The truth about why we walk on two legs

[Rasputin]

Walking on two legs uses up a quarter of the energy it takes to walk on all fours, according to a study that could explain why early human ancestors adopted bipedalism rather than the knuckle-walking of chimpanzees and gorillas.

Explaining why humans went from a four-legged gait to a two-legged, upright posture has proven to be one of the most difficult and contentious issues in evolution.

The study suggests that it all comes down to energy expenditure and how costly it is to move around in terms of the food required.

Scientists compared the amount of energy expended by humans and chimps when walking on a treadmill and found that a two-legged gait is about 75 per cent less costly compared with walking on all fours.

The results provide powerful evidence in support of the idea that the bipedal gait of humans became established because it was more energy efficient and so required less food.

David Raichlen, professor of anthropology at the University of Arizona, said that although in the past scholars have suggested that bipedalism may have something do to with saving energy, there was little hard evidence to support of it.

"For decades researchers have debated the role of energetics and the evolution of bipedalism," Professor Raichlen said. "The big problem in the study of bipedalism was that there was little data out there."

The study, which is published in the journal Science, measured the oxygen used by four adult humans and five adult chimps as they walked on a treadmill. The scientists also measured the force exerted on the treadmill, which enabled them to calculate the amount of muscle power being used.

The scientists found that there was a clear advantage in bipedalism over knuckle-walking, but that there were also substantial differences between individuals which were masked when the entire group was analysed.

On average, the amount of energy used by chimps to walk on two legs or to knuckle-walk on four legs was about the same. However, the chimps who took longer bipedal strides were more energy efficient than those who took shorter ones.

"We were able to tie the energetic cost in chimps to their anatomy," Professor Raichlen said. "We were able to show exactly why certain individuals were able to walk bipedally more cheaply than others, and we did that with biomechanical modelling.

"What those results allowed us to do was to look at the fossil record and see whether fossil hominins [ancestors] show adaptations that would have reduced bipedal energy expenditure."

Such an analysis has revealed that some early human ancestors had developed slightly longer legs. "This tells us that energetics played a pretty large role in the evolution of bipedalism," Professor Raichlen said.

The study can explain the advantage of a bipedal gait once it had come about, but is less convincing when it comes to explaining why our ape-like ancestor went from a four-legged to a two-legged gait in the first place.

Herman Pontzer, professor of anthropology at Washington University in St Louis, said the central aim of the study was to test the idea that two-legged walking is better than four when it comes to burning calories.

"We now have a tried-and-tested and supported hypothesis for why bipedalism was so successful," Professor Pontzer, a member of the research team, said.

The chimps involved in the study were trained to walk on the treadmill. " It took a long time and a lot of treats [to train them]," Professor Pontzer said. "They weigh as much as you do and are five times as strong - so they won't work with you if they don't want to."

Rival theories

* Tree walking: A recent theory suggests that our tree-living ancestors walked upright on branches, using their arms for balance. The idea is based on observing modern-day orang-utans, which often move around in trees by walking on two legs, gripping the branches with their hands.

* A cooling effect: Another idea is that it was cooler to walk upright in savannah grasslands because by doing so there was less surface area of the body exposed to the Sun.

* Wading in water: If our ancestors had to wade through water, they would have learned to walk on two legs. Modern-day chimps often adopt a two-legged gait when walking through water.

[Rasputin]

Misconduct claim fuels clash among “wrist-walker” researchers


In a surprise twist to the already bizarre case of a syndrome whose victims walk on all fours, claims of research misconduct have fueled a bitter dispute among the scientists studying it.

The clash stems in part merely from differing theories on the condition, which the researchers say might shed light on human origins, and which one terms a possible “devolution.”

But intellectual s***mish has itself devolved into raw personal battle, pitting a relatively little-known Turkish researcher against three internationally known U.K. scientists.

He claims that after he invited them to study the syndrome with him in Turkey, they “stole” his credit for discovering it, sold the story for an upcoming BBC documentary and—worst—paid the victims’ family to stop cooperating with him and other researchers.

