Most people don’t give the little toe much thought until they stub it, or until they notice in a photograph how small and slightly crooked it looks next to the others.

When they do notice, the reaction tends to be a version of the same thought — that the toe looks unfinished, as though the body were partway through getting rid of it. That hunch is closer to the truth than most intuitions people have about their own anatomy, though not quite for the reason they assume.

What makes the toe interesting is less its size than how inconsistent it is from one person to the next. The big toe is built to nearly the same specification in everybody, because a foot with an unreliable big toe would have been a serious liability for an animal that walks and runs for a living.

The little toe tolerates far more variation than that. A 2018 study published in Surgical and Radiologic Anatomy examined foot radiographs from more than 900 adults and found the outer two bones of the fifth toe fused into a single segment in roughly four in 10 of them, a rate that varies widely between populations. The fourth toe showed the same fusion far less often, and the third almost never.

In biology, that kind of inconsistency is a clue in itself. Features that matter to survival stay uniform, because individuals who deviate from the design pay for it. When the design loosens up, it usually means the payment has stopped being collected.

Why The Little Toe Lost Its Relevance

Chimpanzee and gorilla feet look more like our hands than like our feet. The toes are long and curved, and the big toe swings out to the side to wrap around a branch, so the outer digits are doing genuine work holding a heavy animal in a tree. A 2018 review in the Journal of Experimental Biology lays out how differently our own feet are put together, while also making the case that the old climbing-versus-walking split is tidier than the evidence really supports.

What is clear is that our lineage gave up the grasping foot. The arch stiffened, the big toe rotated forward into line with the rest and took over the push-off, and the other toes got much shorter. That last change has actually been tested rather than just assumed. A 2009 study , also published in the Journal of Experimental Biology , measured people walking and running barefoot and found that longer toes demand more force and more work from the muscles that flex them, which over evolutionary time is the kind of running cost that selection notices. The outermost toe lost the most in that reorganization and gained the least, since it sits at the far edge of the foot, adds very little to propulsion and grips nothing.

Why We Can’t See The Little Toe Change in Real Time

This is where the popular version of the story goes wrong, and the mistake is a psychologically understandable one. We experience our bodies as things that change, so it feels natural to imagine evolutionary reduction as something happening on a human timescale, generation by generation. It isn’t. You could not measure a difference between your little toe and your great-grandmother’s. The shrinking is visible only by comparison — our toes against an ape’s, our feet against the fossil feet of early hominins.

Biologists call a feature inherited from an ancestor that has become reduced and simplified a vestigial structure. Wisdom teeth are the familiar example , the tailbone is another, and both share the little toe’s habit of varying wildly between people. Their common thread is relaxed selection, which is what happens when the pressure that once maintained a structure disappears and the anatomy is free to drift.

Why We’re Still Unsure About The Little Toe

None of this makes the toe inert. The outer edge of your foot still carries load as you walk, and the little toe contributes to balance and the stream of pressure information your nervous system relies on to keep you upright. People who lose one adapt without much trouble, but that is not the same as the structure doing nothing.

The 2018 radiograph study is blunt about the limits of what we know here, concluding that the fused version of the toe probably makes no difference to how a foot works — so “reduced” may be the more honest word than “vestigial,” a distinction that matters more to anatomists than to anyone buying shoes.

The shoe question is worth settling, though, because it points at another appealing but incorrect intuition. Footwear does measurably reshape a foot within a single lifetime. A 2018 study in Scientific Reports compared men who habitually wear minimal sandals with men who wear conventional shoes and found the minimally shod group had larger intrinsic foot muscles, including the one running along the little-toe side of the foot, and stiffer arches. It is tempting to extend that and assume centuries of narrow shoes are nudging our descendants toward four-toed feet. Acquired damage isn’t inherited, so it isn’t.

For the same reason, confident predictions that humans will lose the toe outright are pure speculation. Sustained selection is what drives that kind of change, the way it eventually left horses standing on a single toe — a shift that a 2017 study in Proceedings of the Royal Society B tracked through the internal bone structure of 13 fossil horse genera, and which took tens of millions of years of pressure to complete. There is no evidence that anyone’s toe size currently affects their odds of having children.

So the little toe will probably stay roughly as it is, faintly absurd and no longer under much scrutiny. All in all, the little toe might look unfinished because nothing is actively “finishing” it yet.

Curious what other than your toe is your body is carrying around from an earlier version of you? Find out how well you really know the human form with this quiz: Human Anatomy IQ Test