Vestigial Traits: Evidence of Evolution in Your Own Body

Human Anatomy and Evolutionary History: A Video Introduction

Evolution you can see on yourself

Yes, your own body carries visible traces of evolution. A tendon in your wrist that many people lack, muscles that once swivelled the ears, goosebumps, a newborn's powerful grip and the small bone at the base of your spine all make most sense as leftovers from ancestors who lived differently. Biologists call such features vestigial: structures that have lost most or all of their original job, even if some now do something else.

The short video below, made by Vox in 2016, walks through several of these features and lets you test a few on your own body in under a minute. This page explains what it shows, adds a few more examples, and clears up the most common misunderstandings about "useless" body parts.

The palmaris longus: a tendon from climbing ancestors

Try this: rest your forearm on a table, palm up, touch your thumb to your little finger and lift your hand slightly. If a narrow band pops up in the middle of your wrist, that is the tendon of the palmaris longus muscle. A sizeable minority of people, often estimated at around one in seven, do not have it on one or both arms, and they show no loss of grip strength.

The muscle is much more developed in primates that use their forelimbs to climb and hang, such as monkeys and lemurs. In humans it does so little that surgeons routinely borrow its tendon for reconstructive operations elsewhere in the body. Its variable presence is exactly what you would expect from a feature that natural selection no longer maintains.

Ear muscles, goosebumps and a baby's grip

Ear muscles

Many mammals, from cats to horses, turn their ears towards a sound. Humans still have the same set of small muscles around the outer ear, the auricular muscles. Some people can wiggle their ears with them, but they cannot meaningfully aim them. Studies have even recorded these muscles twitching faintly towards interesting sounds, a reflex with almost no visible effect.

Goosebumps

When you are cold or frightened, tiny muscles at the base of each hair, the arrector pili, contract and raise the hair. In a furry animal this thickens the coat to trap warmth or makes the animal look bigger to a threat, like a cat arching its back. On mostly hairless human skin, the same reflex just produces bumps.

The grasp reflex

Press a finger into a newborn's palm and the baby grips surprisingly hard; the toes also curl when the sole is touched. In other primates, infants cling to their mother's fur as she moves. Human babies cannot do that for long, and the reflex fades within the first months of life.

The tail you had before you were born

Around four to five weeks after conception, a human embryo has a clear tail with a number of vertebrae. Over the next weeks most of that structure is broken down and absorbed, leaving the coccyx, or tailbone, a small set of fused vertebrae at the base of the spine. The coccyx is not useless today: several muscles and ligaments attach to it, and it helps support you when you sit leaning back. Its form, though, clearly matches the tails of our primate relatives.

Genetics adds more detail. Research published in 2024 pointed to a change in a gene called TBXT that appears to have helped switch off tail growth in the ancestors of apes, including humans; the precise mechanism is still being studied.

More traces: wisdom teeth, the eye's third lid and a broken gene

Wisdom teeth. Our ancestors had larger jaws and a coarser diet that wore teeth down. Many modern people have too little room for the third molars, which is why they often become impacted and are removed.

The plica semilunaris. The small pink fold in the inner corner of each eye is generally seen as the remnant of a nictitating membrane, the see-through third eyelid still working in birds, reptiles and some mammals.

Darwin's tubercle. Some people have a small bump or thickening on the upper rim of the outer ear. It is named after Darwin, who suggested it might correspond to the pointed ear tip seen in many other mammals. Whether that is the full explanation is still debated, but it is a harmless and fairly common variation.

A broken vitamin C gene. Most mammals make their own vitamin C. Humans and other apes carry a damaged version of the key gene, GULO, so we must get vitamin C from food. The fact that the same broken gene appears across primates is strong evidence of shared ancestry.

Myth check: what "vestigial" really means

Myth: vestigial means useless. Charles Darwin discussed "rudimentary" organs in The Descent of Man (1871), and in 1893 the German anatomist Robert Wiedersheim listed 86 human organs he considered vestigial. Many of them were later found to have functions. The appendix, for example, is now thought to support the immune system and may act as a reservoir for helpful gut bacteria. Vestigial describes a structure's history and reduced role, not a total lack of purpose.

Myth: humans evolved from chimpanzees. Humans and chimpanzees share a common ancestor that lived roughly six to seven million years ago. Neither species descends from the other.

Myth: one feature proves evolution on its own. No single body part settles the question, and scientists do not rely on one. The strength of the evidence comes from many independent lines agreeing: fossils, comparative anatomy, embryology and DNA all tell the same story about where we came from.

That is what makes the video worth a minute of your time. It turns a big scientific idea into something you can check at your desk, and every quirk it points to fits the same family tree.

Sources: Video by Vox: "Proof of evolution that you can find on your body" (2016); Wikipedia: Human vestigiality; Wikipedia: Palmaris longus muscle; Wikipedia: Coccyx; Wikipedia: L-gulonolactone oxidase; Wikipedia: TBXT (2024 tail-loss study).

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