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Nuchal Ligament

We can’t recommend a recent episode of the Radiolab podcast—Man Against Horse—highly enough.

It includes:

· Pigs on a treadmill

· Humans racing horses—on foot.

· A discussion about the role of the human butt.

· And a colorful discussion on a longstanding debate at the heart of human evolution.

If you know Radiolab (one of the best podcasts around), you know they find a way to make complex stories interesting and engaging. This episode is a classic.

It starts with a discussion of the butt muscle and leads to the existence of the nuchal ligament, long a point of fascination among evolutionary biologists.

The podcast includes Harvard’s expert, Daniel Lieberman, who has been around the “nuchal ligament” chatter for many years (since 1992).

Here’s how he describes his studies: “I'm interested in how and why our bodies are the way they are and the way in which we evolved.”

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So what’s up with the pigs? It turns out when they run that their heads flop around “in this kind of ungainly manner.”

Pigs don’t have a nuchal (nuchal: of the nape of the neck) ligament.

The nuchal ligament supports the head and neck.

Running animals have nuchal ligaments.

Jackrabbits? Yes.

Dogs? Yes.

Humans? But of course.

Apes? Nope.

Chimps and gorillas? Nope and nope.

Which leads us to human evolution.

Is running what made us human?

Or was it the ability to walk and the tools and brains?

The scientists studied the fossil record, to see if they can figure out when the nuchal ligament showed up.

Turns out, the nuchal ligament started showing up about two million years ago—on homo erectus.

It was the same time that our toes got shorter and around the same time that our feet started to develop an arch (a helpful trait for runners, it acts as a spring).

Us humans have a decent Achilles tendon, too. In chimps, it’s only about a centimeter long.

We won’t list all the anatomical changes here (listen to the podcast!).

But—see what we did there?—it also comes down to gluteus maximus.

The butt is key to running.

In fact, running is a “controlled fall.” The butt makes all the difference (and isn’t a huge factor when you’re walking).

But why did we run? What prompted it?

Did we start chasing animals? There was no bow and arrow until a hundred thousand years ago, so were we hoping our prey would run to the point of exhaustion and then we could bash with a rock?

The Radiolab podcast takes a fascinating detour to a race held regularly in Prescott, Arizona—man against horse. (The winner gets a cool belt buckle.) And then it comes back to this central debate about evolution.

Spoiler alert: we don’t yet know for sure!

But the debate rages—did early man exhaust its prey by chasing it? Or was running prompted by what one scientist called “aggressive scavenging,” which still means you have to run to a kill site to beat out all the other predators who might have been after the same meal.

All we know is we’ve got a nuchal ligament. Next time you head out for a run, at least you know why your head doesn’t bob around in an ungainly manner!








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