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The origin of human bipedalism
July 17, 2007While no one has an authoritative answer, anthropologists have long theorized that early humans began walking on two legs as a way to reduce locomotor energy costs.
In the first study to fully examine this theory among humans and adult chimpanzees, published online July 17 in the Proceedings of the National Academy of Sciences, researchers have found that human walking is around 75 percent less costly, in terms of energy and caloric expenditure, than quadrupedal and bipedal walking in chimpanzees.
That energy savings could have provided early hominids with an evolutionary advantage over other apes by reducing the cost of foraging for food.
Conducted by Herman Pontzer, Ph.D., assistant professor of Anthropology in Arts & Sciences at Washington University in St. Louis; Michael Sokol of University of California, Davis; and David Raichlen of University of Arizona, the study used treadmill trials to analyze walking energetics and biomechanics for adult chimpanzees and humans.
The only other research study on chimpanzee locomotor cost, conducted in 1973, used juvenile chimpanzees, which have different locomotor mechanics and costs than adults.
The team also examined the early hominin fossil record, which they found to include predicted changes consistent with lower energy cost- longer hind legs compared to body mass and structural changes to the pelvic bone allowing for more upright walking.
Analysis of these features in early fossil hominins, coupled with with analysis of bipedal walking in chimpanzees, indicate that bipedalism in early, ape-like hominins could indeed have been less costly than quadrupedal knucklewalking.
"Walking upright on two legs is a defining feature that makes us human," said Pontzer. "It distinguishes our entire lineage from all other apes."
Washington University in St. Louis
Conducted by Herman Pontzer, Ph.D., assistant professor of Anthropology in Arts & Sciences at Washington University in St. Louis; Michael Sokol of University of California, Davis; and David Raichlen of University of Arizona, the study used treadmill trials to analyze walking energetics and biomechanics for adult chimpanzees and humans.
The only other research study on chimpanzee locomotor cost, conducted in 1973, used juvenile chimpanzees, which have different locomotor mechanics and costs than adults.
The team also examined the early hominin fossil record, which they found to include predicted changes consistent with lower energy cost- longer hind legs compared to body mass and structural changes to the pelvic bone allowing for more upright walking.
Analysis of these features in early fossil hominins, coupled with with analysis of bipedal walking in chimpanzees, indicate that bipedalism in early, ape-like hominins could indeed have been less costly than quadrupedal knucklewalking.
"Walking upright on two legs is a defining feature that makes us human," said Pontzer. "It distinguishes our entire lineage from all other apes."
Washington University in St. Louis
Bipedalism Current Events and Bipedalism News RSSEarly hominid first walked on two legs in the woods
Among the many surprises associated with the discovery of the oldest known, nearly complete skeleton of a hominid is the finding that this species took its first steps toward bipedalism not on the open, grassy savanna, as generations of scientists - going back to Charles Darwin - hypothesized, but in a wooded landscape.
Anthropologist's studies of childbirth bring new focus on women in evolution
Contrary to the TV sitcom where the wife experiencing strong labor pains screams at her husband to stay away from her, women rarely give birth alone. There are typically doctors, nurses and husbands in hospital delivery rooms, and sometimes even other relatives and friends. Midwives often are called on to help with births at home.
Did walking on 2 feet begin with a shuffle?
Somewhere in the murky past, between four and seven million years ago, a hungry common ancestor of today's primates, including humans, did something novel.
Evolution tied to Earth movement
Scientists long have focused on how climate and vegetation allowed human ancestors to evolve in Africa. Now, University of Utah geologists are calling renewed attention to the idea that ground movements formed mountains and valleys, creating environments that favored the emergence of humanity.
New findings solve human origins mystery
An extraordinary advance in human origins research reveals evidence of the emergence of the upright human body plan over 15 million years earlier than most experts have believed.
Study Sheds Light on Why Humans Walk on Two Legs
A team of anthropologists that studied chimpanzees trained to use treadmills has gathered new evidence suggesting that our earliest apelike ancestors started walking on two legs because it required less energy than getting around on all fours.
Study identifies energy efficiency as reason for evolution of upright walking
A new study provides support for the hypothesis that walking on two legs, or bipedalism, evolved because it used less energy than quadrupedal knucklewalking.
Early human ancestors walked on the wild side
Arizona State University anthropologist and Institute of Human Origins researcher Gary Schwartz, along with fellow anthropologist Dan Gebo from Northern Illinois University, DeKalb, have studied fossil anklebones of some early ancestors of modern humans and discovered that they walked on the wild side.
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