Evolution’s Biggest Mistakes: 24 Body Parts That Prove We’re Still Works in Progress

Home Biology Evolution’s Biggest Mistakes: 24 Body Parts That Prove We’re Still Works in Progress

Biology

By Chu E. - June 15, 2025

When picturing the human body, it’s tempting to imagine a marvel of flawless engineering. But evolution isn’t a master designer—it’s more like an improviser, tinkering and patching as we adapt to new environments. Instead of streamlining us for efficiency, evolution often leaves behind quirky remnants and awkward leftovers from our prehistoric past. From vestigial organs to odd structural flaws, our anatomy is packed with evidence that we’re still works in progress. Let’s explore 24 body parts that highlight just how imperfectly we’ve been put together.

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1. Appendix

Evolution’s Biggest Mistakes: 24 Body Parts That Prove We’re Still Works in Progress — Source: Unsplash, Aakash Dhage

The appendix is a tiny, finger-like pouch dangling from your large intestine. While its function is still debated, it’s often remembered for its tendency to become inflamed—leading to painful, sometimes dangerous, appendicitis. Some scientists believe the appendix once played a role in digesting tough plant material, a job now obsolete in our modern diets.
Today, it may act as a safe haven for beneficial gut bacteria, but its evolutionary baggage makes it more trouble than it’s worth for many people. Learn more

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2. Wisdom Teeth

Wisdom teeth—also known as third molars—once helped our ancestors grind down tough, fibrous plants and raw meat. But as human diets changed and our jaws evolved to be smaller, these extra teeth often have nowhere to go. The result? Impacted or misaligned wisdom teeth that can cause pain, infection, and often require surgical removal. Their continued presence is a prime example of evolution lagging behind our modern lifestyle, leaving many of us with a literal ache from the past. Source

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3. Tailbone (Coccyx)

The coccyx, or tailbone, is a small, bony structure at the base of the spine—a relic of the tails sported by our distant primate relatives.
While it does provide an anchor for certain muscles and ligaments, it serves little practical purpose in modern humans.
Injuries to the coccyx can be surprisingly painful, a reminder of this evolutionary leftover.
Its mere existence is a subtle but persistent clue to our animal ancestry. Read more

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4. Body Hair

Compared to our primate cousins, humans are nearly hairless, yet we still sport curious patches of body hair that serve little practical purpose today.
While eyebrows and eyelashes help shield our eyes from sweat and debris, and pubic hair may offer some protection or signaling, areas like chest and back hair are mostly evolutionary leftovers.
These vestigial tufts are more about clinging to our ancestral past than providing any real benefit in the modern world. Reference

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5. Erector Pili Muscles (Goosebumps)

Ever wondered why you get goosebumps when you’re cold or scared? This reaction is caused by tiny erector pili muscles at the base of each hair follicle.
For our furry ancestors, contracting these muscles puffed up their fur—making them appear larger to predators and helping trap heat.
In modern humans, with our sparse body hair, the effect is mostly cosmetic and serves no real function.
It’s a quirky, visible sign of our evolutionary roots. Learn more

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6. Tonsils

Tonsils are clusters of tissue at the back of your throat that act as the body’s first line of defense against inhaled or ingested pathogens.
Ironically, they’re also prone to frequent infections—especially in children—which often leads to surgical removal.
The true evolutionary benefit of tonsils is still debated, since living without them generally doesn’t impact a person’s long-term health or immune function.
Their troublesome nature highlights how not every evolutionary feature is a perfect solution. Source

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7. Male Nipples

Male nipples are one of the most curious human features. They develop in embryos before the body’s sex is determined, meaning everyone starts with the same basic blueprint.
After sex differentiation, males simply retain theirs—even though they serve no real functional purpose.
Their presence is a classic example of how evolution often works with existing plans, even when the result isn’t particularly useful.
It’s an anatomical quirk that’s stuck around purely by default. More info

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8. Sinuses

Sinuses are hollow, air-filled spaces tucked within the bones of our skull. While theories suggest their purpose might be to lighten the head, humidify incoming air, or even enhance our voices, their true evolutionary function remains elusive.
What is clear, however, is that sinuses can be a real nuisance—prone to infections, congestion, and pressure headaches.
Their poor drainage and frequent inflammation make them a classic anatomical flaw, illustrating how evolution doesn’t always prioritize comfort. Reference

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9. Palmaris Longus Muscle

The palmaris longus muscle is a slim tendon running down the forearm to the wrist, but about 14% of people don’t have it at all.
This muscle was once helpful for our primate ancestors, aiding in their tree-climbing abilities.
Today, its presence or absence has no impact on grip strength or daily function, making it a fascinating example of evolutionary redundancy.
Check your wrist—you might be missing this evolutionary oddity and never even know it. Read more

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10. Darwin’s Tubercle

Darwin’s tubercle is a tiny, painless bump that sometimes appears on the edge of the upper ear.
It’s a subtle reminder of our distant mammalian ancestors, who had pointed, mobile ears to better detect sounds.
Today, not everyone has this quirky feature, and for those who do, it serves no known function.
It’s just one more small, visible link to our evolutionary past. Source

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11. Little Toe

The little toe once played a significant role for our ancestors, helping with climbing and gripping branches.
In modern humans, it offers only a slight contribution to balance and stability, making it more of a passenger than a driver in our daily movements.
Some evolutionary biologists even speculate that, as we continue to walk upright and wear shoes, the little toe may eventually shrink or disappear altogether.
For now, it remains a small, stubby reminder of our tree-dwelling past. Reference

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12. Third Eyelid (Plica Semilunaris)

