We Get A Completely New Skeleton Every Ten Years

We don't want to alarm you, but the bones you're using right now aren't the ones you were born with. They aren't even the bones you had ten years ago. Yes, some of us switch skeletons more often than we switch mattresses (jury's out on which one's grosser).

Through a process very appropriately known as "remodeling," your skeleton completely regenerates itself over time. Every decade or so, you essentially get a full-body re-boning job, and you don't even have to move out during the renovation. Like a good general contractor, our body tries to balance the processes of bone removal and replacement so our skeletal structure stays strong and un-collapsed. As we age, the whole removal/replacement balance gets shoddier, which leads to problems like bone weakening and osteoporosis. But on the upside, you can now tell your friends you have Doctor Who powers (technically)!

Pre-Osteoclasts Resting Bone Surface Active Osteoclasts Osteocytes Bone Resorption Mineralization Remodeling Cycle Q Osteoblasts Mononuclear Pre-Osteo
AlgaeCal Inc
Your dog is looking at this and going "Dear lord, infinite food."

Replacing bones isn't the only thing done to our skeletons without our input. Apparently, human bodies are fans of the "less is more" philosophy. We're born with over 300 bones, many of which are made of cartilage, but by the time we reach adulthood, we're left with 206. That's because as we grow, our bodies replace the cartilage with bone and fuse some bones together, giving us our final piece count. Or that's the cover story created by the gnomes who steal your bones at night and sell them on eBay.

Your Body Emits (A Teensy Bit Of) Light

"You're glowing!" is a descriptor we usually reserve for pregnant women and/or nuclear power plant workers, but it's true of the rest of us too. A group of Japanese scientists with a bit too much free time have determined that human beings glow in the dark. Using cameras so sensitive they could detect even a single photon, the researchers photographed volunteers in a completely dark room over the course of several days. The result was not a lawsuit from the volunteers, but the first-ever images of the "ultra-weak" photons emitted by the human body (obviously, too weak for the naked eye to detect).

Dak AM A Atllee B oc s St 00el Co C D E
Kobayashi, Et. Al./PLoS One
In the fourth photo, they asked him to remember that time he called his third-grade teacher "mom."

Now, before you start telling people that the sun actually does shine out of your butt, you should know that we don't appear to glow very evenly. Our lips, cheeks, and foreheads emit more light than other, warmer areas, further emphasizing that we give off light, not just heat. Our weak lil' photons seem to keep to a schedule, too. We glow brightest in the late afternoon, then kinda fizzle out to our lowest levels by the late evening.

So what gives us all the shining? It's the same metabolic reactions that cause molecules to get "excited" and light up in other animals -- just not as brightly in our case. And not out of our butts. We think. Japan should probably look into that next.

Your Belly Button Contains A Jungle Of Undocumented Bacteria

Nobody expects a belly button to be a germ-free environment, especially not your old roommate who used it to hold his ketchup while eating shirtless on the couch ("nature's condiment cup"). That said, even researchers were appalled at the amount and types of bacteria living within the average navel.

How much bacteria does it take to shock a scientist? In the first 60 belly buttons they tested, researchers found 2,368 different species of bacteria, 1,458 of which were undocumented species -- as in, new to science. If we apply those numbers to the general population, that means you likely have at least one type of germ nobody's ever heard of living in your tummy right now. The average number of bacterial species present in tested belly buttons was about 67, which makes your navel the germ version of a rainforest.

Real belly button footage recorded through a microscope.

One test subject's belly button contained a bacteria that had previously been found only in soil samples from Japan, where neither the subject nor his navel had ever been. Another belly button contained "extremophile" bacteria normally found in ice caps and thermal vents. All said and done, the results of the initial testing were so unexpected that the navel-gazing researchers launched a "belly button biodiversity project" and published their findings after testing an additional 600 navels. Someone like you could have this generation's penicillin sitting in your belly button, just waiting to be discovered. Anyway, if you absentmindedly touched your belly button while reading this entry, please go wash your hands for 15 minutes now.

Over 90% Of Our DNA Is Mysterious Junk

It seems DNA is like a really expensive cable TV package -- full of stuff, but it's mostly garbage. Scientists have been bickering for decades over how much of our DNA really matters, and how much is just kinda ... there, like that busted N64 in your closet you refuse to throw out. Well, according to a team of Oxford researchers, a mere 8.2% of our DNA is functional, or contributing in some way to the running of our bodies. The other 91.8%, as far as we know, sits there doing absolutely nothing, like a bunch of microscopic freeloaders.

