Why Do Humans Have Belly Buttons And Do Other Animals Have Them Too

The belly button—also known as the navel—is one of the most universal human features, yet few people pause to consider its origin or significance. It’s a small, often unassuming mark on the abdomen, but it carries deep biological meaning. Every human has one, though shapes and sizes vary widely. But what exactly is a belly button? Why do we have it? And perhaps more intriguingly, do other animals share this trait?

The answers lie in our earliest development, long before we take our first breath. The belly button is not just a scar—it’s a permanent reminder of our time in the womb and the vital connection we once had to our mothers. To understand its purpose and prevalence across species, we must explore embryonic biology, evolutionary adaptation, and the diversity of reproductive strategies in the animal kingdom.

The Biological Origin of the Belly Button

The belly button forms during fetal development as a result of the umbilical cord’s presence. This cord connects the developing fetus to the placenta, which is embedded in the mother’s uterine wall. Through the umbilical cord, oxygen and nutrients are delivered from the mother to the growing baby, while waste products like carbon dioxide are carried away for disposal.

The umbilical cord contains three blood vessels: two arteries and one vein. The single vein transports oxygen-rich blood and nutrients from the placenta to the fetus, while the two arteries return deoxygenated blood and metabolic waste. This exchange system is crucial for sustaining life in the womb, where the fetus cannot breathe air or eat food directly.

After birth, the umbilical cord is clamped and cut, typically within minutes. What remains attached to the newborn is a small stump. Over the following one to three weeks, this stump dries up, turns black, and eventually falls off, leaving behind the belly button. The internal portion of the cord—the part connected to the baby’s abdomen—closes off and becomes fibrous tissue, forming ligaments inside the abdominal cavity.

Tip: New parents should keep the umbilical stump clean and dry to prevent infection. Fold diapers below the stump and avoid submerging it in water until it detaches naturally.

Types of Belly Buttons and Their Formation

Not all belly buttons look the same. The final appearance depends on how the skin heals after the umbilical stump detaches. Genetics, the length of the cord, and even the healing process influence whether someone ends up with an \"innie\" or an \"outie.\"

• Innie: The most common type, where the navel appears sunken inward. This occurs when the remaining umbilical tissue pulls inward as it retracts.
• Outie: Less common, appearing as a protrusion. Often caused by excess skin left after the stump falls off or, in some cases, a minor umbilical hernia that resolves itself.
• Stick-out, puffy, or split navels: Variations due to unique healing patterns or anatomical differences in abdominal wall structure.

Despite myths, tugging on an outie will not turn it into an innie—its shape is determined by internal healing, not external manipulation. Some surgical procedures can alter the appearance of the navel, particularly during abdominoplasty (tummy tucks), where the belly button may be repositioned or reshaped.

Do Other Animals Have Belly Buttons?

Yes—but only certain ones. The presence of a belly button is directly tied to whether an animal develops via a placenta and umbilical cord. This means that among animals, only placental mammals have true navels.

Mammals are divided into three major groups based on reproduction:

1. Placental Mammals (Eutherians): These animals, including humans, dogs, cats, elephants, and whales, carry their young internally with a developed placenta. They give birth to relatively mature offspring after a long gestation period. All placental mammals have belly buttons.
2. Marsupials (Metatherians): Animals like kangaroos, koalas, and opossums give birth to extremely underdeveloped young, which then crawl into a pouch to continue development. While they do have a brief umbilical connection, it detaches internally before the joey leaves the birth canal, so no visible navel remains.
3. Monotremes (Prototherians): The rarest group—including the platypus and echidna—lay eggs. Since there is no placental connection at all, these mammals do not have belly buttons.

Among placental mammals, belly buttons are often hard to spot due to fur coverage or subtle scarring. For example, dogs and cats have small, inconspicuous navels located along the midline of the abdomen, just below the ribcage. In marine mammals like dolphins and whales, the navel is streamlined to reduce drag in water, making it nearly invisible.

Animal Group	Umbilical Cord?	Belly Button Visible?	Example Species
Placental Mammals	Yes	Yes (usually small)	Humans, lions, horses, bats
Marsupials	Briefly	No	Kangaroos, wombats, sugar gliders
Monotremes	No	No	Platypus, echidna
Birds & Reptiles	No	No	Eagles, turtles, snakes
Fish & Amphibians	No	No	Frogs, salmon, sharks

“Every placental mammal carries a silent badge of fetal life—the navel. It’s a testament to the shared biology that connects us across species.” — Dr. Lena Torres, Developmental Biologist, University of California

Medical and Anatomical Significance of the Navel

Beyond being a developmental remnant, the belly button has functional importance in medicine and anatomy. Internally, the remnants of the umbilical vessels transform into ligaments. The median umbilical ligament, formed from the urachus (a fetal tube connecting the bladder to the umbilicus), runs from the top of the bladder to the navel. The lateral umbilical ligaments are derived from the fetal umbilical arteries and help define anatomical regions in the lower abdomen.

