The 10 Rarest Body Features You Might Have

Every person is unique, but from a purely scientific point of view, we all share a vast amount of traits that make us virtually indistinguishable when you zoom out far enough. Baseline human beings are equipped with the same one head, two arms, and two legs. We have the same five (or six, depending on the source) senses and the same five major organ systems in our bodies that function in much the same way. The way we observe reality is subject to similar perceptual illusions. Many of our physical traits are passed down from our parents, making our genetics traceable through our ancestry. 

Still, there are plenty of details in the body parts and their functions that differ from person to person. Sometimes, these differences can be quite drastic. For instance, certain genetic traits might give their holder some very obvious benefits — or, for that matter, drawbacks. A person might end up with a look that sets them apart from the general populace, or an ability or body feature that the average human being might not be able to truly comprehend. 

What's more, many of these traits can be so unnoticeable or obvious to their holders that the person might not even be aware that they have them in the first place. In fact, there's a chance that you, right now, could possess one of the following rare body features. Here's a closer look at them and how they can be recognized. 

Figuring out how much sleep you really need can be challenging, especially during hectic times when there are never enough hours in the day, let alone the night. Still, the ballpark figure of a good night's sleep is generally thought to be somewhere around seven to nine hours, depending on the person. If that person enjoys the genetic jackpot known as familial natural short sleep (or FNSS for short), though, they're playing a different game altogether.

FNSS is a genetic mutation that, in effect, can provide the ultimate busy person's superpower: the ability to sleep less and still function normally. It also comes with other benefits: A 2022 study that followed a group of people with FNSS traits found that they tended to be more active, productive, and focused than people without the benefit of the trait. Another study, which was also published in 2022, found some evidence that FNSS may actually prevent Alzheimer's disease — in mice, at least. 

Natural short sleepers were a mystery until 2009, when researchers at UC San Francisco found the first gene that enables a person to survive and thrive on just four to six hours of sleep per night. They found a second gene with similar effects in 2019. Unfortunately, the mutation that causes the trait is rare, and sleep can be a tricky subject to study ... but who knows? If you consistently catch noticeably little sleep and still thrive, you too might have FNSS.

Lush eyelashes are a make-up tutorial staple, so who wouldn't mind a rare genetic tweak that gives them a whole extra set of lashes? Well, that depends entirely on the kind of double eyelashes the person might end up with. Sure, some can indeed look thick and fabulous, but others ... well, let's just say that there are potential downsides.

The condition that causes double eyelashes is known as distichiatis. Some are born with it, others develop it as a symptom of certain eye conditions or physical injuries. The best-case scenario — which the mind might easily go to when we imagine double eyelashes — is simply a second row of lashes, the exact same as the first one. Should that happen, the lashes can potentially be perfectly nice to look at. Unfortunately, a bad roll of the distichiatis dice might not affect all eyelids or could give the person an incomplete second eyelash row — perhaps just an extra lash or two. 

The second row of lashes grows from the meibomian glands located just by the eye, so they're physically very close to the sensory organ itself. As such, they may irritate and even hinder the use of the eye. Apart from the redness, pain, uncomfortable sensations, and potential vision issues, the more exotic downsides of distichiatis include things like open sores on the eye's cornea and infections. Luckily, double eyelashes can be removed and treated in a number of ways if they prove too troublesome. 

Supernumerary nipples, or extra nipples, are precisely what it says on the label. The most commonly known version of this condition is the third nipple, which has been immortalized in popular culture by characters like Chandler Bing (Matthew Perry) of "Friends" fame and James Bond villain Francisco Scaramanga (Christopher Lee) in the 1974 film "The Man with the Golden Gun." In real life, celebrities like Tilda Swinton and Mark Wahlberg also have the condition. However, one extra nipple is by no means the hard cap, and some people can have as many as six supernumerary nipples. Estimates about the condition's rarity vary between studies and demographics, from a 1878 report that stated roughly 0.2% of people have extra nipples to more recent ones that have determined that in some parts of the world — Germany, specifically — the number could be as high as 5.6%. 

