In your genes

This is in your DNA: 12 weird traits passed down from long ago

Image: Cade Proulx

You may have never met your great-great-grandparents, but their biological legacy lives on in you in ways you might not expect. From tiny quirks in your body to odd preferences and physical features, ancestral survival and lifestyle choices have shaped what you carry today. Here are 12 surprising traits that science has linked to deep genetic inheritance.

Image: Katya Ross

A thumb that bends backward at the top joint is known as a hitchhiker’s thumb. It results from a single gene variant.

This trait is controlled by a variation in the gene responsible for joint flexibility. Some people have it in both thumbs, while others only in one. It's a harmless variation that may have been more common in populations requiring greater dexterity.

Image: Max Leveridge

Some babies are born with blue or gray eyes that change color over time. The way this shift unfolds is written in your DNA.

After birth, melanin production in the iris increases over time. Genetic variants in the OCA2 and HERC2 genes regulate melanin levels. These subtle changes can take months or even years to settle into a final eye color.

Image: Alex Guillaume

The ability to roll your tongue into a tube shape is often thought to be purely genetic, and that’s partially true. While you can learn to do it with a lot of practice, studies show it’s also influenced by genes.

Some populations have a higher percentage of tongue rollers, and the trait may have originally been a byproduct of muscle control needed for speech or food manipulation in early humans.

Image: Tim Trad

Acrophobia, or intense fear of heights, has a genetic link tied to survival instincts from your prehistoric ancestors.

People with heightened depth perception or balance issues may inherit a stronger fight-or-flight response to elevation. This reaction likely helped early humans avoid dangerous cliffs or falling from trees.

Image: KaLisa Veer

Strange as it sounds, redheads often experience pain differently. Some studies suggest they have a higher threshold for certain types of pain, while others indicate increased sensitivity to specific stimuli like cold or heat.

This is linked to ancient adaptations in the MC1R gene, which influences melanin production and also affects pain modulation through opioid receptors in the brain. Variants of this gene were more common in populations from colder regions, such as prehistoric Europe.

Image: Chermiti Mohamed

Freckles are genetic, but they bloom with sun exposure due to the way ancestral DNA interacts with UV light.

In fact, the same MC1R gene involved in red hair also influences how melanin clusters into freckles. This is because freckling was advantageous for fair-skinned populations needing some UV protection without full pigmentation.

Image: Anita Jankovic

The ability to digest milk into adulthood is a relatively recent mutation in human history. Populations with pastoralist ancestors—such as Northern Europeans and some East Africans—evolved lactase persistence, the continued production of the enzyme lactase that enables them to digest milk throughout adulthood.

Most of the world remains lactose intolerant, but those with this mutation can thank their ancestors for a genetic advantage linked to dairy-based survival.

Image: Thomas Park

Weirdly enough, some people sneeze when exposed to sunlight or even just bright lights. This phenomenon, known as the "photic sneeze reflex," affects 18–35% of people and is linked to genetics.

While this inherited quirk is harmless, it likely results from crossed nerve signals between the optic and trigeminal nerves, the latter of which controls facial sensations and reflexes like sneezing.

Image: Claudia Love

Also called Morton’s toe, this feature was once thought to improve balance or running efficiency. The trait is hereditary and common in certain populations.

Greek statues often depict this toe shape, suggesting it was either idealized or prevalent in ancient Mediterranean groups. Biomechanical studies show mixed results, but some suggest that a longer second toe can affect posture and gait.

Image: Mika Ruusunen

People with ancestry from colder regions often have inherited a better tolerance to cold. Adaptations such as higher basal metabolic rates, subcutaneous fat distribution, and heat-conserving blood vessel responses are linked to genetic clusters in populations like the Inuit or Sámi.

Genes like UCP1, which influence fat burning and thermogenesis, are more active in these populations.

Image: Marco Bianchetti

Some people have a vestigial muscle in the forearm that others lack entirely. Called the palmaris longus, it once helped tree-climbing primates enhance their arm strength.

Today, about 14% of people are born without it in one or both arms. It has little to no effect on grip strength, making it a living fossil of human evolution. Interestingly, when present, it’s often harvested for surgical grafts because its absence doesn’t impair function.

Image: Bethany Beck

Clockwise or counterclockwise hair whorls are influenced by genetics, and some studies link their direction to the same genes that affect handedness. However, identical twins can sometimes have opposite whorl patterns, suggesting a mix of genetics and early fetal environment.

This trait has no known survival function but may serve as a visible marker of underlying developmental processes during early embryonic growth.

The truth about your brain

You won’t believe what happens in your brain while you sleep

Image: Milad Fakurian

Your brain is one of the most powerful and mysterious organs in your body. It controls everything from your thoughts to your emotions and even processes information at lightning speed. But how much do you really know about it? Some long-believed myths about the brain have been debunked, while other surprising facts reveal just how incredible this organ truly is. Get ready to be amazed by these fascinating brain facts!

