A new study by archaeologists at the University of York (UK) challenges evolutionary theories behind the development of our earliest ancestors from tree dwelling quadrupeds to upright bipeds capable of walking and scrambling. The researchers say our upright gait may have its origins in the rugged landscape of East and South Africa, which was shaped during the Pliocene epoch by volcanoes and shifting tectonic plates.
     Hominins, our early forebears, would have been attracted to the terrain of rocky outcrops and gorges because it offered shelter and opportunities to trap prey. But it also required more upright scrambling and climbing gaits, prompting the emergence of bipedalism.
     The York research challenges traditional hypotheses which suggest our early forebears were forced out of the trees and onto two feet when climate change reduced tree cover. Dr Isabelle Winder, one of the paper's authors, said: "The broken, disrupted terrain offered benefits for hominins in terms of security and food, but it also proved a motivation to improve their locomotor skills by climbing, balancing, scrambling and moving swiftly over broken ground - types of movement encouraging a more upright gait."
     Dr Winder continues: "Our hypothesis offers a new, viable alternative to traditional vegetation or climate change hypotheses. It explains all the key processes in hominin evolution and offers a more convincing scenario than traditional hypotheses."

Edited from The University of York, Red Orbit (24 May 2013), World News Australia (25 May 2013)