When the outstretched arms of a hug are coming in too hot to avoid, what do you do? Whether you light up at the gesture and gladly bear hug it out, or completely recoil at the awkwardness of physical contact, your reaction actually has a scientific explanation. That’s right, experts studied the reasons why people hate hugs, and the data makes a lot of sense. Here’s an excuse to dodge your least favorite relatives the next time they raise their arms.

As with most of our quirks and issues, our comfort with hugging is largely determined by our past experiences. Translation — if you’re skeeved out by hugging, you might be able to blame it on your parents.

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Before you call up mom and dad and give them an earful, you might want to learn the scientific reasoning to use in your argument. As the experts have found out, our varied responses to physical touch are formed pretty early in our lives.

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As Professor Suzanne Degges-White of Northern Illinois University told Time, “Our tendency to engage in physical touch — whether hugging, a pat on the back, or linking arms with a friend — is often a product of our early childhood experiences.”

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Hugging, like many other non-verbal forms of communication including the handshake or facial expressions, triggers responses in our brains. In 2012, a study delved deeper into the Western world’s different ways and reasons for engaging in hugs.

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So what did researchers see when they looked at the data? Well, it made perfect sense. As explained in Comprehensive Psychology, “In a family that was not typically physically demonstrative, children may grow up and follow that same pattern with their own kids.” 

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The friend you insist on hugging no matter how much they squirm? Now, you know that they were mostly likely not accustomed to the routineness of intimate hug while growing up. So maybe give them an extra loving squeeze.

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On the other hand, not every house devoid of physical affection produced people who prefer personal space. In fact, for those kids who really craved hugs and tenderness from their parents, they tend to swing in the opposite direction.

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People who tend to let their hugs linger might fall into into the other category. Degges-White explains, “Some children grow up and feel ‘starved’ for touch and become social huggers that can’t greet a friend without an embrace or a touch on the shoulder.” 

Hugging in childhood has a direct effect on our brains. Too little physical touch results in an underdeveloped vagus nerve. This set of nerves that runs between our spinal cord and abdomen, that helps control our relaxation response time.

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In addition to the vagus nerve, hugging also helps stimulate the production of a crucial hormone — oxytocin. This is the hormone pumped out by the pituitary gland when you’re snuggled up next to a love one and feeling extra cozy.

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In one study, scientists saw that a lack of hugs chemically affects the brains of orphaned children. Professor Darcia Narvaez of the University of Notre Dame noted, “They were hardly touched in the orphanage and so did not display the rise in oxytocin — ‘the cuddle hormone’ — well-cared-for children have when sitting on their parent’s lap.”

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What happens to people who lack the hormone? It goes well beyond hugging. People who have trouble producing oxytocin are also likely to experience social awkwardness and tend to have trouble reading social cues.

Professor Degges-White continued,“People who are more open to physical touch with others typically have higher levels of self-confidence.” That makes sense. A person who shows up to a party and enthusiastically hugs everyone in attendance is likely to work the room like a social butterfly.

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The people who cling to the wall at parties and attach themselves to one friend like a life buoy, maybe skip hugging them. “People who have higher levels of social anxiety, in general, may be hesitant to engage in affectionate touches with others, including friends.” 

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A huge determining factor of our comfort levels with hugs is culture. In America, touching your friends is not nearly as normalized as the affectionate cheek kisses and embraces of European countries.

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Now that you understand the context of hugs, it might be best to heir on the side of caution and hold off on an unanticipated embrace. Once you’ve gauged the comfortability of your relationship, shoot ‘em with the question: “Is it cool if I hug ya?” 

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For those who want to increase their tolerance for hugs and touch, there are options. Professional cuddlers work with clients at their own pace, often times starting with handshakes, to build up their capacity for physical contact.

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Still think hugs are lame? You might reconsider after knowing that they actually boost your immune system. A 2015 study by Carnegie Mellon University showed a 32% increase in immunity for huggers, so germaphobes can’t use that as an excuse to dodge open arms.

