By Patricia Reaney
LONDON, Nov 17 Reuters - Humans were born to run and evolved from ape-like creatures into the way they look today probably because of the need to cover long distances and compete for food, scientists said today.
From tendons and ligaments in the legs and feet that act like springs and skull features that help prevent overheating, to well-defined buttocks that stabilise the body, the human anatomy is shaped for running.
We do it because we are good at it. We enjoy it and we have all kinds of specialisations that permit us to run well,'' said Daniel Lieberman, a professor of anthropology at Harvard University in Massachusetts. There are all kinds of features that we see in the human body that are critical for running,’’ he told Reuters.
Lieberman and Dennis Bramble, a biology professor at the University of Utah, studied more than two dozen traits that increase humans’ ability to run. Their research is reported in the science journal Nature.
They suspect modern humans evolved from their ape-like ancestors about two million years ago so they could hunt and scavenge for food over large distances.
But the development of physical features that enabled humans to run entailed a trade off - the loss of traits that were useful for being a tree-climber.
We are very confident that strong selection for running - which came at the expense of the historical ability to live in trees - was instrumental in the origin of the modern human body form,'' Bramble said in a statement. The conventional theory is that running was a by-product of bipedalism, or the ability to walk upright on two legs, that evolved in ape-like human ancestors called Australopithecus at least 4.5 million years ago. But Lieberman and Bramble argue that it took a few million more years for the running physique to evolve, so the ability to walk cannot explain the transition. There were 2.5 million to 3 million years of bipedal walking without ever looking like a human, so is walking going to be what suddenly transforms the hominid body?’’ Bramble said.
``We’re saying ‘no, walking won’t do that, but running will.’’’
If natural selection did not favour running, the scientists believe humans would still look a lot like apes.
Running has substantially shaped human evolution. Running made us human - at least in the anatomical sense,'' Bramble said. Among the features that set humans apart from apes to make them good runners are longer legs to take longer strides, shorter forearms to enable the upper body to counterbalance the lower half during running and larger disks which allow for better shock absorption. Big buttocks are also important. Have you ever looked at an ape? They have no buns,’’ Bramble said.
Humans lean forward when they run and the buttocks ``keep you from pitching over on your nose each time a foot hits the ground,’’ he added.
HERE’S ANOTHER VIEW ON THE SAME SUBJECT:
WASHINGTON - Runners and joggers, take pride: :rolleyes: Your favorite exercise may be responsible for the evolution of human beings from our ape-like ancestors.
About 2 million years ago, our ancient forefathers developed bones and muscles suited for long-distance running, the better to hunt animals or scavenge for carcasses on the plains of Africa, a team of anthropologists reported Wednesday in the journal Nature.
Over time, they said, these physiological traits separated primitive people from the line that led to chimpanzees - our closest evolutionary relatives - whose bodies remained fitter for climbing trees.
We are very confident that strong selection for running - which came at the expense of the historical ability to live in trees - was instrumental in the origin of the modern human body form,'' said Dennis Bramble, a biology professor at the University of Utah in Salt Lake City. Running made us human, at least in an anatomical sense.’’
Bramble and his partner, Daniel Lieberman, a professor of anthropology at Harvard University in Cambridge, Mass., listed 26 physiological traits that make for endurance, if not speed, in runners. Compared with chimps, for example, humans have shorter arms, longer legs, springy calf and foot tendons, shoulders that rotate and bulky buttocks for better balance.
Your gluteus maximus (main buttocks muscle) stabilizes your trunk as you lean forward in a run,'' said Lieberman. A run is like a controlled fall, and the buttocks help to control it.’’
Another feature early humans developed is a piece of tissue at the back of the skull and neck that acts as a shock absorber and helps the arms and shoulders counterbalance the head as it bobs up and down during a run.
These esoteric features make humans surprisingly good runners,'' Lieberman said. Over long distances, we can outrun our dogs and give many horses a good race.’’
While people cannot run as fast, over short distances, as horses, greyhounds or antelopes, they can keep running for many miles.
Apes, such as chimpanzees, can sprint rapidly, but they do so rarely and only for short distances,'' the researchers wrote. No primates other than humans are capable of endurance running.’’
(EDITORS: STORY CAN END HERE)
Reaction to the Nature paper by other anthropologists was mixed.
Chris Stringer, the head of the human origins program at the Natural History Museum in London, called the paper
a valuable fresh look at our anatomy.'' Philip Rightmire, an anthropologist at the State University of New York in Binghamton, said the Lieberman-Bramble theory was quite convincing. … I support their conclusions.’’
But Rick Potts, the director of the Human Origins Program at the National Museum of Natural History in Washington, cautioned
there is not a lot of fossil evidence to support their scenario.'' Our ancestors learned to walk long before they began to run. Anthropologists think our ancient predecessors, known as Australopithecines (southern apes’’) were able to walk well on two legs at least 4.4 million years ago.
The physical changes that made endurance running possible do not appear in the fossil record until an early species of the human family, known as Homo erectus, arrived about 2 million years ago.
Long legs relative to body mass first appear unequivocally 1.8 million years ago with Homo erectus,'' the Nature researchers wrote. A well-developed Achilles tendon, connecting the calf to the heel, did not appear until 3 million years ago. Natural selection, the mechanism of Darwinian evolution, favored the perpetuation of those physical traits that enabled early humans to run long distances. The ability to outrun an animal or to beat a pack of hyenas to a carcass provided primitive people with a diet rich in proteins and fats. This helped them develop the big brains that distinguish us from other mammals, according to the Nature paper. Anthropologists traditionally thought running was a byproduct of walking and contributed little or nothing to the evolution of hominids, the family that includes archaic as well as modern humans. Bramble pointed out, however, our ancestors walked for 2.5 million to 3 million years without developing the anatomy of modern humans. Is walking going to be what suddenly transforms the hominid body?’’ he asked.
We're saying no, walking won't do that, but running will.'' Other anatomical features that help humans run include: -Wider vertebrae, spinal disks, hips, and knee and ankle joints that cushion the shock of the feet hitting the ground. -Enlarged heel bones and shorter toes for better pushing off during running. -Shoulders that are decoupled from the head and neck, allowing the body to rotate for balance while running. The burly shoulders of chimps and australopithecines are connected to their skulls, the better to climb trees and swing from branches,’’ Lieberman noted.
-A prominent rear end to
keep you from pitching over on your nose each time a foot hits the ground,'' Bramble said. Human buttocks are huge. Have you ever looked at an ape? They have no buns.’’