere, where frigid waves lap against the toe of the South American continent, the sea has no single name. Locals have called it tāralömbi when the water is perfectly calm. Čilamaii are the swells that gather along the coast, mötālömön is the roughening of the water by western breezes. Döna is the term when certain winds ruffle the ocean’s surface in such a way that the movement of fish underneath cannot be discerned and canoes must return ashore.

The Indigenous Yaghan people who have spoken these words are native to Tierra del Fuego—the mosaic of islands, fjords, channels, bays, and coves created by the submerged foot of the Andean mountains in southern Argentina and Chile. The Yaghan and their ancestors are thought to have persisted in this harsh, windy, and cold seascape for thousands of years. There, they have built canoes, from which they hunted sea lions and seals with harpoons. They have caught fish, gathered mussels, made ornaments, and celebrated rites of passage. They have roamed far and wide.

The last truly native speaker of Yaghan, Cristina Calderón, died in 2022. Up to a few hundred members of the group are still alive today—including Calderón’s granddaughter Cristina Zárraga and others who are working to revitalize the language; Yaghan is classified as “dormant” by the Endangered Languages Project.

Dictionaries, it turns out, can be excavated for rich information missing from the archeological record.

Although archaeologists have long been fascinated by the deep history of this seafaring, nomadic people, many of the physical remains their ancestors left behind have been lost to time. Fortunately, they have also left clues in the Yaghan language.

The Yaghan words for the sea were exhumed from a 19th-century Yaghan-English dictionary compiled in the late 1800s by an Anglican missionary. In a recent paper in the International Journal of Historical Archaeology, a team of Norwegian scholars argue that studying this historical snapshot of Yaghan could yield important clues about these people’s lives over the centuries. The same approach could be used for potentially hundreds of other languages, dead, alive, or dormant, across the globe to better understand old ways of life, ancient ecologies, and humans’ connection to the landscape.

Dictionaries, such as the one created for the Yaghan language, it turns out, can be excavated for rich and nuanced information missing from the physical archeological record.

“You could think about language in a similar way as we think about the archaeological sites in a landscape,” says the lead author of the new research, archaeologist Jo Sindre Eidshaug of the Norwegian University of Science and Technology’s Marine Ventures project, an international archaeological research effort. Eidshaug views language as something that “settles” a landscape just like physical artifacts, as people develop knowledge and vocabulary in places where they spent most of their time.

“This kind of research gives us a new tool to understand some [questions about] the life of these people in the past,” adds Angélica Tivoli, an archaeologist at the Austral Center for Scientific Research of the National Scientific and Technical Research Council in Ushuaia, Argentina, who wasn’t involved in the new work.

Today, while language revitalization efforts of Zárraga and others are underway, little Yaghan is currently spoken in Tierra del Fuego. The Yaghan culture and language underwent a devastating decline after Europeans arrived. In the 1880s, about 90 percent of the Yaghan people died from infectious diseases Europeans brought. The decline continued into the 20th century, when many Yaghans continued to die prematurely and faced discrimination for speaking the language. Today’s Yaghan people still fashion traditional harpoon points of whale bone and weave baskets, nowadays mostly to sell to tourists, but they can no longer canoe or boat freely due to restrictions by the Chilean Navy.

Thomas Bridges, who constructed the dictionary, first met the Yaghans as a teenager in 1856 and later lived with them for 30 years. Carefully documenting their language and culture helped Bridges to translate the Gospel of Luke into Yaghan, as part of Anglican missionary tradition to make the Bible accessible in local languages. But while a complete Yaghan Bible may never have come to fruition, Bridges’ dictionary includes about 32,000 words. “That level of detail he was documenting—it’s so beautiful,” says Oxford University ornithologist Andrew Gosler, research director of the Ethno-Ornithology World Atlas which collects Indigenous knowledge on birds. “To be able to document that kind of detail,” he says, demonstrates a closeness with the native speakers.

Because Bridges was merely striving to record the Yaghan vocabulary as comprehensively as possible, his dictionary may be less colored by prejudices and personal agendas than ethnographic reports of the Yaghan by other missionaries and travelers, Eidshaug says. But still, the dictionary is limited in the kinds of questions about the past it can answer. Languages change over time, so it’s unlikely, for example, to shed light on deep archeological questions, such as the origins of the first marine hunter-gatherers in Tierra del Fuego some 7,000 years ago. Or to necessarily give a full picture of the richness and breadth of Yaghan life.

