Grassland theory uproots story of our ancestors’ first steps

The story of how our distant ancestors first came to stand upright may have to be rewritten after a reappraisal of when Africa gained its earliest grasslands.

It was widely thought that ancient apes first adopted a vertical posture while living high in the canopies of dense forests, where the limbs of one tree would have met those of the next.

Being upright, it was reasoned, would have made it easier for these animals to climb and to reach for fruit while balancing on branches. It was thought that only very rarely, if ever, would they have set foot on the ground.