Elementary English material, 24 july 2007

Energy use ‘drove human walking’

Humans evolved to walk upright because it uses less energy than travelling on all fours, according to researchers.

A US team compared the energy used by humans and by chimpanzees in walking.

The human bipedal gait is about four times more efficient than chimps getting around on either two or four legs, the researchers found.

Writing in Proceedings of the National Academy of Sciences (PNAS), they say this may explain why we walk bipedally, and some of our anatomical features.

Other research groups have proposed alternative explanations for our two-legged gait.

Some suggest it evolved because early humans needed to reach upwards to collect food or pass it to a mate, while others maintain it predates four-legged locomotion in primates, citing the often upright posture of orangutans as they move across slim branches.

On the treadmill.

A study from 1973 found little difference in efficiency between two-legged and four-legged walking in primates, but its conclusions had been disputed because only juvenile chimpanzees were used.

We were able to show exactly why certain individuals were able to walk bipedally more cheaply than others
David Raichlen
So David Raichlen from the University of Arizona in Tucson and colleagues set up a study in which five adult chimps were trained to use a treadmill, either on two legs or four.

The subjects were fitted with masks to collect exhaled air so that parameters such as oxygen use could be measured. Blobs of white paint on critical parts of the body such as elbows and knees allowed researchers to analyse the gait using video.

The results were compared with four human subjects using the same treadmill.

Generally, the humans were about four times more efficient than the chimps.

Three of the chimps found bipedal walking used more energy than going on all fours. But one of the others showed the opposite pattern; and intriguingly, she was the only chimp to lengthen her stride.

“We were able to tie the energetic cost in chimps to their anatomy,” noted Dr Raichlen.

“We were able to show exactly why certain individuals were able to walk bipedally more cheaply than others.”

The hypothesis, then, is that early humans began to evolve in a direction which allowed for easy bipedal travel.

David Raichlen suggests that early humans should show adaptations such as a longer leg length, and that there are indications of this in fossils of the genus Australopithecus , such as the famous “Lucy” specimen discovered in Ethiopia in 1974.

Story from BBC NEWS:

Experts seek to save rare turtle

Conservationists and scientists are meeting in Malaysia to hatch a plan to save one of the world’s most critically endangered sea creatures.

Experts say there are fewer than 5,000 leatherback turtles left, but with swift action they believe that their decline can be reversed.

The meeting’s organisers say there is a certain irony in their choice of venue.

Terengganu on Malaysia’s east coast was once home to one of the world’s largest leatherback turtle nesting sites.

Tens of thousands would come ashore each year to lay their eggs.

But no more. Numbers are so low that the state has dropped the turtle as its symbol.

The creatures have fallen prey to humans who either raid their nests for eggs or who catch them in fishing nets at sea.

Funding needed

Peter Dutton, the head of a US government marine turtle research programme, says it is a critical time for the leatherback.

He wants to see more action to protect their nests.

Scientists have already identified the most critical nesting sites and hope that this meeting will decide how best to put into action a plan to save them.

There is broad agreement that the leatherbacks’ decline can yet be stemmed.

However, campaigners say that without reliable funding for conservation programmes, the task of ensuring the survival of the largest of the world’s turtle species will be that much more difficult.

Story from BBC NEWS:

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