At the inner corner of your eye sits the plica semilunaris, a tiny crescent-shaped fold.
This is all that remains of a once-functional third eyelid—found in birds, reptiles, and some mammals—which could sweep across the eye for protection or moisture.
For humans, it’s completely vestigial, serving no real purpose beyond being a curious anatomical leftover.
It’s a subtle sign of how evolution repurposes or abandons features as our needs change. Read more

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13. Plantaris Muscle

The plantaris muscle is a slender muscle running along the back of the calf, and it’s absent in up to 10% of people.
Originally, it may have helped our ancestors grasp objects or manipulate things with their feet.
In modern humans, it serves little practical function and its loss goes unnoticed.
Surgeons sometimes even harvest this tendon for reconstructive procedures, since its absence doesn’t impact mobility or strength. Source

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14. Auricular Muscles

The auricular muscles surround our ears and, in many animals, enable impressive feats like swiveling their ears toward sounds.
For humans, however, these muscles are largely vestigial—most of us can’t move our ears at all.
A lucky few can manage a subtle wiggle, but it’s just a quirky party trick, not a survival tool.
Their presence is a reminder that our bodies still carry the blueprints for abilities we no longer need in daily life. Learn more

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15. Pineal Gland

The pineal gland is a tiny, pinecone-shaped organ deep within the brain.
Today, it’s best known for regulating sleep cycles by producing melatonin.
But its evolutionary story is far stranger—it’s the last remnant of a “third eye” once found in reptiles and amphibians, which helped them sense light directly.
In humans, the pineal gland’s ancient function has faded, leaving behind a mysterious organ that hints at our distant evolutionary connections to the animal kingdom. Reference

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16. Philtrum

The philtrum is the vertical groove that runs from your nose to your upper lip.
For many animals, this groove helps keep the nose moist, aiding in scent detection—a crucial survival tool.
In humans, however, the philtrum has lost its functional value and now stands as a simple facial feature.
It’s another subtle reminder of the sensory priorities of our evolutionary ancestors. Read more

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17. Body Fat Storage

Our ability to efficiently store body fat was once a vital evolutionary advantage, helping our ancestors survive long stretches without food.
In today’s world of abundance, however, this survival mechanism backfires, contributing to widespread obesity, diabetes, and heart disease.
What was once a life-saving adaptation has become a major health challenge for modern humans.
This double-edged sword is a striking example of how evolution’s solutions don’t always fit with our rapidly changing lifestyles. Source

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18. Varicose Veins

Our shift to bipedalism brought many advantages, but it also introduced new problems—like varicose veins.
Standing upright puts increased pressure on the veins in our legs, sometimes causing them to swell, twist, and become painful.
This common condition affects up to 30% of adults, serving as a visible reminder that our bodies are still adjusting to life on two feet.
It’s an evolutionary compromise that hasn’t quite caught up to our modern posture. Reference

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19. Throat and Esophagus Design

The human throat is a marvel of evolutionary compromise—and a bit of a design disaster.
Both food and air share a common pathway, which allows us to speak and swallow, but also dramatically increases the risk of choking.
This precarious arrangement is a direct result of adaptations for complex speech, a trade-off that prioritizes communication over safety.
It’s a sobering reminder that evolution often values new advantages even if it introduces new hazards. More info

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20. Blind Spot in the Eye

Every human eye has a blind spot—a small area on the retina where the optic nerve exits, leaving no room for photoreceptors.
We don’t usually notice it because our brains fill in the gap, but it’s a definite design flaw.
Interestingly, creatures like squids have evolved eyes without this blind spot, thanks to a different anatomical layout.
Our own visual system is a reminder that evolution sometimes settles for “good enough” rather than perfect. Source

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21. Goosefoot Tendon (Pes Anserinus)

The pes anserinus, or “goosefoot tendon,” is a convergence of three tendons on the inside of the knee.
This structure is a remnant from our evolutionary past, originally suited for different styles of movement.
In modern humans, it’s prone to irritation and pain—especially in athletes or older adults.
Its susceptibility to injury highlights how some of our body’s designs are no longer ideally matched to our current way of life. Reference

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22. Subclavius Muscle

The subclavius muscle is a slender band tucked beneath the collarbone, helping to stabilize and move the clavicle.
While it still serves a minor role in shoulder movement, it’s largely irrelevant for most modern humans.
This muscle’s true importance was in our quadrupedal ancestors, who relied on it for the mechanics of walking on all fours.
Today, it’s a vestigial part—rarely noticed and seldom missed if absent or injured. Learn more

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23. Plantar Fascia

The plantar fascia is a thick band of tissue running along the bottom of the foot, supporting the arch and absorbing shock with every step.
While it’s crucial for bipedal movement, its design is far from perfect.
Many people develop painful inflammation known as plantar fasciitis, especially after prolonged standing or running.
This common foot ailment reveals how our evolution toward upright walking still comes with structural compromises. Source

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24. Thymus Gland

The thymus gland plays a critical role in developing the immune system during childhood, training white blood cells to fight infections.
However, as we reach adulthood, the thymus begins to shrink and is eventually replaced by fatty tissue, leaving it nearly obsolete later in life.
This dramatic decline in usefulness raises intriguing questions about its long-term evolutionary purpose and why it fades away just as we grow older. Read more

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Conclusion

Our bodies are living museums, showcasing the quirks and flaws of evolution with every vestigial muscle, redundant organ, and awkward design.
These 24 body parts remind us that nature is a tinkerer, not a perfectionist—constantly adapting, yet never quite erasing the marks of our evolutionary past.
Next time you notice a strange ache or an odd anatomical feature, remember: it’s a testament to the ongoing story of humanity.
Embrace the wonders and imperfections of your anatomy—they’re part of what makes us uniquely human.

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