Supernumerary nipples come in many shapes and sizes, and form during the fetal stage when a tissue strip called the mammary ridge or milk line (which is responsible for developing breasts) fails to set properly in the chest area, leading to the development of more nipples than intended. Often, the extras are just spare nipples without an areola, and look like moles. However, in extreme cases they can be quite bothersome. Extra nipples can potentially develop into complete, fully functioning extra breasts that can lactate, and they can even develop in unfortunate places like in the armpit or near the genitalia. 

Some people's tongues are equipped with a far greater number of taste buds than average, which makes them supertasters. While rare, this trait is somewhat more common than most other features on this list: Some 25% of people have some variety of the supertaster trait, which in many cases is thought to be caused by a particular gene called TAS2R38. 

Supertasting doesn't make every single flavor equally strong. It mostly amplifies bitter flavors, which means that people with this trait can easily be overwhelmed by foods like citrus fruits and spinach. As such, the supertaster gene isn't as much a one-way ticket to a life of gastronomical hedonism as it is a membership card of the Picky Eater Club. It's not all bad, though. While supertasters might find it difficult to eat fruit and vegetables embittered by flavonoids, their heightened sense of taste also enables them to refrain from excess fat and sugar, not to mention harsh-tasting addictive substances like tobacco and alcohol. Their approach toward salt, on the other hand, tends to be of the "more is more" variety. 

Supertasting is speculated to be a holdover from the days when we needed to detect potentially poisonous or spoiled food sources by taste. This, incidentally, puts the other tasting "superpower" to an interesting light; Roughly 25% of people have the opposite of the supertaster trait, and these non-tasters have so few taste buds that they can't necessarily taste bitterness ... or much of anything else, really.  

Taste is not the only sense that can provide a person with minor superpowers. People with tetrachromatic eyes are able to see the world around them far more vividly than others, even though they might not actually know about this ability. Tetrachromacy is a rare condition that's more prevalent in women, almost 12% of whom may have it. It's notoriously difficult to accurately test and determine, so there's a chance that you could potentially have it and not even know.

Tetrachromatic eyes have four types of cone photoreceptor cells in their retinas, instead of the three types most of us have. Since the cones enable us to see colors, this significant increase enables them to perceive far more colors than a normal person. Your average trichromatic eye features short-wave cones, middle-wave cones, and long-wave cones, all of which contribute to seeing the RGB (red, green, blue) color spectrum. Tetrachromacy brings a fourth type of cone — usually orange — into the mix, which increases the ability to see colors considerably more than the 25% one might assume. In fact, the extra type of cone opens up the ROYGBIV (red, orange, yellow, green, blue, indigo, violet) color spectrum ... in other words, the entire visible spectrum of light, as determined by Isaac Newton himself. 

This gives the tetrachromatic eye access to up to 100 million colors. For comparison, trichromats are thought to see around 1 million colors. 

Before we proceed, a fair warning: Anyone who dislikes going to the dentist any more than they absolutely have to will likely balk at the details of this entry. On the other hand, if you do have the kind of hyperdontia that negatively impacts you, there's a chance that you're already aware of it ... if only because it's kind of hard to miss entire extra teeth in your mouth. 

Let's just cut to the chase: Hyperdontia is a condition where supernumerary teeth grow in a person's mouth. If they're lucky, the teeth grow in a spot that doesn't interfere with the regular set too much. If they're not, things could get interesting. Supernumerary teeth come in many shapes and can develop just about anywhere in the mouth, from behind the front teeth to the space between your molars and cheeks. Multiple new teeth can appear in tight-knit groups. They can even fail to emerge properly and end up stuck inside the jaw. Again, this may all be completely harmless, but if the person is unlucky, the extra teeth can cause pain and mess with their more orderly oral siblings, potentially making biting and chewing difficult.  

Fortunately, this overabundance of teeth is not a common ailment, and only affects up to 3.1% of people. If you're eager to find out whether you're one of them and haven't counted your teeth as of late, an adult human should have no more than 32 teeth in their mouth, wisdom teeth included. 

