Extremely rarely, there can be twins with different dads—but fewer than 20 such cases are documented worldwide

Couple welcomes rare quadruplet daughters who are actually a set of twins

The four healthy girls were delivered by cesarean section and joined a larger family that includes their parents and a 2-year-old older brother. Without the use of fertility drugs, quadruplet births are rare, but the chances are even slimmer that they'll be sets of identical twins. Medical professionals say the odds are around one in a million.

Identical twin brothers marry twin sisters in double wedding—and honeymoon together

The couples exchanged vows back-to-back, allowing the brothers to serve as each other's best men, and the sisters to jump in as the maids of honor for one another. The pairs all met in a church youth group while students.Following their wedding, the couples planned to live in neighboring apartments.

Here’s why genetically identical sisters can have different colored eyes

The sequence of DNA that we inherit from our parents encodes directions for making our cells and giving us specific traits. Identical twins have the same DNA sequence, so how can one twin end up with a genetic disorder while the other twin does not? Robin Ball explains how the secret lies in X chromosome inactivation.

Why humans evolved single-child pregnancies

While birthing twins has been a rare occurrence for humans, research suggests that twins were actually the norm much further back in primate evolution. It’s proposed that single-childbearing turned out to be critical for the evolution of larger babies with larger heads. Discover more about the shift that gives insight into primate evolution.

The first criminal conviction through the use of DNA evidence was in 1988

Chromosomes contain markers where short DNA sequences repeat a variable number of times from person to person. A DNA profile is constructed by identifying the number of repeats across 20 regions throughout a genome, which can be compared against a database. DNA paternity tests work similarly by comparing markers between children and their fathers. (Some readers may experience a paywall.)

One dad, one hundred babies

A look at the companies offering surrogacy to the ultrarich—including Chinese men taking their reproductive cues from Elon Musk.

The ultrarare 'Er' blood type has been documented only about 40 times

In 2022, the tragic loss of a pregnancy led researchers to the discovery that the rare "Er" blood type could potentially cause a mismatch in blood types between mother and fetus during pregnancy, with devastating consequences. (Some users may encounter a paywall.)

Scientists first observed a sperm and an egg uniting in 1876

Throughout human history, scholars and researchers have speculated on the origin of human reproduction. It wasn't until the late-19th century that the physical process of egg fertilization via sperm cells was observed (in sea urchins), forming the basis for modern fertility research.

Jeff Bezos’ biological father and mother married as teenagers—and had Jeff a year later

His biological father, Ted Jorgensen, was a circus performer at the time. He later gave up custody of Jeff and became a bicycle repairman in Phoenix, Arizona. Ironically, the last time Jorgensen saw Jeff as a child was in a Walmart where Jorgensen worked. This video dives into the relationship between Jeff Bezos and his estranged biological father, who passed away in 2015.

Without 3-parent IVF, women carrying faulty mitochondrial DNA have few options for children

Women who are carriers of mitochondrial diseases that wish to have children without those conditions cannot be biological parents without three-parent IVF. The alternatives are to adopt or have a child via egg donation.

Imagining how genetics works in 'Harry Potter' and how muggle-born Hermione is a witch

Dr. Robert Pyatt, director of Sanford Health’s medical genetics lab, talks through real-world genetics scenarios in the Harry Potter series, from the Weasley's red hair and freckles to why Hermione, a witch, could be born to "muggle"—or nonmagical—parents.

The origins of Father's Day

Father's Day occurs on the third Sunday in June in the US. It was inspired by the same movement that advocated for Mother's Day, and was first celebrated in 1910. However, the day wasn't official until 1972, many decades after its counterpart, Mother's Day, was formally adopted as a holiday.

Salvador Dalí’s remains were exhumed for a paternity test

Years after Dalí’s death in 1989, fortune teller Pilar Abel filed a suit claiming she was the child of an affair Dalí had with her mother. In 2017, Dalí’s body was exhumed for testing. Dalí was not the father, but the artist’s mustache remained intact decades after his passing.

Unconditional birthright citizenship is rare outside the Americas

Around 30 countries, mostly in the Americas, grant automatic citizenship by birthplace. Elsewhere—especially in Europe, Asia, and Africa—citizenship typically follows jus sanguinis, based on parental descent rather than location of birth.

Some men may be at elevated risk of inheriting tinnitus

A 2017 Swedish Twin Registry study suggests that bilateral tinnitus—when tinnitus occurs in both ears instead of just one—appears to be heritable, at least in men.

Eleanor and Franklin Roosevelt were 5th cousins, once removed

This means the couple shared great-great-great-great-grandparents but from different generations of the same family line. Fifth cousins are considered distant relatives, with only a 10% to 15% chance of sharing detectable DNA.

How couples today manage their finances

In relationships, shared bank accounts used to be the default. Not anymore. Many couples maintain separate finances for practical reasons or to retain greater independence, though many couples experience trust issues as a result. This article checks in on the status of relationship finances and highlights, among other insights, how attitudes toward money are often determined by family history.

Some data links schizophrenia to older paternal age and birth complications

Yet both associations are not yet considered firm enough to definitively be causative. Schizophrenia is a multi-causal syndrome and a mixture of factors, including genetics, are widely believed to be behind its development.

King Henry VIII's first divorce is likely the most famous divorce of all time

How often does a divorce change the course of a nation? When English King Henry VIII wanted to divorce his first wife, Catherine of Aragon, in the 1500s, Catholicism was the national religion. Even though Catherine didn't produce a male heir, religious leaders refused to grant his wish. In response, King Henry turned his country upside down for the chance to marry the second of his six wives.

