Updated April 5, 2022 12k votes 3.2k voters 225.1k views
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Vote up the facts about the human body that weird you out the most.
Generally speaking, human beings come in similar shapes and sizes and exhibit many of the same characteristics. Simply put, humans are a lot alike.
When you look more closely, it's also clear that humans are very, very different. From bodily appendages to what goes on inside one's head, it's the uniqueness of each individual that adds to the overall human experience.
Unless you go looking, you may not know some of what distinguishes one person from another, from other living creatures, and even from previous versions of our species. We found intriguing facts about human bodies that were true revelations. They're weird and fun - and they're things we never knew before.
Take a look and vote up the ones that leave you saying, "That IS weird!"
Humans Have Stripes On Their Skin; You Just Can't See Them
The stripes on humans are named for the German dermatologist who discovered them, Alfred Blaschko. In 1901, he noticed various line patterns on the skin of his patients. Generally, V-shaped lines extend over the spine, U-shaped lines are on the chest and upper arms, and S-shaped lines run across the torso. Additional perpendicular lines go up and down arms and legs, with spirals on the head.
Now known as Blaschko's lines, they are generally not visible to the human eye. They can be seen under ultraviolet light, but emerge with greater clarity in the case of certain medical conditions, mostly dermatological.
To people who have an inner monologue, it may be surprising to learn that not everyone does. And, if you don't have one, you might not even realize an inner voice exists.
Psychologist Russell Hurlburt admits there's an inherent challenge to studying the voices inside people's heads - or a lack thereof. His research has found that "Most people think that they think in words, but many people are mistaken about that." Visualizing one's self in a situation is more common for many humans - essentially thinking in images instead of words.
Writing things down is also essential for individuals who don't have an inner voice, but some people claim there's very little thought at all in many instances. That said, many people think in multiple ways and have several inner voices going simultaneously.
While Hurlburt found that his subjects only talked to themselves about 25% of the time, investigation into how that inner conversation takes place has revealed additional findings. A 2015 study concluded that "internal interlocutors" fell into four categories (faithful friend, ambivalent parent, proud rival, and helpless child), while a subsequent 2019 study indicated that inner dialogues were derived from "self-reflection, self-observation, cognition, and... accompanying activities."
As far back as the 1970s, there were studies indicating the human body had more bacterial cells than human cells. While bacteria in and on humans is "essential to your health," according to microbial ecologist Ruth Ley from the Max Planck Institute, it was determined that, in the words of UC San Diego's Rob Knight, "you're more microbe than you are human." Researchers in the 2010s sought to quantify just how much of a difference there was in terms of human versus bacteria.
At its highest estimations, the ratio between bacterial and human cells was 10:1. That has since been lowered, with scientists like Ron Sender, Shai Fuchs, and Rob Milo offering a 1:1 ratio instead. The revised numbers allow researchers (and anyone who wants to drop a surprising fact at a dinner party) "a better estimate to quote" without losing sight of the symbiosis between humans and bacteria.
It Takes Longer To Grow Back A Toenail Than It Does To Grow A New Human
A human pregnancy lasts 38 to 40 weeks, or roughly 10 months. If a woman's toenail fell off on the same day she got pregnant, she'd still be waiting for it to grow back when her child was born.
While not everyone's toenails grow at the same rate, regrowing one can take as many as 18 months. This also depends on the toe, with less time needed to grow a small nail for your pinky toe than a big-toe nail.
Toenails consist of keratin, the same foundation for hair and fingernails (as well as animal hooves, horns, and claws). Even though humans have both toenails and fingernails, it takes two or three times as long for the former to grow than for the latter. Scientists aren't entirely sure why, but theorize it has to do with the different uses for and blood flow to the hands and feet.
Almost Half Of All Humans Have An Extra Bone In Their Knee
In school, we learned that the human body has 206 bones. Aside from rare instances of extra bones taking shape, this has, for the most part, been true. One possible outlier has always been a person with a fabella - a second kneecap of sorts.
About 100 years ago, less than 10% of humans had a fabella, but according to research from 2019, that percentage has more than tripled. In 2018, 39% of people were believed to have fabellae.
This tiny sesamoid bone grows in the tendons in one's knee and may be occurring more often in humans due to increased pressure placed upon knee joints. As humans weigh more, the body could be making additional bones to strengthen the knee. But, as researchers point out, "it could be doing nothing at all."
Some People Have A Bony Ridge On The Roof Of Their Mouth, While Others Don't
If you take your tongue and run it along the roof of your mouth, you may not feel much. For individuals with torus palatinus, however, it's a very different experience.
For most humans, the roofs of their mouths are fairly smooth and have only a slight ridge. Torus palatinus results in the growth of a pronounced ridge that can vary significantly in size. More common in women and individuals of Asian descent, torus palatinus affects as much as one-quarter of the world's population.
In contrast to torus palatinus is a condition called torus mandibularis, which causes bony growth on the bottom of the mouth and is more common in males. Both torus palatinus and torus mandibularis are harmless and likely due to genetics and/or bruxism, but they can make dental X-rays very uncomfortable, due to the film-holding tabs pushing against the bony protrusions.