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Even for the non-huggers out there, if you have kids, hugging is a necessity. It’s a formative part of their growth that will only make your child a more confident nurturing person while making your life a little less chaotic.

In many ways, it seems that human beings have evolved to become huggers. And many everyday behaviors actually offer hidden benefits. Just like a family hug is often followed by a warm meal, it seems that the act of cooking says a lot about who we are as a species.

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Unless you’ve got an insatiable appetite for sushi or carpaccio, chances are that you eat mostly cooked meat. And when you think about it, most of your diet is introduced to some form of heat prior to consumption.

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Even the least exotic meal you can imagine was probably cooked at some point. Ground flour is baked into bread. Potatoes are boiled or fried. Even peanuts are usually roasted before being slathered onto a PB&J. But why?

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According to Richard Wrangham, a biological anthropology professor at Harvard, it’s this culinary process that defines our species and has allowed humans to flourish. And he theorized that cooking offers more benefits than most of us realize.

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As for those advantages, most of us would immediately jump in and explain that cooking meat kills bacteria and prevent sickness. That’s certainly true. But that doesn’t capture the full picture.

Building on Wrangham’s work, Karina Fonseca-Azevedo published a paper with her Brazilian colleague Suzana Herculano-Houzel that put forth the daring idea that cooking physically turned our ancestors into human beings! It goes back to a key moment in history.

Nobody knows exactly when or how fire was discovered, but our best estimates indicate that some predecessor of homo sapiens came across this wonder about 2 million years ago. For these primitive creatures, it was a revolutionary development.

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Besides providing warmth, one of the first applications of fire would have been cooking food. It’s important to remember that putting a slab of beef on the grill doesn’t just heat it up. A drastic chemical reaction takes place.

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Cooked meat undergoes a process called denaturation, which is a fancy way of saying the protein fibers force out water and become softer. Plant matter, too, usually softens up when exposed to heat. To the Brazilian scientists, this change means everything.

Fonseca-Azevedo and Herculano-Houzel believe that the evolution of human beings came down to chewing time. Cooking, of course, adds an extra step to caloric intake. Because this food is more tender, we can process and digest it much more quickly.

The immediate benefit of that sped-up process would be giving early people time to do other activities — like socialize around the fire, for instance. That opportunity would set us apart from fellow primates, and that’s not the only way.

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The Brazilian scientists took a look at Professor Wrangham’s hypothesis that fire drastically affected human evolution. He argued that the warmth and convenience caused us to become less hairy, walk more upright, and form complex social structures. But they took his ideas a step further.

Our dietary needs are quite different from that of any other primate. Your typical monkey can afford to nibble on raw food over a long course of time because it doesn’t need the same amount of calories. One of our most advanced body parts forced this difference.

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That’s the brain. Despite many apes being larger than us, most actually have smaller brains. From an evolutionary perspective, this size difference stems from encephalization, whereby the organ and intelligence grow together. Fonseca-Azevedo and Herculano-Houzel wrote that this process largely depended on our cooked foodstuffs.

“In primate evolution, developing a very large body and a very large brain have been mutually excluding strategies,” their paper explained. So in subsisting on super-efficient cooked food, early humans gave their brains the chance to develop. And as for other primates?

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You might notice that, compared to us, gorillas have incredibly large abdomens. According to the theories of the aforementioned scientists, they grew these big bellies to adjust to their raw diet, at the expense of their brain development.

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Of course, many modern-day nutrition gurus will be quick to jump in and point out the benefits of a raw diet. There’s no doubting that the trendy meal plan has helped many of us lose weight, but lighter doesn’t necessarily mean healthier.

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The bare truth is that raw foods alone don’t give us the full caloric intake we need. In response, the human body begins consuming its own fat reserves. That’s why it’s an effective weight loss plan, though there is a way to eat only raw without wasting away.

