10 Things About Humans Biologists Can’t Explain

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Compared to our ancestors, we’ve come a long way in our scientific understanding of our own species – especially in the last decade or so. With some unprecedented advances in fields like medicine, neuroscience, and evolutionary biology in the past few years, we’re now much closer to understanding our place in the universe – at least scientifically, if not philosophically – than we’ve ever been. 

Despite all that, though, there are quite a few mysteries about the human race that we’re still not able to solve, no matter how hard we try. In fact, some of them get more baffling the more we try to understand them. As our improved tools and techniques get better at solving long-standing riddles about how our species works in most areas, for a handful of them, all they do is shine a light into the hole and reveal just how deep and dark it actually is.

10. Memory

On the face of it, memory isn’t a difficult thing to understand. We experience something, encode it on our brain as learned information, and retrieve it at a later date if we need to access it again. The procedure is almost entirely involuntary, unless we’re trying to cram for a test or otherwise actively pushing our brain to store some specific information for a specific use later.

While the process of storing memories is fairly well understood, what we simply don’t get is how the brain retrieves that information, as memory recall is one of the biggest mysteries of neuroscience (which is saying a lot, as the brain has a lot of other mysterious features). We just don’t know what happens in the brain whenever the frontal cortex sends a signal meant to retrieve a particular memory, or even what parts of the brain are utilized in the process, except the hippocampus, where we know new memories are encoded when they’re formed.

9. Aging

For thousands of years, aging has remained a particularly irksome problem for the human race, as it ensures that no matter how healthy we keep ourselves, all of us die at some point. What most people don’t realize, though, is that there’s no scientific or biological reason behind why we age that we know of. In fact, it’s entirely possible to stop the damage to living cells caused by aging. In one study, researchers were able to restore the vision of mice by reversing the damage that accumulates in their DNA as they aged, effectively restoring those cells to a younger, more functional state.

That tells us that we do have a fair understanding of what aging does to the body, though we still don’t know why it happens at all. For one, the stem cells are programmed to produce less and less red blood cells as we age, though no one’s sure if it happens because the cells are just programmed to do so from birth, or if there’s something in our environment that causes it. The mitochondria – the power producing part of the cell – also plays an unexplained role, as it gets damaged and functions less efficiently over time for all of us, ultimately causing death, though again, we’re not sure exactly what causes it. 

8. Sleep

Why do we sleep? Most of us assume that it’s the body’s natural way of resting after a long day, though that hardly explains it. We’ve to sleep for the same amount of time no matter how much physical or mental exertion we’ve gone through in the day, or even if we’ve spent the whole day doing nothing but sitting on the couch. Evolutionarily speaking, too, falling almost unconscious for eight hours or so everyday would have been detrimental to our survival during our hunter-gatherer days, suggesting that whatever’s happening inside the body during the time must be very important. 

While there are plenty of theories, there’s still no consensus among the scientific community as to why we sleep at all. One of them is that it’s an energy-saving state without much activity that allows the brain to recuperate, though research has found that the longer you stay awake, the more active your brain is when you finally get to sleep. There’s also all the dreams that only happen during the REM phase of sleep, the duration of which decreases as you age. The brain is hardly inactive during that time, even if it’s active in a slightly different way than it is when we’re awake. 

7. Laughter

No matter where you go in the world, laughter is something all humans understand. Hardly anyone, though, understands why we do it, exactly when we do it, or even what happens inside the brain when we laugh. Scientifically speaking, laughter is one of the longest-standing mysteries of human behavior, and we’re still no closer to understanding it.

Contrary to popular belief, we don’t always laugh in response to something happy or positive. It can happen with tickling, drugs, mental disorders or a variety of other things not related to happiness in any way. It’s also hardly ever in response to something funny, as studies have found that most laughter is involuntary and in response to social cues that – on their own – aren’t humorous at all. It’s also not a strictly human response developed for our unique social environment, either; many primate species laugh, too. 

Then there’s the question of exactly what parts of the body are involved when we laugh. If you thought it was just the brain, it’s not, as for quite a few people, laughing engages motor functions in other, seemingly-unrelated parts of the body, such as the legs, hands and torso

6. Left-Handedness

The prevailing theory about why some people are left-handed is that it depends on the differences between the right and left part of the brain. Studies, however, prove that it has nothing to do with the brain. It’s a decision taken by the spinal cord well before the brain has fully developed inside the womb, and we still don’t have a reliable way to predict – even with genetics – whether someone would turn out to be left or right handed. Then there’s the question of why around 90% of the population is right-handed, as it sounds like something that’d be more or less evenly spread out. As it stands, it’s another one of those mysteries that we’ve known about for a while, though still haven’t been able to solve despite our ever-evolving arsenal of scientific tools.

There’s also the evolutionary and social aspect of it. Being left-handed is a clearly disadvantageous trait, as everything seems to be designed keeping right-handers in mind. Historically, too, left-handedness has been seen as a sign of evil in many societies around the world – the word ‘sinister’ actually comes from a latin word that means ‘ on the left side’. If it was genetic – and we have no reliable research to prove that it definitely is – the trait should have been weeded out of the population by now. 

5. The Placebo Effect


On paper, the Placebo effect – short for any medical remedy that’s effective just by the way of believing that it is – has no reason to work. It flies in the face of the modern scientific method involved in medicinal research, and sounds like one of those ‘mind over matter’ schools of alternative healthcare that actual doctors hate so much.  

