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Why Humans' Ancestors Began Walking Upright

What prompted our earliest ancestors to leave the safety of the trees and begin walking upright on two legs? Traditional theories point to climate changes that reduced tree cover and forced them to forage and hunt on solid ground. But a new study suggests a different evolutionary stimulus.

Archaeologists at the University of York in Britain say early hominins - our earliest ancestors - were attracted to the rugged terrain created by volcanoes and earthquakes of the Pliocene era, 2 million to 5 million years ago. Rocky outcrops and gorges offered shelter and hunting opportunities, but required scrambling and climbing and the ability to move quickly over broken ground. In the journal Antiquity, European researchers say that encouraged a more upright gait and also greater hand and arm dexterity - which in turn led to hominins using crude tools.

Isabelle Winder, one of the paper's authors, suggests living in such a challenging landscape led to "improved cognitive skills such as navigation and communication abilities," continuing the evolution into the species we are today.

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