10 Biological Mysteries We Can’t Explain

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Biology is a far-reaching field that includes the study of all living organisms. Given the vast cache of information that this contains, it is no surprise that it also includes a lot of uncertainties.

Today we take a look at some of the greatest mysteries from biology that keep scientists awake at night.

10. Darwin’s Abominable Mystery

We start off with a classic, one which Charles Darwin himself referred to as an “abominable mystery” in a letter to botanist Joseph Dalton Hooker – the sudden explosion of flowering plants or angiosperms in the fossil record of the Early Cretaceous period.

If we are being specific, Darwin was only referring to dicotyle flowering plants in his letter, meaning the ones with two embryonic leaves, but over the decades, the question came to include all angiosperms – how did they diversify so fast in such a short period? Darwin himself was particularly vexed about this problem not only because it seemed to contradict his theories, but also because some of his opponents were using the mystery to advocate for “divine intervention.” 

In his later years, Darwin floated the idea that there might have been an undiscovered island or even a continent somewhere where angiosperms originated and evolved in isolation for millions of years before making their way into the rest of the world and into the fossil record known at the time. 

The issue has been puzzling biologists for almost 150 years. There are ideas – in early 2021, a new study from the University of Bristol suggested that flowering plants simply appeared millions of years earlier than previously thought, thus giving them more time to diversify. But without solid proof, Darwin’s mystery remains as abominable as ever.

9. Walking in Circles

Next time you find yourself in an open field, close your eyes and try to walk in a straight line. You’ll find that it is harder to do than you might expect. In fact, multiple studies performed over decades suggest that it might even be impossible. Time after time, people who have been blindfolded end up walking in circles, even though they think that they are walking straight.

Sometimes you don’t even need the blindfold. In one study done in 2010, the walkers were allowed to see and were simply asked to walk in a straight line on a cloudy day and still couldn’t do it. It seems that humans need an external focal point (like the Sun, or a mountain, or a tall building) in order to keep in a straight line.

Why exactly this is the case remains a mystery, as scientists have ideas, but no definitive answers. Years ago, they used to think that this could be due to a limb imbalance – one leg could be longer or stronger than the other one, which would cause an asymmetrical gait. The 2010 study ruled that out and, instead, the team behind it believes that the cause might be the inherently faulty nature of our vestibular system which is responsible for our balance. Normally, the brain would correct these small errors by using external landmarks for recalibration but, when those disappear, we end up walking in circles.

8. The Paradox of the Plankton

In ecology, there is an idea called the competitive exclusion principle, also known as Gause’s Law, which states that two species that are competing for the same limited resources cannot stably coexist. In the long run, one of the species will always have an advantage, no matter how minor, which will allow it to dominate the other species and even drive it to extinction. Scientists have seen this happen again and again, yet there is one group of organisms that seems to be exempted from the rule – plankton.

The so-called paradox of the plankton has been around since 1961 when it was first described by British ecologist G. Evelyn Hutchinson, who noted that most environments that contain plankton always have a diversified variety. He referred specifically to phytoplankton, which consists of microalgae, observing that most lakes have anywhere between 10 and 100 types of phytoplankton at any given time.

Of course, since Hutchinson’s time, our understanding of ecology has advanced. There are several hypotheses that could explain the paradox – the lack of long-term environmental equilibrium in lakes, predators eating the dominant phytoplankton, the unpredictability created when species compete for multiple resources. There are several possibilities, but we are still waiting on one answer which definitively solves the paradox.

7. The Sex Life of the Blue Whale

The blue whale is the largest animal that has ever lived on this planet. You would think that would make it relatively easy to track but, in fact, it is a very reclusive and solitary animal, especially when compared to other whales. There is much we still don’t know about the social hierarchy and interactions of blue whales, but it is their mating and birthing habits that remain a total mystery to us.

Don’t get us wrong, scientists have studied the anatomy of blue whales, so they know the mechanics involved, but they are in the dark when it comes to the mating behavior of the blue whales, or whey they go to breed and to give birth. We have yet to capture footage of two blue whales mating so we have to infer some things from the behavior of their close cousin, the humpback whale, which is far less shy when it comes to performing on camera.

Humpback whales engage in something called a heat run, where one or more males would chase a female whale over huge distances in the hopes of getting to mate with her. Back in 2017, some researchers believed they filmed, for the first time, two blue whales doing the same thing, but other experts remain unconvinced. 

6. The Yawn

The simple yawn – it’s something that all of us have done. Most of us do it every day, in fact, and it has been observed in other animals such as dogs, apes, even reptiles. It is a reflex where we suddenly inhale a lot of air and stretch the eardrums, and then we exhale. A lot of times we also stretch our limbs, and this combination is known as pandiculation. But the question remains – why do we do it?

Ideas on why we yawn date all the way back to ancient times when Hippocrates hypothesized that we did it in order to eliminate “bad air.” Then, during the 18th century, scientists came up with the slightly more scientific notion that yawning was a way for the body to increase oxygen levels in the bloodstream, thus raising our heart rates and making us more alert. This idea has also been dismissed nowadays since modern tests showed no oxygen increase following yawns. 

At the moment, the favored hypothesis suggests that yawning is used to cool down the brain, but it still remains an uncertain topic that will need more research before a conclusive answer.