The researchers arrived at this number by comparing human DNA with DNA from other mammals. The logic is that if evolution decides to keep some genetic material when a species splits into several, it's because it serves some purpose, not just because it looks pretty.

Divergence time (My) 46 91 137 182 228 8 248 genome) 6 186 (Mb) buman of (% 4 124 sequence sequence Constrained 2 62 Constrained 0.0 0.2 0.4 0.6 0.8 1
Rands, Et. Al./PLoS Genetics
If we're understanding this graphic correctly, horses are 0% beard.

So ... how did that other stuff get there? And what is it, exactly? The short answer is that nobody freaking knows. Some scientists insist that "junk DNA" is a myth, and that we simply don't yet understand what all those seemingly useless gene sequences actually do. Maybe they were useful in some way to our ancestors (like, a sixth sense that tells you a mammoth is about to evacuate all over you). Or it could be alien code. Or the key to curing cancer. Or winning lottery numbers. Or maybe evolution hasn't gotten around to clicking "Empty Recycle Bin" for a few million years. We can relate.

You Might Be Missing Some Muscles

When we think about our bodies, most of us assume we're the standard model. Sure, the finishing touches are different -- there are different skin tones and facial features, and some of us get the premium butt, or extra thick hair, or a bonus nipple -- but on some basic level, we're all generic humans, right?

Nope! There's a whole lot more variety in human construction than you might think, particularly when it comes to muscles. For example, there's about a 50% chance you're missing your palmaris longus muscle in one or both arms. It's not a muscle humans need (anymore), so you might not even notice it's missing until you, say, read an article on the subject and glance down at your wrists, then quietly freak out for the rest of the day.

Sorry about the existential crisis.

There are a handful of other muscles you may or may not have, depending on what parts the factory was out of the day you were assembled. Some 8% of the population is missing their pyramidalis, a muscle that normally hangs out in your abdominal wall doing ... not a whole lot. Between 7-20% of people are missing a plantaris muscle, which runs along the back of your calf. Most bizarrely, only an estimated 8% of humans have a muscle in their chests called a sternalis, which means doctors aren't super used to seeing it. One poor woman underwent exploratory surgery before doctors figured out that the growth in her chest wasn't cancer or a xenomorph waiting to burst out.

Women Incorporate Cells From Their Children, Becoming "Micro-Chimeras"

When people say that having a kid changes you, they're usually talking about how you'll get less sleep and be able to name every godforsaken character on Peppa Pig. But no, for a mother, having a kid literally changes you, on a cellular level. Forever.

We've talked about the genetic oddities called chimeras -- people who contain two sets of DNA, usually after absorbing their twin while in utero. While that horror show of a scenario is extremely rare, multiple studies have shown a far more common one: women keeping cells from children they've carried. A 2014 study found that 70% of the 272 women studied had male cells living in their bodies, years after they gave birth to sons. Meanwhile, 37 out of 59 women in another study had male cells in their brains, in some cases decades after evicting the little dude living in their uteruses.

And those numbers don't account for the cases caused by daughters, since it's easier to spot Y chromosomes in an XX body. Science calls these women "microchimeras," which makes them sound like some tiny Harry Potter monster.

Maternal Cells Parent 1 Parent 2 Fetal Cells Fetal Cells Offspring 1 Offspring 2
Boddy, Et. Al./BioEssays
Dad feels kind of left out from the glitter-throwing party.

So how do these foreign cells stick around for so long? Fetal cells are almost like stem cells, in that they are kinda "generic" and easily incorporated into existing tissues. Plus, since half the DNA is the same, the mother's body is like "Oh hey, you belong here" and spreads them out as needed. There's even evidence that women with higher number of microchimeric cells have lower instances of diseases, ranging from Alzheimer's to cancer. Other studies have shown that fetal cells will gather at a cesarean scar, differentiate into epithelial cells, and help heal the wound. Who knew motherhood gives you superpowers? Well, besides every mother.

For more, check out What Your Doctor Wants To Tell You, But Can't (From A Medical Physician):


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