12 Common Things Science Still Hasn't Figured Out

Laughter: Still a scientific mystery
Laughter: Still a scientific mystery
iStock/pixelfit

We’ve learned enough about physics to send humans to the Moon. We’ve discovered that DNA carries our genetic information. Scientists have even gotten closer to solving the mystery of whether cats can behave as both solids and liquids [PDF].

But there are still some basic questions we haven’t answered, including these frustratingly persistent scientific mysteries.

1. Why We Cry

Some of us tear up watching a sad movie; sometimes, we're so happy that we burst into tears. But according to science, crying in response to intense emotions doesn’t seem to be a useful behavior, and it might not have a biological purpose.

What science does know is that not all tears are created equal. The chemical composition of the tears produced when we cry, which are called psychic tears, is slightly different from the composition of the tears that lubricate and help expel foreign bodies from the eyes. This has led some to theorize that the chemical makeup of psychic tears makes them emotionally healing. But evidence showing that the chemical differences have substantial psychological effects—let alone that such effects explain why crying evolved—is lacking.

And that’s not where the theories end. Some evolutionary psychologists think that crying may have evolved as a distress call that brings help: In a 2009 paper, one researcher suggested that tears may signal submission and helplessness by blurring vision, which prompts others to aid (or at least not harm) the crier. But other researchers have pointed out that we often cry after a stressful situation has resolved, not while it’s in progress and we need to signal for help; it’s also typical for people to avoid crying publicly and to look unfavorably on those who do. In any case, these hypotheses, like most in evolutionary psychology, are difficult to test.

2. How to Cure Hiccups

Maybe you hold your breath. Maybe you chug water. Unfortunately, nothing has been found to reliably eliminate hiccups, despite the overwhelming number of folk remedies on the internet. This sad state of affairs is likely due to insufficient research: Serious cases of the hiccups are rare, and the mild cases are brief and don’t usually cause problems.

Most of the treatments for severe cases of hiccups—doses of sedating antipsychotics like haloperidol, vagus nerve stimulation, digital rectal massage—aren’t exactly things you could try on your own. For now, you’ll have to endure hiccups or stick with unproven, but usually harmless, solutions. At least they give you an excuse to eat peanut butter by the spoonful.

3. How General Anesthesia Works

As you’re rolling into surgery, you probably assume that your doctors not only know how to perform the procedure, but understand how the drugs that knock you out actually do so. But you’d be wrong. Scientists do know that local anesthetics like Novocain block pain signals before they reach the central nervous system by altering the function of specific proteins on nerve cells. But the molecular basis of general anesthesia is more of a mystery. These drugs seem to interfere with the functions of a variety of proteins on nerve cells in the central nervous system, but how they accomplish this is not well understood. General anesthetics come in a variety of types, and they likely don’t all work the same way, so developing models of how the compounds work on the molecular level may continue to be a challenge.

4. How Tylenol Kills Pain

A layperson taking Tylenol to relieve pain might think it works like non-steroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen and aspirin, which block some enzymes and, in turn, the pain- and inflammation-causing chemicals they produce. But that’s not the case—acetaminophen, the active ingredient in Tylenol, seems to need specific chemical conditions to work on those enzymes, and it doesn’t appear to reduce inflammation as the NSAIDs do.

Some researchers think acetaminophen may alter the way pain is perceived by interacting with certain proteins on nerve cells, possibly including serotonin receptors, cannabinoid receptors, opioid receptors, and specific channels on nerves in the spinal cord that transmit pain and itch signals. Acetaminophen byproducts have also been shown to activate these channels rather than shutting them down, further complicating the question.

5. Why We Sleep

Too little sleep impairs thinking in the short term and increases the risk of several serious diseases in the long term, while complete sleep deprivation is fatal. We may have evolved to sleep because it aids healing, memory consolidation, and other important processes, but we still have much to learn about the ways sleeping achieves these ends. Other roles for sleep, like conserving energy during times when it wouldn’t be advantageous to be awake (for example, during scorching-hot days in Death Valley) have been proposed as well.

At least for now, we don’t have a single, conclusive answer to the question of why we sleep. But no matter how sleeping arose, we can probably accept that it provided a substantial evolutionary advantage once in place, since sleep is found across much of the animal kingdom.

6. Why Only Some Thunderstorms Produce Tornadoes

A standard explanation of how tornadoes form is that they’re spawned when cold, dry air mingles with warm, humid air—that’s how we justify the fact that Tornado Alley in the central United States, where Arctic air, air from the Southwest, and air from the Gulf of Mexico mix, has so many tornadoes. But that’s not the whole story. These conditions do create more thunderstorms, but not all thunderstorms include tornadoes, and scientists aren’t sure why.

In some cases, tornadoes may form is when there are temperature changes in the air flowing downward around mesocyclones (vortexes within the types of storms tornadoes can come from). This idea has theoretical and experimental support, but even without these temperature variations, tornadoes can still form, demonstrating how much more we have to learn about the phenomenon.

