School series 76

 Why Do Humans Walk on Two Legs?

Look at a dog, a cat or a horse. They move on four legs.

Look at us—we walk on two.

Why did humans end up with two legs instead of four?

The answer lies in evolution.

Our distant human ancestors gradually developed the ability to walk upright. This way of moving, called bipedalism, offered several advantages.

Standing and walking upright freed our hands.

With our hands available, our ancestors could carry food, hold objects, use tools and eventually make increasingly complicated things.

Walking on two legs also allowed us to see over grass and spot things farther away.

But walking upright required major changes to the body. The human spine developed its characteristic curves, the pelvis became shaped for upright walking, the legs became longer and stronger, and our feet developed arches that help support the body and absorb the impact of walking.

Animals evolved differently because they faced different needs.

A horse needs four powerful legs for running. A monkey needs limbs suited to climbing. A kangaroo has developed a completely different way of moving.

So evolution did not decide that two legs were “better” than four.

Each animal's body evolved to suit the way it lives.

And perhaps the greatest advantage humans gained from walking on two legs was not simply faster movement.

It was this:

Our hands were freed—and our hands helped us build our civilisation.