In Praise of Walking summary

In these blinks we’re going to be talking about how humans walk. But first, let’s consider a very different creature: the humble sea squirt.

In its early stages of development, the sea squirt darts around in rock pools in search of food. To facilitate this movement, the young sea squirt develops one eye, a brain, and a spinal cord.

But then, one day, the sea squirt undergoes a pretty major transition. It finds a rock, attaches itself to it, and never moves again. Stuck in place, it then eats its brain, eye, and spinal cord. It just doesn’t need them anymore.

Why are we telling you this? Well, the lesson the sea squirt teaches us is this: if you don’t move around, you might as well eat your brain – literally.

The key message here is: Moving around might seem simple, but it requires brain power.

OK, sure. But humans aren’t quite the same as sea squirts! Right? Actually, we might be a little closer than you’d imagine.

Developmental biologists recently compared the genes of two seemingly different species: the little skate – a type of fish – and the mouse. And it turns out they share many genes related to movement. These shared genes determine their spinal cords, the placement of their limbs or fins, and the nearby muscles and nerves. This research shows that genes relating to walking stretch so far back in evolutionary history that they mostly developed underwater.

However, although we share so much with our ancestors, human walking is unique. Even our closest relatives, apes, generally use all four limbs. So why did we evolve to be upright? Well, our method of walking on two legs is more efficient. We can cover greater distances and carry stuff as we go – whether it’s children, weapons, or food.

Yet as efficient as it might be, walking on two legs is hard. When they’re learning, toddlers take an average of 2,368 steps – and 17 falls – per hour. And robots have yet to fully excel at human-style walking.

We have our brains to thank for mastering this complex task. One thing the brain is particularly good at is staying balanced. It does this via inertial guidance, which means it’s continuously calculating to calibrate our position. Trace the line from the corner of your eye to your ear canal; your brain will always try to keep this line parallel with the ground.

Not every aspect of walking is controlled by the brain, though. The spinal cord handles the central pattern generators that control the rhythmic patterns we need for breathing, the beating of the heart, and walking.

The spinal cord, you’ll recall, is another thing the adult sea squirt eats once it’s secured to its rock. We humans, though, make the most of our ability to move around. You could say walking rocks!