Once a week.
Subscribe to our weekly newsletter.
Your genetics influence how resilient you are to the cold
What makes some people more likely to shiver than others?
Some people just aren't bothered by the cold, no matter how low the temperature dips. And the reason for this may be in a person's genes.
Our new research shows that a common genetic variant in the skeletal muscle gene, ACTN3, makes people more resilient to cold temperatures.
Around one in five people lack a muscle protein called alpha-actinin-3 due to a single genetic change in the ACTN3 gene. The absence of alpha-actinin-3 became more common as some modern humans migrated out of Africa and into the colder climates of Europe and Asia. The reasons for this increase have remained unknown until now.
Our recent study, conducted alongside researchers from Lithuania, Sweden and Australia, suggests that if you're alpha-actinin-3 deficient, then your body can maintain a higher core temperature and you shiver less when exposed to cold, compared with those who have alpha-actinin-3.
We looked at 42 men aged 18 to 40 years from Kaunas in southern Lithuania and exposed them to cold water (14℃) for a maximum of 120 minutes, or until their core body temperature reached 35.5℃. We broke their exposure up into 20-minute periods in the cold with ten-minute breaks at room temperature. We then separated participants into two groups based on their ACTN3 genotype (whether or not they had the alpha-actinin-3 protein).
While only 30% of participants with the alpha-actinin-3 protein reached the full 120 minutes of cold exposure, 69% of those that were alpha-actinin-3 deficient completed the full cold-water exposure time. We also assessed the amount of shivering during cold exposure periods, which told us that those without alpha-actinin-3 shiver less than those who have alpha-actinin-3.
Our study suggests that genetic changes caused by the loss of alpha-actinin-3 in our skeletal muscle affect how well we can tolerate cold temperatures, with those that are alpha-actinin-3 deficient better able to maintain their body temperature and conserve their energy by shivering less during cold exposure. However, future research will need to investigate whether similar results would be seen in women.
Skeletal muscles are made up of two types of muscle fibres: fast and slow. Alpha-actinin-3 is predominantly found in fast muscle fibres. These fibres are responsible for the rapid and forceful contractions used during sprinting, but typically fatigue quickly and are prone to injury. Slow muscle fibres on the other hand generate less force but are resistant to fatigue. These are primarily the muscle you'd use during endurance events, like marathon running.
Our previous work has shown that ACTN3 variants play an important role in our muscle's ability to generate strength. We showed that the loss of alpha-actinin-3 is detrimental to sprint performance in athletes and the general population, but may benefit muscle endurance.
This is because the loss of alpha-actinin-3 causes the muscle to behave more like a slower muscle fibre. This means that alpha-actinin-3 deficient muscles are weaker but recover more quickly from fatigue. But while this is detrimental to sprint performance, it may be beneficial during more endurance events. This improvement in endurance muscle capacity could also influence our response to cold.
While alpha-actinin-3 deficiency does not cause muscle disease, it does influence how our muscle functions. Our study shows that ACTN3 is more than just the "gene for speed", but that its loss improves our muscle's ability to generate heat and reduces the need to shiver when exposed to cold. This improvement in muscle function would conserve energy and ultimately increase survival in cold temperatures, which we think is a key reason why we see an increase in alpha-actinin-3 deficient people today, as this would have helped modern humans better tolerate cooler climates as they migrated out of Africa.
The goal of our research is to improve our understanding of how our genetics influence how our muscle works. This will allow us to develop better treatments for those who suffer from muscle diseases, like Duchenne muscular dystrophy, as well as more common conditions, such as obesity and type 2 diabetes. A better understanding of how variants in alpha-actinin-3 influences these conditions will give us better ways to treat and prevent these conditions in the future.
Victoria Wyckelsma, Postdoctoral Research Fellow, Muscle Physiology, Karolinska Institutet and Peter John Houweling, Senior Research Officer, Neuromuscular Research, Murdoch Children's Research Institute
- How humans evolved to live in the cold - Big Think ›
- Being fit boosts your tolerance for cold weather ›
- Spending the summer swimming? Get a full-body dryer - 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.