In other places, like Australia, male linguists have been historically more likely to ask men than women about their practices, documenting little on activities traditionally carried out by women, notes linguist Luisa Miceli of the University of Western Australia. Bridges also mostly worked with only one Yaghan couple—Okokko and Camilenna—to understand the language, possibly limiting his view of the communities’ activities as a whole, Gosler says. And, many concepts in Yaghan are so specific to culture and place that they’re hard, if not impossible, to fully encapsulate in other languages, adds Zárraga, who learned the language as an adult from her grandmother.

But the dictionary might have encoded detailed knowledge about the kinds of resources, practices, and deep environmental understanding that were assembled over hundreds or thousands of years in Tierra del Fuego, much of which hasn’t been preserved in the archeological record. “The kind of environmental knowledge that is picked up in this language has an antiquity to it,” Eidshaug says.

Most physical traces of Yaghan culture, like any remnants of foraged feasts, were lost to time.

Wherever they went, Yaghans accumulated knowledge and vocabulary about their environment—the climate, the sea and its inhabitants, the coastline, the beach, and the forested hinterlands of Tierra del Fuego. Archaeological studies have mostly focused on shell middens along the coast—ring-shaped piles of shells that were discarded around dwellings—where animal bones and bone tools were preserved thanks to the alkaline chemistry of the shells.

The dictionary catalogs commonly hunted and foraged foods that don’t preserve—fast-degrading things like crab shells, berries, and fungi—in line with some ethnographic reports. Eidshaug counted 48 Yaghan terms for local fungi, many that describe their ripening in rich detail. For example, auačix, the round yellow summer fungus that grows on the šöšči tree: čikidönara describes immature fungi; pöša the second stage just before the fungus opens in holes and gets puffy; and dönara is when they are fully ripe, shortly after falling from the trees.

Most physical traces of the central vehicle of Yaghan culture, the bark canoe, like any remnants of auačix feasts, were also lost to time. Yet the dictionary describes in detail the resources and strategies involved in canoe-making. Bark is cut from the šöšči tree, and wood fiber called uri is used for sewing. Hūšun—seed stalks of wild celery—are sewn as pads into the seams to make them waterproof. Tstāgi soil is used to cement the seams. Tatega—pieces of young smooth bark—are attached to the canoe’s upper edges to protect paddlers from blisters. Through words like these, “we get a broader picture of the material culture,” Eidshaug says.

The dictionary also offers a window into some of the intangibles of Yaghan culture and worldview. Some entries pertain to rituals, such as kīna, an initiation ceremony for boys aged 12 to 17. The Yaghan word “to go” is often combined with prefixes to indicate direction; some denote the cardinal directions like north and south, but others indicate “toward land” or “away from shore,” illustrating how people mentally divided their landscape. Other entries explain how Yaghans kept time according to the seasonal changes in nature around them. Čgaiaŋgūta is the season for ripe auačix fungus. Čīyāgörana is the season when šöšči tree bark loosens, hākūa for making spring canoes. Iūan is the time when older crabs carry the younger ones, čīiūaiella the time after they’ve separated.

Information buried in the dictionary might also help interpret the physical archeological record. In the dictionary, for instance, Uštānim is described as a porpoise jaw used as a comb. Isöska is the lower jaw bone of a whale used as spear bones. Dictionary entries of this type could help archaeologists make sense of a hodgepodge of bones found underneath shell middens, and perhaps provide important context to certain tools, Tivoli says. “Maybe it’s a way of calling our attention to look deeper into the archaeological record,” she says.

Many nouns describe local animals, which represent a third of the dictionary. The wealth of different terms for certain animals—such as for shellfish—may reflect a recent increase in their importance as a resource relative to other creatures.

This new, linguistic approach to uncovering more about a long-lived culture as described in Eidshaug’s paper is quite valuable, says archaeologist Flavia Morello of Chile’s Institute of Patagonia and the Cape Horn International Center, both part of the University of Magallanes. It shows how dictionaries can act as gateways to unique cultures and in doing so help foster a deeper societal appreciation for cultural diversity and the kinds of relationships humans can cultivate with landscapes. “It’s very inspiring as a paper,” she says.

