脖子的进化让大脑更上一台阶

What’s in a neck? Well, it’s a good place to hang a pendant or a tie. Or to rest your head. Now scientists say that by separating our heads from our bodies, the neck gave our brains a leg up in evolution. Their findings appear in the online journal Nature Communications.

Not all animals have necks. A fish's head is pretty much continuous with its body. And a fish gets around just fine. Nerves based in the fish’s brain instruct its fins to move, and off it goes.

But something happened when our aquatic ancestors first slithered onto the land. The source of the nerve cells that power the animals’ forelimbs shifted, from the brain to the spinal cord. That move allowed the body to grow more distant from the head, taking the arms with it. And so the neck was born.

That neck, say the scientists, was more than just a way to keep the head off the shoulders. The anatomical relocation improved dexterity by leaving the arms free to move in new ways. And the resulting flexibility helped shape the evolution of our heads and our hands, and how we can use them together to do all sorts of nifty things—like tie a perfect Windsor knot.

—Karen Hopkin