100 Mysteries of Science Explained

by Popular Science

  In 2006, developmental psychologist Judith Rich Harris suggested a far more gruesome mechanism. As humans became hairless as a result of chance mutations, they split geographically from their hairy cousins. Once hairlessness was in style, any hirsute baby born to a hairless tribe was abandoned. As hairlessness became the norm, a thick fur coat would have become so rare that hairy humans would have been seen as animals and hunted for food. The days before waxing were savage indeed.

  The romantics of the world believe in love at first sight. Science, however, suggests that a number of chemicals in the brain, as well as genetics and background, all shape the process of falling in love and, perhaps more importantly, how long love lasts.

  What Is the Science Behind Love?

  Helen Fisher is a biological anthropologist at Rutgers University in New Jersey and a leading researcher of the science behind love. She divides the process of falling and staying in love into three stages—each driven by corresponding hormones that play a part in directing our actions. First, humans meet someone who excites them sexually, with testosterone—in both men and women—playing a part. Once two people establish a mutual attraction, they move on to romantic love, the head-over-heels stage of a relationship.

  Working in the brain at this point is dopamine, which creates the emotional high of being in love. At the same time, other chemicals, including adrenaline, make the heart pound a little harder when the beloved is around.

  The third stage, sustaining a loving relationship, is possible, in part, because of oxytocin. Scientists have studied the role this hormone plays in creating a bond between a mother and her child. Oxytocin also helps build the bonds of attachment between partners. Studies done by Beate Ditzen at the University of Zurich indicate that the hormone makes lovers more able to express their feelings and be supportive of each other. Oxytocin also reduces cortisol, a hormone that stimulates stress. Genes may play a part in how receptive someone is to the power of oxytocin.

  Once we find the right person, our body responds in particular ways. Couples with successful, lasting relationships show fewer signs of stress (measured by the fight-or-flight syndrome scale) when they’re conversing, while couples facing rocky times show signs of stress even when talking about mundane things. This increased stress between partners can affect their immune and endocrine systems, raising the risk of disease.

  Despite these findings, Fisher believes that biology alone does not determine whom we fall in love with and whether the relationship lasts: “your culture, your background, and…your upbringing” also play a role. But below the surface of our thoughts, biology does indeed operate in shaping our love lives.

  Why Does Sunlight Make Some People Sneeze?

  Gesundheit! You step out into bright sunshine after spending a couple of hours in a dark movie theater and immediately experience a sneezing fit. Does this happen to you often? Does it happen to your children?

  The Sun induces sneezing in 10 percent of the U.S. population, says Louis J. Ptácek, a neurologist at the Howard Hughes Medical Institute in Maryland and a professor at the University of California at San Francisco. Just how and why this happens, though, has remained a mystery ever since Aristotle raised the question some 2,300 years ago.

  Research suggests that the photic sneeze reflex, or PSR, is inherited, but scientists have yet to pinpoint the gene or genes responsible. “There’s precious little known about PSR, and part of that is because it’s not a disease,” Ptácek says. “No one dies from it.”

  One theory is that the gene involved—whatever it is—crosses wires in the brains of those with PSR. For these people, light entering their eyes activates their brain’s visual cortex but also stimulates the motor region that causes the diaphragm to quickly contract, forcing a sharp burst of air out through the nose.

  Although Sun-triggered sneezing is more of a quirk than a serious condition, Ptácek says, understanding the science behind it could shed light on the underlying biology of other reflex phenomena, such as certain types of epilepsy.

  The question “what is consciousness?” Is really two questions: why are we awake and aware, and how does a physical network of electrical impulses give rise to our subjective experiences?

  What Is Consciousness?

  Perhaps not surprisingly, neither scientist nor philosopher has developed a convincing answer to either question beyond Descartes’ “cogito ergo sum” (I think, therefore I am).

  In the 1970s, Tulane University biopsychologist Gordon Gallup developed the “mirror test” of self-recognition. If a person or creature recognizes a red dot on his or her forehead in the mirror, the test presumes that the subject is conscious. The mirror test grew out of a modern interpretation of Descartes’ maxim that knowledge of self implies consciousness.

  Yet it remains unclear why some animals (e.g., humans, primates, dolphins, magpies) pass the test and most others don’t. Researchers generally believe that there are specific brain centers that are crucial to awakening and that there is probably something about the complexity of the network of electrical connections in the brain that gives rise to consciousness. How exactly one leads to the other remains a mystery.

  Trying to distill the subjective human experience from individual parts of the brain has proven an even more futile undertaking. Adherents of a field called “integrated information theory” argue that some systems are too complex to be understood by breaking them into their constituent parts, and certainly the brain is the most complex biological system known to mankind. This theory gets us closer to understanding why conventional approaches can’t explain consciousness, but doesn’t go as far as to explain how consciousness should arise out of complex network effects.

