Human ancestors developed the ability to walk upright while living in trees rather than on open land as previously believed, scientists say.

The traditional view that our ancient relatives developed the ability to manage on two feet only when they moved out of the forests to live on the open savannahs of east Africa is mistaken, according to ground-breaking new research.

British scientists, who spent a year in Indonesian rainforests observing orang-utans, believe the common ancestors of all great apes - including humans - developed the ability to move upright so they could reach fruit on small branches and move between trees.