7. Why We Itch

At a basic level, itch is an unpleasant sensation that triggers the urge to scratch. Scratching could end up making an itch worse, but it may also serve a purpose. Mechanical itch—the kind triggered when fine hairs on your body are disturbed—may alert you to the presence of biting insects or parasites, and scratching could brush them away.

This hypothesis is difficult to test, and it doesn’t cover chemical itch caused by histamine and other scratch-provoking substances. Long after you’ve missed your chance to brush a mosquito off your skin, histamine in the itchy bump it has left behind continues to compel you to scratch. Whether this type of itching serves a purpose, or is simply an incidental activation of the itch system, isn’t conclusively known.

8. How We Age

Despite what many beauty experts claim, no one really has aging figured out. Reactive chemicals called free radicals are often blamed, but they’re not the sole cause of aging, and our cells have numerous ways to help keep damage caused by excess free radicals to a minimum. Shortening of the telomeres, the protective caps of DNA at the ends of each chromosome, is another frequently cited cause of aging—but it’s not the only factor. Numerous other contributors to aging have been discovered, but no single factor explains all or even most of the aging process, making this a difficult question to answer.

9. Why We Laugh

Laughter, like crying, may have developed as a social tool. Laughter doesn't appear to be a uniquely human behavior, and it may not even be limited to primates. Rats produce laughter when tickled, for example, and many other social animals, such as dolphins [PDF], make specific sounds associated with play-fighting that have been likened to laughter.

A leading hypothesis for why we laugh is that laughter promotes pro-social behavior by letting playmates know that the fighting is just a game. But even if our interpretations of these behaviors are correct, it’s possible that humans evolved different uses for laughter after our evolutionary splits with other animal species, making the reason for human laughter another open question.

10. How and Why Animals Migrate Back to Their Birthplaces

Some animals migrate to the sites of their birth to mate—a practice known as natal philopatry—with stunning precision. Female Antarctic fur seals, for example, can return to within one body length of their exact birthplaces to breed.

But how do they get there after months or years away? One possibility is that some migratory animals navigate by sensing variations in Earth’s geomagnetic field. While this makes sense given that some migratory animals, such as sea turtles, are known to be highly sensitive to these variations, it has not been conclusively demonstrated that they navigate this way.

Other creatures, such as Pacific salmon, may use smell to direct them toward their breeding grounds. These fish have been shown experimentally to be able to home in on chemical cues from the water in which they developed into adults. But these chemical breadcrumbs wouldn’t be detectable across the vast ocean, meaning that even if the salmon use them to navigate, they must also have a way to direct themselves close enough to the source to smell them. The complete mechanisms behind natal philopatry, even in this well-studied case, are still unknown.

11. What Dreams are For

If the question of why we sleep is complicated, the question of why we dream is even more so. Dreaming—especially with vivid, fanciful dreams—is most correlated with rapid eye movement (REM) sleep, which itself is poorly understood. One thought is that dreaming evolved to help us sort out or rehearse solutions to problems in our waking lives, but there is no hard evidence that this is the case.

Although our dreams may feel significant to us, it’s also possible that they serve no purpose—they may simply be a byproduct of other processes that occur during REM sleep. Studying the neurological basis of the strange and highly subjective experience of dreaming is complicated, which is why understanding the origin of dreaming is still beyond our grasp.

12. How Turbulence Happens

Understanding how turbulence works is incredibly important from an engineering perspective, since it affects everything from how internal combustion engines work to how far golf balls can travel. And now that most of classical physics (encompassing the laws of mechanics, thermodynamics, and so on) has long been established, turbulence is considered one of the biggest remaining problems in the field. No one has figured out a way to perfectly model turbulent flow.

Modeling turbulence requires the Navier–Stokes equations, which describe the motion of fluids (liquids, gases, and plasmas). And that’s the main problem: These equations themselves are poorly understood—so much so that producing a proof about one of their basic properties is one of the seven Millennium Prize Problems. It’s considered one of the most important open classic questions in math—and there's a million dollars waiting for anyone who can figure it out.

5 Signs Humans Are Still Evolving

Lealisa Westerhoff, AFP/Getty Images
Lealisa Westerhoff, AFP/Getty Images

When we think of human evolution, our minds wander back to the millions of years it took natural selection to produce modern-day man. Recent research suggests that, despite modern technology and industrialization, humans continue to evolve. "It is a common misunderstanding that evolution took place a long time ago, and that to understand ourselves we must look back to the hunter-gatherer days of humans," Dr. Virpi Lummaa, a professor at the University of Turku, told Gizmodo.

But not only are we still evolving, we're doing so even faster than before. In the last 10,000 years, the pace of our evolution has sped up, creating more mutations in our genes, and more natural selections from those mutations. Here are some clues that show humans are continuing to evolve.

1. Humans drink milk.

Historically, the gene that regulated humans' ability to digest lactose shut down as we were weaned off our mothers' breast milk. But when we began domesticating cows, sheep, and goats, being able to drink milk became a nutritionally advantageous quality, and people with the genetic mutation that allowed them to digest lactose were better able to propagate their genes.