The navel also serves as a key landmark in abdominal surgery. Surgeons use it to orient themselves during laparoscopic procedures. In fact, many minimally invasive surgeries insert tools through or near the belly button because the scar tends to be hidden and well-concealed post-recovery.

Occasionally, medical conditions can affect the navel. These include:

• Umbilical Hernia: When part of the intestine pushes through a weak spot in the abdominal wall near the navel. Common in infants and often resolves without treatment.
• Omphalitis: A bacterial infection of the umbilical stump in newborns. Requires prompt antibiotic treatment.
• Urachal Cysts or Sinuses: Rare conditions where remnants of the urachus fail to close completely, potentially leading to infection or drainage.

In rare cases, adults may experience pain or discharge from the navel due to retained embryonic structures. While uncommon, such symptoms warrant medical evaluation.

Fun Facts and Cultural Perspectives

The belly button has captured human imagination far beyond biology. Culturally, it has been viewed in diverse ways:

• In ancient Greece, exposed navels were considered symbols of beauty and athleticism, often depicted in statues of gods and athletes.
• In parts of India and the Middle East, adorned belly buttons are associated with fertility and sensuality, especially during traditional dances like belly dancing.
• The “navel-gazing” idiom, derived from the Sanskrit term *nābhicintanam*, originally referred to deep meditation on the self in yogic traditions—not mere self-absorption, as it's sometimes misused today.

Interestingly, belly buttons accumulate lint, bacteria, and dead skin cells. A 2009 study by the Belly Button Biodiversity Project found over 2,300 bacterial species in human navels, many previously unknown to science. Most are harmless, but poor hygiene can lead to odor or infection.

Tip: Clean your belly button occasionally with warm water and mild soap, especially if you’re prone to sweating or wearing tight clothing. Use a cotton swab gently—never aggressively.

Mini Case Study: The Belly Button Biodiversity Project

In 2011, scientists at North Carolina State University launched the Belly Button Biodiversity Project to explore microbial life in human navels. Volunteers swabbed their belly buttons, and researchers analyzed the samples. They discovered astonishing diversity: some individuals hosted rare microbes similar to those found in soil or extreme environments. One participant’s navel contained a bacterium previously identified only in Japan.

This project highlighted that even a small, seemingly insignificant body part can harbor complex ecosystems. It also reinforced the idea that each person’s microbiome is unique—like a fingerprint. While not medically critical, understanding skin flora helps scientists learn about immune responses, skin health, and even disease prevention.

FAQ About Belly Buttons

Can you live without a belly button?

Yes. Some people are born without a visible navel due to rare conditions like omphalocele, where abdominal organs develop outside the body and are later surgically placed inside. Others may lose their natural belly button due to trauma or surgery. Artificial navels can be reconstructed for cosmetic purposes.

Why do belly buttons smell?

A smelly navel usually results from trapped sweat, dead skin, and bacteria. Poor hygiene, obesity (which can cause skin folds), or infections like candidiasis contribute to odor. Regular cleaning typically resolves the issue. Persistent foul smell with discharge should be evaluated by a doctor.

Are outies less common than innies?

Yes. Approximately 90% of people have innie belly buttons. Outies occur in about 10% of the population and are often due to how the umbilical stump healed. True outies caused by umbilical hernias usually resolve by age 1–2 in children.

Step-by-Step Guide: How to Keep Your Belly Button Healthy

Maintaining a clean and healthy navel is simple but often overlooked. Follow these steps:

1. Daily Check: During showers, pay attention to your belly button. Look for redness, swelling, or unusual discharge.
2. Gentle Cleaning: Use lukewarm water and a mild, fragrance-free soap. Gently rub around and slightly inside the navel with your fingertip or soft washcloth.
3. Drying: Pat the area dry thoroughly. Moisture trapped in the navel can promote bacterial or fungal growth.
4. Exfoliate Occasionally: Once a week, use a gentle exfoliant to remove dead skin buildup, especially if you notice dark lint or odor.
5. Monitor Changes: If you observe persistent pain, pus, or a growing lump near the navel, consult a healthcare provider.

Checklist: Signs Your Belly Button Needs Medical Attention

• Redness or warmth around the navel
• Pain or tenderness to touch
• Discharge (yellow, green, or bloody)
• Foul odor that doesn’t improve with cleaning
• Swelling or bulge that appears new
• Fevers accompanying navel symptoms

Conclusion

The belly button is far more than a quirky indentation on the abdomen. It is a biological signature of our prenatal life, a marker of our mammalian heritage, and a window into both health and evolution. From the moment of birth, it becomes a lifelong companion—one that silently tells the story of how we began.

And while humans may be the most vocal about their navels, we’re not alone. Across the animal kingdom, placental mammals share this quiet bond, each carrying a faint scar of the lifeline that once sustained them. Whether nestled beneath fur or hidden in folds of skin, the belly button is a universal symbol of connection, growth, and the intricate journey from embryo to life.

💬 Did you know all placental mammals have belly buttons? Share this article with someone who’s curious about the science behind everyday wonders—and maybe compare navels while you’re at it!