Researchers from UCL, the University of Kent, and Duke University, USA, studied the behaviors of wild chimpanzees living in the Issa Valley of western Tanzania, for 15 months.
The chimpanzees' habit, which was a 'savanna-mosaic', a mix of dry open land with few trees and patches of dense forest, was very similar to that of our earliest human ancestors.
Their findings suggest an open environment encouraged prehistoric humans to walk upright – and instead suggest that they may have evolved to walk on two feet to move around the trees.
The study found the Issa chimpanzees spent the same time in trees as other chimpanzees living in forests, despite their open habitat. They did not prefer the land over trees.