The gene was first identified in 2002 in a population of northern Europeans that lived between 6000 and 5000 years ago. The genetic mutation for digesting milk is now carried by more than 95 percent of northern European descendants. In addition, a 2006 study suggests this tolerance for lactose developed again, independently of the European population, 3000 years ago in East Africa.

2. We're losing our wisdom teeth.

Our ancestors had much bigger jaws than we do, which helped them chew a tough diet of roots, nuts, and leaves. And what meat they ate they tore apart with their teeth, all of which led to worn-down chompers that needed replacing. Enter the wisdom teeth: A third set of molars is believed to be the evolutionary answer to accommodate our ancestors' eating habits.

Today, we have utensils to cut our food. Our meals are softer and easier to chew, and our jaws are much smaller, which is why wisdom teeth are often impacted when they come in — there just isn't room for them. Unlike the appendix, wisdom teeth have become vestigial organs. One estimate says 35 percent of the population is born without wisdom teeth, and some say they may disappear altogether.

3. We're resisting infectious diseases.

In 2007, a group of researchers looking for signs of recent evolution identified 1800 genes that have only become prevalent in humans in the last 40,000 years, many of which are devoted to fighting infectious diseases like malaria. More than a dozen new genetic variants for fighting malaria are spreading rapidly among Africans. Another study found that natural selection has favored city-dwellers. Living in cities has produced a genetic variant that allows us to be more resistant to diseases like tuberculosis and leprosy. "This seems to be an elegant example of evolution in action," says Dr. Ian Barnes, an evolutionary biologist at London's Natural History Museum, said in 2010 statement. "It flags up the importance of a very recent aspect of our evolution as a species, the development of cities as a selective force."

4. Our brains are shrinking.

While we may like to believe our big brains make us smarter than the rest of the animal world, our brains have actually been shrinking over the last 30,000 years. The average volume of the human brain has decreased from 1500 cubic centimeters to 1350 cubic centimeters, which is an amount equivalent to the size of a tennis ball.

There are several different conclusions as to why this is: One group of researchers suspects our shrinking brains mean we are in fact getting dumber. Historically, brain size decreased as societies became larger and more complex, suggesting that the safety net of modern society negated the correlation between intelligence and survival. But another, more encouraging theory says our brains are shrinking not because we're getting dumber, but because smaller brains are more efficient. This theory suggests that, as they shrink, our brains are being rewired to work faster but take up less room. There's also a theory that smaller brains are an evolutionary advantage because they make us less aggressive beings, allowing us to work together to solve problems, rather than tear each other to shreds.

5. Some of us have blue eyes.

Originally, we all had brown eyes. But about 10,000 years ago, someone who lived near the Black Sea developed a genetic mutation that turned brown eyes blue. While the reason blue eyes have persisted remains a bit of a mystery, one theory is that they act as a sort of paternity test. “There is strong evolutionary pressure for a man not to invest his paternal resources in another man’s child,” Bruno Laeng, lead author of a 2006 study on the development of blue eyes, told The New York Times. Because it is virtually impossible for two blue-eyed mates to create a brown-eyed baby, our blue-eyed male ancestors may have sought out blue-eyed mates as a way of ensuring fidelity. This would partially explain why, in a recent study, blue-eyed men rated blue-eyed women as more attractive compared to brown-eyed women, whereas females and brown-eyed men expressed no preference.

Now Ear This: A New App Can Detect a Child's Ear Infection

iStock.com/Techin24
iStock.com/Techin24

Generally speaking, using an internet connection to diagnose a medical condition is rarely recommended. But technology is getting better at outpacing skepticism over handheld devices guiding decisions and suggesting treatment relating to health care. The most recent example is an app that promises to identify one of the key symptoms of ear infections in kids.

The Associated Press reports that researchers at the University of Washington are close to finalizing an app that would allow a parent to assess whether or not their child has an ear infection using their phone, some paper, and some soft noises. A small piece of paper is folded into a funnel shape and inserted into the ear canal to focus the app's sounds (which resemble bird chirps) toward the child’s ear. The app measures sound waves bouncing off the eardrum. If pus or fluid is present, the sound waves will be altered, indicating a possible infection. The parent would then receive a text from the app notifying them of the presence of buildup in the middle ear.

The University of Washington tested the efficacy of the app by evaluating roughly 50 patients scheduled to undergo ear surgery at Seattle Children’s Hospital. The app was able to identify fluid in patients' ears about 85 percent of the time. That’s roughly as well as traditional exams, which involve visual identification as well as specialized acoustic devices.

While the system looks promising, not all cases of fluid in the ear are the result of infections or require medical attention. Parents would need to evaluate other symptoms, such as fever, if they intend to use the app to decide whether or not to seek medical attention. It may prove most beneficial in children with persistent fluid accumulation, a condition that needs to be monitored over the course of months when deciding whether a drain tube needs to be placed. Checking for fluid at home would save both time and money compared to repeated visits to a physician.

The app does not yet have Food and Drug Administration (FDA) approval and there is no timetable for when it might be commercially available. If it passes muster, it would join a number of FDA-approved “smart” medical diagnostic tools, including the AliveKor CardiaBand for the Apple Watch, which conducts EKG monitoring for heart irregularities.

[h/t WGRZ]

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