The US president who had the most children

John Tyler, America’s 10th president, was born in 1790, yet still has one living grandchild. This bizarre phenomenon can be explained by his 15 children, which he had throughout all stages of his adult life. Tyler had eight children with one wife and seven with another, leading him to hold the title as the US president with the most children. Tyler was also the first US president to get married while in office.

The grandfather paradox of time travel

If you went back in time and killed your grandfather when he was a child, what would happen to you? One of your parents would never be born, so you wouldn’t be born either. But, if you’re never born, how could you kill your grandfather in the first place? This so-called grandfather paradox is something physicists, philosophers and sci-fi writers constantly ponder. Read the piece to learn how they’ve been trying to reconcile it.

As of 2021, 25% of 40-year-olds in the United States had never been married

If you’re in your forties and without a college degree, you’re significantly less likely to have ever been married now than in the past. Ditto for Black 40-year-olds and middle-aged men. There’s been a huge jump from the 6% of 40-year-olds who had never been married in 1980. Despite the historical significance of marriage, the trend away from wedded bliss has been rising steadily over the past three decades.

Salvador Dalí believed he was his own dead brother, who had died nine months before he was born

The first successful organ transplant was performed in 1954

The successful kidney transplant procedure, at what's now-called Brigham and and Women's Hospital, ushered in a new medical era and gave hope to patients with organ failure. The recipient, 23-year-old Richard Herrick, lived eight more years after receiving the donated organ from his living twin brother, Ronald.

USA Today asked readers about their grief—and received more than 700 responses

The submissions included one moving story of two women whose sons died by drug overdose. The duo wrote that they found each other in a support group and decided to navigate their respective difficult situations by starting a podcast together called "Two Moms with Two Dead Kids," which focused on what life was like in the years following the deaths of their children.

A 1993 deal with the government exempts British Royals from paying inheritance taxes

When Queen Elizabeth II died, King Charles didn't have to pay any inheritance taxes on the money he received from his mother. That's because of a unique deal the royals made with the UK government in the 1990s, in an effort to preserve the assets of the royal family that are synonymous with the institution.

Indefinite cloning of some endangered species may not sustain their longevity because cloning success rates decrease as genetic mutations accumulate.

While atoms are normally made of protons, neutrons, and electrons, exotic ones have been built with antimatter—alternate versions of normal matter that live for fractions of a second and are about a billion times as rare.

About 2,000 US babies are born annually without some portion of their limbs, potentially leading to a lifetime of pricey prosthetics.

The United States is one of only around two dozen countries with a fully federal system of government, in which power is divided between national and state governments.

US housing costs have risen by roughly 175% between 1991 and 2026—but a growing number of Gen Zers are becoming homeowners anyway. In 2025, 4% of homebuyers were Gen Z, up from 3% the year before.

The hormonal disorder PCOS was renamed PMOS in 2026, a move designed to improve care and research by shifting the focus to the hormonal causes of this condition that affects 1 in 8 women.

Some Pokémon have been named after real and fictional organisms, while some real-world species have been named after Pokémon, such as Chilicola charizard and Binburrum zapdos.

Chaos theory—informally known as the butterfly effect—is the reason why weather forecasts are presented with probabilities rather than certainties.

While the first exchange-traded fund (a 'basket' of different assets that can be bought and sold on a stock exchange) in the US only launched in 1993, the global ETF market has grown to more than $10T in the short time since.

Children are now three times more likely to say they want to be a YouTuber when they grow up than an astronaut, with some even attending 'YouTube camps' that teach kids how to create content for the platform.

Explore fun facts from the USPS, including unique post office buildings, a stamp that traveled past Pluto, and more.

Warren Buffett's former professor Benjamin Graham is known as the 'father of value investing,' a strategy in which investors seek to buy stocks trading below their intrinsic worth.

The Brothers Grimm were lawyers before they were storytellers, but became interested in fairy tales as they began investigating how rules and customs had been passed down through cultures.

Many legends about George Washington, including his supposed wooden teeth and the story of cutting down the cherry tree, lack evidence.

Double world record holder Hunter Ewen helped conquer his fear of balloons, called globophobia, by training to win Guinness World Record titles for balloon inflation.

The syncytiotrophoblast is the outer layer of the placenta and the largest human cell, spanning an area about twice that of a king-sized bedsheet.

Crows are believed to have intelligence on par with a seven-year-old child and demonstrate complex behaviors, from problem-solving with tools to recognizing human faces.

According to the physics of black holes, our 4D reality may be a hologram—a projection of information coded on a 2D surface on the edge of the universe.

In 1963, a basement renovation in Turkey revealed a passageway to a hidden, multilevel underground city that once housed as many as 20,000 people

The Great Salt Lake's distinct dual coloration results from high-salinity organisms that only live in the northern portion and produce a purple protein.

At the beginning of the 20th century, a group of young men ate standard American food—replete with food additives like borax and formaldehyde—as part of government research to better understand food safety.

One of the most famous portraits ever taken is 'Afghan Girl' (1984) by Steve McCurry, yet the subject Sharbat Gula went much of her life without being identified or benefitting from the image's success.

Browse a detailed visual analysis of over 200,000 similes—comparisons that often use 'like' or 'as'—from popular fiction to see how frequently writers the same idiomatic expressions.

One disco producer saw 'Star Wars' four times on its opening weekend and was so inspired that he recorded the album 'Star Wars and Other Intergalactic Funk,' which produced a chart-topping single.