  With the failure of classical physics to provide an explanation for consciousness, physicists have proposed that the mind may arise via quantum mechanical processes. (Quantum mechanics is the study of relationships between subatomic particles.) Some interpretations of quantum mechanics imply that the world only takes the order it does when observed by a conscious individual. Conversely, the resolution of the random, quantum universe within very small structures in the brain may itself trigger consciousness. However, if these structures do exist, scientists have yet to discover them.

  If the search for consciousness seems hopeless at this point, there may be good reason. University of Miami philosopher Colin McGinn believes that the mind is fundamentally incapable of understanding itself. If true, consciousness will forever remain the ultimate science mystery.

  Can the Food You Eat Affect Your Descendants’ Genes?

  A recent study suggests that the same vitamins in spinach that perform instant wonders for Popeye’s biceps might pack longer-lasting effects, such as dictating the hair color and health of future generations. Your lunch order could make a bigger difference than you think.

  A 2006 study led by David Martin, an oncologist at the Children’s Hospital Oakland Research Institute in California, tested whether a mouse’s diet alone can affect its descendants. The researchers fed meals high in minerals and vitamins—such as B12, which fortifies leafy greens—to pregnant mice that have a gene that makes their fur blond and also increases the likelihood that they will grow obese and develop diabetes and cancer. On the new diet, the mice produced brown-haired offspring that were less vulnerable to disease. Even when the second-generation mice were denied the supplements, their offspring retained the improved health and still grew dark fur coats.

  Martin’s study isn’t the first to note this type of generation-spanning phenomenon. In 2002, Swedish researchers digging through century-old records determined that a man’s diet at the onset of puberty affected his grandson’s vulnerability to diabetes. The study tracked 303 men, and those with an abundant supply of food were four times as likely to have grandchildren die of diabetes. Though far from exhaustive, the study indicated that genes are more susceptible to outside forces than has been commonly believed.

  But don’t start your teenager on that all-spinach die
t just yet—scientists warn that the influence of diet on human gene expression is not fully understood. Nevertheless, Martin says, “The general implication for human health is an obvious one: An external agent can have an effect for a very long time. Given how long human generations last, the environmental exposures experienced by a pregnant mother can still have an effect 100 years later.”

  Are Telomeres the Key to Immortality?

  Thanks to recent breakthroughs in genetics research, we may be on the verge of discovering a fountain of youth in our own genetic material.

  In 2009, three researchers—Elizabeth Blackburn of the University of California, San Francisco, Carol Greider of Johns Hopkins University, and Jack Szostak of Massachusetts General Hospital—won the Nobel Prize in Medicine for their work linking the aging process to telomeres. Telomeres are clusters of DNA that cap the chromosomes of complex organisms, protecting the rest of the genetic code during cell division. As cells age, these caps grow smaller, exposing the DNA to breaks and mutations that can lead to cancer or cell death.

  These discoveries hint at a connection between telomeres and the broader aging process. People of an advanced age do tend to have cells with shorter telomeres when that cell is of a type that replicates frequently. Analysis of the white blood cells of Hendrikje van Andel-Schipper, a Dutch woman who lived to the age of 115, revealed extremely short telomeres on such cells compared with cells that divide infrequently (such as nerve cells). Similarly, patients who suffer from accelerated aging diseases have also been shown to possess much shorter telomeres than unaffected individuals of a similar age.

  So can we prevent or even reverse aging by preserving our telomeres? Maybe. While early results indicate a correlation between shorter telomeres and aging, this does not by itself imply a causal relationship. It could be that the two processes simply coincide or even that aging itself is what causes telomeres to shrink. And even if the relationship is causal and significant, how do we take advantage of this fact? Gene therapy is still in its infancy. Worse still, telomerase, the enzyme that inhibits the decay of telomeres, is also present in 90 percent of cancerous cells; by preventing cell death, we may grow malignant tumors.

  It’s worth considering that this relationship serves a purpose. Our genetic code may have evolved to encourage cells to die in order that they might not grow into cancer. If there is indeed a fountain of youth, it may behoove us to blaze a different path on our way there.

  Why Do We Have an Appendix?

  For decades, scientists have thought that the appendix no longer serves a purpose for the human body. That notion came in part from Charles Darwin. He theorized that the appendix and a section of the small intestine it’s attached to, the caecum, once played a role in digestion for our ancestors.

  The caecum was where intestinal bacteria used to digest leaves were found. But, according to Darwin’s thinking, as humans evolved and began eating more fruit, which was easier to digest, the caecum shrank, and the appendix was no longer necessary.

  Recent research, however, suggests the appendix is still important. In 2007, scientists at Duke University Medical Center said circumstantial evidence convinced them that the appendix stores helpful bacteria.

  When an infection causing intestinal stress strikes, diarrhea forces most of the good bacteria out of the body along with everything else in the digestive tract. But some of the good bacteria take refuge in the appendix. The tissue there is similar to tissue in the lymphatic system, part of the body’s immune system. While the intestinal bacteria hide out in the appendix, the lymphatic system protects them from the illness ravaging the body. When the illness is over, the bacteria go back into the intestinal system to repopulate it with helpful bacteria.

