Why do we stand on two legs? | BBC Ideas

Humans are among the very few creatures who stand on two legs.

We take it for granted but being upright is quite a skill.

Take a normal four-legged chair - simple, stable,

or even a three-legged stool. But try a two-legged seat...

Human babies spend around 2,000 hours in their first year

developing the coordination and strength to stand.

It's the same amount of time

an Olympic athlete puts into a year's training.

Standing up is a major achievement, not only in our lives

but also in human evolution.

Why did we do this? We'll probably never know for sure

but there's no shortage of theories.

Hunters needing to take food home from the site of a kill

or conserve energy to outrun other animals.

Perhaps it was to carry and protect babies or was it for sexual display?

Some say it was our environment, as forests died back

it became easier to find food by walking than by climbing.

And the higher your head, the further you can see.

Plus being upright means less of your body

exposed to the midday African sun.

So maybe we stood up just to stay cool.

There is agreement on one thing, standing freed our hands

to become immensely sensitive and versatile tools

and with that came a big increase in brain capacity.

So from many points of view, standing is clearly a very good idea,

giving us a whole new level of control and power.

However, out of the millions of species on this planet

being a permanent biped is incredibly rare.

Some animals, baboons and bears, meerkats and chimpanzees

can occasionally pull off a two-legged trick but permanently?

Something we share with only a very few creatures on Earth.

Like some obscure rodents,

wallabies, ostriches and the giant pangolin.

Turns out this biped thing is quite tricky.

Think of robots -

tech companies have invested massively to crack this problem

of how you get a robot standing up on two legs.

And the Daleks? They don't even try.

So while they can destroy the universe,