5. ACHOO Syndrome

Did you ever sneeze after looking at the Sun or any other bright lights? Chances are that about a third of you answered “Yes,” while everyone else has no idea what we’re talking about. This is due to the photic sneeze reflex, also called the autosomal dominant compulsive helio-ophthalmic outburst, or ACHOO Syndrome, for short. It is a reflex where a sudden exposure to bright lights makes you sneeze. It affects up to 30 percent of people and we have no idea why. It might be a genetic quirk that can be inherited from your parents, or it could be brought on by a physical problem such as a deviated nasal septum.

Some of history’s greatest minds have suffered from ACHOO Syndrome. Aristotle believed that it was the heat of the sun that was responsible. During the 17th century, English philosopher Francis Bacon proved him wrong with a simple experiment, by walking out into the bright sun with his eyes closed. The heat was still there, but no sneezes. Then, when he opened his eyes, he sneezed. He thought that maybe the sunlight caused the eyes to tear up, and the extra moisture irritated the nose. Nowadays, we know that he was wrong, too, because the effect takes place too fast for this to happen, but what exactly causes ACHOO remains a puzzle.

4. No Oxygen Needed

Even the most basic concepts of biology can still be proven wrong or, at least, incomplete. Scientists from Tel Aviv University showed that back in 2020 when they accidentally discovered the first known animal that does not need oxygen to live. 

The organism in question is an 8-millimeter white parasite called Henneguya salminicola. It attaches itself to a wide variety of salmon species and causes a condition known as “milky flesh” or “tapioca” disease. We’ve known about this parasite for over a hundred years, but it wasn’t until scientists sequenced the genome of the Henneguya genus that they discovered that H. salminicola did not have any mitochondria, which enables aerobic respiration. 

In fact, the parasite didn’t have any mitochondrial genes, which suggests that the creature somehow evolved to obtain energy without oxygen, although how exactly it does this remains a mystery at the moment. Other organisms such as amoebas and fungi can do this, but H. salminicola is the first case of something which can be classified as an “animal” lacking aerobic respiration.

3. The G-Spot Dispute

Back in the 1950s, a German gynecologist named Ernst Gräfenberg claimed to have discovered “an erotic zone located on the anterior wall of the vagina along the course of the urethra that would swell during sexual stimulation.” His work was largely ignored by the general public until the early ’80s when a new team of scientists led by Professor Beverly Whipple published a book on the subject which became an international bestseller. They, too, touted the existence of this erogenous, but elusive zone on the female body. They even had a name for it – the Gräfenberg spot, or G-spot for short.

There’s just one problem – the G-spot doesn’t exist. Or maybe it does. But probably not. If that sounds a bit confusing to you, that is because the scientific community is still divided over the existence of the G-spot, even though they’ve been looking for it for almost 70 years. 

It seems that every few years, someone new comes along and claims that they have found the fabled G-spot, only to be refuted by other experts. Maybe one day, someone will finally locate it, but until then, the mythical G-spot remains the stuff of legends.

2. The Origin of Viruses

By this point, you don’t need us to tell you that, despite being submicroscopic, viruses can have a giant impact on the world. Technically, viruses are not “alive” because they cannot reproduce, instead replicating inside the cells of host organisms that can range from giant mammals to single-cell bacteria. This often has an adverse effect on the hosts and it can even kill them, so it is no surprise that scientists have studied viruses in-depth to try and learn as much about them as possible.

That brings us to a big question – where did viruses come from? Their origin is incredibly difficult to study because they didn’t leave behind a physical fossil record so we don’t even really know where to place them on the evolutionary timeline. One idea known as the “virus-first hypothesis” puts them at the very beginning, before the appearance of cellular life. 

Another notion called the regressive hypothesis suggests that viruses appeared when single-cell organisms began forming mutualistic relationships. Over time, the relationship became parasitic, as the smaller of the two organisms steadily became dependent on the other organism and lost the ability to build proteins, but still retained its ability to replicate and turned into a virus.

Then there is the progressive or the escape hypothesis, which suggests that viruses evolved from broken pieces of genetic material that managed to escape their original organisms and attach themselves to different ones.

These are the three classic hypotheses on the origin of viruses, but they are hardly the only ones and none of them have enough support to be considered definitive. Unless a major breakthrough comes along, it is highly likely that this is one topic that will forever remain a mystery.

1. The Cambrian Explosion

For billions of years, life on Earth was very basic, consisting mainly of single-cell organisms alongside very basic multicellular organisms. Then, around 540 million years ago, an event called the Cambrian Explosion happened, which saw an incredible divergence of species. In a period of around 20 million years, which is very short on an evolutionary scale, almost all major animal groups appeared in the fossil record. 

But what exactly caused the Cambrian Explosion? That is a question that does not have a categorical answer, even though many scientists have studied it. One popular hypothesis says that the event was triggered by a dramatic and sudden increase in the oxygen levels in the atmosphere, reaching levels similar to modern times. But then a different study argues for the exact opposite – that it was a lack of oxygen that led to the Cambrian Explosion, not an abundance.

Believers of the Snowball Earth hypothesis claim that primordial Earth could have suffered a massive ice age that froze most of the planet’s surface, and that it was the end of this ice age that triggered the rapid divergence of species. And then there are some who argue that the explosion wasn’t a singular event, but rather a series of “pulses of evolutionary innovation” that occurred one after another.

Without a doubt, the Cambrian Explosion was a crucial event in the history of life on Earth, but one that scientists are struggling to explain.


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