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Unraveling the mystery behind dogs' floppy ears
Dogs' floppy ears may be part of why they and other domesticated animals love humans so much.
- Nearly all domestic animals share several key traits in addition to friendliness to humans, traits such as floppy ears, a spotted coat, a shorter snout, and so on.
- Researchers have been puzzled as to why these traits keep showing up in disparate species, even when they aren't being bred for those qualities. This is known as "domestication syndrome."
- Now, researchers are pointing to a group of a cells called neural crest cells as the key to understanding domestication syndrome.
The grey wolf's sense of smell can detect prey nearly two miles away, and it can hear subtle sounds up to ten miles away. At night, it sees in the dark. When chasing prey, it can reach a speed of 35 mile per hour and deliver crushing bites with 1,500 pounds of pressure per square inch of jaw. Wolf packs have also been known to take down much larger prey, like moose or bison.
As for their distant cousins, the domesticated dog, I once had a dog who would fart himself awake at night and stare accusatorily at me.
Despite their differences, grey wolves are the closest living relative to the domesticated dog. They share an extinct, unknown ancestor, an apex predator that likely hunted ancient megafauna. But at some point, one of the descendants of that ancient ancestor learned how beneficial it was to hunt alongside humans. In tracking game, we became closer as hunters. Eventually, proto-dogs left the wildness behind and began to transform. Their ears became floppier, their coats grew lightly-colored patches. Their personality — perhaps after getting to know human children over centuries — became more playful and less fearful. The changes continued: their snout shortened, and their teeth and brain shrunk.
Just like that, Fenrir transformed into Scooby-Doo.
How did this change happen?
The common logic says that the wolves' new environment, one spent in frequent contact with humans, put a pressure on them to become friendlier. Eventually, humans began breeding these dogs for certain desirable traits, such as a border collie's herding instinct or a pug's cute (and extremely unhealthy) squashed snout.
This is true to an extent. But upon observing other animals undergoing domestication, scientists noticed something strange. They all seemed to change in the exact same way.
Consider, for instance, the case of Dmitry Belyaev, a Soviet biologist who experimented with breeding wild foxes. The sole basis of his experiment was to take a generation of wild foxes and breed the ones friendliest to humans. The experiment is still ongoing today, nearly 60 years and many fox generations later. Now, the foxes are exceptionally friendly (though not quite ready to be pets). In addition, like domesticated dogs, their coats have splashes of lighter color, their tails curl, and their ears are floppy.
Similar changes have been observed in domesticated cats, horses, pigs, ferrets, camels… the list goes on. Somehow, selecting for friendliness towards humans in animals — domesticating them — causes a constellation of seemingly unrelated physiological changes. Researchers have given this mystery a name: Domestication syndrome.
Now, researchers have discovered a compelling reason why these changes are indeed related, and it has to do with something called neural crest cells.
Hijacking stem cells for a friendlier wolf
Neural crest cells are a kind of stem cell, meaning that as an animal's body develops in the womb, these cells differentiate into more specialized cells that eventually become different parts of the body. Crucially, neural crest cells contribute to the development of the adrenal medulla, which is part of the adrenal gland in the brain.
This structure is responsible for releasing adrenaline and noradrenaline in response to stressful stimuli: essentially, it contributes to the flight-or-fight response, fear, and stress. Wild animals obviously need their neural medulla to be sensitive. For a grey wolf, the world is a dangerous place, not least because of humans. But if we want a wolf to be more like a dog, less inclined to fear humans and behave aggressively, then we would breed two relatively unafraid wolves together, selecting for a weaker neural medulla. If their adrenal medulla is less developed, then at some point the wolf's neural crest cells were somehow repressed during its development.
Over time, selecting for animals with fewer neural crest cells produces a friendlier critter. But these cells play a diverse role in the body: they're stem cells, so they become many different things. Among these, neural crest cells become melanocytes, which create darker colors in skin or fur. Because the development of neural crest cells is degraded in domesticated animals, these cells don't have the chance to spread uniformly throughout the body. Instead, distant regions in the body become splotchy, which is why many dogs have lighter patches of fur above their eyes or on their chest.
As the dog develops in the womb, its neural crest cells are located in the spot that will eventually become the base of the tail. Because these cells are repressed in domesticated dogs, they can't spread throughout the body. As a result, distant regions like the skull, brain, ears, and facial and chest fur are often affected.
Wilkins et al., 2014
Cartilage, too, is derived from neural crest cells, which is why domesticated animals tend to have floppy ears. The skull and brain are also dependent on these cells, which is why domesticated dogs have smaller brains than wolves, shorter snouts, and smaller teeth.
