Utternonce
Wed, Jul-18-07, 06:17
WASHINGTON (Reuters) - A spine specialist trying to figure out
why people so often have bad backs says he has come up with a
new theory about when and how early humans evolved the ability
to walk upright.
The uncannily human-looking backbone of a 21
million-year-old precursor of humans and apes gives the
first clue, said Dr. Aaron Filler of the Cedars Sinai
Medical Center in Los Angeles.
A major change in the vertebrae that allowed this pre-human to
stand upright and carry things also made it easier to crush
and strain the spongy discs between each vertebra, Filler, a
medical doctor with a doctorate in anthropology proposes.
That, in turn, explains why back pain is a leading cause of
disability, he said.
Writing in the journal Neurosurgical Focus on Sunday, Filler
said one main clue was a bone feature called the transverse
process, which sticks out from the side of the hollow, round
vertebrae, Filler said in a telephone interview. This is where
muscles attach to the spine.
"The vertebra is transformed in a way that literally reverses
the mechanics of the spine," Filler said. "The bone lever of
the vertebrae gets switched from bending the spine forward to
bending the spine back."
Most vertebrates are oriented forward, to walk on all fours.
The transverse process is at the front of each vertebra,
facing the animal's belly. This is true of monkeys, too.
But in humans and in the 21 million-year-old fossil of a
creature called Morotopithecus bishopi, a tree-dwelling,
ape-like creature that lived in what is now Uganda, the
transverse process has moved backward, behind the opening for
the spinal cord.
Great apes, such as chimpanzees, share this feature.
'THE UPRIGHT APE'
The fossil was discovered in the 1960s but no one noticed the
important change until 1997, when paleontologist Laura
MacLatchy of the State University of New York at Stony Brook
reported on the remarkable features of Morotopithecus.
"That means that upright posture bipedalism goes back 20
million years, not just 5 or 6 million years," said Filler.
In his study and in a book published last week called "The
Upright Ape -- a new origin of the Species," Filler argues
that this common ancestor, and ancestors going back many
millions of years before, walked upright. Homo sapiens, the
human species, continued upright, while apes evolved back
toward all fours, he argues.
"When you look at most ape species, their spines and most of
their bodies still look pretty monkey-like," Filler said.
He also said humans evolved a new structure of muscles that
pull the body from side to side while standing.
"This is very important for carrying an infant or child,"
Filler said. "From the point of view of back pain, now we have
big muscles doing this heavy work that never did before. They
can get torn and strained."
The backward orientation also allows the cushiony discs to get
crushed, Filler said. "In most animals the vertebrae get
spread apart when they carry infants on their backs when on
all fours," he said.
What further differentiates humans from apes is the
positioning of the place where the spine attaches to the hips,
said Filler, who dissected the backbones of dead gibbons,
chimpanzees and macaque monkeys and compared them to bones
from living and extinct species of other animals and fossils
from various pre-humans.
why people so often have bad backs says he has come up with a
new theory about when and how early humans evolved the ability
to walk upright.
The uncannily human-looking backbone of a 21
million-year-old precursor of humans and apes gives the
first clue, said Dr. Aaron Filler of the Cedars Sinai
Medical Center in Los Angeles.
A major change in the vertebrae that allowed this pre-human to
stand upright and carry things also made it easier to crush
and strain the spongy discs between each vertebra, Filler, a
medical doctor with a doctorate in anthropology proposes.
That, in turn, explains why back pain is a leading cause of
disability, he said.
Writing in the journal Neurosurgical Focus on Sunday, Filler
said one main clue was a bone feature called the transverse
process, which sticks out from the side of the hollow, round
vertebrae, Filler said in a telephone interview. This is where
muscles attach to the spine.
"The vertebra is transformed in a way that literally reverses
the mechanics of the spine," Filler said. "The bone lever of
the vertebrae gets switched from bending the spine forward to
bending the spine back."
Most vertebrates are oriented forward, to walk on all fours.
The transverse process is at the front of each vertebra,
facing the animal's belly. This is true of monkeys, too.
But in humans and in the 21 million-year-old fossil of a
creature called Morotopithecus bishopi, a tree-dwelling,
ape-like creature that lived in what is now Uganda, the
transverse process has moved backward, behind the opening for
the spinal cord.
Great apes, such as chimpanzees, share this feature.
'THE UPRIGHT APE'
The fossil was discovered in the 1960s but no one noticed the
important change until 1997, when paleontologist Laura
MacLatchy of the State University of New York at Stony Brook
reported on the remarkable features of Morotopithecus.
"That means that upright posture bipedalism goes back 20
million years, not just 5 or 6 million years," said Filler.
In his study and in a book published last week called "The
Upright Ape -- a new origin of the Species," Filler argues
that this common ancestor, and ancestors going back many
millions of years before, walked upright. Homo sapiens, the
human species, continued upright, while apes evolved back
toward all fours, he argues.
"When you look at most ape species, their spines and most of
their bodies still look pretty monkey-like," Filler said.
He also said humans evolved a new structure of muscles that
pull the body from side to side while standing.
"This is very important for carrying an infant or child,"
Filler said. "From the point of view of back pain, now we have
big muscles doing this heavy work that never did before. They
can get torn and strained."
The backward orientation also allows the cushiony discs to get
crushed, Filler said. "In most animals the vertebrae get
spread apart when they carry infants on their backs when on
all fours," he said.
What further differentiates humans from apes is the
positioning of the place where the spine attaches to the hips,
said Filler, who dissected the backbones of dead gibbons,
chimpanzees and macaque monkeys and compared them to bones
from living and extinct species of other animals and fossils
from various pre-humans.