The upright posture of human beings has been a mystery for decades to researchers, but new evidence suggests the way we walk in a bipedal fashion is caused by the nature of the ground around volcanic eruptions.
Archaeologists from the University of York theorize that the upright gait practiced by humans may have developed due to the rugged landscape of southern and eastern Africa. The ground in that part of the world was formed by the actions of volcanoes and tectonic shift during the Pliocene Era, which created rocky outcrops and gorges.
Researchers theorize that hominins, ancestors of true humans, were attracted to these formations for shelter and to trap food. As they scrambled along the rocky outcrops, the hominins would have been forced to employ climbing and scrambling gaits more often than when on the ground. This could have led to the adoption of full-time bipedalism by our distant ancestors, according to the study.
"The broken, disrupted terrain offered benefits for hominins in terms of security and food," said Dr Isabelle Winder, co-author of the paper announcing the results, "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."
Archaeologists involved in this study believe that once hominins' hands were freed from walking, they could be used to steady the creature as it walked across the rugged terrain. This could have also led to greater dexterity in hands, helping to foster tool-making and use.
"For an animal moving on rough ground, the land is made up of lots of small, broken surfaces at different heights and angles," said Winder. "If you use four limbs to carry your weight, the chances are higher that you will be unable to position yourself effectively or that one of your hands or feet will slip. It is to your advantage if you can balance on just two or three limbs and use the others to steady yourself."
Earlier ideas about the rise of upright posture in human beings often centered around climate change as a catalyst driving early hominins from the trees on to the ground. This made researchers question how our distant ancestors could have survived the many predators of the region. The rock formations may have provided excellent hiding spots.
The results of the study were published in the journal Antiquity.