If you look at other animals besides dogs, these traits hold true. Domesticated horses have spotted pelts. Cats often have bands of color (although they rarely have floppy ears). Domesticated mice, foxes, ferrets, birds, and even fish all share some combination of these different traits.
A delicate balance
Human beings have bred these animals for friendliness, but as an unintended side effect, we have changed their physiology in drastic ways. While their appearance is drastically different, the changes in their genome can almost be considered subtle. There are many genes responsible for the production of neural crest cells. When any one of these genes is completely shut down, it's often fatal for the animal. Or, if these genes are downregulated too much, then we begin to see genetic disorders appear such as Waardenburg syndrome, Treacher Collins syndrome, or Mowat-Wilson syndrome (interestingly, one of the symptoms of Mowat-Wilson syndrome is excessive friendliness).
In domesticated animals, many of these genes are just ever-so-slightly downregulated to put the right limit on neural crest cell production during an animal's development. As a result, you get a healthy, friendly, floppy-eared dog instead of an apex predator fetching the paper for you in the morning.
- Bill Nye Talks to Dogs and Explores the Lessons of Canine Evolution ›
- Are humans domesticated animals? ›
- Urban foxes self-evolve, exhibiting Darwin’s domestication syndrome - Big Think ›
So much for rest in peace.
- Australian scientists found that bodies kept moving for 17 months after being pronounced dead.
- Researchers used photography capture technology in 30-minute intervals every day to capture the movement.
- This study could help better identify time of death.
We're learning more new things about death everyday. Much has been said and theorized about the great divide between life and the Great Beyond. While everyone and every culture has their own philosophies and unique ideas on the subject, we're beginning to learn a lot of new scientific facts about the deceased corporeal form.
An Australian scientist has found that human bodies move for more than a year after being pronounced dead. These findings could have implications for fields as diverse as pathology to criminology.
Dead bodies keep moving
Researcher Alyson Wilson studied and photographed the movements of corpses over a 17 month timeframe. She recently told Agence France Presse about the shocking details of her discovery.
Reportedly, she and her team focused a camera for 17 months at the Australian Facility for Taphonomic Experimental Research (AFTER), taking images of a corpse every 30 minutes during the day. For the entire 17 month duration, the corpse continually moved.
"What we found was that the arms were significantly moving, so that arms that started off down beside the body ended up out to the side of the body," Wilson said.
The researchers mostly expected some kind of movement during the very early stages of decomposition, but Wilson further explained that their continual movement completely surprised the team:
"We think the movements relate to the process of decomposition, as the body mummifies and the ligaments dry out."
During one of the studies, arms that had been next to the body eventually ended up akimbo on their side.
The team's subject was one of the bodies stored at the "body farm," which sits on the outskirts of Sydney. (Wilson took a flight every month to check in on the cadaver.)Her findings were recently published in the journal, Forensic Science International: Synergy.
Implications of the study
The researchers believe that understanding these after death movements and decomposition rate could help better estimate the time of death. Police for example could benefit from this as they'd be able to give a timeframe to missing persons and link that up with an unidentified corpse. According to the team:
"Understanding decomposition rates for a human donor in the Australian environment is important for police, forensic anthropologists, and pathologists for the estimation of PMI to assist with the identification of unknown victims, as well as the investigation of criminal activity."
While scientists haven't found any evidence of necromancy. . . the discovery remains a curious new understanding about what happens with the body after we die.
Metal-like materials have been discovered in a very strange place.
- Bristle worms are odd-looking, spiky, segmented worms with super-strong jaws.
- Researchers have discovered that the jaws contain metal.
- It appears that biological processes could one day be used to manufacture metals.
The bristle worm, also known as polychaetes, has been around for an estimated 500 million years. Scientists believe that the super-resilient species has survived five mass extinctions, and there are some 10,000 species of them.
Be glad if you haven't encountered a bristle worm. Getting stung by one is an extremely itchy affair, as people who own saltwater aquariums can tell you after they've accidentally touched a bristle worm that hitchhiked into a tank aboard a live rock.
Bristle worms are typically one to six inches long when found in a tank, but capable of growing up to 24 inches long. All polychaetes have a segmented body, with each segment possessing a pair of legs, or parapodia, with tiny bristles. ("Polychaeate" is Greek for "much hair.") The parapodia and its bristles can shoot outward to snag prey, which is then transferred to a bristle worm's eversible mouth.
The jaws of one bristle worm — Platynereis dumerilii — are super-tough, virtually unbreakable. It turns out, according to a new study from researchers at the Technical University of Vienna, this strength is due to metal atoms.