Look at the research backing it, however, and it starts to become clear that the phenomenon isn’t just real, but is also backed by science in ways that we simply don’t understand. Many studies have concluded that placebos work in a wide variety of use cases, even when you explicitly tell the patient that they’re being given a medicine that doesn’t contain any medicine at all. Bafflingly enough, the opposite of the Placebo – the Nocebo, wherein the condition of the patient has deteriorated merely by telling them that the medicine won’t work, despite continuing to administer the real thing – has been found to be equally effective. Moreover, the effect is only getting stronger and more powerful with time; another one of its many aspects that we’ve just barely started to notice, let alone fully understand.

4. Anesthesia

For most of our history, people going through surgery haven’t had the option to do it without all the pain, save for mild pain relievers like opium that do almost nothing for serious procedures like amputations. The advent of anesthesia changed that, and with it the world of healthcare, around 170 years ago. For most of us today, it’s unimaginable to think that it hasn’t always been the norm.

While anesthesia is undeniably awesome, we still don’t quite understand exactly what it does to the brain. It has to do with the larger question of how consciousness works – which we’d get to in a bit – though anesthesia is a particularly mysterious part of the equation.  

For one, we have no idea why it just affects the brain and no other part of the body. Even in the brain, patients under anesthesia seem to have the rest of their functions – like cognitive ability – active and working like when they’re awake, except they’re unconscious and don’t seem to feel any pain. We simply have no idea what part of the brain it changes, either, and whether it works the same for everyone, all of which is probably why anesthesiologists are by far the highest paid medical professionals almost everywhere in the world.

3. Sex

There’s no doubt that sex is amazing and a wide variety of creatures found on Earth use it for reproduction, though evolutionarily speaking, it doesn’t make a whole lot of sense. Scientists have been trying to answer why we developed sexual reproduction in the first place for a while – as it provides no immediate benefits over asexual reproduction – though to little success.

The prevailing theory so far has been that it helps weed out harmful genes from the pool, which may as well be true, though that’s nowhere near worth the massive evolutionary cost it comes with. Sexual beings only pass on half of their genes to their offsprings, as one half of the population – males – don’t reproduce. That’s massively detrimental to survival in a competitive place like Earth – as asexual creatures pass 100% of their genes without all the hassles of going out and trying to find a mate suitable for reproduction. 

Moreover, one study proved that the rate of harmful mutations in any given species is far too low to justify its role in the evolution of sex. Despite that, around 99% of all multicellular organisms on Earth reproduce sexually, suggesting that it must have some clear benefits over asexual reproduction. What they are, however – apart from the obvious fact that sex feels great – is still one of evolutionary biology’s biggest mysteries.

2. The Microbes Inside Us

We’ve known for a while that the human body isn’t all human, as microbes make up a sizable part of our total DNA. While there have been exaggerated claims about how much that is in numbers – some have even inaccurately claimed that more than 90% of it is microbes – it’s only in recent years that we’ve found out that the true ratio of human cells to microbes in our body is somewhere around 1.3:1. That may be quite surprising in itself, though if we dig a bit deeper into the subject, it gets weirder. 

According to a recent study, our body isn’t just mostly made up of microbes, but about 99% of them are completely alien to us, as well as far more diverse than we previously thought. They don’t match up with our genetic databases on any of the microbial species we know of on Earth, and we’d require entirely new classifications to even document them. 

Moreover, we don’t know exactly what it is that these microbes do in the body, either. While we know that the babies that are unable to foster a diverse colony of gut bacteria at birth go through many health problems later in life, we only have theories and guesses as to why that is. 

1. Consciousness

The question of ‘what is consciousness?’ has been answered by different professionals in different ways over the years. Philosophers use it as undeniable proof of the significance of our species’ place in the universe. Astrophysicists see it as only one of the many improbable outcomes to come out of an infinite universe with infinite possibilities, and so on. For neuroscientists and biologists, though, the answer isn’t that clear, to the extent that it’s perhaps the biggest mystery of our body we know of. 

Biologically speaking, what’s the line that separates the physical lump of biomass, brain, neurons and all the other things that make up our body from the conscious beings with emotions and the ability to experience the world around them that we all are? If we assemble a fully-functioning model of our body in the lab, simulate all the connections between all the different parts with our advances in prosthetic tech, and try to get it to come alive, there’s no doubt that we’d fail. After all, if we’re just a random grouping of molecules and atoms that have – through all the random processes that have given birth to life on Earth over billions of years – come alive, we should be able to easily replicate it in controlled conditions. 

And yet, we can’t. Many people would say that it’s the same difference as being alive or dead, though looking at how many people suffering from disorders that render them unconscious are still alive in every sense of the word, that doesn’t seem to be it. Is it just our ability to form subjective emotions? Scientists are already hard at work trying to implement AI to make robots that can feel emotions, as it’d make them much better at whatever job they’re meant to do. There’s no doubt that they’d easily succeed, too – AI has already advanced far enough to do that – though no one would call them ‘conscious’ in any way. What is it about the specific grouping of our body and the brain that controls it that makes all of it greater than the sum of its parts?

As it stands, it’s not a question that we’d be able to answer any time soon. We’ve used neuroscience, quantum mechanics, evolutionary biology, and a bunch of other fields to try and understand exactly what makes us conscious, though to little success. If we can solve it, however, it could open doors in a lot of other fields and massively improve the quality of life on Earth, especially for people suffering from rare, long-term diseases that directly attack whatever it is in the brain that makes it conscious.


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