Archaeologists elsewhere are increasingly interested in leveraging language in similar ways. Miceli and her colleagues recently published a pilot study to explore what kind of information they could glean—from dictionaries of 10 Aboriginal languages in Australia—about domestic fire use, and whether this could be useful in guiding archaeologists in excavating sites, Miceli says. Past collaborations between archaeologists and linguists have often centered on answering questions about the likely homeland of ancestral languages, and how and why they spread, rather than using vocabulary to help with archaeological excavations. “That, I think, is quite new,” Miceli says.

Eidshaug and his colleagues also applied this same proof of concept to a dictionary of Norwegian as it was spoken among coastal fisher-farmers and other people in the area in the 1840s. And there are many more old dictionaries of languages waiting to be excavated from archive shelves.

In the case of the Yaghan, the hope is that such investigations not only answer archaeological curiosities but also help the living communities engage more deeply with their past. “We’ve connected several times with archaeologists who study artifacts and middens, and it has always been an interesting topic for us Yaghans,” says Zárraga, who spoke with me through an interpreter from her native Spanish language.

Zárraga spent a decade living with her grandmother, learning Yaghan practices, values, and language—and about her grandmother’s experience as the culture around her eroded. “It was … very pure cultural knowledge that my grandmother had, through the language,” Zárraga recalls. She is working to carry this ancestral knowledge forward in time. She’s already written two educational books on the Yaghan language and has plans for a Yaghan-Spanish dictionary. Eidshaug, meanwhile, has digitized Bridges’ dictionary to make it more easily accessible.

Though media reports often described her grandmother as the last Yaghan speaker, Zárraga hopes her efforts will ensure that the language and its embedded information will not molder in archives, and that the unique culture it described won’t go the same way. “That’s why it’s very, very important, all of these things that my grandma gave me,” she says. “So we are not the last ones.”

Katarina Zimmer is a freelance science and environment journalist.

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Scientists say they have identified Earth’s oldest rocks. It could reveal an unknown chapter in our planet’s history

By Katie Hunt, CNN

A rocky outcrop in a remote corner of northern Quebec appears serene in its eerie isolation on the eastern shore of Canada’s Hudson Bay.

But over the past two decades, this exposed remnant of ancient ocean floor, known as the Nuvvuagittuq Greenstone Belt, has been a heated scientific battleground in the quest to identify Earth’s oldest rock.

New research suggests that the geological site harbors the oldest known surviving fragments of Earth’s crust, dating back to 4.16 billion years ago. It’s the only rock determined to be from the first of four geological eons in our planet’s history: the Hadean, which began 4.6 billion years ago when the world was hot, turbulent and hell-like.

“Rocks are books for geologists … and right now we’re missing the book (on the Hadean). The Nuvvuagittuq Greenstone Belt would be at least one page of that book, so that’s why it’s so important,” said geologist Jonathan O’Neil, author of the research published Thursday in the journal Science.

The Nuvvuagittuq Greenstone Belt has been dated several times by different research groups, with widely divergent results. Most agree the rock is at least 3.75 billion years old — but that wouldn’t make it Earth’s oldest.

The Acasta Gneiss Complex, a group of rocks exposed along a riverbank nearly 200 miles (300 kilometers) north of Yellowknife, in northwestern Canada, is more widely agreed to be the planet’s oldest geological formation. These rocks are unambiguously dated at 4.03 billion years old, marking the boundary between the Hadean Eon and the next chapter in Earth’s history: the Archean. (There are older rocks on the planet — but not from the planet — that aren’t part of this debate: Some meteorites are 4.5 billion years old.)

A controversial 2008 paper coauthored by O’ Neil, who has been studying the site since he was a doctoral student, argued Nuvvuagittuq Greenstone Belt was 4.3 billion years old; however, other geologists took issue with the limits of the dating techniques and how the data was interpreted. With this latest paper, O’Neil, now an associate professor at the University of Ottawa in the department of Earth and environmental sciences, aims to prove his critics wrong.

How to date rock

Dating rocks involves using radiometric techniques that harness the natural and spontaneous radioactive decay of certain elements in the rock, which acts as a type of clock.

O’Neil uses an hourglass analogy: Imagine counting grains of sand at the top (radioactive elements) and bottom (elements produced from radioactive decay). Knowing the speed of the flowing grains (which represents the decay rate), allows scientists to date rocks. Some of these radiometric clocks are robust and can withstand the high temperatures and pressures Earth’s crust has endured over the eons, while others are more affected by these processes.

The gold standard and easiest way to date very old rock formations is with a very tough mineral known as a zircon. These tiny crystals incorporate a bit of uranium into their structure, and researchers can pinpoint their age by measuring the radioactive decay of uranium atoms, which turn into lead at a known rate.