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Suzana Herculano-Houzel crunched the numbers and found that to properly survive on a raw diet, humans would need to spend nine hours out of the day eating. Maybe that sounds like a fun life plan at first, but it would quickly become a real chore.

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In that case, just keep on cooking. That flame-broiled meal is what separates us from the cavemen, after all. Meanwhile, scientists have traced fascinating evolutionary purposes within other parts of our bodies.

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These days, a well-kempt beard is all about style. It’s the best way for hipster bros to assert their dominance at their local craft brewery or record store. Of course, the beard isn’t just a trend; it’s a legacy as old as humanity itself.

Facial hair detractors may claim that beards make their wearers “look like a caveman,” but that’s exactly how the style started out. In a prehistoric age where our species struggled to survive, beards were everywhere.

We know that much from preserved remains, plus the fact that homo sapiens lacked the tools to properly shave. That led biologists Ethan Beseris, Steven Naleway and David Carrier to wonder if this hair actually helped men survive this fraught period.

At the very least, historical trends supported this theory. In civilizations from ancient Greece to India, beards signified leadership and strength. A wiseman or general wasn’t complete without a decent set of whiskers. But this symbolism didn’t last forever.

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The Romans popularized shaving in the Western world, as beards went out of fashion and often proved to be a very grabbable liability on the battlefield. While this transition didn’t mark the permanent decline of the facial hair, it may have taken us further from the style’s origins.

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As the average joe became more entrenched in respectable society, the beard survived, though it morphed into various forms that didn’t project the same raw testosterone as those of the Spartan warriors. But this team of biologists believed facial hair has uses that we’ve completely forgotten.

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What if, they asked themselves, beards could somehow protect the men who grew them? On the surface, this does seem like a far-fetched hypothesis. A few bristles on your cheeks won’t exactly stop a Floyd Mayweather strike, after all.

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Even so, the scientists wouldn’t be deterred. They began their investigation by revisiting the writings of one of the greatest minds of their field, who believed that facial hair might have helped move humans to the top of the food chain.

This was none other than Charles Darwin, who, in his observations that formed the bedrock of evolution, noted that male primates have more facial hair and more aggression than their female counterparts. He deduced that there had to be a correlation.

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Similarly, Darwin viewed the lion’s mane as a natural barrier around the vulnerable areas of the neck and head — plus a sign of male virility. Beseris, Naleway, and Carrier guessed that a man’s beard could function the same way. But they needed proof.

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To prove that facial hair wasn’t just another vestigial organ — a part of the body that no longer has any biological use, like the appendix or projections of skin that cause goosebumps — the biologists looked for ways that whiskers could be handy in a fight.

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So they devised an experiment to see if facial hair really could absorb or shield its owner from damage. Naturally, their study took a more scholarly route than simply punching guys with and without chinstraps, and then asking them to fill out a survey.

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Luckily for all of us, the experts passed on their initial idea to use samples from human corpses and instead tested out damage on highly realistic models. But to simulate facial hair, they did gather some tissue from the animal kingdom.

Beseris, Naleway, and Carrier wrapped their models in sheepskin — sheared to three different lengths — to test out the usefulness of various beard thicknesses. From there, all they had to do was get a little bit destructive.

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Placing samples of sheepskin-wrapped “bone” inside a chute, they pummeled their models with a metal rod. As some models broke to smithereens and others held fast, they noticed an interesting pattern emerge in their force sensor.

The “bearded” samples fared far better than those covered in sheepskin that was completely plucked or shaved. These fibers amazingly absorbed about 30% of the impact! Additionally, an amount of force that broke nearly all the shaved models broke under half of the hairier subjects.

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While a beard wouldn’t make a man invulnerable, the scientists determined that it did partially protect against damage — particularly blunt force trauma, like that from a fist. Facial hair, though it comes in many forms, basically functions as a layer of bubble wrap, except manlier.

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The biologists also tied their findings to the historical associations that the beard has “with high masculinity, social dominance, and behavioural aggressiveness, as it may function as a true indicator of level of invulnerability to facial injury.”