Unlike several other body features listed in this article, heterochromia can be very easy to spot. All you need to do is look in a person's eyes. 

Heterochromia means that a person's irises have different colors, and it's a condition people may be born with or acquire later in life. It can be either partial — for instance, the two eyes are otherwise similar but a section of one iris differs — or the eye colors can be completely different. Furthermore, partial heterochromia can manifest in several striking ways, such as central heterochromia (a ring of one color right around the pupil and another color surrounding that) or segmental heterochromia, which features multiple "segments" of color in the iris. 

This striking feature is caused by uneven melanin distribution in the eyes, affects an estimated 1% of people, and is typically completely harmless. In some cases, however, heterochromia can indicate an underlying medical situation, and it can potentially manifest after an injury or even as a reaction to medication. Perhaps most interestingly, this physical feature isn't limited to just eyes; Scalp hair heterochromia can cause a person's hair to grow in different colors. 

Synesthesia affects at least 4% of all people and gets their senses tangled in a way that triggers multiple senses when only one should be working on the task at hand. It's a feature that's often associated with artists. Musicians Tori Amos and Billy Joel are among celebrities who have a form of synesthesia, and Academy Award-winning actor Geoffrey Rush also has the condition. Rush found out about his ability to associate a variety of sensory experiences with particular colors when he was a child. "When I was in school, in the very early days, we would learn the days of the week," he said in an interview with Psychology Today. "And for some reason the days of the week just instantly had strong color associations."

Rush's account described day-color synesthesia, which causes one to associate weekdays with specific colors. Elsewhere in the interview, he also describes other forms of visual synesthesia, such as associating vocal patterns with colors. However, synesthesia comes in many forms, not all of which include color at all. For instance, auditory-tactile synesthesia associates sounds with specific physical sensations, and hearing-motion synesthesia adds sound effects to things that move. 

Despite the attention famous people with synesthesia have attracted, there's still much we don't know about the condition, which could have as many as 150 different varieties. One of the strangest is time-space synesthesia, which has been described as the ability to "see" time by associating the passage of days, months, and years with visual imagery. 

Even on a list of rare body features, few people would expect to see an entry about a specific extra bone some people's skeletons may have. However, that's exactly what a cervical rib is. Around 1% of people have one or two of these secret extra ribs in their bodies, and might not even notice their existence. After all, who would suspect a surprise like that in their own skeleton?

The cervical rib is caused by a genetic mutation and grows between the lowest vertebra in the cervical spine and the topmost rib, which it may or may not be attached to. In effect, it's located more or less behind the collarbone. It comes in several varieties, from a small but complete rib to an insignificant bit that sticks out of the lowest neck bone. 

Though having extra bones in the body may seem like a grisly concept, there's a decent chance that a cervical rib is completely harmless and doesn't affect a person's life in any way at all. Then again, there's also a possibility that the rib's positioning disrupts an artery or a nerve, and it may potentially cause various issues such as pain and numbness in the arm. In particularly bad cases, the cervical rib can be surgically removed — after all, it's a spare part that doesn't actually serve any useful function in the body. 

Have you ever been able to recognize a note by the ear? If so, there's a chance that you might be one of the rare people with the hearing-themed special trait known as perfect pitch.

Perfect pitch hearing may seem like the kind of concept that's easiest to associate with the kind of a super-serious musician who's a borderline caricature of the profession. However, it's actually a rare trait that just about anyone could have, regardless of whether they're a layperson or a working musician. Also known as absolute pitch, it's simply the ability to identify — or, if you're a decent singer, produce — a particular note without any context to compare it to.  

Estimations of the condition's rarity vary: Some say only 0.01% of people have perfect pitch, though research among music students has found that around 4% might have some form of the ability. Still, it's definitely rare enough to count as a pretty cool trait. By the way: If you know that you don't have perfect pitch but would like to, it's the kind of physical trait that you can hone, and there's some evidence that a person can improve their perfect pitch ability with training.