Since all known cases of the mutation came from that family, this stopped his research, he wrote in an email: “They actually bought the family.”

Two experts in research ethics contacted by World Science said such a payment sounds ethically dubious. A third said it might be wrong, or just rude, depending on the details of the case.

Nicholas Humphrey, one of the U.K. scientists, declined to discuss the alleged payment, citing confidentiality agreements related to the documentary.

But he denied having usurped credit, saying he duly acknowledged the Turkish researcher, Uner Tan. A published paper by Humphrey notes Tan’s invitation and says Tan conducted initial studies on the affected people, whom Humphrey dubbed “wrist-walkers.”

Humphrey, of the London School of Economics, added that the syndrome’s real discoverer seems to have been not Tan but another scientist, Osman Demirhan, who didn’t answer emails from World Science.

Jemima Harrison of Passionate Productions in Marlborough, U.K., who directed the documentary and others for the BBC, also declined to discuss the dispute. The film is to appear March 17, she said.

While Humphrey may be dealing with a misconduct claim, Tan is on the defensive for another reason: his science. He has raised controversial hypotheses on the syndrome—that it represents “backward evolution” or “devolution,” and other still more unusual concepts—provoking deep skepticism, even ridicule.

“Is this a hoax?” asked Thomas Suddendorf, a psychologist at the University of Queensland in Brisbane, Australia, after seeing a paper by Tan from the March issue of the International Journal of Neuroscience. Humphrey claimed Tan’s bizarre theories are why an initially friendly working relationship between the two began fraying.

Tan, of Cukurova University Medical School in Adana, Turkey, answered the criticism by saying reverse evolution is well studied. For instance, U.S. scientists wrote in the Oct. 2003 issue of the research journal Trends in Ecology and Evolution: “Evolution in reverse is a widespread phenomenon in biology; however, many researchers are only just beginning to take notice” of its importance.

Even more people will notice the wrist-walkers if the BBC documentary airs as planned. But Tan is not happy with how this notice has been arranged.

He wrote in an email that Humphrey’s team, besides selling what Tan called his discovery, apparently paid the wrist-walkers’ Turkish family to turn away other researchers who had been studying them. The family, which is poor, got 1,000 euros (about $1,200 US) and newly installed water and electric service, Tan wrote.

There was no word on who would pay any future bills in such an arrangement, nor on who might have paid for the rest of it. Humphrey’s paper says Trinity College in Cambridge, U.K., helped fund the research.

One scientific ethics expert said a deal such as the one Tan described might be unethical, or simply rude, depending on the details of the case.

“It might be a matter of research etiquette,” and nothing worse, wrote Jonathan Moreno, who directs the University of Virginia’s Center for Biomedical Ethics in Charlottesville, Va. From the family’s standpoint, “There’s no obligation to be in research at all,” thus no requirement to stay in a particular study.

But two other experts said they would seriously question such a transaction.

“I’m suspicious all over the place,” said Arthur L. Caplan, director of the University of Pennsylvania Center for Bioethics in Philadelphia. He said such a deal should have been pre-reviewed by one of the ethics panels that research institutions appoint for such purposes.

Humphrey wouldn’t say whether that occurred. His two co-authors in the research project didn’t answer emails.

Payments to research participants are normal, Caplan said, but must be vetted to ensure they’re neither unfairly small, nor too large: “You’re not supposed to bribe people into being subjects.”

He added that participants should have advocates to advise them of their rights and the risks, such as the possibility that they might become subjects of a media circus. Humphrey’s paper says a friend advised the family.

Michael Kalichman, director of the Research Ethics Program at the University of California, San Diego, wrote in an email that this sort of transaction generally “wouldn’t be right in terms of the protection of research subjects and it certainly wouldn’t be right in terms of the sharing of research knowledge.”

[shareholder]

the evolutionary advantage to walking on two legs was two arms were freed up and this allowed the creation of tools such as the sharpening of sticks for hunting.

[reza-george]

The energy efficiency theory is interesting.