Metals, not minerals
Fireworm, a type of bristle wormCredit: prilfish / Flickr
This is pretty unusual. The study's senior author Christian Hellmich explains: "The materials that vertebrates are made of are well researched. Bones, for example, are very hierarchically structured: There are organic and mineral parts, tiny structures are combined to form larger structures, which in turn form even larger structures."
The bristle worm jaw, by contrast, replaces the minerals from which other creatures' bones are built with atoms of magnesium and zinc arranged in a super-strong structure. It's this structure that is key. "On its own," he says, "the fact that there are metal atoms in the bristle worm jaw does not explain its excellent material properties."
Just deformable enough
Credit: by-studio / Adobe Stock
What makes conventional metal so strong is not just its atoms but the interactions between the atoms and the ways in which they slide against each other. The sliding allows for a small amount of elastoplastic deformation when pressure is applied, endowing metals with just enough malleability not to break, crack, or shatter.
Co-author Florian Raible of Max Perutz Labs surmises, "The construction principle that has made bristle worm jaws so successful apparently originated about 500 million years ago."
Raible explains, "The metal ions are incorporated directly into the protein chains and then ensure that different protein chains are held together." This leads to the creation of three-dimensional shapes the bristle worm can pack together into a structure that's just malleable enough to withstand a significant amount of force.
"It is precisely this combination," says the study's lead author Luis Zelaya-Lainez, "of high strength and deformability that is normally characteristic of metals.
So the bristle worm jaw is both metal-like and yet not. As Zelaya-Lainez puts it, "Here we are dealing with a completely different material, but interestingly, the metal atoms still provide strength and deformability there, just like in a piece of metal."
Observing the creation of a metal-like material from biological processes is a bit of a surprise and may suggest new approaches to materials development. "Biology could serve as inspiration here," says Hellmich, "for completely new kinds of materials. Perhaps it is even possible to produce high-performance materials in a biological way — much more efficiently and environmentally friendly than we manage today."
Dealing with rudeness can nudge you toward cognitive errors.
- Anchoring is a common bias that makes people fixate on one piece of data.
- A study showed that those who experienced rudeness were more likely to anchor themselves to bad data.
- In some simulations with medical students, this effect led to higher mortality rates.
Cognitive biases are funny little things. Everyone has them, nobody likes to admit it, and they can range from minor to severe depending on the situation. Biases can be influenced by factors as subtle as our mood or various personality traits.
A new study soon to be published in the Journal of Applied Psychology suggests that experiencing rudeness can be added to the list. More disturbingly, the study's findings suggest that it is a strong enough effect to impact how medical professionals diagnose patients.
Life hack: don't be rude to your doctor
The team of researchers behind the project tested to see if participants could be influenced by the common anchoring bias, defined by the researchers as "the tendency to rely too heavily or fixate on one piece of information when making judgments and decisions." Most people have experienced it. One of its more common forms involves being given a particular value, say in negotiations on price, which then becomes the center of reasoning even when reason would suggest that number should be ignored.
It can also pop up in medicine. As co-author Dr. Trevor Foulk explains, "If you go into the doctor and say 'I think I'm having a heart attack,' that can become an anchor and the doctor may get fixated on that diagnosis, even if you're just having indigestion. If doctors don't move off anchors enough, they'll start treating the wrong thing."
Lots of things can make somebody more or less likely to anchor themselves to an idea. The authors of the study, who have several papers on the effects of rudeness, decided to see if that could also cause people to stumble into cognitive errors. Past research suggested that exposure to rudeness can limit people's perspective — perhaps anchoring them.
In the first version of the study, medical students were given a hypothetical patient to treat and access to information on their condition alongside an (incorrect) suggestion on what the condition was. This served as the anchor. In some versions of the tests, the students overheard two doctors arguing rudely before diagnosing the patient. Later variations switched the diagnosis test for business negotiations or workplace tasks while maintaining the exposure to rudeness.
Across all iterations of the test, those exposed to rudeness were more likely to anchor themselves to the initial, incorrect suggestion despite the availability of evidence against it. This was less significant for study participants who scored higher on a test of how wide of a perspective they tended to have. The disposition of these participants, who answered in the affirmative to questions like, "Before criticizing somebody, I try to imagine how I would feel if I were in his/her place," was able to effectively negate the narrowing effects of rudeness.
What this means for you and your healthcare
The effects of anchoring when a medical diagnosis is on the line can be substantial. Dr. Foulk explains that, in some simulations, exposure to rudeness can raise the mortality rate as doctors fixate on the wrong problems.
The authors of the study suggest that managers take a keener interest in ensuring civility in workplaces and giving employees the tools they need to avoid judgment errors after dealing with rudeness. These steps could help prevent anchoring.
Also, you might consider being nicer to people.