However, the Nuvvuagittuq Greenstone Belt — which was mapped after a geological survey in the 1960s but first attracted scientific attention in the early 2000s — contains very few rocks bearing zircons as they rarely occur in specimens with lower levels of silicon, including ones that were once ancient ocean crust.

“We tried to find zircons. They’re just not there, or formed at a later time during the metamorphism or cooking of the rocks,” O’Neil said. Metamorphic rock is that which has been transformed by heat, pressure or other natural forces.

Instead, for the new study, O’Neil turned to the rare earth element samarium, which decays into the element neodymium. It’s a technique that has been used to date meteorites because the elements were only active more than 4 billion years ago.

“The controversy about the age is that some people believe the clock we use is not good or it was affected (by other geological processes),” he said.

“It’s a debate about what exactly we are measuring in time because we can’t use zircon, and some people in my field would only be convinced by zircons.”

O’Neil said the technique was valuable in this case because it’s possible to measure the decay of two variants, or isotopes, of samarium into two distinct isotopes of neodymium — essentially getting two clocks for the price of one. The latest paper focused on a specific type of metamorphic ancient rock — metagabbroic intrusions — sampled from within the belt, and the two data points converged on the same age: 4.16 billion years old.

This age, the study concluded, meant that “at least a small remnant” of Hadean crust was preserved in the Nuvvuagittuq Greenstone Belt, which would provide invaluable insights into Earth’s origins and how life formed.

Nearby rocks from the same location may preserve various signatures of life from the eon, as well as microfossils, tiny filaments and tubes formed by bacteria, noted Dominic Papineau, a senior research scientist at the Institute of Deep-sea Science and Engineering at the Chinese Academy of Sciences. He wasn’t involved in the latest research but has studied fossils from the site.

“The rocks that were newly dated come from the mantle, which is not thought to harbour life or be habitable for life,” said Papineau, who is also an honorary professor of Precambrian biogeochemistry and exobiology at the University College London.

“However, the adjacent sedimentary rocks are now confirmed to be at least 4,160 million years old, which is ‘only’ about 400 million years after the accretion of our planet and of the Solar System,” he added in an email.

“Evidence of very early life in these sedimentary rocks indicate that the origin of life can take place very quickly (relatively speaking), which increases the probability that life is common and widespread in the universe.”

Debate put to rest?

It’s not yet clear whether Nuvvuagittuq outcrops will become widely accepted as Earth’s oldest rocks, according to other scientists who were not involved with the research.

Bernard Bourdon, a geochemist at the Lyon Geology Laboratory in France who had previously taken issue with the earliest dates for Nuvvuagittuq Greenstone Belt published by O’Neil, said he was “more convinced” by the latest work, and it was “well improved” on previous studies.

“What is better, compared to the 2008 paper, is the fact that the two techniques … they give the same age. That’s good. That’s where we criticized the first results,” Bourdon, who is also research director at French scientific research body CNRS, said.

“In the end, I think there’s more credibility to the age,” he said, adding that he had some “small doubts” and would like to investigate the data more in depth.

The age of the rocks “remains an unsolved mystery,” according to Hugo Olierook, a geoscientist and senior research fellow at Curtin University in Australia.

“In the absence of ‘easy’ minerals to date, they have turned to whole-rock, which is fraught with problems as whole-rock samples have multiple minerals,” Olierook said via email.

“It only takes one of these minerals to have been altered and their age ‘reset’ to a younger age for the whole house of cards to fall over,” he added, noting that very high and low temperatures can naturally alter the crystallization age of minerals in rock.

Very little is definitive when dealing with rocks and minerals that have complex geological histories spanning more than 4 billion years, according to Jesse Reimink, the Rudy L. Slingerland Early Career Professor of Geoscience at Penn State University.

“Even if these rocks are ‘only’ 3.8 billion years old, it is quite amazing that they are preserved. This current work presents more compelling data, supporting an age of 4.15 billion years ago, than that which was previously produced, which was already compelling,” Reimink said.

“The timescales are so long, and the history of these rocks and minerals is so tortured, that gleaning any primary information from them at all is pretty amazing.”

