In your genes

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

Credit: 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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

From cave paintings to touch screens

Where is the @ sign called "cinnamon bun"? Decoding typographic symbols

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Symbols are everywhere—from ancient manuscripts to Instagram captions. Elegant, cryptic, or quirky, certain typographic characters have communicated their meanings across mediums for centuries. The @ symbol, for example, appeared in merchant notes long before its use in email. And the asterisk has been catching eyes since ancient Greek scholars marked corrections with "little stars." In this article, we dive into the origins of these everyday symbols—you may never look at a question mark the same way again!

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We’ll start at the very beginning. Alpha, or α, is the first letter of the Greek alphabet, represented by a character similar to our lowercase "a." It traces back to the Phoenician letter aleph, which meant "ox." It was expressed with a shape that resembled the animal’s head: 𐤀.

So yes, we could say that our letter "A" is distantly derived from a drawing of a head. Because of its position at the start of the alphabet, the term alpha often refers to the first in a series—alpha particles, alpha software, and even alpha wolves are examples. It’s associated with leadership, hierarchy, and beginnings.

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We know that pi (π) represents the ratio between the circumference and diameter of a circle, which is roughly 3.14. Because of this, Pi Day is celebrated on March 14th (3/14), often accompanied by mathematical discussions and, well, pies. But what’s the origin of the "T"-like symbol?

Simply put, π is the lowercase letter "p" in the Greek alphabet. In the 18th century, Welsh mathematician William Jones adopted it in place of the word perimeter, since it’s the first letter of that word in Greek (περίμετρος). Since then, the symbol has been used to represent the mathematical constant we know today.

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The "at" sign (@) has a wide array of names around the world. Some of them refer to its curious shape: in Italy, it’s called chiocciola (snail), and in Sweden, kanelbulle (cinnamon bun). Although we now see it daily in email addresses and on social media, its earliest documented use dates back to the 16th century, when merchants and scribes used it to mean "at the rate of" or "each"—for example: "5 apples @ $2."

In the 1970s, however, an American scientist used it to send the first email. The symbol came in handy for separating the user’s name from the machine or server name. Five decades later, not a day goes by without millions of people hitting that key to use the symbol.

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We see it in titles (Law & Order), in company names (Ben & Jerry’s), and even in abbreviations (R&B). The ampersand symbol (&) is considered one of the oldest symbols still in regular use today. It originated as a ligature—a combination of the Latin letters E and T from the word et ("and").

In 1st-century Roman cursive, scribes began merging e and t for quicker writing; the "&" shape evolved over time, becoming more stylized during the Middle Ages. The name ampersand emerged in the 1800s, when, in early grammar schools, children reciting the alphabet would conclude with "&" (then considered the 27th letter) by saying: "and per se and" (meaning "and, by itself, means ‘and’"). Over time, this phrase slurred into ampersand.

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Some call it the "hash," the number sign, or the pound sign. Today, many know it as the "hashtag," owing to its use as a tagging device on social media. Its formal name, however, is the "octothorpe."

The octothorpe may have evolved from the Roman shorthand symbol ℔, which meant "pound in weight." Over time, it gained horizontal strokes, transforming into the # shape we recognize today. Since the 1960s, many people have known it as the "#" key on telephone keypads. In 2007, Twitter product designers adopted the symbol to group conversations—an idea that worked so well it soon spread across most social media platforms.

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In typographic terms, it’s called an "interrogation point." It marks a simple, direct question when placed at the end of a sentence, but we’ve also come to associate it with playful surprises or enigmas—like mystery boxes in games. But who decided that the dotted curl would stand for questions, though?

The question mark evolved from the Latin word quaestio ("question"). Early scribes abbreviated quaestio as "qo," placing the "o" above the "q." Over time, the "q" curved downward, and the "o" became the dot—forming the "?" we know today. By the 13th century, the modern question mark shape was widely adopted by European scholars. It became a standard punctuation mark with the rise of printing during the Renaissance.

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So, what about the punctuation mark for exclamation? The exclamation mark has origins not too different from the question mark. In Latin, the word io (an exclamation of joy or triumph) was written with the "i" above the "o." Over time, scribes stylized this into "!", with the "i" becoming the vertical line and the "o" turning into the dot.

Still, it wasn’t until the 15th century that it became a standard symbol in writing. Before that, people relied on word choice or context to convey emphasis. Even today, some writers choose to avoid it. Style guides like The Chicago Manual of Style recommend using exclamation marks sparingly, arguing that "good writing" shouldn’t need them.

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The percentage sign, used to express a fraction out of a hundred, is another example of a symbol that evolved over the centuries into a scribble in itself. In Latin, per centum was used often, meaning "per hundred." When written down in early manuscripts, it was abbreviated as "pc" or "p100." Over time, the "p" disappeared, and the "100" was transformed into the two dots we recognize today.

Did you know that there is a similar sign meaning "per thousand"? The symbol "‰" (per mille) is a lesser-known cousin of the percentage sign and is still used in scientific and financial contexts.

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The "asterisk," as we know it today, was already drawn in cave paintings. Simple as it is, the figure must have always been compelling. The first time it was used to mark corrections or omissions in texts was by an early Greek scholar. They called this sign asteriskos, meaning "little star."

As early as the Middle Ages, it began being used around words or sentences to imply emphasis—similar to how we use it today in digital texts. In plain-text formats, we use the "" symbol to make specific words or letters appear bold.

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The crossed-out "S" represents currency in the United States and many other countries, including Canada and Australia. In fact, the dollar sign originated from the symbol used in business correspondence to refer to the Spanish peso in the 18th century, also known in British America as "pieces of eight."

The peso was abbreviated as "ps" or "P$," representing "peso" and "silver." Over time, the "P" evolved, and scribes began merging it with the "S" into a single character. This stylization eventually led to the familiar "$," with one or two lines crossing the capital "S." The dollar sign became widely adopted in the United States after the country's independence.