5 Mysteries of the Human Body Science STILL Can't Explain

Hi, it's Mike Chen. In the past few centuries, we, well, most of us, have discovered that the world is actually round and not flat, and we won't fall off if we go over the edge. We found out that the center of our galaxy is the Sun, not the Earth, and there are infinite other galaxies apart from our own. It is amazing how researchers have been able to uncover mysteries millions of miles away from our planet, making one wonder why they still don't have answers to some of the more personal questions, maybe some involving our own anatomy. So in this video, we're going to give you some of the greatest unsolved mysteries of the human body. We'll start with number five, and this is a question that some 10% of the human race has been asking themselves for the longest time. Why am I left-handed? And of course, a right-handed person would think, okay, so what's the big deal? A hand's a hand, left or right, as long as it works fine, it's all good. But the lefties know better, because most mass-produced equipments or mugs or anything are actually designed for the right-handed people. This is everything from scissors to desks to spiral notebooks, seemingly everyday equipment that are a nightmare for left-handed people. And yet, that is nothing compared to how they were treated in the ancient times, when being left-handed practically meant that you're the spawn of the devil. In fact, the English word sinister, which basically means evil, was derived from the Latin word sinistra, which originally meant left. A study published in 2013 states that left-handedness is caused by gene and gene mutation, which influence the so-called left-right asymmetry in the body and the brain. The study, which involved some 2,600 people, explains that the more gene mutation a person has towards one direction, left or right, the more one will likely use that side as the dominant hand. Although this still doesn't explain why only about 1 out of 10 people are left-handed. Other experts believe genetics are only responsible 25% of the time, saying that it does tend to run in the family, but much less so than other inherited traits like height and intelligence. And to make it more mysterious, they say that left-handedness is just a random selection. Next up, Number 4. Why Do Humans Have Different Blood Types? It has frustrated many physicians for most part of history, knowing that there was a way they could have saved more lives by giving blood to a patient. The first recorded blood transfusion happened in the 1600s to disastrous results when a doctor injected calf's blood into a madman, which resulted in his death soon after. This incident discouraged doctors from using blood to cure a patient again until the 19th century, when British physician James Bundle got tired of watching women die of childbirth. He knew that blood transfusion was a possible solution and suspected that human patients should only receive human blood. So he designed a system of funnels and tubes to transfuse blood from a donor, then collected a total of 14 ounces of blood from several donors to test on his first patient, a man who was bleeding to death. This had a relatively successful result, as the patient felt better for two days before ultimately dying as well. The same procedure was tested on ten more subjects, only four of them lived. It wasn't until the 1900s that they finally found out why blood transfusion sometimes ended up in tragedy. It was when Australian biologist and physicist Karl Lindsteiner discovered that there are different blood types, and mixing one with another could be fatal. By testing the blood of his colleagues, he found out that not all blood types match, and when they didn't, the mixture produces tiny clumps. Transfusing the wrong blood type would cause tiny clots that would clog the blood vessels, a very dangerous situation for our patients. Lindsteiner was responsible for identifying blood types A, B, and O, with AB found later on. But his discovery definitely paved the way for safe blood transfusion in the past century. And yet the question remains, why do humans have different blood types? Some say blood types evolved along with our ancestors, as well as the kind of food they ate at the time. It was believed that type O blood arose from the hunters of Africa, type A with the dawn of agriculture, type B around 10,000 to 15,000 years ago along the Himalayan highlands, and AB, the modern combination of the two. However, a separate study to test this theory in Belgium says there is no direct connection between our blood type and supposed diet. Then there are others who say different blood types evolved to fend off natural diseases. For example, studies show that people with O and B blood types have stronger resistance to malaria, while group A is more resistant to cholera. Despite the attention this topic has received from many scientists, no conclusive findings has ever been made, and the evolution of blood types remains to be a mystery. 