February 15, 2013
Backaches Evolved Once We Started To Walk Upright
Lee Rannals for redOrbit.com — Your Universe Online
Feeling like your feet are a little sore or you have a backache after a day of shopping or walking around town? Well, scientists now say you can blame that on evolution.
Bruce Latimer, an anthropologist from the Case Western Reserve University School of Dental Medicine, says adapting to upright walking has resulted in physical challenges that affect most humans.
"If an engineer were given the task to design the human body, he or she would never have done it the way humans have evolved," Latimer said. "Unfortunately, we can't go back to walking on four feet. We've undergone too much evolutionary change for that–and it is not the answer to our problems."
Applying Darwin's theory of evolution to the human condition gives scientists a peak at why humans suffer from physical ailments in a way other animals do not, according to Latimer, a faculty member of the Department of Orthodontics at Case Western Reserve University.
When humans began to evolve from four-footed walking, so did issues with having flat feet and bunions, to slipped discs, hernias and fallen pelvic floors. It also helped to reshape the face and head, creating problems like wisdom teeth.
Latimer will be talking about physical problems of the spine, specifically, which developed into an S-shaped structure as humans evolved from a species who walked on all fours, to bipedal walking. However, not all the changes were bad, because those done to the spine resulted in protecting the body's most important area, the birth canal.
As the spine developed in curves, it became stressed at certain points, which resulted in conditions as swayed backs, hunchback, and scoliosis. The spine also suffers from how we walk, one foot forward at a time with the opposite side arm swinging in step.
"This creates a twisting motion that, after millions of twists over time, the discs between the vertebrae begin to wear out and break down resulting in herniated discs. In addition, age related bone loss (osteoporosis, the brittle bone disease) also a human condition, further complicates problems," said Latimer.
He said there are few early species of ancient human hominids who lived past 50 years, and most died between 30 and 40. The human body takes a physical beating and most people struggle with some kind of pain as the body ages.
"The original design specs for the human body were designed to last about 40 years," he said.
According to a study published in 2010, humans first gained their upright posture and gait millions of years ago. Archaeologists unearthed fossil footprints in Laetoli, Tanzania, indicating these early hominids were walking with a human-like striding gait as long as 3.6 million years ago. To understand it, the team collected 3D models of the footprints, and examined the relative depth of footprints at the heel and toe, finding these depths are about equal when made by a person walking with an erect gait.
“What is fascinating about this study is that it suggests that, at a time when our ancestors had an anatomy well-suited to spending a significant amount of time in the trees, they had already developed a highly efficient, modern human-like mode of bipedalism,” said biological anthropologist Adam Gordon, who collected the 3D models of the footprints.