The vestigial palmaris longus tendon in the human wrist

Touch your thumb to your pinky and flex your wrist. See that thin cord popping up? That’s the palmaris longus, a piece of biological bloatware left over from our tree-climbing days.

It’s a legacy driver evolution forgot to uninstall. It helped ancestors grip branches, but it’s useless for us. About 15% of the population has already "deleted" it via mutation with zero issues.

Surgeons love this glitch, though. They harvest this spare part to fix important bits like torn ligaments. You’re essentially carrying a built-in hardware repair kit.

Wait, why hasn't evolution finished deleting this useless cord for everyone yet?

Evolution is the ultimate 'if it ain't broke, don't fix it' developer. Since this tendon doesn't kill you or stop you from having kids, there’s zero pressure to push a mandatory update.

It’s a 'neutral mutation.' In the grand OS of human biology, it’s like a legacy file that doesn't take up enough RAM to cause a crash. It just sits there, harmless and ignored.

Unless having a wrist tendon suddenly becomes a fatal disadvantage, it’ll keep being copied into the source code of future generations by sheer inertia.

What other weird legacy files are still clogging up our human OS?

Your body is a museum of abandoned hardware. Take the tailbone; it’s the literal stub of a tail ancestors used for balance. Now it’s just a mounting bracket for a peripheral you sold on eBay ages ago.

Then there’s goosebumps, powered by tiny muscles. For hairy ancestors, this was a 'scare tactic' or 'thermal patch.' For you, it just makes you look like a plucked chicken when you're chilly.

We’re a walking 'System 32' folder full of ancient files that nobody dares to delete because the whole OS might crash.

Hold on, if these are harmless files, why does the appendix randomly explode?

The appendix is the ultimate bloatware gone rogue. It likely started as a high-performance leaf-processing app for our herbivore ancestors. Today, it’s basically a tiny safe house for gut bacteria, acting like a backup drive to reboot your microbiome after a total system wipe like food poisoning.

The glitch is the hardware design. It’s a narrow, dead-end tube. If a tiny bit of data—aka waste—gets stuck, the pressure builds until the whole component goes nuclear. It’s a legacy part that’s prone to fatal overheating because the uninstall process has been stuck at 99% for a million years.

But how do those 'good' bacteria actually survive the 'wipe' to begin with?

Think of the appendix as a high-security bunker located off the main gut highway. When a 'forced format'—aka explosive diarrhea—flushes your system, the massive flow of fluid clears out almost everything in its path.

Since the appendix is a dead-end street, the 'good' bacteria inside just hunker down and wait. They’re physically shielded from the literal storm passing by in the main colon.

Once the coast is clear, these survivors crawl out to 're-sync' your gut. They multiply fast, reclaiming the territory before dangerous 'squatter' bacteria can move into the empty real estate.