The ascent of man: Why our early ancestors took to two feet

May 24, 2013

A new study by archaeologists at the University of York 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 may have its origins in the rugged landscape of East and South Africa which was shaped during the Pliocene epoch by volcanoes and shifting .

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.

The study, 'Complex Topography and : the Missing Link', was developed in conjunction with researchers from the Institut de Physique du Globe in Paris. It is published in the journal Antiquity.

Dr Isabelle Winder, from the Department of Archaeology at York and one of the paper's authors, said: "Our research shows that bipedalism may have developed as a response to the terrain, rather than a response to climatically-driven vegetation changes.

"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."

The research suggests that the hands and arms of upright hominins were then left free to develop increased and tool use, supporting a further key stage in the evolutionary story.

The development of running adaptations to the skeleton and foot may have resulted from later excursions onto the surrounding flat plains in search of prey and new home ranges.

Dr Winder said: "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.

"Our hypothesis offers a new, viable alternative to traditional vegetation or hypotheses. It explains all the key processes in hominin evolution and offers a more convincing scenario than traditional hypotheses."

Explore further: Researcher finds earliest evidence of human ancestors hunting and scavenging

More information: 'Complex Topography and Human Evolution: the Missing Link' is published in Antiquity

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1 / 5 (3) May 24, 2013
They developed Arthritis of the Elbows & Bush growth in the Forests got so thick that they had to use their forelimbs quite often to make way for grasping what is ahead! STUPIDS ...I have read only the Title and not the article. That laborious Task is next.
1 / 5 (1) May 25, 2013
Those that let go off their fore limbs and saw the Predator at a distance survived relative to those that were still relying on their 4 limbs...or had shorter limbs.

Moral of the Story: Whatever Mutation helped making the incumbent survive...just as immunity to pathogenic bacteria!
1 / 5 (1) May 25, 2013
For that matter, the intelligent that did not see much use for forelimbs the on soil saw their prey more and survived avoiding, hunger, starvation, brain-stroke & Death. They did keep their rear avoid soiling up....That is what is called Intelligence!
5 / 5 (1) May 25, 2013
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.

Which sort of begs the question why all the other predator (and prey) species in that area did not go for bipedalism.

The big difference here seems tool use. Humans make a lot more use of tools than other animals - and using tools gives a big advantage. So any member of the species that can use his tools more efficiently/for more of the time (by having his hands free due to bipedalism) has a food gathering/survival (and hence breeding) advantage.
not rated yet May 26, 2013
"The big difference here seems tool use."

I agree with Antialias. Bipedalism frees the hands for wielding rocks and clubs and spears.
With these primitive tools early hominins could defend themselves in the open and also hunt more effectively. Bipedalism also would also enable homonins to carry more food to shelter, whether it be trees or "rocky outcrops".

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