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Chasing Lost Languages

Author Laura Spinney on the 3 greatest revelations she had while writing Proto: How One Ancient Language Went Global

By Laura Spinney

If humans have been talking for 200,000 years—for most of our species’ existence, that is—then an estimated half a million languages might have been spoken in all. To put that number in perspective, around 7,000 languages are spoken today. And because writing was only invented about 5,000 years ago, the vast majority of those half a million languages are lost to us, having been spoken in a preliterate world and died before they could be recorded. That’s half a million distinct systems of knowledge including histories, myths, songs, pharmacopoeias, recipes, jokes, prayers, and swear words that have vanished into oblivion. (It’s possible some of the earliest languages were signed rather than spoken.)

Even if that number is off, which it might be because researchers disagree about when humans started speaking—some argue it was around 100,000 years ago, others that speaking predates our species—we can be confident that the number of languages that have ever been spoken dwarfs those that are spoken today. I find this fact dizzying and—I can’t help it—tragic. Think of all those ways of knowing and doing that have been invented and lost, only—in some cases—to be invented again. Think of all that gossip!

But it also has some quite staggering implications for our understanding of language. It means that living languages likely represent less than 2 percent of humanity’s full linguistic range, and a non-random sample at that—one heavily shaped, for example, by Western imperialism. And it gets worse. Perhaps only 10 percent of the languages that make up that 2 percent are well documented. When you consider that linguists continue to record previously unrecorded languages and to discover novel linguistic features in the process—as they are doing today in Papua New Guinea, for example—you realize how laughably little we know about what language is and what it does.

At the turn of the 14th century, when Latin was already dead except as a language of scholars and priests, a Tuscan writer called Dante Alighieri observed that many words were almost identical across the Romance languages. He went on to make the frankly heretical suggestion that this was because the various flavours of Romance were all descended from Latin. At the time, in Europe, there was no concept of language evolution. The Bible held that linguistic diversity and its corollary, mutual bewilderment, was the punishment visited on humanity by God for the impertinent construction of the Tower of Babel—and medieval Europeans took the Bible literally.

Living languages likely represent less than 2 percent of humanity’s full linguistic range.

For Dante’s contemporaries, language was static until God said otherwise. Dante argued that al contrario, languages change infinitesimally all the time. It was like a person growing up, he explained: A baby becomes a child becomes a man. People had no trouble grasping this even though they didn’t perceive the baby morphing before their eyes. Unfortunately, for all his literary panache, the celebrated author of the Divine Comedy found himself roundly ignored on this point.

It took another couple of centuries for people to accept that languages change. Even today, though most people readily acknowledge linguistic evolution, some balk at the idea that their own language is in a state of flux. And yet, though that flux is heavily context-dependent, and happening at different rates in different languages, it is incontestably real.

One way that all languages change is simply through young children learning them. It’s a fidelity issue: In reproducing what they hear, infants unconsciously introduce tiny deviations from the template presented to them. But people can also innovate deliberately, by borrowing a foreign word or grammatical construction, or by mimicking an accent. They might do so because they want to sound like someone else, or for the opposite reason—to distinguish themselves from the exotic-sounding other.

These opposing forces have operated throughout our species’ existence, and the upshot is that languages and dialects have diverged and split, but also, occasionally, converged. The resulting branchings and fusings reflect the language’s journey through the world—the different speech communities its speakers have encountered and their receptiveness, or otherwise, to those communities.

You could think of a language, then, as a sort of chronicle of the past, but one composed collectively and in large part unconsciously. By poring over the language’s internal workings, historical linguists can “read” that chronicle. This revelation was balm to my soul, after the earlier one that most languages are lost to us, because it means that we can salvage some of our unwritten past. Linguists can reconstruct living languages’ prehistory, to some extent, and even those languages’ long-dead ancestors. They can only do so up to about 10,000 years back, however, because beyond that threshold data become so scarce that it is difficult to distinguish the different forces shaping a language—to tell loan from inheritance, say.

That leaves at least 190,000 years of the human backstory an impenetrable black box. It’s still dizzying, I’d say. Still tragic

Laura Spinney is a writer and science journalist. Her writing on science has appeared in The Guardian, The Economist, Nature and National Geographic, among others. She is the author of two novels, The Doctor (2001) and The Quick (2007), and a collection of oral history, Rue Centrale (2013). Her bestselling non-fiction account of the 1918 flu pandemic, Pale Rider: The Spanish Flu of 1918 and How it Changed the World (2017), was translated into more than 20 languages. Her latest book, Proto: How Once Ancient Language Went Global, the story of the Indo-European languages, appeared in 2025.