By Keerthi Chandrashekar / ( | First Posted: May 24, 2013 05:12 PM EDT

The left half shows the traditionally held hypothesis that humans began walking upright after moving from the trees due to the climate change, while the right side shows the new suggested theory that it was actually the rugged terrain of East and South Africa that led to upright walking (Photo : Dr. Isabelle Winder/Antiquity )

Why and where humans first began walking upright on two feet has never been definitively answered, and a new study out of the University of York only looks to add more fuel to the debate. According to York archaeologists, the move to walk upright on two feet came about because of the rugged landscape of East and South Africa.

Apparently, two feet was simply a better way than four limbs to traverse the African terrain shaped by moving tectonic plates and volcanoes.

"Previous models based on adaptations to forest or savannah are challenged here in favour of physical incentives presented by steep rugged terrain-the kind of tectonically varied landscape that has produced early hominin remains. "Scrambler man" pursued his prey up hill and down dale and in so doing became that agile, sprinting, enduring, grasping, jumping two-legged athlete that we know today," reads the study abstract, published in the journal Antiquity.

A commonly held previous theory holds that humans took to walking on two feet from their treetop lives when climate change eroded canopy cover, forcing humans to the ground.

Using two feet instead of all four limbs to travel around could have also had another interesting side effect. The archaeologists suggest that having two hands free led to many other evolutionary developments, such as tools.

"The varied terrain may also have contributed to improved cognitive skills such as navigation and communication abilities, accounting for the continued evolution of our brains and social functions such as co-operation and team work," Dr. Isabelle Winder from the Department of Archaeology at York said.

"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."

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