well, thumbs up, right?

But it's not always been that way.

In the Roman era, a thumbs up meant death for a gladiator.

If the gladiator was to be spared,

the referee would press the thumb to the top of the fist.

If he flicked it up, it was bad news.

There's a common misconception that a thumbs down meant death back then.

It's thought to have stemmed from this painting by Jean-Léon Gérôme

in 1872,

which shows a colosseum crowd with arms outstretched

and thumbs pointing to the ground.

He got it wrong.

It's though the positive meaning of thumbs up

started with English archers in the Middle Ages.

A fist with thumb up measured the correct brace height of the longbow,

so the gesture came to mean "All is well. Ready for battle."

Another origin of the gesture comes from merchants in Medieval times.

They would seal a deal

by licking their thumbs and pressing them together,

so a thumbs up came to mean "done deal".

Allied fighter pilots in World War Two

used the gesture to indicate "chocks away"

when they were ready for take-off,

and it's thought that American GIs spread the gesture throughout Europe.

Even today, Italians call it...

Hitchhikers around the world hope to "thumb a lift" from passing traffic,

but watch out in Greece, Sardinia and the Middle East,

where a thumbs up sign is an insult

and is more likely to get you into trouble than the next town.

When a scuba diver gives a thumbs up,

it means it's time to swim back to the surface.

This signal has been known to confuse beginners.

A wiggled thumbs up means the number 10 in American sign language,

while a flat palm under a thumbs up is the sign for "help."

In the 1990s, influential US movie reviewers Siskal and Ebert,

used a thumbs up or thumbs down rating system on their TV show.

They even trademarked the phrase "two thumbs up".

Now, thumbs up and thumbs down signs are everywhere on the internet.

Hoping for your approval.

Or otherwise.