The silent killer continues to claim lives
The average eye has three cones, which means you can recognize colors in the red, green, and blue spectrums. However, there are also tetrachromats who have four cones in their eyes. They can see ultraviolet shades, allowing them to appreciate 100 million distinct colors.
If you've hiked up a mountain, then you know it's brutal. So how do indigenous groups like Tibetans survive at altitudes as high as Mount Everest? Researchers believe that because their ancestors lived in high regions for thousands of years, they developed red blood cell adaptations that make it possible to survive with low levels of oxygen.
More prevalent in women, this extra rib can sometimes be spotted near the cervical spinal region. It can vary in size and only causes discomfort if it grows.
Gray eyes are one of the rarest eye colors, and less than 3% of the global population has them. Although chances of meeting someone with this feature are slim, your best bet is in Eastern and Northern Europe.
See also: Rare cancers that challenge the medical profession
Those with distichiasis carry a second set of eyelashes that grow from the inner mucosal layer of the eye. This defect happens when epithelial germ cells fail to differentiate between certain glands.
Everyone has a gene called proprotein convertase subtilisin/kexin type 9 (PCSK9). However, a small number of people carry a lesser amount. This deficiency reduces the risk of heart disease and cholesterol.
Fingerprints are unique. However, there are only three different patterns. Around 65% of people have hoops, 30% have fingerprints in the shape of a whirl, and only 5% possess the unique arch pattern.
We live in a right-handed world, with around 90% of people being right-handed. Most of the remaining 10% are left-handed. But then there are a small number of ambidextrous folks, those who can can perform all tasks equally well with either hand.
Known as preauricular sinus, only 5% of the world population has it. It's essentially a sinus tract traveling under the skin that doesn't belong there. It has no use and it's not dangerous.
Researchers at the Queensland Brain Institute discovered that a person’s ability to find their way is learned gradually, and that the brain eventually becomes attuned to a sense of direction in new environments.
A rare body feature, heterochromia is an inherited condition when a person has two different colored eyes. Heterochromia is derived from the ancient Greek words heteros, meaning "different" and chroma, meaning "color."
Certain animals, like dolphins and bats, can navigate through emitting a sound and locating its echo. But did you know some humans can too? Although it’s rare, some people can "see in the dark" by replicating this process.
There's a rare condition that results in a person lacking some, or all, of their nails. It's called anonychia congenita, and it happens because of a mutation in a gene that controls the manufacturing of a protein called R-spondin-4. This is the same gene that tells the body's tissues and cells how to develop.
About one in 500 infants are born with an extra finger or toe, a condition called polydactyly. Extra digits can be removed surgically, but a study found that in some cases having six fingers on a hand can be beneficial. For example, one can perform more complex movements, and also do some tasks with one hand that normally require two.
Known as globe luxation, this extremely rare condition makes the eyes protrude out of their sockets. People with the condition should see their eye doctor on a regular basis.
People with a mutation of the DEC2 gene can sleep around six hours a night and still be completely fine. Those with the condition are known as familial natural short sleepers (FNSS).
Someone with piebaldism has a lack of melanocytes, the cells that produce hair pigment, in portions of their hair. Usually above the forehead in the front of their hairline, they'll sport a lock of white hair strays. It's also common to see white eyebrows and eyelashes with unpigmented patches.
People with polycoria have two pupils in at least one eye. Each pupil functions separately, and contracts with light changes. Although you might think that having double the pupils would lead to even better vision, polycoria actually does the opposite.
Known as palmaris longus, it was basically a muscle that helped our ancestors climb trees. And while we don’t use it anymore, some people still have it.
Having "perfect pitch" doesn’t mean one is a great singer. This rare condition allows people to precisely identify musical notes, which means they can hear a D minor and name it on the spot.
If you have a hard time holding your breath for 30 seconds underwater, imagine 10 minutes! However, the Bajau, sea nomads in Southeast Asia, have this skill. This is because they evolved an extra-large spleen that serves as a repository of oxygen-rich blood cells.
Known as dextrocardia, around 1% of people have this condition. People with a right-sided heart can live perfectly ordinary lives, but on occasion they can suffer some side effects like breathing difficulties and a compromised immune system.
A person with synesthesia might see a color when they read a particular word or number. Or they might experience a sensation of taste when hearing a certain sound. Occurring in 3-5% of the world population, one sense automatically triggers another sensory experience.
Sometimes called face blindness, a person with prosopagnosia is unable to recognize familiar people, discern one unfamiliar face from another, or even recognize one's own face. This rare condition involves a mutation affecting the area of the brain that coordinates facial perception and memory.
The average person has around 10,000 taste buds. But some people have a much higher concentration of taste buds. This means people with this condition often have very strong reactions to bitter foods, like broccoli or grapefruit.
Also known as Rh-null blood, this blood type is so rare because it has no antigens. Anyone can receive the blood, and its healing properties are better than others. Fewer than 50 people in the world have this blood type.
While most of us have the occasional bad hair day, there's an actual condition called "uncombable hair syndrome." It's the result of genetic mutations, which affect proteins that form the hair shafts on the head. Instead of the usual rounded cross-section, people with this syndrome grow hair with a cross-section that makes it impossible for the hair to be combed flat. The hair will then stand out from the scalp.
Some people have the LRP5 gene mutation, which means they have extremely dense bones.
If you have a second toe that is larger than your first, then you are part of the 22% of people who have Morton’s toe. This feature is believed to be an evolutionary remnant of pre-human toes.
Click on to discover some of the rarest features very few people have.
Rare human body features you didn’t know exist
Discover the wonders of human physiology
HEALTH Curiosities
With billions of people walking on this planet, it's no surprise that we're all unique. And while we have many common features in our bodies, it's only natural that there are some that are truly rare and different. But some of these differences are especially extraordinary on a biological level. From a rare blood type to additional ribs, and an immunity to sleep deprivation, you'd be surprised to learn that these body features actually exist.
Click on to discover some of the rarest features very few people have.