Moreover, the beard’s location is particularly strategic as the jawbone is “one of the most commonly fractured facial bones in interpersonal violence.” Facial hair essentially protects the mandible by cushioning a blow and spreading the force across a broader area.

The experimenters did concede that this effect could fluctuate quite a bit depending on beard length, density, and texture. So while you might be better off fighting bearded, you might not want to pick a fight right away. The one thing we know for sure is that the human body is full of mysteries.

1. This fact will make you blush. That redness in your cheeks comes from all the capillaries throughout the body opening up in diameter. That means your entire system is turning redder — even the lining of your stomach.

2. We’ve all seen a character in a movie come up with a bright idea, right as a lightbulb appears over his head. It’s not that far from the truth. As a matter of fact, the electrical signals coursing through your brain are sufficient to power an actual bulb!

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3. Why don’t you quit the sit-ups and focus on other muscles? After all, your face can contort into roughly 7,000 different expressions. It’s time to practice in front of the mirror until you can give Jim Carrey a run for his money.

4. You might have some trouble falling asleep at times, but be grateful you don’t have Exploding Head Syndrome. People with this condition will sometimes hear an imagined loud bang, possibly accompanied by a flash of light, when they doze off.

5. Climbing up Rapunzel’s hair might’ve come from a fantasy story, but it’s not that far from the truth. Human hair is next to indestructible, as each strand is strong and slow to decay. Only fire can turn it to smithereens.

6. Do you have a taste for the finer things? Do you also hit your head a lot? If so, you might suffer from a rare condition called Gourmond Syndrome, which drives you to consume gourmet food.

7. Forcing a smile, even in your darkest moods, might actually make you happy. When your facial muscles enter that position, they trigger the release of dopamine and serotonin in your brain, which will brighten your state of mind.

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8. Most people know that veins, arteries, and capillaries ferry blood throughout the body, but have no idea just how intricate the circulation system is. If you laid out all your blood vessels into a straight line, they would circle the Earth twice!

9. Small as they may be, babies actually have more bones in their bodies than full-grown adults. It’s a difference of about 300 to 212, actually. The number decreases over time as individual bones fuse together.

10. Although mammals have distinct types of enamel coating their teeth, a harder mineral composition doesn’t always make a difference. For instance, scientists determined that our chompers are just as strong as a shark’s. Take that, jaws!

11. If you don’t like what you see on the scale, don’t blame yourself. Many of your organs weigh far more than you think. For one, the average person’s skin makes up a whopping 16% of their weight.

12. You spend a lot more time with your eyes closed than you think. While awake, the average person has their eyelids shut for about 10% of the time — mostly due to blinking!

13. Here’s some vital advice for any theme park fans who fear they’re too short to ride the big coasters. You’re at your tallest in the morning, as the spine gradually compresses as the day goes on. So hit Six Flags as soon as it opens.

14. Don’t let Hannibal Lecter know, but your liver actually regenerates! Even if reduced to one-quarter of its full size, it can grow back given enough time and nutrients. That’s why it’s possible to have a liver transplant from a living donor.

15. Ever wonder why old men seem to wear their pants so high? Maybe it’s fashion, but it could also be because humans shrink half an inch every decade after they reach age 30. Time to buy some new slacks, grandpa!

16. Nothing beats hanging with your buds — your taste buds, that is. Unfortunately for all the flavor fans out there, you lose about half of them by the time you turn 60. Better cherish them while you can.

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17. Kissing isn’t only good for stoking romantic flames! Because the act causes your mouth to produce more saliva, which in turn washes away plaque, kissing prevents the formation of cavities! That’s really good news if you happen to be dating a dentist.

18. Cannonball! That’s something your unconscious actually shouts when you hit the water, as your body undergoes a “diving reflex.” This instinct shuts down nonessential functions so that you can focus on survival. With that in mind, enjoy your swim.

