Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Lessons from the orangutans: Upright walking may have begun in the trees

01.06.2007
By observing wild orangutans, a research team has found that walking on two legs may have arisen in relatively ancient, tree-dwelling apes, rather than in more recent human ancestors that had already descended to the savannah, as current theory suggests.

These findings appear in the 1 June 2007 issue of the journal Science, published by AAAS, the nonprofit science society.

Upright walking, or bipedalism, has long been considered a defining feature of humans and our closest ancestors. One of the most popular explanations, known as the savannah hypothesis, suggests that the ancestors to chimps, gorillas and humans descended from the trees and began walking on the ground on all fours.

Over time, this four-legged gait would have evolved into the "knuckle-walking" that chimps and gorillas still use today and then into upright, two-legged walking in humans.

... more about:
»bipedal »bipedalism »canopy »orangutan

Paleontologists have conventionally used signs of bipedalism as key criteria for distinguishing early human, or "hominin," fossils from those of other apes. But, this distinction is complicated by recent fossil evidence that some early hominins, including Lucy (Australopithecus afarensis), lived in woodland environments, while even earlier forms such as Millennium Man (Orrorin) appear to have lived in the forest canopy and moved on two legs.

"Our findings blur the picture even further," said Robin Crompton of the University of Liverpool in Liverpool, Great Britain, who is one of the study's authors. "If we're right, it means you can't rely on bipedalism to tell whether you're looking at a human or other ape ancestor. It's been getting more and more difficult for us to say what's a human and what's an ape, and our work makes that much more the case."

Crompton and his colleagues, Susannah Thorpe and Roger Holder of the University of Birmingham in Birmingham, Great Britain, came to their conclusions by observing wild orangutans in Sumatra, Indonesia. Orangutans spend almost their whole lives in trees, making them useful models for how our ancestors moved around several million years ago.

To collect the data, Thorpe spent a year living in the Sumatran rainforest and recording virtually every move the orangutans made. Then, she and her colleagues used these observations to test the hypothesis that bipedalism would have benefited tree-dwelling ape ancestors.

Because these ancestors were probably fruit-eaters, as orangutans are, they would have needed a way to navigate the thin, flexible branches at the tree's periphery, where the fruit typically is. Moving on two legs and using their arms primarily for balance, or "hand-assisted bipedalism," may have helped them travel on these branches.

The researchers analyzed nearly 3,000 examples of observed orangutan movement, and found that the orangutans were more likely to use hand-assisted bipedalism when they were on the thinnest branches. When bipedal, the animals also tended to grip multiple branches with their long toes.

On medium-sized branches, the orangutans used their arms more to support their weight, changing their moving style to incorporate hanging. They only tended to walk on all fours when navigating the largest branches, the researchers found.

Hand-assisted bipedalism may have offered several advantages that allowed our arboreal ancestors to venture onto thin branches. They could have gripped multiple branches with their toes and distributed their center of gravity more effectively, while keeping one or both of their long arms free to reach for fruits and other supports.

Orangutans also keep their legs straight while standing on bending branches, the authors report. The exact benefit of the straight legs is still unclear, but when humans run on springy surfaces, we also keep our weight-bearing legs relatively straight, so this may have an energy-related advantage.

"Our results suggest that bipedalism is used to navigate the smallest branches where the tastiest fruits are, and also to reach further to help cross gaps between trees," said Thorpe.

The authors propose an evolutionary scenario that begins as other researchers have envisioned. Somewhere toward the end of the Miocene epoch (24 to 5 million years ago), climate in East and Central Africa became alternately wetter and drier, and the rainforest grew increasingly patchy. Apes living in the forest canopy would have begun to encounter gaps between trees that they could not cross at the canopy level.

The Science authors suggest that early human ancestors responded to this by abandoning the high canopy for the forest floor, where they remained bipedal and began eating food from the ground or smaller trees. The ancestors of chimps and gorillas, on the other hand, became more specialized for vertical climbing between the high canopy and the ground and thus developed knuckle-walking for crossing from one tree to another on the ground.

"Our conclusion is that arboreal bipedalism had very strong adaptive benefits. So, we don't need to explain how our ancestors could have gone from being quadrupedal to being bipedal," Thorpe said.

Observations of orangutan movement should be useful for conservation efforts, according to Thorpe. These animals are seriously endangered, primarily due to habitat destruction.

"If you can understand how they cross gaps in the forest, you can learn about effects that living in logged or degraded habitat would have on their locomotion. These could affect energy levels, for example, if they have to go to the ground, which is incredibly risky because the Sumatran tiger is down there licking its lips. The Sumatran orangutan population is predicted to be extinct in the next decade if habitat degradation continues. Our research further highlights the need for protecting these animals," she said.

Natasha Pinol | EurekAlert!
Further information:
http://www.aaas.org

Further reports about: bipedal bipedalism canopy orangutan

More articles from Life Sciences:

nachricht Scientists spin artificial silk from whey protein
24.01.2017 | Deutsches Elektronen-Synchrotron DESY

nachricht Choreographing the microRNA-target dance
24.01.2017 | UT Southwestern Medical Center

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Scientists spin artificial silk from whey protein

X-ray study throws light on key process for production

A Swedish-German team of researchers has cleared up a key process for the artificial production of silk. With the help of the intense X-rays from DESY's...

Im Focus: Quantum optical sensor for the first time tested in space – with a laser system from Berlin

For the first time ever, a cloud of ultra-cold atoms has been successfully created in space on board of a sounding rocket. The MAIUS mission demonstrates that quantum optical sensors can be operated even in harsh environments like space – a prerequi-site for finding answers to the most challenging questions of fundamental physics and an important innovation driver for everyday applications.

According to Albert Einstein's Equivalence Principle, all bodies are accelerated at the same rate by the Earth's gravity, regardless of their properties. This...

Im Focus: Traffic jam in empty space

New success for Konstanz physicists in studying the quantum vacuum

An important step towards a completely new experimental access to quantum physics has been made at University of Konstanz. The team of scientists headed by...

Im Focus: How gut bacteria can make us ill

HZI researchers decipher infection mechanisms of Yersinia and immune responses of the host

Yersiniae cause severe intestinal infections. Studies using Yersinia pseudotuberculosis as a model organism aim to elucidate the infection mechanisms of these...

Im Focus: Interfacial Superconductivity: Magnetic and superconducting order revealed simultaneously

Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.

While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Sustainable Water use in Agriculture in Eastern Europe and Central Asia

19.01.2017 | Event News

12V, 48V, high-voltage – trends in E/E automotive architecture

10.01.2017 | Event News

2nd Conference on Non-Textual Information on 10 and 11 May 2017 in Hannover

09.01.2017 | Event News

 
Latest News

Breaking the optical bandwidth record of stable pulsed lasers

24.01.2017 | Physics and Astronomy

Choreographing the microRNA-target dance

24.01.2017 | Life Sciences

Spanish scientists create a 3-D bioprinter to print human skin

24.01.2017 | Health and Medicine

VideoLinks
B2B-VideoLinks
More VideoLinks >>>