Image: Natasha Connell

You’ve probably heard this one before, but it’s completely false! While it’s true that not all parts of the brain fire at the same time, imaging studies show that most regions are active throughout the day, even when we sleep.

Your brain is constantly working, controlling bodily functions and emotions, and processing information. So next time someone says you’re only using 10% of your brain, you can confidently tell them that’s just a myth!

Image: Aarón Blanco Tejedor

Here’s a weird fact: While your brain processes pain signals from the rest of your body, it has no pain receptors of its own. This is why surgeons can perform brain surgery on conscious patients without causing them pain.

However, the membranes and tissues surrounding the brain do have pain receptors, which is why headaches and brain injuries can be so excruciating.

Image: Usman Yousaf

How come we have headaches if the brain has no pain receptors? Well, that’s because headaches are triggered by chemical activity in the brain, changes in nerves and blood vessels, and even fluctuating serotonin levels.

In some cases, hormones like estrogen can also play a role, which explains why migraines are more common in women.

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Dreams are proof that your brain never rests! (Warning: this fact can make you feel exhausted.) While you sleep, your limbic system, that is, the part of the brain that deals with emotions, becomes especially active, which is why dreams often feel so intense.

On average, humans experience four to seven dreams per night, even if we don’t always remember them. And what about that scary nightmare about falling? Well, you can thank your amygdala, the brain’s fear center, for that one.

Image: Brett Jordan

Have you ever walked into a room and instantly forgotten what you were after? That’s because short-term memory only lasts about 20-30 seconds! That’s not enough!

Your brain holds a limited amount of information in its active state before deciding whether to store it or discard it. Ironically, we can’t really choose what makes the cut, but we do hope these facts stay with you!

Image: BUDDHI Kumar SHRESTHA

That sharp, icy pain when you eat something too cold? It’s your brain’s way of telling you to slow down! Officially called sphenopalatine ganglioneuralgia, a brain freeze happens when cold food or drinks rapidly chill the blood vessels in your throat, causing them to constrict and then rapidly expand. This sends pain signals to your brain, warning you of the sudden temperature shift. It’s annoying, but it’s actually your body trying to protect itself!

Image: Josh Riemer

You didn’t need us to tell you, but let’s look at the details: The average person has between 12,000 and 60,000 thoughts per day. What’s even more interesting? 95% of those thoughts are the same ones you had yesterday. Is that not surprising enough? Hear this out: 80% of them tend to be negative. That’s because our brains are wired for survival, constantly analyzing risks and potential dangers.

Image: Terry Vlisidis

Even though it only makes up about 2% of your body weight, your brain employs a major quantity of energy! It consumes 20% of your oxygen and blood supply, making it one of the most demanding organs in your body.

If your brain goes without oxygen for just five minutes, brain cells start dying, leading to irreversible damage. This is why deep breathing and cardiovascular exercise are great for brain health!

Image: Alexander Andrews

Do you know that feeling when you hit the back of your head and see stars? That’s because your occipital lobe, which controls vision, is located at the back of your brain. If you get hit there, your brain momentarily misfires, causing flashes of light.

Interestingly, your brain processes vision on the opposite side; while your right brain controls your left eye, your left brain controls your right eye. It’s one of the many ways the brain operates in a complex way.

Image: Rodion Kutsaiev

Believe it or not, your brain generates between 12 and 25 watts of electricity when you’re awake. If you can’t really grasp how powerful that is, check this out: It’s enough to power a small light bulb! Your brain’s electrical activity is what allows neurons to send signals at speeds of up to 260 miles per hour.

Image: Robina Weermeijer

Your brain may be the fattiest organ in your body, consisting of at least 60% fat! This is why consuming healthy fats, like omega-3s and omega-6s present in fish, for example, is essential for brain health.

Healthy fats stabilize brain cell walls, reduce inflammation, and support cognitive function. So go ahead and enjoy that avocado toast, it’s food for your brain!

Image: Robina Weermeijer

It’s not just your memory that fades over time; the brain itself physically shrinks as one gets older. It continues developing until your late 40s, but after that, it slowly decreases in size.

Now, size doesn’t equal intelligence, so a smaller brain doesn’t necessarily mean a less capable one. Staying mentally active, exercising, and eating brain-boosting foods can help keep it in top shape!

Image: Lisa Yount

We often think of cholesterol as bad, but your brain actually depends on it! In fact, 25% of your body’s cholesterol is stored in your brain, where it helps with learning and memory. However, unlike other organs, the brain can’t absorb cholesterol from the blood, it has to produce its own. So, while too much cholesterol in the body can be harmful, the right amount is vital for brain function. At least you can use that as an excuse to get that burger!