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19. Grab a tissue for this factoid. Humans have three unique types of tear compositions, which differ depending on the cause (strong emotion, cleansing, reaction to irritant). Use all three in the kitchen; they’re like nature’s seasoning!

20. A 2013 NASA study determined that astronauts can grow up to two inches in space! This boost is thanks to the vertebra in the spine, which expand when not under the pressure of gravity.

21. The acid in your stomach could dissolve a razor blade. Testing this fact might require a trip to the hardware store (followed by a trip to the hospital), but you can also just take the word of experts on the Internet. Your call.

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22. Stomach? Pff. Who needs it? You can live with out it, actually. A fair amount of the stuff squished into your body isn’t really necessary, including your spleen, a lung, a kidney, and 80% of your intestines.

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23. Your epidermis is showing! Don’t try to remove it, either, because it’d be fruitless: that outer layer of skin completely regenerates every two to four weeks. Every year, in fact, you lose about one-and-a-half pounds of dead skin.

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24. Anyone who has ever broken a bone might not believe this one, but your bones are really, really strong. Pound for pound, their durability and strength blows steel out of the water. In fact, you could stack the weight of five pickup trucks—about 19,000 pounds—onto one cubic inch of bone without breaking it (though it depends how quickly the force is applied).

Popular Science Monthly

25. Believe it or not, your eye color isn’t necessarily static: About 10 to 15 percent of the Caucasian population undergoes eye-color changes. Careful though. Too dramatic a change can mean that you’re coming down with a nasty eye disease such as Fuch’s heterochromic iridocyclitis, Horner’s syndrome, or pigmentary glaucoma.

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26. Your lungs have a surface area roughly equal to that of a tennis court—that’s about 2,800 square feet. Can they take the force of a fierce Rafael Nadal backhand, though? That remains to be seen.

27. Believe it or not, 150,000 hairs sprout from the average human head, and each one of those hairs can support a weight of about three ounces. By combining the strength of each of your luscious locks, you could support 12 tons, or roughly the weight of two elephants! Maybe the story of Rapunzel isn’t so far-fetched after all?

28. In a standoff between hunger and sleep, hunger would win every time. That’s because you can live about three (tragic and horrific) weeks without eating, but a mere 11 days without sleep, you’ll start shutting down.

29. Your pinky—not your thumb—is actually where a good amount of your hand’s strength comes from. Turns out losing a pinky will cost you more than the ability to drink with class, it actually supports half of all the strength of your hand!

30. Your small intestine is about 20 feet long (oddly enough, the large intestine is only five feet long). That means you could loop your lower intestine around the rim of a basketball hoop and have it touching the ground on both ends. That’s a lot of guts all up inside you!

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31. You’ve likely seen the red or violet eyes of an albino animal or human. In actuality, albinism leads to no pigment in the iris; light simply bounces right off the eye and then exits. This produces the “red” effect, and it’s the same lighting trick at work in red-eye photographs.

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32. If you’re healthy and average, it’s possible to produce four gallons of sweat per day. Even more fascinating: you don’t just keep sweating until you shrivel up and die. Your body will shut down and force you to cool off—or die trying—before you run out of liquid for sweat.

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33. You produce more body heat than you might think. Over the course of an hour, you radiate 350,000 joules of energy; that’s enough to match a light bulb’s output or boil a half-cup of water in just half an hour.

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34. Over the course of your life, you’ll produce enough saliva to fill up two swimming pools. Unless you’re like one of Pavlov’s dogs come dinnertime—then you might drool a bit more. The good news? In half of a lifetime, you can have the pool you’ve always dreamed of.

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35. Human beings are the only living things which sleep on their backs. So that’s one way in which the movie Ted isn’t quite realistic, in case you were wondering.

36. Over the course of a person’s lifetime, they spend about 2 weeks kissing. Now that’s what we call a fortnight! And as a bonus, human lips are hundreds of times more sensitive than the tips of a person’s fingers.