  This role for the appendix might be more important in parts of the world where sanitation is suspect and diarrhea common. Duke University Medical Center professor William Parker, who led the 2007 study, says, “In industrialized societies with modern medical care and sanitation practices, the maintenance of a reserve of beneficial bacteria may not be necessary. This is consistent with the observation that removing the appendix in modern societies has no discernible negative effects.”

  Parker has continued to study the appendix. Among his recent findings: More mammals have an appendix than previously thought (50 out of 361 animals studied, including rabbits, wombats, and opossums), and the appendix has evolved at least 32 times among them. What’s still unsure is, if the appendix plays such an important role in preserving health, why don’t even more mammals have one?

  We’ve heard that everyone’s fingerprints are unique, and we know that law enforcement officials often use them to track down criminals. But why humans have those prints is still an open question.

  Why Do We Have Fingerprints?

  Many scientists once thought fingerprints help us hold onto objects. From an evolutionary perspective, getting a better grip on tools or weapons would have made life easier for early humans. In 2009, Dr. Roland Ennos of Manchester University designed an experiment that tested the gripping power of our fingerprints. He used a machine equipped with weights to pull strips of Perspex, a kind of acrylic, across a subject’s fingertips. The machine measured the amount of friction created as the acrylic passed over the tip. In the real world, a high amount of friction between two solid objects in contact with each other would indicate a better grip. In the experiment, the fingertips created some friction on the acrylic, but not as much as Ennos had expected.

  Ennos compares our fingerprints to the tires on a race car. Ridges in the tire reduce the surface area of the tire in contact with the road, which reduces friction. The ridges on fingertips have the same effect. Smooth skin has more surface area and so more friction when in contact with an object than fingerprints do. Where fingerprints might provide more grip, Ennos suggested, is when we grab objects with rough surfaces. The ridges on the fingertip extend into the object’s depressions and increase the contact area.

  At almost the same time Ennos was doing his research, a team of French scientists suggested a possibility for why we have fingerprints. They think fingerprints help gather information about objects we touch and send signals about them to the brain via the nervous system. In their study, the scientists outfitted one artificial hand with grooves on its tips to simulate fingerprints. Another robotic hand had smooth “skin.” The hand with the fingerprints was much more sensitive to different surface textures. According to Georges Debrègeas, who helped lead the study, “We believe that fingerprints act like antennas, amplifying the signal.”

  Other theories about the possible role of fingerprints suggest that they help to divert water and keep our hands dry or that they prevent blisters. To support that second theory, Ennos notes we rarely get blisters on our fingers or the other parts of the body with natural ridges, such as the palms of our hands and the soles of our feet. The ability to pin down what role our fingerprints actually play could help scientists develop more lifelike prosthetic hands.

  What Happens When You Die?

  Different religions throughout the world claim to understand what happens to us after we die. Scientists are not as certain. They can explain, of course, what happens in and to our bodies at the moment of death and just after.

  To doctors, clinical death comes when the heart goes into cardiac arrest, which can occur from a variety of causes—from a car accident to illness. In effect, most of us die from cardiac arrest. The heart stops beating, cutting off the flow of blood, and thus oxygen, to the brain. Next comes biological death, as the brain, other organs, and cells stop functioning because of a lack of oxygen.

  Before reaching that point, however, in the window between clinical and biological death, doctors have been able to start the heart beating again, thus preventing death, or irreversible brain damage due to lack of oxygen. Thanks to research over the past several decades, doctors can now revive people whose hearts have stopped beating for as long as two hours, without any brain damage.

  Sam Parnia
, who studies heart resuscitation at the State University of New York at Stony Brook, says doctors now know that some cells, including brain cells, can function without oxygen for longer periods than once thought. After cardiac arrest, Parnia says, people enter a “gray zone, where death can be reversed.” The key is chilling the body by about seven degrees as quickly as possible, so doctors can begin the resuscitation process.

  Parnia’s work has convinced him that even after cardiac arrest has led the brain to shutdown, a person’s consciousness can remain intact for up to several hours, though in what Parnia calls a hibernated state. That fact could explain the “near-death experiences” (NDEs) some revived patients report. But beyond those few hours, most researchers believe, consciousness disappears, since, as scientist Richard Dawkins has said, the brain creates consciousness. Without a functioning brain, there can be no consciousness.

  Not all scientists, though, share this view. Dr. Robert Lanza believes that quantum physics allows for the possibility that human consciousness is separate from the brain, and that consciousness continues after the body dies. Space and time are not external realities, he argues, but products of our consciousness. The world, in reality, has no space or time, and “death does not exist in a timeless, spaceless world.”

  Whatever religions teach about life after death, it’s clear science is still trying to solve the mystery of what happens after we die. David Wilde, a British research scientist studying NDEs said in 2014, “We are still very much in the dark about what happens when you die ….”