Humans Born to Run

An interesting article from the New York Times.

http://www.nytimes.com/2004/11/17/health/17cnd-run.html?ex=11017189...
=1&en=4d03771feace25d8


November 17, 2004
Even Couch Potatoes May Have Been Born to Run By JOHN NOBLE WILFORD

The evolution of a physique for long-distance running is what made
humans look the way we do now - whether winning a marathon, nursing a
strained Achilles' tendon or sitting on an ample gluteus maximus in
front of the TV.

The apparently crucial role of running in human evolution, overlooked
for the most part in previous research, is being proposed today in an
article in the journal Nature by two American scientists.

While walking upright first set early human ancestors apart from
their ape cousins, the scientists write, it may have been the ability to
run long distances with springy step over the African savanna that
influenced the transition to today's human body form.

Endurance running, unique to humans among primates and uncommon in
all mammals other than dogs, horses and hyenas, apparently evolved at
least two million years ago and probably enabled human ancestors to hunt
and scavenge for food over large distances. And that, in turn, probably
proved decisive in their pursuit of high-protein food for development
of larger brains.

The scientists, Dr. Dennis M. Bramble of the University of Utah and
Dr. Daniel E. Lieberman of Harvard, reported that their analysis of the
fossil record showed striking anatomical evidence for the capability
of prolonged running in the Homo genus as early as two million years
ago.

'Today, endurance running is primarily a form of exercise and
recreation, but its roots may be as ancient as the origin of the
human genus," the scientists concluded in the article.

Dr. Bramble, a professor of biology and a specialist in the
biomechanics of animal locomotion, said, "Running made us human, at least in an
anatomical sense," adding that he and Dr. Lieberman were "very
confident that strong selection for running was instrumental in the origin of
the modern human body form."

Other paleontologists not involved in the research praised the
hypothesis as an important insight into the apparent significance of
long-distance running in human survival and evolution. But they
raised questions over what stimulated the physical transition that led to
this human capability.

By two million years ago, Dr. Bramble and Dr. Lieberman noted, early
species of the Homo family, beginning at least with Homo erectus, had
long, slender legs for greater strides. They had shorter arms and a
narrower ribcage and pelvis. Their skulls included features to help
prevent overheating. A ligament attached to the base of the skull
kept their heads steady as they ran.

Although tissues do not fossilize, traces of muscle and tendon
attachment points on bones of early species revealed an extensive
network of springy tendons along the back of their legs and feet,
including a well-developed Achilles' tendon that anchors the calf
muscles to the heel bone. Tendons served to store and release elastic
energy during running, but were not needed for ordinary walking.

And there was the gluteus maximus, the muscle of the buttocks.
Earlier human ancestors, like chimpanzees today, had pelvises that could
support only a modest gluteus maximus, nothing like the strong buttocks of
Homo.

"Have you ever looked at an ape?" Dr. Bramble said. "They have no
buns."

Dr. Lieberman, a paleontologist, explained: "Your gluteus maximus
stabilizes your trunk as you lean forward in a run. A run is like a
controlled fall, and the buttocks help to control it."

The two scientists speculated in the article and in interviews that
running by early human ancestors was more than simply a natural step,
so
to speak, beyond upright walking. These apelike ancestors, the
scientists noted, were walking almost three million years before they
became runners and began to assume more modern physiques.

In such ancestors as the Australopithecus genus, famous for the 3.2
million-year-old Lucy skeleton, the physical characteristics favoring
running were either absent or underdeveloped.

Somehow, the scientists continued, those early ancestors who
developed
primitive running attributes must have improved their chances of
survival and reproduction. They were not as swift in a sprint as
their
contemporary four-legged competitors for prey. But their ability to
run
greater distances than other predators must have been an advantage in
making a kill or at least scavenging the kills of their swifter
rivals.

But running came to early Homo at a cost: the loss of physical traits
useful for climbing trees for refuge and food. By this time, other
scientists have noted, climate change had diminished the woodlands of
East Africa, leaving more open grasslands to run long distances over.

Dr. Philip Rightmire, a paleoanthropologist at the University of
Binghamton in New York, said the Bramble-Lieberman hypothesis was "a
pretty compelling picture of the importance of running in human
evolution, and, over all, I'm very impressed."