3. Why Do We Yawn? Everybody yawns. Cats, dogs, humans, even babies still inside the womb all do this one contagious act. And though we know that it often happens when we're sleepy or when we see someone else yawn, we don't know exactly why. Among the first theories can be traced back to the father of medicine, Hippocrates, who theorized that yawning precedes fever and is the body's way of removing bad air from the lungs – a mistake that took years to debunk. The age-old explanation was that yawning also allows us to inhale oxygen-rich air which enters our bloodstreams and help us feel more awake. Unfortunately, this too remains to be a myth, as no concrete evidence has ever been found to prove it. However, in 2007, psychologist Professor Andrew Gallup conducted a series of studies that brought him closer to finding out why we yawn, and he says it's because yawning actually cools the brain. Because the human brain is the central processing unit of our body, it takes up 40% of our metabolic energy and does heat up more than our other organs. The study found that when we yawn, that big gulp of fresh air travels through our blood vessels and as we expand our jaws, we increase the rate of blood flow to the skull, bringing cooler blood to the brains. Gallup says we yawn at an average rate of 8 times a day, mostly before we fall asleep when our body and brain temperatures are at their highest point, and when we wake up when But then if that is the real reason for yawning, why is it so contagious? Another study suggests that we yawn as a sign of empathy, much like smiling when we see someone smile and frowning when we see someone frown. Experts say that yawning is contagious in 60-70% of the population and that people yawn just by seeing a photo of yawning or simply reading about it. They also found that this occurs more often to individuals who scored high in emphatic understanding. Although it seems as if scientists have made headway on the study of yawning in the past decade, they have yet to conclude whether their findings are sufficient to solve the mystery of yawning. And I don't know if it's a good thing that people out there are actually being paid to find out why we yawn. Next up, Number 2. Why the sudden twitch just when we're about to sleep? Most of us are familiar with the sensation, the feeling of falling from a tree combined with a blast so realistic you'd think you actually fell. We often mistake it for a hallucination, a dream, or worse, a nightmare. But this is actually a natural phenomenon that researchers say happens to 60-70% of the population. A hypnic jerk or sleep alert is the sudden muscle spasm that escapes just before we fall asleep. Researchers say this is the result of the battle between the reticular activating system or the part of the brain that keeps you awake and the ventrolateral preoptic nucleus which controls sleep. As each brain system struggles to remain in charge, the involuntary jerk occurs. Some theories suggest that the hypnic jerk is an evolutionary reflex that once upon a time kept tree-dwelling primates safe while they were snoozing. Although this happens to more than half of the human race, researchers don't see it as a medical condition or a phenomenon that requires immediate attention and so no conclusive study has ever been made. But what scientists are very curious about brings us to the number one item in this video, dreams. Specifically, why do we dream? Considering it happens to every single one of us every single night, the fact that it remains a mystery is fascinating. The thing is, we don't know a lot. But we do know that dreams are often at their most vivid during REM, or the phase of our sleep characterized by rapid eye movement. A study by French doctor Michel Jouvet found that during REM, our brain activity is similar to that of when we are awake, although it is combined with low muscle tone throughout the body. So again, why does dreams occur? Well, there are a few theories. One, dreams help our brains sort out all the memories we made during the day. From something as routine as what we have for breakfast to major incidences like getting a promotion at work, it definitely has a lot to process in our 6 to 8 hours of sleep. Experts believe that dreams aid the brain to choose which memories to keep and which to let go. A particular study shows that people who are learning new things during the day, for example, an American studying the Korean language, tend to have more dream activity at night, further supporting the theory that dreams have a hand in selecting which short-term memories to convert into long-term. There are also those who think that dreams are a form of consciousness that unites past and present experiences to prepare us for the future, and that they work as the brain's defense against possible threats and challenges. Another theory is that dreams reflect our true emotions. To be productive during the day, our brains work full-time to concentrate on our daily tasks like that final exam for a college student or the big presentation for an advertising agent. Succumbing to our emotions like panic, fear, and anxiety would distract us from our goals. It is during sleep when everything slows down and we lose control of how our mind works and our emotions struggle to have a space in our brains. Researchers believe that a fear of a possible imminent breakup or high hopes for a proposal will follow up in symbolic scenarios in our dreams. Basically, they say that dreams help us maintain our psychological and emotional balance. Yet, there are those who believe that dreams are nothing but random and insignificant byproducts of the brain, especially during REM when we have an excess of neural activity. They say that these are just thoughts that don't get a chance to show up when we are awake and are too focused on other more important matters. Of course, many more theories about dreams are floating around in the scientific world. But as extensive as some of the studies are, experts admit that until they fully understand the workings of our complex brains, they will never comprehend the true purpose of dreams. And I always thought that maybe dreams were kind of our way of connecting with each other. And maybe when we're sleeping, we're actually watching what we're doing in a different dimension. I don't know. I just thought it was really interesting. That, of course, is just my opinion, but let me know yours in the comments below. Thank you all so much for watching. I'll see you later.